STAAD.Pro Standard Training Manual - Bentley Institute.pdf

STAAD.Pro Standard Training STAAD.Pro 2007

TRN011200-1/0002

Copyright Information

Trademarks AccuDraw, Bentley, the “B” Bentley logo, MDL, MicroStation and SmartLine are registered trademarks; PopSet and Raster Manager are trademarks; Bentley SELECT is a service mark of Bentley Systems, Incorporated or Bentley Software, Inc. Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries. Adobe, the Adobe logo, Acrobat, the Acrobat logo, Distiller, Exchange, and PostScript are trademarks of Adobe Systems Incorporated. Windows, Microsoft and Visual Basic are registered trademarks of Microsoft Corporation. AutoCAD is a registered trademark of Autodesk, Inc. Other brands and product names are the trademarks of their respective owners.

Patents United States Patent Nos. 5,8.15,415 and 5,784,068 and 6,199,125.

Copyrights ©2000-2008 Bentley Systems, Incorporated. MicroStation ©1998 Bentley Systems, Incorporated. IGDS file formats ©1981-1988 Intergraph Corporation. Intergraph Raster File Formats ©1993 Intergraph Corporation. Portions ©1992 – 1994 Summit Software Company. Portions ©1992 – 1997 Spotlight Graphics, Inc. Portions ©1993 – 1995 Criterion Software Ltd. and its licensors. Portions ©1992 – 1998 Sun MicroSystems, Inc. Portions ©Unigraphics Solutions, Inc. Icc ©1991 – 1995 by AT&T, Christopher W. Fraser, and David R. Hanson. All rights reserved. Portions ©1997 – 1999 HMR, Inc. All rights reserved. Portions ©1992 – 1997 STEP Tools, Inc. Sentry Spelling-Checker Engine ©1993 Wintertree Software Inc. Unpublished – rights reserved under the copyright laws of the United States and other countries. All rights reserved. STAAD.Pro Standard Training

Oct-08 Copyright © 2008 Bentley Systems Incorporated

Table of Contents Table of Contents

i

Module 1: Introduction

1.1 About this STAAD.Pro Training Manual

1-2

1.2 STAAD.Pro Workflow Process

1-3

Module 2: Model Generation

2-1

2.1 Pre Processor: Model Generation

2-2

2.2 The Start Page

2-3

2.3 Starting a New Project

2-7

2.4 Elements of the STAAD.Pro Screen

2-12

2.5 Job Setup

2-15

2.6 STAAD.Pro Structural Elements

2-16

2.7 Working with Grids

2-19

2.8 Entering Structure Geometry

2-27

2.9 Modeling Exercise 1

2-46

2.10 Editing Structure Geometry

2-48

2.11 Viewing Structure Geometry

2-82

2.12 Modeling Exercise 2

2-99

Module 3: Property Assignment

Oct-08

1-1

3-1

3.1 Steel Design Model Geometry

3-2

3.2 Working with Groups

3-4

3.3 Assigning Member Properties

3-11

3.4 Member Beta Angle

3-32

3.5 Assigning Member Specifications

3-45

3.6 Assigning Supports

3-60

3.7 Assigning Loads

3-69

3.8 The Material Page

3-85

i Copyright © 2008 Bentley Systems Incorporated

Table of Contents

Table of Contents

Module 4: Analyzing the Model

4-1

4.1 Preparing for the Analysis 4.2 Performing the Analysis

4-10

4.3 How Does STAAD.Pro Generate Results?

4-11

4.4 Viewing the Output File

4-13

Module 5: The Post Processor

5-1

5.1 Introduction to the Post Processor

5-2

5.2 Coordinate Systems for Reporting Results

5-3

5.3 Sign Conventions for Reporting Member End Forces

5-6

5.4 How to Determine if Results are Available

5-9

5.5 Activating the Post Processor

5-12

5.6 Displaying the Displacement Diagram

5-14

5.7 Displacement and Reactions Tables

5-19

5.8 Beam Analysis Results

5-28

5.9 Verifying the Results

5-44

5.10 Viewing Results with Member Query

5-48

5.11 Using Structural Tool Tips to View Results

5-53

5.12 Labeling the Structure Diagram

5-55

5.13 Individual Control of Labels

5-62

5.14 Animation

5-65

5.15 Plotting Output from STAAD.Pro

5-69

5.16 Simple Query

5-72

Module 6: Steel Design

Table of Contents

4-2

6-1

6.1 Introduction to STAAD.Pro Steel Design

6-2

6.2 How to Specify Steel Design Parameters

6-4

6.3 How to Use the Check Code Command

6-18

6.4 Checking Steel Design Results

6-25

6.5 Optimizing Steel Designs

6-30

6.6 Statically Indeterminate Structures

6-34

6.7 Finalizing the Design

6-39

6.8 Additional Comments Regarding Design Commands

6-51

ii Copyright © 2008 Bentley Systems Incorporated

Oct-08

Table of Contents

Module 7: Finite Element Modeling

7-1

7.1 Introduction to Finite Element Analysis 7.2 How to Create Finite Elements

7-12

7.3 How to Create Plates with Nodes Off-Grid

7-18

7.4 Mesh Generation

7-20

7.4.1 Using Structure Wizard to Generate a Mesh

7-21

7.4.2 Creating a Mesh From a “Super-Element”

7-26

7.4.3 How to Use the Mesh Generation Cursor

7-29

7.4.4 Using the Editor to Create a Mesh

7-37

Module 8: Concrete Design

Oct-08

7-2

8-1

8.1 Concrete Design Example Problem

8-2

8.2 Defining Model Geometry

8-4

8.3 Defining Element Properties

8-6

8.4 Adding the Supports

8-11

8.5 Defining Beam – Slab Monolithic Action

8-13

8.6 Defining the Slab

8-16

8.7 Tools for Viewing Plates

8-20

8.8 Plate Orientation and Local Coordinate System

8-21

8.9 Defining Plate Properties

8-27

8.10 Plate Element Specifications

8-29

8.11 Assigning the Loads

8-32

8.12 P – Delta Analysis

8-37

8.13 Providing Analysis Instructions

8-43

8.14 Running the Analysis

8-45

8.15 Viewing the Results

8-46

8.16 Reinforced Concrete Design

8-49

8.17 Understanding Concrete Design Results

8-59

8.18 Additional Concrete Modeling Examples

8-65

iii Copyright © 2008 Bentley Systems Incorporated

Table of Contents

Table of Contents

Module 9: Exercise Problems

Table of Contents

9-1

9.1 Exercise Problem One

9-2

9.2 Exercise Problem Two

9-4

9.3 Exercise Problem Three

9-6

9.4 Exercise Problem Four

9-11

9.5 Exercise Problem Five

9-17

9.6 Exercise Problem Six

9-23

iv Copyright © 2008 Bentley Systems Incorporated

Oct-08

1-1

Introduction Module 1 The following topics are included in this module. 1.1 About this STAAD.Pro Training Manual ........................................ 2 1.2 STAAD.Pro Workflow Process ......................................................... 3

STAAD.Pro Standard Training Manual

1-2

Module 1

1.1

About this STAAD.Pro Training Manual In the portion of this manual that covers the training instructions, the following conventions are used: Bold text in a box indicates actions that you are requested to perform. Italic text indicates the names of commands, menus, dialog boxes, edit box titles, etc., and suggestions or actions that are optional, but not essential. Underlined text indicates titles of books or reference documents. Text in the form of Tools | Orphan Nodes | Highlight indicates a string of sequential mouse clicks to be chosen from a menu. Shaded text indicates information that provides useful commentary, but is not essential to the flow of the training. Brackets { } indicate metric units or alternate instructions that are to be used if working in metric. However, all screenshots shown in this manual are based on English units. This STAAD.Pro Training Manual is intended to be used in conjunction with a Bentley Institute STAAD.Pro Training course. Depending on the specific course and presentation format, different Modules may be combined to create the overall course content. It is assumed that the reader has access to a working copy of STAAD.Pro to mirror some of the training steps and to complete the exercises and tutorials. In this manual, the first instance of a command is the most completely documented. Subsequent references to that command may not be as thorough since some general familiarity is assumed.

STAAD.Pro Standard Training Manual Module 1

1.2

STAAD.Pro Workflow Process The process of modeling and designing in STAAD.Pro can be summarized into the following general workflow process, which is suggested inherently by the on-screen organization of the tabs within the program:

Modules 2 and 7

1.

Basic Geometry: Define the basic geometry of the structure using beams, columns, plates and/or solid elements.

Modules 3 and 11

2.

Section Properties: Define the sizes of members by width, depth, cross sectional shape, etc.

3.

Materials Constants: Specify material such as timber, steel, concrete, or aluminum to define Poisson’s Ratio, Coefficient of Thermal Expansion, density, etc.

4.

Member Specifications: Define member orientations, member offsets, member releases where moment transfer is to be limited or eliminated, and conditions that only allow a partial transfer of certain types of forces such as tension-only.

5.

Supports: Define support locations and boundary conditions including moment fixity, support stiffness, and support angle.

6.

Loads: Assign loads such as self-weight, dead, live, wind and seismic, and define load combinations.

Modules 4 and 12

7.

Analysis Instructions: Indicate the type of analysis to be performed (regular analysis, P-delta, Buckling, Pushover, etc.) and define associated options.

Modules 5 and 13

8.

Post Processing Commands: Extract analysis results, review deflected shapes, prepare shear and moment diagrams, generate tables to present results, etc.

9.

Design Commands: Specify (for steel, concrete, timber, etc.)

Modules 6,8,10,14

1-3


1-4

Module 1

-End of Module-

2-1

Model Generation Module

2

The following topics are included in this module. 2.1 Pre-Processor: Model Generation ...................................................... 2 2.2 The Start Page .................................................................................... 3 2.3 Starting a New Project ...................................................................... 7 2.4 Elements of the STAAD.Pro Screen ............................................. 12 2.5 Job Setup ........................................................................................... 15 2.6 STAAD.Pro Structural Elements ..................................................... 16 2.7 Working with Grids ......................................................................... 19 2.8 Entering Structure Geometry ........................................................... 27 2.9 Modeling Exercise 1 ........................................................................ 46 2.10 Editing Structure Geometry ........................................................... 48 2.11 Viewing Structure Geometry ......................................................... 82 2.12 Modeling Exercise 2 ...................................................................... 99


2-2

Module 2

2.1

Pre-Processor: Model Generation All structural analysis software generally consists of three parts: •

Pre Processor:

•

Analysis Engine: Calculates displacements, member forces, reactions, stresses, etc.

•

Post Processor:

Generates the model, assembles and organizes all data needed for the analysis.

Displays the results.

In STAAD.Pro, these features are integrated into a unified graphic user interface (GUI) or working environment; you do not need to leave one module to access another. In this module, we will focus on the model generation aspect of STAAD.Pro using the Pre Processor’s graphical environment to define the geometry of our structure.


2.2

The Start Page Start STAAD.Pro(double-click the STAAD.Pro icon on the desktop or navigate through the Start menu in the lower-left corner of the desktop). The STAAD.Pro Start Page is displayed.

Figure 2. 1 The Start Page is divided into five sections that can be used to achieve the following: Project Tasks: •

Start a New Project using the STAAD.Pro wizard.

2-3


2-4

Module 2

• •

Open an existing file using the traditional Windows browse dialog enhanced with a model preview window. Open an existing file from ProjectWise, Bentley’s engineering project team collaboration system.

•

Set the program behavior with the Configuration options.

•

Setup the automatic Backup configuration requirements.

•

Access the License Management Tool to view and set configuration variables for the Bentley SELECT license, such as the server name and site activation key.

Recent Files: •

Access the last 6 models opened.

•

See a preview of each model in the list by hovering the cursor over the model name.

•

Data bubbles are populated with the file path and project information entered in a specific Job Info dialog.

Help Topics: •

Quick access to the online Help document.

•

Locate technical support centers and find contact details.

•

Find the latest information on the program online from the Product News link.

•

Access the growing STAAD.Pro online knowledge base.

•

Determine What’s New in the latest release of STAAD.Pro.


License Configuration: •

Indicates which SELECT licenses are being used by the current session of STAAD.Pro using the following color coding scheme: If the license is available it is marked with a green circle:

Figure 2. 2 Licenses that have not been selected are marked with a grey circle:

Figure 2. 3 If the selected license cannot be obtained or is not available from the server, it will be shown with a red circle:

Figure 2. 4 STAAD News: •

Displays the most current information about STAAD and Bentley, such as program updates, seminars, and training courses, using an RSS (Really Simple Syndication) reader.

•

Each news items is identified with a title that acts as a link to a website containing more information on that particular item.

Automatic Backup: •

Click Backup Manager… in the Project Tasks area of the Start Page.

2-5


2-6

Module 2

•

STAAD.Pro has the ability to perform automatic saves at a user-specified frequency to protect against loss of data.

•

Backup Manager also provides tools to view, compare, open, and restore backup saves from earlier times.

•

Even with powerful backup and restore features, good practice would dictate executing manual saves after significant modeling steps by using File | Save from the Menu Bar.

•

Under normal conditions this is a user preference item.

•

In order to ensure uniformity, this training session is accompanied by a dataset of standardized STAAD.Pro training files.

•

To avoid frequent messages during training, disable the Auto Save option by removing the check from the Enable Auto Save checkbox, and then click OK.


2.3

Starting a New Project Click New Project in the Project Tasks box on the STAAD.Pro Start Page. The New dialog provides input for: • • • • •

Structure type – See structure type descriptions below. File Name File Location Length Units Force Units

Four structure types are available: Space: •

Acceptable for any configuration of model geometry and loading.

•

Permits three-dimensional structures.

•

Permits loading in any direction.

•

Permits deformations in all three global axes.

•

Coordinate system follows right-hand rule.

•

Best practice is to orient Y axis up (so gravity pulls in negative Y-direction), see “Notes about Coordinate System Orientation” below.

Plane: •

Acceptable only for two-dimensional models in the XYplane with no loading or deformations perpendicular to this plane.

•

All loads and deformations are in the plane of the structure.

2-7


2-8

Module 2

Floor: •

Acceptable for two-dimensional models in the XZ-plane with loading and deformations perpendicular to this plane.

•

All loads and deformations are parallel to the global Yaxis.

Truss: •

Permits loading in any direction, but members only provide axial resistance. Members cannot resist bending or shear loads.

•

Permits three-dimensional structures.

•

Permits deformations in all three global directions.

•

Coordinate system follows right-hand rule.

Structure types Plane, Floor and Truss all conserve system resources by taking advantage of declared conditions to reduce the complexity of the stiffness matrix. With today’s computers, this is no longer necessary, but the program still provides these options for the convenience of long-time users who have become accustomed to using them. •

Select Space as the structure type.

Notes about Coordinate System Orientation: •

The location of components of a STAAD.Pro model is defined with reference to the origin point of the global coordinate system.

•

This coordinate system is a bit different than that used in CAD programs such as MicroStation.


•

In STAAD.Pro, the Y axis points in the vertical direction, and a plan view is represented by the XZ plane.

•

STAAD.Pro provides a Set Z Up option for CAD users, but you should be aware that many options of the program will not work with Set Z Up; the wind load generator is one example.

•

STAAD.Pro also provides tools for re-orienting the coordinate axis when importing or exporting to a CAD program.

•

It is probably a better idea to reorient the coordinate system when importing or exporting and to use STAAD.Pro’s default global coordinate system, rather than using Set Z Up, while working within STAAD.Pro.

•

Enter My Dataset 2_1 in the File Name field.

•

The Location field provides a default path. To change the button, and point to the location where Location click the you wish to save the file.

Notes about the unit system: •

Two base unit systems are available: English and Metric.

•

Base unit selection controls the units used to display results in tables and reports.

•

Base unit selection also dictates what type of default values the program will use when material constants are assigned based on material types (Modulus of Elasticity, Density, etc.).

•

A default base unit setting was chosen at the time of installation.

2-9


2-10

Module 2

•

The default base unit setting can be changed after installation by following the steps in the commentary below. Click File | Configure from the Start Page, or click Configuration… in the Project Tasks section of the Start Page. Select the Base Unit tab in the Configure Program dialog. Choose the desired unit system from the Select Base Unit drop-down combo box, and then click Accept.

•

The base unit system for a new project is based on the default base unit setting at the time the new project file is created, but can be modified on a model by model basis by selecting the desired units using the radio buttons in the Length Units and Force Units categories on the New dialog.

•

Select Foot {Meter} for Length Units and KiloPound {KiloNewton} for Force Units.

•

Click the Next button.

A second dialog appears offering quick access to a variety of common “next steps”, including: • Add Beam

Sets the program up with the Snap Node/Beam dialog and a snap grid to begin constructing a structure made of beams and columns.

• Add Plate

Sets the program up with the Snap Node/Plate dialog to construct a structure made of plates.

• Add Solid

Sets the program up with the Snap Node/Solid dialog to construct a structure made of solids.


• Open Structure Wizard • Open STAAD Editor • Edit Job Information

•

Opens a library of ready-made structure templates which can be extracted and modified parametrically to generate the model geometry or some of its parts. Allows you to build your model using the STAAD syntax commands in the STAAD editor (non-graphical interface). Automatically opens the Job Information dialog where you can enter information relative to the job, such as client name, job number, comments, etc.

Select the Edit Job Information option and click Finish.

2-11


2-12

Module 2

2.4

Elements of the STAAD.Pro Screen The elements of the STAAD.Pro Graphical User Interface (GUI) screen are identified in the figure below.

Status Bar

Figure 2. 5 Menu Bar •

Near the top of the screen.

•

Gives access to all of the STAAD.Pro menu functions.

•

Many of the same functions are also available from the Toolbar and from the Page Control.

Tool Bar •

Near the top of the screen.

•

Gives access to the most frequently used commands.


•

Tool Bar is dockable – layout can be reconfigured.

•

Customized tool bars can be created.

•

Hover the mouse over any icon for Tool Tip Help.

Main Window •

Large central area of screen where the model and graphical results are displayed.

•

Background color can be set to either white or black using the File | Configure menu on the Start Page.

Status Bar •

Displayed at the bottom of the screen.

•

Presents helpful information regarding the status of the program.

•

Displays cursor position, current input units, current program operating mode, hints for using the program, etc.

Page Control •

A set of tabs to the left of the Main Window.

•

Page Control can also be closed from within the Mode menu to free the screen area for other uses.

•

Each tab allows you to perform specific tasks.

•

Organization of the Pages, from top to bottom, represents the logical sequence of operations in STAAD.Pro.

•

Generally progress through the pages from top to bottom and enter all the data that are relevant to your project.

2-13


2-14

Module 2

•

Page names may or may not appear on Page tabs depending on screen resolution and size of STAAD.Pro window, but the icons on the Page Control tabs always appear.

•

Each page has some sub-pages.

•

The Pages that display depend on the current Mode of operation, which can be set from the Mode menu in the Menu bar.

Data Area •

Generally appears on the right side of the screen.

•

Displays dialogs, tables, lists, etc.

•

Context-sensitive to the type of operation being performed.


2.5

Job Setup •

Setup is the top page in the Page Control area when in Modeling mode.

•

When the Job sub-page is selected, the Job Info dialog is displayed in the Data Area.

•

Provides facility for defining job name, client’s name, job number, engineer’s and checker’s initials and dates, comments, etc.

•

Information entered in the Job Info dialog will be printed in the output reports and shown in the Recent Files section of the Start Page.

•

The use of this dialog is optional.

•

To see how this information appears on output reports, and on the Start Page, enter the following sample information now:

•

Job: Job

•

Client: Client

•

Job No.: Job No.

•

Rev: Rev

•

Part: Part

•

Ref: Ref

2-15


2-16

Module 2

2.6

STAAD.Pro Structural Elements STAAD.Pro provides five types of elements to use in modeling structures: Beams: •

Linear structural members.

•

The terms “member” and “beam” are synonymous.

•

Use of the term “beam” should not be taken to imply that the member cannot take an axial load.

•

Selected in STAAD.Pro by either the Beams Cursor or the Geometry Cursor.

Nodes: •

Points of connectivity between structural entities.

•

The terms “joint” and “node” are synonymous.

•

Selected in STAAD.Pro by either the Nodes Cursor or the Geometry Cursor.

Plates: •

Finite element commonly used to model “surface structures” such as walls, slabs, plates or shells.

•

May be either 3-noded (triangular) or 4-noded (quadrilateral).

•

Selected in STAAD.Pro by either the Plates Cursor or the Geometry Cursor.


Solids: •

Finite element enables the solution of structural problems involving three dimensional stresses.

•

Solids are useful for solving problems such as stress distribution in concrete dams, soil and rock strata, etc.

•

Solid elements consist of 8 nodes.

•

Solids most commonly take the form of cubes, but, by collapsing various nodes together, an 8-noded solid element can be degenerated into forms with 5 to 7 nodes.

•

Selected in STAAD.Pro by either the Solids Cursor or the Geometry Cursor.

Surfaces: •

Useful in the rapid modeling of walls, slabs and planar surfaces.

•

Similar to plate elements in terms of structural behavior, but faster and easier to model.

•

The entire wall or slab can be modeled with just a few "Surface" entities.

•

When the program goes through the analysis phase, it will automatically subdivide the surface into elements.

•

Selected in STAAD.Pro by either the Surface Cursor or the Geometry Cursor.

2-17


2-18

Module 2

Guideline for selection of Plate elements or Solid elements: If the ratio of the width of the shortest side to the thickness is less than 10, use solid elements.

t

t >10t

<10t

Use Plate Element Figure 2. 6

Use Solid Element


2.7

Working with Grids •

Grids assist with model construction by providing dimensional control and snap points.

•

Multiple grid systems can be created and saved in one model.

•

Only one grid system can be displayed at a time.

•

Three types of grids can be defined: Linear, Radial and Irregular.

Types of grid systems: •

•

Linear •

Two-dimensional system of regularly spaced linear (but not necessarily orthogonal) construction lines creating a plane of snap points.

•

Plane is defined as being coincident with the global XY, XZ, or YZ planes, or at an angle skewed with respect to the global planes.

•

Location of the origin can be defined with respect to the global X, Y, and Z coordinate system.

Radial •

Two-dimensional system of regularly spaced radial and circumferential construction lines creating a plane of snap points.

•

Plane is defined as being coincident with the global XY, XZ, or YZ planes, or at an angle skewed with respect to the global planes.

2-19


2-20

Module 2

•

Location of the origin can be defined with respect to the global X, Y, and Z coordinate system.

•

Well-suited for drawing circular models using piece-wise linear techniques.

•

The following diagram shows an example of a radial grid system defined in the XY plane:

Figure 2. 7 •

Irregular •

Two-dimensional system of regularly or irregularly spaced linear (but not necessarily orthogonal) construction lines creating a plane of snap points.

•

Plane is defined as being coincident with the global XY, XZ, or YZ planes, or at an angle skewed with respect to the global planes, or at an arbitrary plane. An arbitrary plane can be specified by checking the Use Arbitrary Plane box and entering the two points that define the normal vectors of the X and Y directions of the


plane. (The other point to establish the X and Y normally is the origin.) The following diagram shows an example of defining an arbitrary plane by defining the X and Y normal vectors.

Figure 2. 8 Spacing of the gridlines can vary in both directions. Spacing between successive gridlines is specified in the Relative gridline distances group box as shown below.

Figure 2. 9 Useful in creating openings in shear walls using the surface element. To set up grids: •

Ensure that the model named MY Dataset 2_1.std is open.

2-21


2-22

Module 2

•

Click the Geometry page tab in the Page Control area.

•

Click the Beam sub-page tab. This is the place we would have come if we had chosen the Add Beam option in the Where do you want to go? dialog when first starting the model.

•

A default grid appears in the Main Window.

•

The Snap Node/Beam dialog appears in the Data Area. Grid layout is controlled by this dialog.

•

Close the Snap Node/Beam dialog, and note that it can be reopened by clicking Geometry | Snap Grid/Node | Beam , or by clicking on the Snap Node/Beam toolbar button

.

•

Click Create… in the Snap Node/Beam dialog.

•

Note that the list at the top of this secondary dialog is currently set to Linear, but also offers the Radial, and Irregular grid type options. Keep it set to Linear for this example.

•

Type Training Grid in the Name field.

•

Click the X-Y radio button in the Plane category. Options are available to coordinate the new grid with any of the global axis planes.

•

Click the X-X radio button in the Angle of Plane ° category and enter a value of 45 in the field.

•

This rotates the grid plane 45° about the X axis. Note that you will not see any changes taking effect on the grid system currently displayed on the screen, the active grid system, because we are editing a different grid system.


•

Enter (10, 10, 0) {(3, 3, 0)} in the grid origin fields. Note that the Grid Origin can also be changed from the default location of (0, 0, 0) by using the icon to select an existing node in the model to represent the new origin.

•

Set the number of Construction Lines to 12 in both the X and Y directions by clicking the up arrow in the column labeled Right.

•

Set the Spacing field to 1 {0.25) ft {m} in both the X and Y directions.

•

Keep the Skew ° set to 0 in both the X and Y directions. A note about skewed grid lines: use caution to set the correct Spacing value when using skewed grids. The Spacing value is not measured perpendicular to the grid lines it applies to.

•

Click OK.

•

Training Grid (Linear) now appears in the list of available grid systems in the Snap Node/Beam dialog, but Default Grid (Linear) is still the active grid system.

•

Click the checkbox in front of Training Grid (Linear) to make it the active grid system. Default Grid (Linear) is automatically deselected, and the Main Window now displays the new grid.

•

The Active Grid Labels Setup category in the Snap Node/Beam dialog controls how the labels will appear for the currently selected grid system whenever it is the active grid. Since these settings are specific to individual grid systems, they can be set differently for each grid system in the model.

2-23


2-24

Module 2

•

The End(s) lists offer different options for labeling the ends of the gridlines. Keep them set to Start.

•

Click the up arrow in the Freq. column corresponding to the Y grid lines to increase the number to 2. This reduces the labeling frequency of the Y grids to every other grid line.

•

Click the X and the Z buttons in the row corresponding to the Y grid lines. (Y should already be selected.) This displays X, Y, and Z coordinate labels at all Y grid lines.

•

The labels are currently showing coordinate values in the global coordinate system with respect to the global origin located at (0, 0, 0).

•

Click the Local Coordinate checkbox, and note the difference.

•

This alters the display so that coordinates are reported in terms of a coordinate system that is local to the current grid. The origin of the local coordinate system is located at the origin of the grid system (global coordinate (10, 10, 0) {(3, 3, 0)} ), and with X and Y vectors lying in the plane of the grid. Looking at the Y grid line labels, the X coordinate now reads 0 instead of 10 {3}. The X-axis labels now read in whole numbers instead of fractional values in decimal format.

•

Click the Local Coordinate checkbox again to deselect.

•

Click the Rel.Coords checkbox, and note the difference.


•

Coordinates are now shown as relative offsets from the local origin of the grid system (global coordinate (10, 10, 0) {(3, 3, 0)}) measured in the global X, Y, and Z directions. Looking at the Y grid line labels, the X coordinate reads 0 instead of 10 {3}. The X grid line labels read in fractional values in decimal format, but they start at 0 instead of 10 {3}.

•

Click the Rel. Coords checkbox again to deselect.

•

Click the X and the Z buttons in the row corresponding to the Y grids lines, to deselect both. Now only the Y coordinate labels should be displayed at every other Y grid line.

•

Click the down arrow in the Freq. column corresponding to the Y grid lines to decrease the number to 1. This sets the labeling frequency back to labeling every Y grid line.

•

Click the Axis Ids checkbox, and note how it displays an axis prefix on each grid label. This can be helpful to establish orientation, especially in radically rotated grid systems.

•

Click the Axis Ids checkbox again to deselect.

•

Click Font… and note the options that are available to change the font and color of the labels.

•

Click Cancel to close the Font dialog and return to the Snap Node/Beam dialog.

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•

Click the Delete button in the Snap Node/Beam dialog to delete Training Grid (Linear).

•

Click the Default Grid (Linear) checkbox to make it the active grid system. Training Grid (Linear) is automatically deselected.

•

Click File | Close to return to the Start Page.

•

Click No when asked if you want to save the file.


2.8

Entering Structure Geometry Drawing beams: •

On the Start Page, click Open Project… and point to the location of the dataset installation.

•

Select Dataset 2_2.std and click Open .

•

Click on the Geometry page tab in the Page Control area. The Beam sub-page tab will be active by default.

•

Click Geometry | Snap Grid/Node | Beam.

•

The default grid appears in the Main Window. If working in metric, Metric Grid (Linear) should be the active grid.

•

Follow the steps outlined below to construct this simple portal frame:

Figure 2. 10

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•

The Snap Node/Beam button in the Snap Node/Beam dialog should be automatically activated, so that the “hot spot” follows the cursor and snaps to grid intersections. (If not click the Snap Node/Beam button.)

•

Notice the text prompt in the Status Bar at the bottom of the screen that says, “Add nodes/beams to line intersections using cursor. Hold CTRL key down to reset.”

•

Notice that the cursor only snaps to grid intersections.

•

Click at the origin (0, 0, 0) to create the first node.

•

The “hot spot” appears and a line will start “rubber-banding” from the origin.

•

Move up the grid and click again at (0, 8, 0) {(0, 2.5, 0)} to draw the first member. The starting end of a member is also referred to as End A or Node A; the other end is called End B or Node B.

•

Now the “hot spot” appears at the end of the first member, indicating that it is the starting point for the next member.

•

Move to (7, 8, 0) {(2, 2.5, 0)} and click again.

•

Move to (7, 0, 0) {(2, 0, 0)} and click one more time. The coordinates of the current cursor position are always provided in the Status Bar at the lower right corner of the screen.

•

Click the Snap Node/Beam button to stop drawing beams. Note that the grid could have been set up with 7 lines {8 lines} to the right of the origin, and 8 lines {10 lines} above the origin. This would eliminate having to constantly check


cursor location by counting grid lines or looking at the coordinate readout. Another good way to set the grid for this example would have been to set the grid to 1 line to the right of the origin in the positive X direction, and 1 line above the origin in the positive Y direction, then set the spacing to 7 feet {2 meters} in the X direction and 8 feet {2.5 meters} in the Y direction. Use the grid to its best advantage. •

Grids can be adjusted on the fly.

•

Nodes that have already been placed will NOT move with the grid. They maintain their coordinates once they have been placed.

•

To demonstrate this, make sure Default Grid (Linear) {Metric Grid (Linear)} is still the active grid system, and then click the Edit… button.

•

Edit the Spacing of the X grid lines to 1.5 {0.35} and press the tab key.

•

Note that the grid changed in the Main Window, but the existing nodes did not move with the grid.

•

Edit the Spacing of the X grid lines back to 1 {0.25}, and then click OK.

•

A copy of this model is already saved in this state in the dataset, and is named Dataset 2_3.std.

•


•

Click No when asked if you want to save the changes.

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How to move the “Hot Spot”: •

Open the file named Dataset 2_3.std.

•

Click on the Geometry page tab in the Page Control area.

•

Click on the Beam sub-page tab.

•

Click Geometry | Snap/Grid Node | Beam to open the Snap Node/Beam dialog.

•

Ensure that Default Grid (Linear) {Metric Grid (Linear)} is activated (has a check in the checkbox). The Snap Node/Beam button in the Snap Node/Beam dialog should be automatically activated, so that the “hot spot” follows the cursor and snaps to grid intersections. (If not, click the Snap Node/Beam button.)

•

Click at (7, 0, 0) {(2, 0, 0)} and note that the cursor is “rubberbanding” from that location. This is where the cursor was when the last node of the portal frame was placed.

•

Press and hold the Control (Ctrl) key.

•

Move the cursor around and notice that the line is no longer “rubber-banding” from the previous click location. The last node will no longer be considered the starting point of the next member.

•

While holding the Control (Ctrl) key, click on the node at (7, 8, 0) {(2, 2.5, 0)}.

•

Release the Control (Ctrl) key, and note that the cursor is now “rubber-banding” from the node at (7, 8, 0) {(2, 2.5, 0)}.

•

Click on the node at (0, 0, 0) to draw the first diagonal.


The Status Bar in the lower left corner of the screen displays some instructions for the currently active command or program mode. Remember to check this area any time you are in doubt about what response the program expects from you. Right now, it provides a hint regarding use of the Control (Ctrl) key to move the “hot spot.” •

Press and hold the Control (Ctrl) key.

•

While holding the Control (Ctrl) key, click on the node at (0, 8, 0) {(0, 2.5, 0)}.

•

Release the Control (Ctrl) key, and click on the node at (7, 0, 0) {(2, 0, 0)} to add the second diagonal.

•

Click the Snap Node/Beam button once more to stop drawing beams.

•

Keep this model open for use in the next section.

How to “Undo” an operation: •

Ensure that Dataset 2_3.std is still the active model.

•

Assume that the diagonal members were just added in error.

•

They could be deleted by methods that will be illustrated in a later section.

•

Or, the Undo command could be used in this case.

•

Click the Undo icon Beam twice.

•

The diagonals are deleted.

•

For demonstration purposes, click the Redo icon

twice, or click Edit | Undo Add

twice.

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•

The diagonals are restored.

•

Click the pulldown arrow to the right of the Undo icon

.

This function provides the ability to Undo multiple commands at one time. The Redo icon also has this feature. •

A list of modeling steps is presented with the most recent step on top. Double click the second Add Beam item in the list to undo the most recent two steps.

•

The diagonal members are deleted. STAAD.Pro will purge the Undo cache if changes are made in the command file editor and the Save command is issued. Nothing that was done before the command file was changed and saved will be available to Undo. There is an Undo feature in the command file editor, but once changes are saved and the editor is closed, that cache is purged as well. The Undo command from the Main Window cannot undo changes made in the command file editor.

•

Click the pulldown arrow to the right of the Redo icon

•

Double click the second Add Beam item in the list to restore the diagonal members.

•


•


•


.


Using the “Add Beams” Tool: •

Reopen the file named Dataset 2_3.std.

•

This returns us to a version of the portal frame model that does not already have the cross braces.

•

The model automatically opens to the Job sub-page of the Setup page in the Page Control area.

•

Note that no grid is currently displayed.

•

The Add Beams tool members to a model.

•

It will automatically snap to existing nodes in the structure and allow a beam to be added between two existing nodes, without the use of a grid.

•

Only adds one beam at a time.

•

Does not use the last node as the beginning for the next beam.

•

Click the Add Beams tool

•

Note that the black triangle in the lower right corner of this icon indicates that there are additional tools available “beneath” the visible icon.

•

To display the other tools associated with this icon, click and hold the left mouse button while pointing to one of these icons.

provides another way to add

on the Geometry toolbar.

The Add Beams tool is also accessible from the Menu Bar by clicking Geometry | Add Beam | Add Beam from Point to Point. •

The mouse cursor changes to the Add Beams cursor.

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•

Click at the lower left node in the portal frame, and note that a line starts “rubber-banding” between that node and the cursor location.

•

Click at the upper right node. A single member has now been created between those two nodes. Note no “rubberbanding”.

•

Draw the other diagonal in a similar manner.

•

Note that these members were drawn without the use of grids.

•

The Add Beam tool can also be used to add a beam where there is no node.

•

Click near the middle of the horizontal member.

•

Click Yes in response to the prompt asking if you want to add a node. The Insert Nodes into Beam dialog offers many ways to specify the location of new nodes to be added.

•

Enter 0.5 in the Proportion field, and click the Add New Point button. A value of 3.5000 {1.0000} appears in the Insertion Points box.

•

Click OK. A new node is created at the specified location, and the text prompt in the lower left corner of the screen indicates “Click on node at start of beam”.

•

Click on the node that was just created. A line starts “rubber-banding” between that node and the cursor location.

•

Click near the middle of the vertical member on the right.

•

Click Yes to the prompt about adding a new node.


•

This time, click the Add Mid Point button, and then click OK. Note that this is a faster method of adding a node at the midpoint than the method used on the horizontal member.

•

Click on this new node to finish adding the new member.

•

An even faster method would be to use the Add Beam between . This is one of the additional tools Mid-Points tool available “beneath” the Add Beams icon.

•

Click and hold the left mouse button while pointing to the Add Beams tool.

•

When the sub-toolbar pops up, keep the left mouse button depressed and point the cursor to the Add Beam between MidPoints tool

, and then release the mouse button.

•

The Add Beam between Mid-Points tool now remains the visible icon.

•

Click the Add Beam between Mid-Points tool. The message in the Status Bar says “Select First Beam”.

•

Click on the vertical member on the left. The message in the Status Bar now says “Select Second Beam”, and the line starts “rubber-banding” from the mid-point of the vertical member.

•

Click on the left-hand member of the top horizontal beam.

•

Another diagonal member is created as shown below:

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Figure 2. 11 •

Click the Add Beam between Mid-Points toolbar button again to turn the tool off. An alternate method to turn the tool off would be to click Geometry | Add Beam | Add Beam between Mid-Points from the Menu Bar.

•


•


•


Creating geometry using the spreadsheet: •

On the Start Page, click Open Project… and point to the location of the dataset installation.

•

Select Dataset 2_2.std and click Open .


•


•

Click the Beam sub-page tab. Grids will intentionally be left off to illustrate that this method of entering geometry is completely independent of grid systems.

•

Node 1 has already been entered. In the Nodes spreadsheet in the Data Area, input the following coordinate values, using the tab or arrow keys to move between cells: Node 1 2 3 4

(X, Y, Z) (0, 0, 0) (0, 8, 0) {(0, 2.5, 0)} (7, 8, 0) {(2, 2.5,0)} (7, 0, 0) {(2, 0, 0)}

•

The nodes appear in the Main Window as their coordinates are entered in the spreadsheet.

•

In the Beams spreadsheet, input the following node numbers, using the tab key to move between cells: Beam 1 2 3 4 5

Node A 1 2 3 1 2

Node B 2 3 4 3 4

•

The beams appear in the Main Window as their end nodes are entered in the spreadsheet.

•

Note that this portal frame has been created completely independently of any grid systems.

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•

It is not necessary to save this model. The dataset already contains a file in this state named Dataset 2_4.std.

•


•


How to use the Structure Wizard: •

Structure Wizard is a powerful and useful utility for creating structures from a built-in library of standard prototype structures.

•

For a demonstration of some of its capabilities, Structure Wizard will be used to build a model of the structure shown in the figure below:

Figure 2. 12 •

The general procedure will be to create the structure geometry in three steps:


•

Get the basic truss unit from Structure Wizard.

•

Add a column.

•

Use the Mirror command to create the left side. This will be demonstrated in a later section.

Creating the Truss: •

Click New Project… from the Project Tasks section of the Start Page.

•

Click Space type structure in the New dialog.

•

Enter STRUCTURE WIZARD for the File Name. STAAD.Pro will automatically append the .std extension.

•

Select Foot {meter} for Length Units and KiloPound {KiloNewton} for Force Units.

•


•

Click the Open Structure Wizard checkbox in the Where do you want to go? dialog, and then click the Finish button. The Structure Wizard can also be accessed from within STAAD.Pro at any time by using the Geometry | Run Structure Wizard command.

•

The STAAD.Pro graphic environment now appears, and the Structure Wizard window opens. Note the radio button options to toggle between Prototype Models and Saved User Models.

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STAAD.Pro provides the ability to save user models in a parametric format that allows them to be recalled and modified quickly. •

Select Prototype Models.

•

Click File | Select Units in the Structure Wizard’s Menu Bar. The Select Units dialog opens and allows a choice of unit systems to use in the definition of the prototype structure. This does not necessarily have to be set to the same units as the main STAAD.Pro model. This makes it possible to create a prototype in one unit system and then merge it into a model with a different unit system.

•

Ensure that the units are set to Feet {Meters}, and click OK.

•

Click the Model Type list in the upper left corner and note the built-in categories of structure prototype models that are already available.

•

Select Truss Models in the Model Type list. Structure Wizard displays six types of truss prototype models on the left side of the window.

•

Double-click the North Light truss icon to create the right half of the truss structure. Another option to select the North Light prototype is to drag and drop the North Light structure type icon over to the right side of the Structure Wizard window, where the coordinate axes tripod is displayed.

•

The Select Parameters dialog contains fields for entering parametric dimensions for the structure. Note that the units are in feet {meters}, as expected.


•

Enter values as shown in the figure below:

Figure 2. 133 In this example, the Width is set to 0, because only a planar model is desired, not multiple units in the third direction. {For metric units, set the Length dimension to 7.5 meters and the Height to 3 meters}. •

just to the right of the Click the button with 3 dots in it No. of bays along length field. A dialog is displayed showing the current breakdown of bay lengths. By default, the program sets the bay lengths equal. This dialog permits the individual bay lengths to be revised manually, but it enforces the constraint that the sum of the bay lengths must remain the same as the overall length of the truss. For this example, leave the bay lengths set to their default values.

•

Click OK or Cancel to dismiss this dialog.

•

Click the Apply button in the Select Parameters dialog. The structure now appears on the right side of the Structure Wizard window.

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•

The local origin for the structure is indicated by a colored coordinate axis tripod. Note the location of the origin and the orientation of the local coordinate axes. It will be useful to know where the local origin is when importing the structure into the STAAD.Pro model. The coordinate axis tripod shows that the origin is located at the lower left corner of the truss.

•

The structure can be viewed from various angles by dragging it with the mouse. It helps to grab the structure near the top of the view, and think of it as being encapsulated in a transparent sphere.

•

Press and hold the Control (Ctrl) key, and note how it locks the structure so that it only rotates about one of the two orthogonal axes in the plane of the screen.

•

Press and hold the Shift key, and note how it locks the structure so that it only rotates about one of the three local axes indicated by the tripod. The axis of rotation is controlled by where the structure is grabbed with respect to the three reference circles shown on the screen.

•

After rotating the structure in either the Shift key or Control (Ctrl) key modes, just click the mouse anywhere in the right side of the Structure Wizard window to return to “clear sphere” rotation mode.

•

Now, pull down Structure Wizard’s File menu and select Merge Model with STAAD.Pro Model. If you do not see the Merge Model with STAAD.Pro Model command, check to be sure that you have pulled down Structure Wizard’s File menu, not the File menu in STAAD.Pro’s Main Window.

•

Click Yes in the next dialog to confirm the intent to transfer the prototype structure into the STAAD.Pro project.


•

Some discussion about units… •

The purpose of the Paste Prototype Model dialog is to adjust the position of the prototype model when it is placed in the STAAD.Pro model. Therefore, the units provided in the Paste Prototype Model dialog are controlled by the Set Current Display Unit… setting in the STAAD.Pro main menu. (Tools | Set Current Display Unit…)

•

By contrast, the purpose of the Select Parameters dialog is to create the geometry of the prototype within the Structure Wizard. Therefore, the units provided in the Select Parameters dialog are controlled by the Select Units setting in the Structure Wizard main menu. (File | Select Unit).

•

For this reason, it is possible that the units that come up in the Paste Prototype Model dialog could be different than the units that come up in the Select Parameters dialog.

•

By default, a prototype model will be placed into a STAAD.Pro model so that the origin of the prototype model coincides with the origin of the STAAD.Pro model.

•

The Paste Prototype Model dialog currently provides two methods to shift the insertion point of the prototype model to a location other than (0, 0, 0) in the STAAD.Pro model: •

By distance between following two nodes and specifying two reference nodes, or

•

By the following X, Y, and Z values and entering the desired coordinate location.

If the prototype model were being merged into a STAAD.Pro model that already contained some elements, a third option to locate the prototype model would be available. This option uses a Reference Pt button to allow the prototype model to be

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inserted at any existing point on the STAAD.Pro model. This option will be demonstrated in a later section. •

The truss is to be supported by 15-foot {5-meter} columns. If the coordinate location of the bottom of the columns is to be at Y = 0, then the truss should be inserted 15 feet {5 meters} in the positive Y direction from the origin of the global coordinate system.

•

Select By the following X, Y, and Z values in the Paste Prototype Model dialog, and enter a value of 15 ft { 5 meters} in the Y field.

•

Click OK. The structure is transferred into the STAAD.Pro model. The Structure Wizard is dismissed, and the STAAD.Pro Main Window is now visible.

•

Click the Geometry | Beam page in the Page Control.

•

In the Nodes table in the Data Area, note that the Y coordinate for nodes 1 through 5 is 15 ft. {5 m}, indicating that the truss was indeed inserted 15 feet {5 meters} above the STAAD.Pro origin.

Adding the column: •

The next step in creating this model is to add the column at the shallow end of the truss. But first, the node at the base of the column must be created.

•

In the Nodes table of the Data Area, input the coordinates (25, 0, 0) {7.5, 0, 0} on the line for node 11.

•

The newly created node 11 appears in the diagram in the Main Window.


•

Click Geometry | Add Beam | Add Beam from Point to Point. The cursor changes to the Add Beams cursor.

•

Click the node on the shallow end of the truss and click again at the new node.

•

Click the Add Beams off.

icon to turn the Add Beams tool

This tool remains active until it is turned off. •

The remaining steps for completing this model will be demonstrated in a later section.

•

A copy of this model is already saved in this state in the dataset, and is named Dataset 2_STRUCTURE WIZARD.std.

•


•

Click No when asked if you want to save.

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2.9

Modeling Exercise 1 Create this model by applying the modeling techniques that have been presented up to this point. Some abbreviated notes are provided below for general guidance if necessary.

Figure 2. 14 Tips: •

New Project… from the Start Page, Project Tasks category.

•

Space, My Exercise 1, Foot {Meters}, KiloPound {KiloNewton}, Add Beam.

•

Geometry Page, Beam Sub-page, Snap Node/Beam dialog, Edit…, adjust grid to suit.


•

Note the order of the node numbers in the figure.

•

Press and hold Control (Ctrl) to move the “hot spot”.

•

Snap Node/Beam to stop adding members.

•

Close button to dismiss the Snap Node/Beam dialog.

•

File | Close, Yes to save.

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2.10

Editing Structure Geometry How to use the cursors in the STAAD.Pro Selection toolbar: •

In the Project Tasks section of the Start Page, click Open Project… and open the model called Dataset 2_5.std.

•

The Selection toolbar is normally docked vertically on the left side of your screen.

•

Hover the cursor over any of the toolbar buttons and a tooltip help label pops up with the function of the toolbar button.

•

Twelve different cursors are available for selecting the various types of STAAD.Pro entities.

•

Each cursor selects specific types of objects for editing or manipulation.

•

Having specific cursors can be very convenient when assigning properties where various types of entities are crowded together.

Cursor

Selects

Nodes Cursor

Nodes only

Beams Cursor

Members only

Plates Cursor

Plate elements only

Surface Cursor

Surface entities only

Solids Cursor

Solid elements only

Geometry Cursor

All types of entities


Select Text

Text labels only

Load Edit Cursor

Loads only

Support Edit Cursor

Supports only

Member Release Edit Cursor

Member releases only

Filtered Selection Cursor Select Joints

Multiple types of geometric entities with specific attributes Connections defined in the RAM Connection module

Cursor Facts: •

The Nodes Cursor selects the nearest node when you click anywhere in the drawing area.

•

The Beams Cursor selects/deselects individual members by clicking on them. Multiple members are selected by pressing Control (Ctrl) and clicking.

•

The Geometry Cursor selects all entities in a certain area, no matter what type of entities they are.

•

The Select Text Cursor is disabled or “grayed out” if there are no text objects in the model.

•

The Filtered Selection Cursor helps quickly identify the location of entities with certain attributes. (This cursor type will be easier to demonstrate once the model has properties assigned to the members.)

•

The Select Joints cursor is disabled or “grayed out” unless you are in the RAM Connection module and at least one connection has been defined.

•

In addition to using the toolbars, you can also choose cursors from the Select menu on the Menu Bar.

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•

•

•

Another related toolbar, the Labels toolbar, contains more cursors that are used to turn individual labels on and off. It is explained in more detail in the Module 5 – The Post Processor. Click Select | Selection Mode, and note that three options are available: Drag Box, Drag Line, and Region. This works hand-in-hand with the cursor choice. The cursor choice controls WHAT items will be selected. The Selection Mode controls HOW those items will be selected.

Drag Box: •

Creates a rectangular selection box.

•

When the Beams Cursor is used in the Drag Box mode, the rule is that a member will be selected if the box includes the mid-point of the member. This holds true regardless of which direction the box is placed (left to right, right to left, top to bottom, or bottom to top).

Drag Line: •

Creates a selection line.

•

When the Beams Cursor is used in the Drag Line mode, any beam crossed by the Drag Line will be selected.

Region: •

Creates a selection polygon of any shape.

•

The polygon is always closed, and left-clicking with the mouse inserts additional vertices.

•

Can be used to create very irregular shapes to selectively include and exclude various items.


•

•

Double-click to stop creating more vertices and execute the selection. Similar to Drag Box, a member will be selected if the region includes the mid-point of the member.

Additional options for member selection: •

Click Select | By List | Beams… from the Menu Bar.

•

The Select Beams dialog will open with a list box listing all the beams in the model. •

One option is to select from the list of all beams in the model by clicking individual beam numbers in the list. Control (Ctrl) + click will select multiple beams. Shift + click will select a contiguous group of beam numbers.

•

Another option is to type the desired beam numbers in the Enter list field, separated by spaces.

•

To demonstrate the use of the “To” command to select a range of members, enter 1 To 3 in the Enter list field.

•

Click the Select Listed Entities button followed by the Close button.

•

Click Select | By All | All Beams from the Menu Bar to quickly select all beams in a model.

•

Click Select | Entity at Node | Beams from the Menu Bar to select all beams that connect to a particular node to be chosen from a list.

•

Click Select | By Inverse | Inverse Beam Selection from the Menu Bar to invert the current selection status of all beams in the model. Selected beams become deselected and vice versa.

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•

Click Select | Beams Parallel To | (X or Y or Z) from the Menu Bar to select all beams that are parallel to the selected axis.

•

And others.

How to delete members graphically: •

Ensure that the cursor type is the Beams Cursor. Check the Selection toolbar in the upper left corner of the screen or pull down the Select menu to see which cursor is active.

•

Hold Control (Ctrl) and click on the two highlighted members in the view below.

Figure 2. 155 •

Press the Delete key on the keyboard, or click the Delete icon on the Menu Bar, or click Edit | Delete.

•

Click OK to confirm.

•

Sometimes deleting members leaves nodes without structural element attachment, known as Orphan Nodes.


•

If Orphan Nodes are created when members are deleted graphically, STAAD.Pro will prompt for a decision as to whether to delete these nodes or not.

Using the spreadsheets to delete or modify geometry: •

It is also possible to delete beams (one at a time or many at once) from the Beams spreadsheet. This method may be useful if the beams to be deleted are in sequential numerical order, making them easy to select from a list.

•


•


•

Notice the Nodes and Beams tables in the Data Area that resemble spreadsheets. If the table names are not visible, make their windows wider.

•

These tables are actually compatible with Microsoft Excel worksheets. They can be copied and pasted into Microsoft Excel. The structure geometry can also be created in a spreadsheet and then copied and pasted into STAAD.Pro. When pasting from Excel, select the first row in the STAAD.Pro table, right mouse click, and choose Paste. Use the column mapping table to map the data into the appropriate columns.

•

Table data can also be copied and pasted from RAM Advanse into STAAD.Pro.

•

These tables are completely interactive with the graphics display.

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•

Ensure that the Beams Cursor is active, and click on any member.

•

The corresponding member in the table is highlighted.

•

Select the Nodes Cursor and fence around any node.

•

The line in the Nodes table corresponding to that node becomes highlighted.

•

Click any row in the Beams or Nodes tables and the corresponding beam or node is highlighted in the graphic display.

•

Change one of the coordinates in the Nodes table and watch the display change, then change it back to its original value.

•

Delete any line from the Beams spreadsheet and note the effect in the graphic display.

•

Click Undo to get the beam back. If Orphan Nodes are created when members are deleted from the spreadsheet, STAAD.Pro does not automatically prompt for a decision as to whether to delete them or not. However, they can be automatically detected with Tools | Orphan Nodes | Highlight, or they can be automatically deleted with Tools | Orphan Nodes | Delete.

•

A copy of this model is already saved in the dataset, and is named Dataset 2_6.std.

•


•



Using the STAAD.Pro Editor to modify structure geometry: •

Click Open Project… in the Project Tasks section of the Start Page .

•

Open Dataset 2_6.std.

•

As you create your structure using the graphic interface, STAAD.Pro converts your actions into a command language and stores them in a command file, a simple text file in ASCII format.

•

STAAD.Pro appends the command file with the extension .std.

•

Experienced STAAD.Pro users often find that if they just want to make a quick change to a value, it is easier to edit the value in the command file, rather than modifying it with the graphic interface. Early releases of STAAD did not include a graphical user interface (GUI). All program input had to be performed by writing statements in a command file. The STAAD.Pro Examples manual contains twenty-nine example problems and fourteen verification problems created using the input file as the primary input method. You can study these examples if you wish to learn how to write or interpret STAAD.Pro command files. You can also issue a command using the graphic interface, and then open the command file to see what the equivalent command language is.

•

Open the editor by clicking Edit | Edit Input Command File or by clicking the

•

icon on the File toolbar.

Any standard text editor can actually be used to create or edit the STAAD.Pro input file.

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Module 2

•

The STAAD.Pro command file editor offers the advantage of syntax checking.

•

In the STAAD.Pro editor, STAAD.Pro keywords, numeric data, comments, etc., are displayed in distinct colors: •

Red

= Commands

•

Black

= User-defined text labels and names

•

Blue

= Numerical values

•

Green = Remarks and comments

•

The command language syntax resembles ordinary English. From the Joint Coordinates statement, you can see that the node definitions consist of node numbers followed by the XYZ coordinates. Node data fields are separated (delimited) by semicolons (;).

•

Find the coordinates of node number 3, and edit the Y coordinate from 8 to 12 {from 2.5 to 4}.

•

Click File | Save and then File | Exit in the STAAD Editor’s menu bar (not the STAAD.Pro menu bar).

•

Click the Geometry tab.

•

Note that node number 3 in the graphic display has moved. The node table in the Data Area now shows a value of 12 {4} for the Y coordinate of node number 3.

•

Go back into the editor and change the Y coordinate for node 3 back to 8 {2.5}.

•

Click File | Save and then File | Exit in the STAAD Editor’s menu bar.


•

Remember to never make changes in the command file and in the graphics input mode simultaneously.

•

Always be sure to save and close the command file before going back to working on the model in the graphic interface.

•


•


How to merge members: •


•

Click View | Structure Diagrams… from the Menu Bar.

•

Click the Labels tab.

•

Click the checkboxes to view Beam Numbers and Node Points, and then click OK.

•

Notice that the top horizontal beam is segmented into three individual members of various lengths, with two intermediate nodes. This was caused by the diagonal members that were modeled and then subsequently deleted.

•

Since there is no longer a reason to maintain those particular intermediate nodes, they can be removed, and the individual members can be merged into one.

•

Ensure that the Beams Cursor is active, and select the three horizontal members.

•

Click Geometry | Merge Selected Members.

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•

The Merge Selected Beams dialog opens, and the three member numbers are listed.

•

In the Beam No. to Keep list, choose 10. If materials and properties had already been assigned, this dialog also provides the ability to specify which to keep as multiple members are merged into one.

•

Click Merge and Close.

•

The top horizontal member has been consolidated into one member with number 10.

How to split a beam into two or more members: •

Ensure that Dataset 2_7.std is still open.

•

Assume that the top horizontal member needs to be segmented into three, equal-length segments.

•

Select the top horizontal member.

•

Click Geometry | Split Beam.

•

The Insert Nodes into Beam dialog displays the member number and length. It contains three options for specifying where to insert new nodes along the beam: Add New Point, Add Mid Point, Add n Points. Add New Point: •

Distance from the starting node to the new node can be entered in the Distance field, or

•

A ratio can be entered in the Proportion field, where the value represents distance from the starting end of the


member to the new node divided by the total length, expressed as a decimal value. For example, to add a node ¼ the distance from the starting end to the ending end, type 0.25 in the Proportion field. Add Mid Point: •

Creates an insertion point at the midpoint of the member.

Add n Points: •

Enter the number of nodes to insert into a beam in the “n =” field. The program divides the beam into n+1 equal segments, separated by n nodes.

•

Enter a value of 2 in the n = field.

•

Click Add n Points.

•

Click OK.

Geometry | Insert Node… and Geometry | Split Beam are identical commands provided for convenience. The Insert Node command is also accessible through the menu that pops up from a right-click of the mouse in the Main Window. Note that the Insert Node command will not appear in the popup menu unless at least one member has been selected.

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How to create a connection between two intersecting members: •

Ensure that Dataset 2_7.std is still open.

•

The two diagonal members form a cross-brace, but there is currently no connection between them. The cross braces are independent members, and cannot transfer any load to each other.

•

Assume that the intent is for the bracing members to be connected and to transfer load at their intersection.

•

This condition can be achieved easily in STAAD.Pro by splitting and connecting these members at their intersection.

•

To highlight the two diagonal members, ensure that the Beams Cursor is active.

•

Click on one of the cross-braces, hold down the Control (Ctrl) key, and then click on the other cross-brace.

•

Click Geometry | Intersect Selected Members | Intersect . The Enter Tolerance field in the Intersect Members dialog is an option through which to tell the program to find the point of closest approach between 2 lines even when they do not intersect each other. It is useful in a case when a mathematical precision related error in the respective node coordinates causes the 2 lines to be in different planes. For lines which truly intersect each other, the tolerance can be set to zero, and the intersect members command will function properly.

•

Leave the Tolerance set to 0 and click OK.

•

Click OK to acknowledge the message box indicating that two new beams have been created.


•

Both diagonal members have been split into two, and a new node now exists at the intersection point.

•

In the Intersect Selected Members sub-menu, there is another option called Highlight.

•

The Highlight function also requests a tolerance value like the Intersect function.

•

The Highlight function then graphically highlights all intersecting members in the structure that satisfy the tolerance. This is a useful tool in models with many crossing but unattached members. The highlighted conditions can be graphically examined and selectively split or left as-is.

•


•


•


How to renumber beams and nodes: •


•


•


•

Click on the Symbols and Labels icon toolbar.

•

Click Beam Numbers on the Labels tab, Beams category, and then click OK.

in the Structure

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•

Looking at the Beams spreadsheet and Nodes spreadsheet, note that the member numbers and node numbers are not in consecutive numerical order due to editing. Having members and nodes in numerical order can be a convenience in interpreting results output.

•

Click Select | By All | All Beams. All the members in the model are highlighted.

•

Click Geometry | Renumber | Members….

•

Click Yes in the next dialog to proceed by confirming that renumbering is an irreversible operation.

•

Keep the value set to 1 in the Start numbering from field of the Renumber dialog. This dialog provides multiple criteria for renumbering and allows the assignment of a hierarchy, or “sorting order”, during the renumbering process.

•

Click Member No. from the Available Sort Criteria column and move it to the right by clicking appears under Selected Sort Criteria.

so Member No.

•

Click the Accept button.

•

Click OK to acknowledge.

•

The Beams table shows that beam numbers now run from 1 to 11.

•

Click Select | By All | All Nodes. All nodes in the model are highlighted.

•

Click Geometry | Renumber | Nodes….


•

Click Yes in the next dialog to proceed by confirming that renumbering is an irreversible operation.

•

Keep the value set to 1 in the Start numbering from field of the Renumber dialog.

•

Click Joint No. from the Available Sort Criteria column and move it to the right by clicking Selected Sort Criteria.

so it appears under

•

Click the Accept button.

•

Click OK to acknowledge.

•

The Nodes table shows that node (joint) numbers now run from 1 to 9. Note: If the program fails to renumber, or if it leaves gaps in the numbering sequence, closing the model and reopening it may reinitialize the renumbering process.

•

Beams and nodes can also be renumbered by editing the command file.

•


•


•


How to copy and paste nodes: •


•

Click View | Structure Diagrams .

•

Click the Labels tab, select Node Numbers, and click OK.

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•

Assume that the goal is to add a 2.5 foot {0.75 meter} long horizontal cantilever on the left side of node 6.

•

Click Geometry | Snap/Grid Node | Beam.

•

Note that there is no existing grid defined that would help with this cantilever.

•

One option is to create a new grid system.

•

Another option is to edit the existing grid system.

•

A third option is to edit the Nodes spreadsheet in the Data Area.

•

To demonstrate a fourth option, start by activating the Nodes Cursor.

•

Click node number 6.

•

Click Edit | Copy . Note that next to the Copy command, the corresponding shortcut key Ctrl+C is shown on the right side of the Edit menu. This is a standard Windows shortcut to the Copy command. Instead of selecting Edit | Copy, you can also hold down the Control (Ctrl) key and press the C key.

•

Click Edit | Paste Nodes. Another alternative is to right-click and choose Paste Nodes, or simply use the standard shortcut key, Control (Ctrl)+V.

•

Enter a value of -2.5 {-0.75} in the X field of the Paste with Move dialog, and then click OK.


•

A node number 10 is added to the model.

•

Press Shift+K to switch on the Node Points option if it is not clearly visible.

•

Click Geometry | Add Beam | Add Beam from Point to Point.

•

Click on node 6 and then click on node 10 to create the cantilever.

•


•


•


How to copy and paste members: •


•


•

Click the Labels tab, select Node Numbers, and click OK.

•

Now assume that a cantilever is to be added at the top of this portal frame, to align with the cantilever at mid-height.

•


•


•

Note that the Nodes spreadsheet indicates that there are currently 10 nodes in the model.

•

Select the cantilever on the left side of the portal frame using the Beams Cursor.

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•

Click Edit | Copy .

•

Click Edit | Paste Beams . If the distance between node 6 and node 2 is known, then it could be entered in the field for the Y move value in the Paste with Move dialog. In this case, it is easier to use the other option.

•

Check the By distance between following two nodes radio button.

•

Enter 6 for Node 1 and 2 for Node 2, and then click OK.

•

A new cantilever is added at the level of the top of the portal frame. Note that the Nodes spreadsheet now indicates that there are 11 nodes in the model. The significance of this is that STAAD.Pro automatically handles the condition at node 2, and does not allow the Paste with Move command to create a duplicate node at that location.

•

The Copy and Paste Beams commands can also be used to copy and paste a group of members all at one time.

•


•


•



Mirroring Structure Geometry: •

The Mirror command will be used to complete the model that was started earlier in the How to Use the Structure Wizard section.

•

Open the file named Dataset 2_STRUCTURE WIZARD.std.

•

With the Beams Cursor active, place a drag box around the entire structure to select all beams in the model.

•

Click Geometry | Mirror…. This command can also be accessed by using the Generate Mirror icon,

, on the Generate toolbar.

•

The Mirror dialog opens. This dialog contains a schematic diagram to help explain the use of the control options.

•

Click the Y-Z radio button in the Mirror Plane category, to indicate that the mirror plane will be parallel to the Y-Z plane.

•

Leave the Plane Position at its present setting of Plane at X = 0. In this case the mirror plane goes through the origin, so it is located correctly by the default value. Note that the Plane Position category also provides the ability to locate the mirror plane graphically by clicking on a node that lies in the plane using the Highlight Nodes icon,

•

.

Click Copy in the Generate Mode category. In this case the intent is to create the full truss by mirroring and copying the first half.

•

Leave the Mirror Member Orientation option deselected. This option is discussed in detail in another Module.

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•

Click OK. The other half of the truss is mirrored, and the display returns to the Main Window.

•

Click inside the Main Window to deselect all members.

•

Note that the Mirror command does not create a duplicate member or duplicate nodes at the center of the truss. STAAD.Pro will not duplicate any members that lie in the mirror plane.

•

To have STAAD.Pro prove this for you, follow the step-bystep instructions in the commentary below. •

Click Tools | Check Duplicate | Nodes .

•

Leave 0 in the Enter Tolerance field in the Remove Duplicate Nodes dialog, and click OK.

•

A message box appears confirming that no duplicate nodes were found.

•

Click OK to dismiss the message.

•

Click Tools | Check Duplicate | Members.

•

A message box appears confirming that no duplicate members were found.

•

Click OK to dismiss the message.

•


•


•



How to use “Translational Repeat”: •


•

Click Select | By All | All Beams.

•

Click Geometry | Translational Repeat…, or click on the Translational Repeat icon

•

on the Generate toolbar.

Translational Repeat is another way of copying and pasting a group of members, and it has some advantages over simply copying and pasting the members. Note that a very common mistake in STAAD.Pro is to open a dialog like the 3D Repeat dialog that acts on a member or group of members, without first selecting any members. Always start by selecting the members to be operated on before selecting Translational Repeat, or any other command that does something to selected members. If no members are selected initially, a dialog similar to the following will be displayed when the OK button is clicked:

Figure 2. 166 STAAD.Pro allows the warning message box to be dismissed, and the members to be selected without closing the Translational Repeat dialog.

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•

Suppose the goal is to model two additional portal frames, 15 feet {4.5 meters} apart, and to link the portal frames with members connecting the columns, the free ends of the cantilevers, and the intermediate nodes along the roof member, but we do not want any grade beams linking the portal frames at the bases of the columns.

•

Click the Z radio button in the Global Direction category of the 3D Repeat dialog.

•

Set the value to 2 in the No. of Steps list.

•

Enter 15 {4.5} in the Default Step Spacing field, and press the Tab key to see the change reflected in the Step/Spacing table. Note that the spacing values listed in the table could be edited individually, if variable step spacings were required.

•

Toggle on the Link Steps checkbox. This causes the program to create transverse members in the Z direction, connecting all nodes on the portal frames. Notice that the Open Base checkbox becomes active when the Link Steps checkbox is toggled on.

•

Toggle on the Open Base checkbox. This prevents the generation of members connecting the bases of the portal frame columns.

•

The Generation Flags category controls the items that are copied when the Translational Repeat command is used.

•

There are three options for Generation Flags: All, Geometry Only, or Geometry and Property Only. The following table indicates which items do and do not get copied in a Translational Repeat based on the Generation Flags setting.


All

Geometry Only

Geometry and Property Only

Members and Nodes

Yes

Yes

Yes

Materials (ex. Steel)

Yes

No

Yes

Yes

No

Yes

Yes

No

No

Supports

Yes

No

No

Loads

Yes

No

No

Properties (ex. section and beta angle) Member Specifications (ex. truss and member releases)

•

Keep the default setting of All in the Generation Flags category.

•

Click the Renumber Bay checkbox.

•

A new column labeled Number From appears in the table. This is a way of providing a user-specified starting number for the members generated in each of the steps.

•

Enter a value of 101 in the Number From column for Step 1, and enter 201 for Step 2.

•

Click OK.

•

Click Yes to acknowledge the dialog warning that this is an irreversible operation. The additional copies are created along with the horizontal linking members as requested by the Link Steps option. Note that no linking members were generated at the base due to the Open Base option.

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•

twice, and note that horizontal Click the Rotate Up icon members were generated between the intersections of the diagonal bracing. Use the Beams Cursor to select and delete these two members.

•


•

Click the Labels tab, turn on Node Points, and click OK.

•

Note that nodes were automatically copied, even though only beams were selected.

•


•

Click the Labels tab, turn off Node Points, turn on Beam Numbers, and click OK.

•

Note that the member numbers range from 1 through 13 in the original portal frame, 101 through 113 in the first copy, and 201 through 213 in the second copy as requested by the renumber bay option.

•

Note that Translational Repeat has two advantages over the simple Copy-Paste Beams technique: •

It allows more than one copy to be created in a single operation.

•

The newly created members can be automatically linked to each other with new members.

•


•


•



How to use “Circular Repeat” •

The Circular Repeat command is useful for creating structures that are radially symmetrical. Its function and usage are similar to the Translational Repeat command.

•


•


•

Click the Labels tab, turn on Beam Numbers, and click OK.

•

Click member 13 (the tallest column) with the Beams Cursor.

•

Click Select | By Inverse | Inverse Beam Selection to select everything EXCEPT member 13.

•

Click Geometry | Circular Repeat….

•

Leave the Axis of Rotation set to the (global) Y axis in the 3D Circular dialog.

•

The Through category provides three methods to specify a point through which the Axis of Rotation must pass: by clicking on a node, by entering a node number, or by providing the coordinates.

•

, then click on node #11 Click the Highlight Node icon (the node at the bottom of the tallest column). The number 11 appears in the Node field. The X Coordinate field reports a value of 20 {6}, and the Z Coordinate field reports a value of 0.

•

Activate the Use this as Reference Point for Beta angle generation checkbox. This option is explained in the commentary below.

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•

Assume that the web of a column (in a structure to be copied with Circular Repeat) is oriented so that it points through the Axis of Rotation. If the checkbox for Use this as Reference Point for Beta angle generation is activated, then the web of that column will be rotated as copies are generated, so that the webs of the columns in all of the copies also point through the Axis of Rotation.

Resulting column orientations when Use this as Reference Point for Beta angle generation IS activated Figure 2. 177

Resulting column orientations when Use this as Reference Point for Beta angle generation is NOT activated Figure 2. 18

•

Leave the Total Angle set to its default value of 360 degrees.


Total Angle is the angle subtended by the arc through which the copies are rotated. A positive angle value rotates the copies in the positive direction of the chosen axis (right hand rule). •

Set the No. of Steps to 8. No. of Steps is the number of copies of the selected geometry that STAAD.Pro will generate. The program divides the total angle by the number of steps you specify, and places copies of the selected geometry at the division points.

•

Toggle on the Link Steps and Open Base checkboxes, and leave the Geometry Only checkbox deselected. See the section on the Translational Repeat command for detailed explanations of these options.

•

Click OK.

•

STAAD.Pro creates eight frames arranged symmetrically about (20, 0, 0) {(6, 0, 0)}.

•


•

Click the Labels tab, turn off Beam Numbers, and click OK.

•

Note that the program does not create duplicate members at the 8 th step of the 360 degree Total Angle we specified, since the original members are already there. The program actually created only 7 copies of the selected geometry rather than 8.

•

If the Total Angle had been set to 315 degrees and only 7 steps had been requested, the resulting structure would have been identical, except that the Link Steps option would not have linked the 7 th step at 315 degrees to the original frame at 0 degrees.

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•

The selection to be copied included every member except for the tallest column at the center of the circular repeat. Note that even if the entire frame had been selected, including the tallest column, STAAD.Pro would not have generated duplicate members at that center column location

•


•


•


How to identify and remove “Orphan Nodes”: •

Reopen Dataset 2_11.std.

•


•


•


•

Click the Labels tab, turn on Beam Numbers, and click OK.

•

Select the line corresponding to member 13 in the Beams spreadsheet, and press the Delete key.

•

Click OK in the dialog confirming the delete.

•


•

Click the Labels tab, turn on Node Numbers and Node Points. Turn off Beam Numbers, and click OK.

•

Note that node 11 is not connected to any member. This node is referred to as an Orphan Node.


•

The presence of orphan nodes may cause the program to fail to analyze the structure successfully. In a simple model like this, you could highlight node 11 with the Nodes Cursor and press the Delete key to delete it. But in a more complex model, orphan nodes created by modeling changes might not be so obvious.

•

STAAD.Pro provides two options for addressing Orphan Nodes.

•

Click Tools | Orphan Nodes | Highlight.

•

This highlights any orphan nodes in the model. It is possible that this node may be needed for upcoming modeling steps. The Highlight option makes orphan nodes stand out graphically, so they are easier to evaluate and act on individually.

•

Click Tools | Orphan Nodes | Remove.

•

The Orphan Node 11 is deleted.

•


•


•


How to combine two STAAD.Pro models by copy and paste: •

STAAD.Pro offers the ability to simultaneously run two separate instances of the program. This makes it possible to combine two STAAD.Pro files by copy and paste methods.

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Module 2

•

The following steps outline a procedure to combine the two simple frame models shown below from separate STAAD.Pro models.

Figure 2. 199 •

Ensure that one instance of STAAD.Pro is open.

•

Click Open Project… in the Project Tasks section of the Start Page.

•

Open the file named Dataset 2_BOTTOM.std.

•

Start a second instance of STAAD.Pro.

•

When the second instance of STAAD.Pro opens, note that there are now two instances of STAAD.Pro running on the Windows task bar at the bottom of the screen.

•

Click Open Project… in the Project Tasks section of the Start Page.

•

Open the file named Dataset 2_TOP.std.

•

There are now two separate STAAD.Pro files open concurrently. They can be differentiated by the filenames shown in the Title Bars of the two windows.

•

Select all the members in the structure titled TOP by dragging a fence around the structure.


•

Click Edit | Copy .

•

Switch back to the model titled BOTTOM by clicking the button for the other instance of STAAD.Pro on the Windows taskbar.

•

Click Edit | Paste Beams to open the Paste with Move dialog.

•

To insert the braced structure so that it sits atop the two columns of the portal frame, the origin of the braced frame needs to be inserted at the top of the left-hand column, which is 10 feet {3 meters} in the positive Y-direction from the origin of the project’s global axis system.

•

However, in more complicated situations involving 3-D structures, it might not be so easy to mentally calculate where to insert a copied structure into an existing model. This is a good application for the Reference Pt option in the Paste with Move dialog. The procedure described here can also be used for inserting a Structure Wizard model into an existing STAAD.Pro model.

•

With the Reference Pt button, the graphic interface can be used to tell the program where to insert the copied structure without needing to know the actual coordinates of the desired insertion point.

•

The process is to pick a Reference Pt on the structure being copied, and then pick an Insertion Point on the existing model.

•

STAAD.Pro will insert the second structure so that the Reference Pt coincides with the Insertion Point in the model.

•

Click Reference Pt in the Paste with Move dialog.

•

The Specify Reference Point dialog opens showing a graphic of the model titled TOP (the model to be copied and pasted).

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•

A prompt in the dialog indicates “click on the node to act as the reference point”. The node in the lower left-hand corner is currently selected, but it is hidden by the coordinate axis tripod.

•

Use the arrow keys on the keyboard to rotate the structure until the node at the lower left-hand corner of the frame is visible.

•

The current Reference Point is highlighted, and can be changed by clicking on any node in the view.

•

Click on any other node in the frame to see how STAAD.Pro highlights the selected insertion point. Then click back on the node in the lower left-hand corner of the frame, and click OK.

•

The STAAD.Pro Main Window now displays the model titled BOTTOM (the model that will receive the paste). The mouse cursor changes to the Connection Point Cursor. A prompt in the lower left-hand corner of the screen indicates, “Click on node to move reference point to.”

•

Click on the top of the left-hand column. The Paste with Move dialog reappears, confirming the new Y coordinate value of 10 feet {3 meters}.

•

Click OK.

•

Click OK again to acknowledge the Duplicate nodes ignored message. This message box indicates that STAAD.Pro will not create duplicate nodes at the tops of the two columns.

•

The two models are merged at the defined connection point. They now both exist in the new model, which could be further edited, saved, etc…


•

A copy of this model is already saved in this state in the dataset, and is named Dataset 2_COMBINED.std.

•

Click File | Close.

•


•

Click File | Exit. Allow the program to close without saving the model.

•

Click on the second instance of STAAD.Pro on the Windows task bar to make it active.

•

Click File | Close. This example obviously uses very simple models to demonstrate the copy and paste function, but a more realistic real-world application for this function might be: •

A complex structure or building, where…

•

A common grid is established and shared by using Save As… or by exporting the grid file, so…

•

Multiple STAAD.Pro files are generated based on the original grid, and…

•

Multiple engineers work on different areas or different floors simultaneously in separate files, until…

•

Individual files are combined into one single model using copy and paste methods, and…

•

The entire structure is analyzed and designed.

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2.11

Viewing Structure Geometry How to control the display of beam and node numbers: •

Re-open the file named Dataset 2_3.std.

•

Make sure the Beams Cursor is active.

•

Hover the cursor over the horizontal member. The structural tool tip help pops up to display the beam number.

•

Additional information such as member length, incidences, etc. may also be displayed.

•

Click View | Structural Tool Tip Options….

•

Click Beam in the Tool category.

•

Note the other options that are available to display for beams.

•

Note that Tip Delay can be adjusted to control the delay time before the tool tip is displayed. The Tip Delay is in units of milliseconds, so 500 = ½ second delay.

•

Make sure that Number and Length are selected in the Options category, and then click OK.

•

Hover the cursor over the horizontal member again, and note that the tool tip now provides the beam number and the member length as requested.

•

Click View | Structural Tool Tip Options… again.

•

Click Node in the Tool category.

•

Make sure that Node Number, Coordinate, Displacement, and Support are all selected in the Options category, and then click OK.

•

Click the Nodes Cursor icon to activate it.


•

Hover the cursor over the node in the lower left corner, and note that only node number and coordinates are displayed. This is because supports have not yet been assigned in this model and displacements have not been calculated.

•

Another way to display beam or node numbers is with the Query function.

•

Double-click on the horizontal member with the Beams Cursor.

•

A dialog opens providing the beam number and other information about the beam.

•

Right now there is not much information in this dialog because only member geometry has been defined so far.

•

After properties have been defined and an analysis has been run, this dialog will be filled with information on the member including properties, analysis results, shear, bending and deflection diagrams, etc…

•

The Query feature can also be used to get a node number or other information about a node by activating the Nodes Cursor and double-clicking on the node of interest.

•

Double-click various nodes in the model with the Nodes Cursor. Notice that the node number and coordinates update in the Node dialog for each node.

•

Note that the Tables category in the Node dialog provides direct access to several tables pertaining to nodes in general: •

The Nodes button opens the Nodes table, which provides the coordinates of all the nodes in the model. The current node is highlighted in the table.

•

The Loads button opens the Load Values table, which indicates the magnitudes and directions of any loads applied to the nodes, if any have been defined. Again, the current node is shown highlighted in the table.

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•

The Supports button opens the Supported Nodes table, which provides information about supports, if any have been defined.

•

The Reactions button leads to the Support Reactions table.

•

The Displacements button leads to the Node Displacements table. Both the Reactions button and the Displacements button trigger the Results Setup dialog to open, in order to select which loads and nodes will be reported on. Neither table is available for this model in its current state, because no loads have been applied and the model has not been analyzed.

•

Click the Close button in the Nodes dialog.

•

It is also possible to display beam and node number labels, as well as many other types of labels, directly on the structure diagram in the Main Window, as explained in the following section.

How to display structure labels: •

With the file named Dataset 2_3.std still open, right-click in the Main Window.

•

A pop-up menu appears with some of the most frequently used commands in STAAD.Pro.

•

Select the Labels… command. The Diagrams dialog opens with the Labels page active. The Labels page can also be accessed quickly from the Symbols and Labels icon

on the Structure toolbar.


•

The Labels page is an extremely useful page that is used frequently.

•

It provides options for labeling Nodes, Beams (Members), Plates, Solids, Surfaces, Physical Members, Loads, Properties, General display information, etc...

•

Click the Node Numbers checkbox in the Nodes category and the Beam Numbers checkbox in the Beams category.

•

Click OK.

•

Notice that the node and beam numbers now appear in the Main Window, next to the corresponding beam or node. If it is difficult to differentiate between the node labels and the beam labels, their graphic appearance can be modified individually. This will be covered in an upcoming section on “How to control label appearance”.

•

Click the Symbols and Labels icon toolbar to return to the Labels page.

•

“Hotkeys” are shown in parentheses following the various label names. These hotkeys are available for most of the labeling options.

on the Structure

A reminder is shown at the bottom of the Labels page indicating, “For quick access to the labels using keyboard hotkeys, press Shift + the letter shown in brackets.” For example, to display node numbers, simply hold down the Shift key and press the N key without leaving the Main Window. •

Click OK to close the Diagrams dialog.

•

Hold down the Shift key and press the N key repeatedly. Note that the node numbers are toggling on and off without having to leave the Main Window.

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•

Click the Symbols and Labels icon toolbar again.

•

By default, certain labels will only appear when particular pages are active in the Page Control area.

•

For example, items under Loading Display Options will only appear when the Load sub-page of the General page is active. To override this default, select the radio button labeled Always Use Current Label Settings located at the bottom of the Labels page.

•

Another commonly used option on the Labels page is Beam Ends labeling in the Beams category. It is particularly useful while modeling and interpreting results, as it establishes the orientation of Beam members.

•

Beam Ends labeling identifies the starting end (also called End A) and the ending end (End B) of each beam by showing each end in a characteristic color.

•

On the Labels page, two colored squares labeled Start Color and End Color identify the color used to denote each end of a beam. By default the starting end is green and the ending end is blue.

on the Structure

These can be changed by clicking on the colored squares, and choosing new color(s) from the color selection palette. •

The assignment of starting and ending ends is based on the direction the beam was originally drawn. For example, if a column is drawn starting at the bottom, the bottom end will be the starting end.

•

It is often important to know which end is the starting end and which end is the ending end, for instance, when you are assigning member releases to only one end of the beam.


•

If the Beam Ends checkbox is toggled off, the beam end colors will be displayed on an individual beam when the Beams Cursor is hovered over that beam.

•

Hover the cursor over the horizontal beam at the top of the frame to see the Beam Ends colors displayed.

•

If the Beam Ends checkbox is toggled on, the beam end colors will be displayed on all beams in the model, all the time, until the feature is toggled off again.

•

Leave this file open for use in the next section.

How to control label appearance: •

With the file named Dataset 2_3.std still open, press the Shift + N “hotkey” to turn on all node numbers if necessary.

•

To differentiate between node numbers and beam numbers, the appearance of these labels can be modified.

•

Click View | Options…. The Options dialog opens.

•

Select the Node Labels tab.

•

Pull down the Style list on the Node Labels page, and note the various built-in styles that are available for node numbering.

•

The alignment (positioning) of the labels can be controlled in both the vertical and horizontal directions.

•

If the Opaque option is selected, any model geometry that tends to interfere with the node number labels will be “whitedout” to clarify the labeling.

•

Click on the Font… button in the lower left corner of the dialog.

•

Select Arial Black for the Font, Bold for the Font Style, select Blue for the Color, and click OK.

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•

Click OK in the Options dialog.

•

It should now be very easy to distinguish node numbers from beam numbers.

•

To see another helpful labeling option, click Tools | Options, and select the Beam Labels page.

•

Toggle on the checkbox labeled Angle Text.

•

Click OK to dismiss the Options dialog.

•

The beam labels will now be oriented parallel to the members they correspond to, making it even easier to associate the members and the numbers. These settings are saved in a text file named StaadPro20070.ini, which is saved in the Windows (or WINNT) folder, so the settings affect all STAAD.Pro models that are opened on a particular computer.

•

Click File | Close. It is not necessary to save this version of the model.

How to display member lengths and the distance between two nodes: •

Open the file named Dataset 2_9.std. Assume the goal is to determine the lengths of the diagonal members of the frame.

•

One method is to use the Dimension Beams tool.

•

Press the Shift + B hotkey to turn on beam numbers.

•

Hold Control (Ctrl) and click the four diagonal members, numbered 3 , 4 , 10, and 11 , with the Beams Cursor.

•

Click Tools | Dimension Beams….


•

Ensure that the Display radio button is selected in the Display/Remove Dimension dialog.

•

Click Dimension to Selected Beams in the Options category. Note that the Dimension to Selected Beams option will be “grayed out” if no members are selected.

•

Click Display , and drag the Display/Remove Dimension dialog out of the way. The dimensions for the four selected members are displayed.

•

Two limitations to this tool should now be obvious: •

First, for structural elements consisting of multiple segments, the Dimension Beams tool is inconvenient because it reports the individual member lengths rather than the overall length.

•

Second, the Dimension Beams tool only works on members. It cannot be used to measure the distance between two nodes like node 1 and node 4 that do not have a member modeled between them. (Remember that Shift + N is the hotkey to show node numbers.)

•

For these kinds of conditions, there is a more appropriate tool.

•

Click the Remove radio button in the Display/Remove Dimension dialog to clean up the display.

•

Click Dimension to View in the Options category.

•

Click Remove. All dimensions in the view are removed.

•

Click Close.

•

Click Tools | Display Node to Node Distance. An alternate method of accessing this tool is to click the Display Node to Node Distance icon toolbar.

in the Structure

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•

All existing nodes in the model become bold, and the cursor changes to indicate that STAAD.Pro is in the node to node distance measuring mode.

•

Click node 1, then click node 3. The dimension 10.63ft {3.20 meters} is displayed for the overall length of the brace.

•

Click node 2, then click node 4. Both cross braces are now dimensioned, but the labels may be overlapping and difficult to read.

•

Click View | Options…, and choose the Dimension page.

•

Click the Angle Text checkbox, and then click OK to clarify these dimensions. The dimensions are now rotated parallel to the members they reference, making the display much easier to interpret.

•

To remove one dimension at a time, use the Display Node to Node Distance tool to click between the two nodes again.

•

Click Tools | Display Node to Node Distance again to stop adding or removing dimensions.

•

The command and the icon act as a toggle, so selecting it the first time turns the mode on; selecting it a second time turns the mode off.

•

To remove one dimension, ensure that the dimensioning mode is active, and then click the end nodes of the dimension to be removed.

•

Click Tools | Remove Node Dimension to remove all dimensions at once.

•



How to control the view: •

Open the file named Dataset 2_15.std to experiment with the view control tools.

•

STAAD.Pro provides a variety of View Management options for viewing the structure. There are tools for changing the perspective of the Main Window, and also for creating separate view windows of all or part of the structure.

•

STAAD.Pro provides two toolbars for changing the viewing aspect: the Rotate toolbar and the View toolbar.

•

The Rotate toolbar is docked in the upper left corner of the STAAD.Pro screen by default, but can be dragged to any desired location.

•

It contains fourteen buttons for changing the viewing angle. The functions of the Rotate tools are generally evident from their names. Click on each tool and observe its effect. • • • • • • • • • • • • • •

•

View From +Z View From -Z View From +X View From -X View From +Y View From -Y Isometric View Rotate Up Rotate Down Rotate Left Rotate Right Spin Left Spin Right Toggle View Rotation Mode is used to select a node to serve as the center of view rotation.

The View toolbar is docked in the top middle of the STAAD.Pro screen by default. It, too, can be dragged to any desired location.

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•

The View toolbar contains twelve buttons for changing the viewing distance and location: Display Whole Structure • Turns on all members in the structure • Returns structure to the Isometric View orientation • Resizes the structure to the maximum size that will fit within the Main Window. Dynamic Zoom • Provides a fence to select a portion of the model to be magnified in a separate Zoom window. • The extent of the fence remains visible as a heavy rectangle in the Whole Structure window as long as the Zoom window remains open. • The fence can be repositioned by dragging the fence with the cursor in the Whole Structure window to view different parts of the structure in the Zoom window. • Scroll bars are provided to move side to side, and up and down. • Plus (+), minus (-) and extents (E) buttons are provided in the lower right corner of the window to adjust the zoom level. • Several Dynamic Zoom windows can be opened at the same time. Each of their respective fence rectangles remains visible in the Whole Structure window as long as the Zoom window remains open.


Zoom Extents • Performs similar to Display Whole Structure with the exception that Zoom Extents does not turn on elements that are not currently displayed. • For example, if some elements have been turned off in a view by using View | View Selected Objects Only, those particular elements will remain invisible when Zoom Extents is used. • Returns structure to the Isometric View orientation. • Resizes the structure to the maximum size that will fit within the Main Window. Zoom In • Zooms in on the model a set amount with each click. Zoom Out • Zooms out a set amount with each click. Zoom Factor • Zooms in or out based on the factor entered in pop-up dialog. • Factors greater than 1 will zoom in. • Factors less than 1 will zoom out. Zoom Previous • Restores the view to the previous zoom level. • Only retains one previous zoom step set by Zoom Factor or Zoom Window.

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Module 2

Zoom Window • Provides a fence to select a portion of the model to be magnified in the current window. Previous Selection • Returns the selection state to the condition it was in one step prior to the current state. Pan • Allows the model to be repositioned within the current view. • Zoom level remains unchanged. • Pan remains active until it is toggled off. Magnifying Glass • Provides a quick way to temporarily enlarge a portion of the structure for closer inspection. • Click this tool, and then click and hold left mouse button to see how the magnifying glass works. 3D Rendered View • Displays the model in a new window with its assigned sections. • Provides controls for adjusting lighting. • Dynamic panning is enabled. Click and rotate with cursor. •

All functions in the View toolbar are available in the View pull-down menu.


•

All functions in the Rotate toolbar are also available in the View pull-down menu under the Orientation item, although they are in a slightly different format.

•

In addition to these tools, note that often the mouse itself is all that is necessary.

•

Roll the wheel on the mouse to see how it zooms in and out.

•

Click and hold the wheel to grab the model and pan.

•

Another way to change the view is with the arrow keys. Click in the Main Window to make it active. Then use the arrow keys to rotate the model up, down, left or right.

How to display only selected objects in the Main Window: •

With the file named Dataset 2_15.std still open, assume the goal is to turn off the display of the hip rafters and central column.

•

Click the View From +Z

•

Click Select | Selection Mode | Drag Line.

•

Drag a horizontal line across all rafters, just below the vertex. All rafters and the central column are selected.

•

Click Select | By Inverse | Inverse Beam Selection. The selection inverts.

•

Click View | View Selected Objects Only .

•

All unselected objects become invisible.

•

Click the Isometric View

icon.

icon.

The structure is displayed without the hip rafters and central column.

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Module 2

•

Click View again, and note the check mark next to the View Selected Objects Only command, indicating that the command is toggled on.

•

Click View | View Selected Objects Only once again to restore the entire structure to the Main Window. Another option is to click the Display Whole Structure icon.

How to isolate a portion of the structure into its own view: •

With the file named Dataset 2_15.std still open, assume the goal is to isolate the framing members in the horizontal plane at the eave of the hip roof.

•


•

Click Select | Selection Mode | Drag Box.

•

Click and drag a fence around the framing members at the elevation of the eave. Make the box large enough to completely include the members in the horizontal plane, but small enough not to include the mid-points of any of the other members.

•

Click View | New View.

•

Choose the option to Create a new window for the view in the New View dialog, and then click OK.

icon.

A new window is created in which only the members in the horizontal plane at the eave elevation are visible. •

Click the Isometric View

•

Click View | View Management | Save View…. The Save View As dialog opens.

icon.


•

Enter the name Eave, and click OK. This isometric view has now been saved.

•


•


•

Enter the name Edge, and click OK. This side view has now been saved.

•

Click the View From +Y

•


•

Enter the name Plan, and click OK. This plan view has now been saved.

•

Click Tools | Cut Section…. The Section dialog opens.

•

On the Range By Joint tab, click the X-Y Plane radio button.

•

Click the arrow on the With Node # list, and select node #10, which is the node at the peak.

•

Click OK, and the Main Window displays a section view of the structure showing the members that lie on the X-Y plane that cuts through node #10.

•


•

Enter the name Section, and click OK. This section view has now been saved.

•

To access the saved views, click View | Open View…. The Open View dialog opens. Select Eave in the Views category, select Display the view in the active window, and click OK.

icon.

icon.

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•

The Main Window and any other views that have been created can be moved, resized, minimized, maximized, closed, etc. Three standard window controls (Minimize, Maximize, and Close) appear in the upper right corner of each window.

•

To move a window, hover the mouse over the window’s title bar, hold down the left mouse button, then drag the window to the desired location.

•

Windows can be resized by dragging the sides or corners in or out.

•

Grids can be displayed in any window, not just in the Main Window.

•

Click Geometry | Snap/Grid Node | Beam and then activate the desired grid system in the Snap Node/Beam dialog.

•

Note that Views are saved in an auxiliary file named modelname.REI_SPRO_Auxilary_Data and not in the .std file itself.

•



2.12

Modeling Exercise 2 Create this model by applying the modeling techniques that have been presented up to this point.

Figure 2. 200 Tips: •

Open Dataset 2_COMBINED.std.

•

Create connection between cross members at intersection.

•

Translational Repeat once in the Z direction at Z = 15 feet {4.5 meters}.

•

Link steps, open base.

•

Delete the horizontal beam that connects the cross-braces at their intersection points.

•

Use arrow keys to rotate model to match the figure above.

•

Click File | Save As, and name the model MY EXERCISE 2.

•


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-End of Module-

3-1

Property Assignment Module

3

The following topics are included in this module. 3.1 Steel Design Model Geometry .......................................................... 2 3.2 Working with Groups ........................................................................ 4 3.3 Assigning Member Properties .......................................................... 11 3.4 Member Beta Angle ......................................................................... 32 3.5 Assigning Member Specifications ................................................... 45 3.6 Assigning Supports ........................................................................... 60 3.7 Assigning Loads................................................................................ 69 3.8 The Material Page ............................................................................ 85


3-2

Module 3

3.1

Steel Design Model Geometry This section uses the model shown below to demonstrate the assignment of member properties, material constants, supports, and loads to the structure.

Figure 3. 1 •

There is one aspect of the model geometry that should be reviewed before proceeding.

•

This model was created using the Mirror command.

•

In the Mirror dialog, an option called Mirror Member Orientation was left unselected.

•

If the Mirror Member Orientation feature is turned on, the program attempts to mirror the member orientation, in addition to the member geometry, as shown below:


Figure 3. 2 •

The implications of this selection will be explained in detail later in this section.

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3-4

Module 3

3.2

Working with Groups •


•

When working with structural models, it sometimes helps to cluster a set of entities under a single umbrella for ease of handling the data associated with those entities. For example, one may wish to have all the principal rafters of a warehouse structure made of a common structural section such as a C10x15 channel. If there are many rafters, it helps to be able to refer to all of them as a group, rather than working with all of the rafter members individually

•

This process of clustering is referred to in STAAD.Pro as the formation of groups.

•

This can save a lot of time when assigning attributes to members of the structure. STAAD.Pro allows properties to be assigned to a group using a single instruction, rather than having to repeatedly select the individual members in order to assign various properties to them. For instance, in the STEEL DESIGN example project, the bottom chord of the truss consists of eight members. If we cluster these members into a group, we will not have to select eight members individually in order to assign properties to them. Similarly, assigning group names to the members comprising the top chord, the two columns, and the truss webs will make the process of assigning data to these members a lot easier. Creating New Views is another method of filtering STAAD.Pro entities, as presented in a different module.


However, creating Groups has an advantage over creating a new view, because groups actually become part of the STAAD.Pro input file. •

Groups remain part of the model after the current STAAD.Pro session is closed. So, if you provide your input file to another STAAD.Pro user, they will be able to use the groups you created.

•

Four groups will be created for the STEEL DESIGN example: Group name

Description

_BOTC

Truss bottom chord

_TOPC

Truss top chord

_COL

Columns

_WEB

Truss webs

•

Click Tools | Create New Group…. The Define Group Name dialog opens.

•

STAAD.Pro group names must start with an underscore character (refer to Section 5.16 of the Technical Reference manual for additional information on forming group names).

•

However, if the underscore is not entered manually in the Define Group Name dialog, STAAD.Pro will add it automatically when the dialog is closed.

•

Choose the Beam option in the Select Type list. A common mistake is to leave the Select Type option set to Node, when the intent is to group beams.

•

Enter _BOTC in the Group Name field, and click OK.

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Module 3

•

The Create Group dialog lists the group names that are currently available to assign to (or associate to) members in the model. Currently, the only available group name is _BOTC.

•

In the Assign methods category, there are three options available to associate group names with members. See the commentary below for a description of each option: •

Associate to View – associates the highlighted group name with all of the members in the view.

•

Associate to Selected Geometry – associates the highlighted group name with all of the currently selected members. (Currently “grayed out” because no members are selected.)

•

Associate to List – associates the highlighted group name with all of the members whose numbers are entered in the List field.

•

The goal is now to associate the group name _BOTC with the bottom chord members of the truss.

•

Leave the Create Group dialog open, then click Select | Beams Parallel To | X from the main menu. The bottom chord members (and only the bottom chord members) will be selected.

•

Notice that the Associate to Selected Geometry radio button in the Create Group dialog is now active.

•

Click the Associate button at the bottom of the Create Group dialog. STAAD.Pro associates the bottom chord members with the group named _BOTC. It also displays the member numbers in the List field and changes the 1:_BOTC listing in the Create Group dialog to say


(Beam Assigned), implying that the group name has been assigned to at least some beams in the model. •

Click the Create button in the Create Group dialog again.

•

Choose the Beam option in the Select Type list.

•

Enter TOPC (this time, without the leading underscore) in the Group Name field, and click OK.

•

Note that STAAD.Pro automatically inserted the required leading underscore in _TOPC in the Create Group dialog.

•

Click inside the Main Window to deselect all members.

•

Hold the Control (Ctrl) key and click the top chord members one at a time using the Beams Cursor to select them. Due to the inclined orientation of these members, there is no easier method to select them. 2:_TOPC (Beam Unassigned) is currently highlighted in the Create Group dialog by default. The Assignment Method is set to Associate to Selected Geometry by default.

•

Click the Associate button. The top chord members are assigned to the _TOPC group, and their member numbers appear in the List field.

•

Click the Create button.

•


•

Enter _COL in the Group Name field.

•

Click OK.

•

Click the Create button.

•


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3-8

Module 3

•

Enter _WEB in the Group Name field.

•

Click OK. Note that the list of group names in the Create Group dialog provides an indication as to which type of elements can be included in each group. (All four of our groups can only be assigned to beams.) Also note that the list of group names in the Create Group dialog provides an indication as to which of the group names have been assigned to at least some members in the model and which group names are currently unassigned. The group names _COL and _WEB remain unassigned at this time.

•

Click on _COL.

•

Click on the column at the left side of the model, then press and hold Control (Ctrl) and click on the column at the right side of the model.

•

Choose the Associate to Selected Geometry Assign Method, and then click Associate. The remaining members are the truss webs. They could be selected using the tedious method of clicking on them one at a time. A more efficient method would be to use the groups we have created to select all of the members in the three existing groups, and then use an Inverse Selection command to select the remaining members not included in the three existing groups.

•

Click Select | By Group Name….

•

Click on all three group names in the Select Groups dialog. Note that STAAD.Pro allows more than one group to be selected without having to hold down any keys.


•

Click Close. The top chord, bottom chord and columns will be highlighted in the Main Window indicating that they are all selected.

•

Click Select | By Inverse | Inverse Beam Selection. The selection is inverted so only the truss web members are selected.

•

Click the _WEB group in the Create Group dialog.

•

The Assign Method defaults to Associate to Selected Geometry.

•

Click Associate. The webs are now assigned to the _WEB group.

•

Select _BOTC and click on the Highlight button. The members of the selected group should be highlighted in the Main Window.

•

Verify by selecting each group name one at a time and clicking Highlight. If no members are highlighted after selecting a group name and clicking the Highlight button, check to make sure that the group is indicated as a Beam group type in the list of groups in the Create Group dialog. If any of the groups accidentally got created as Node type groups, they will need to be deleted and recreated as Beam type groups, before the members of this model can be correctly assigned their group name.

•

If any members were unintentionally omitted from a group, they can be added to the group using the Create Group dialog, or they can be added to the list in the Input File using the STAAD.Pro Editor.

3-9


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Module 3

•

If, later on, a member is removed from the model, and if that member was part of one of the defined groups, STAAD.Pro will remove the member number from the group automatically. Note that STAAD.Pro also allows groups of plate or solid elements to be created. However, these options weren’t offered in the list box of the Define Group Name dialog, because they only appear if the model contains plates or solids.

•

Click the Close button to dismiss the Create Group dialog.

•


•


•



3.3

Assigning Member Properties •


•

Click the General page tab in the Page Control area. Note that the general progression is to work from top to bottom of the Page Control area to complete the steel design example.

•

The General page has five sub-pages: • • • • •

Property Spec Support Load & Definition Material

•

The Property sub-page will be active or “in focus,” when the General tab is selected.

•

The Data Area on the right side now contains a dialog labeled Properties - Whole Structure (referred to from here on as the Properties dialog). Note: if the Properties dialog is ever closed, it can be recalled by clicking on the Property sub-page of the General page.

•

The Properties dialog is used to assign properties: cross section, modulus of elasticity, Poisson’s ratio, density, and thermal coefficient for steel, concrete or aluminum members.

•

Standard cross sections can be chosen from tables or custom sections can be defined.

•

The following standard sections from the American steel table database will be used in the current model:

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3-12

Module 3

Columns

Wide flange: W 18 x 35

Bottom chord

Channel: C 12 x 30

Top chord

Rectangular HSS: 7 in. x 4 in. x 3/16 in.

Webs

Angle: 3 in. x 3 in. x ½ in.

•

Assigning properties is a two-step process. First, pick the sections/materials to assign to the structure. The program maintains the list of these sections in the Properties dialog. Then, use the list to assign the sections/materials to selected members.

•

Click the Section Database button in the Properties dialog.

•

Note the tabs across the top of the Section Profile Tables dialog for access to section tables for different materials. •

Steel - provides access to a list of steel tables of more than fifteen different countries.

•

Coldformed Steel - provides access to a list of tables from various manufacturers of cold-formed steel products.

•

Timber - provides access to an extensive list of wood sections comprised of various combinations of species, grades, and sawn lumber sizes. Also includes properties for Glued-Laminated material.

•

Aluminum - provides access to the American Aluminum table.

The American - W Shape table from the Steel tab is active by default. •

Click American Steel Joist, and note that many common joist designations are available.


Click on any of the other country names to see the libraries that are available for use with international codes. •

Click American | W Shape.

•

Scroll down through the shapes listed in the Select Beam category, and click on W18x35.

•

Note the radio buttons on the right side of the dialog under the Type Specification heading. •

ST specifies a single section from the standard table.

•

T is used to indicate a T-shaped section formed by cutting through the middle of the web of a standard W section.

•

CM is used to specify a composite section comprised of a concrete slab on top of a wide flange steel shape. When this radio button is selected, the CT, FC and CW edit boxes become active. •

CT is the thickness of the concrete

•

FC is the strength of the concrete

•

CW is the width of the concrete (as defined by code, not the width of the beam – see Technical Reference manual Section 5.20.1, Note 1, p. 5-64).

•

Three more radio buttons allow the specification of top and/or bottom cover plates.

•

Information on all these specifications is available in Section 5.20.1 of the Technical Reference manual.

•

Make sure the ST radio button is selected.

•

Below the Select Beam list is the View Table button. This button accesses a section properties table for the section type selected (in this case, the American W-Shapes).

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Module 3

•

Below the View Table button is the Material checkbox. This checkbox is toggled on by default. When it is on, default material constants such as the Modulus of Elasticity (E), density, Poisson’s ratio and the coefficient of thermal expansion (alpha) are also assigned to the members, in addition to the selected section properties.

•

Material constants are determined based on the material selected in the Material list. The Material list is currently set to STEEL based on the selection of a W18x35 from the Steel tab.

•

Section 5.26.2 of the Technical Reference manual provides standard values assigned if the Material checkbox is toggled on.

•

If the Material checkbox is toggled off, the material constant values can be assigned later using Commands | Material Constants.

•

Leave the Material checkbox toggled on and the material set to STEEL. This will associate steel material properties with the W18x35 once it is added to the list of available sections.

•

Click Add. W18x35 appears as an available section in the Properties dialog.

•

Click on the Channel tab.

•

Scroll down to the C12 sections, and click on C12X30.

•

Leave the Type Specification set to ST (Single Section from Table).

•

There are also options to specify Double Channels in the Backto-Back and Front-to-Front configuration. The Material checkbox is checked by default, and the material list is set to STEEL.


•

Click the Add button. The C12X30 section is added to the list of sections in the Properties dialog.

•

Click on the HSS Rectangle tab. This example problem requires a 7 in. x 4 in. x 3/16 in. rectangular hollow structural section (HSS7x4x3/16). In STAAD.Pro nomenclature, this will be listed as HSST7x4x0.188, with the wall thickness being a decimal value instead of a fraction.

•

Scroll through the list of HSS sections and click on HSST7X4X0.188 . The Material checkbox should remain checked, and the material list should be set to STEEL.

•

Click the Add button. The section is added to the list in the Properties dialog.

•

Click the Angle tab.

•

The following figure, from the Technical Reference manual (Section 2.2.1) illustrates how angles are specified in STAAD.Pro

Figure 3. 3 •

The angle code L is followed by numbers representing the length of the longer leg in tenths of an inch, the length of the shorter leg in tenths of an inch, and the thickness of the steel in sixteenths of an inch.

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3-16

Module 3

•

Therefore, the 3 in. x 3 in. x ½ in. angle section for the truss webs would be specified as L30308.

•

Click on L30308 to highlight it.

•

Leave the Type Specification set to ST (Single Section from Table). The Material checkbox should remain checked, and the material list should be set to STEEL.

•

Click the Add button. The L30308 section is added to the list of sections in the Properties dialog.

•

Click the Close button to dismiss the Section Profile Tables dialog.

•

The Values button in the Properties dialog accesses a table listing only the sections that appear in the Properties dialog and their properties. This table is provided for quick reference only. Properties may not be edited in this table.

•

Click the Define button in the Properties dialog.

•

The Property dialog includes various types of cross sections, including: • • • • • • • •

•

Circle Rectangle Tee Trapezoidal General Tapered I Tapered Tube Assign Profile

Each page contains a schematic representation of the cross section and fields to parametrically define the cross section dimensions.


•

The General tab can be used to define the cross section dimensions of any irregular-shaped section.

•

Tapered I and Tapered Tubes are for creating sections whose dimensions vary from one end of the member to the other.

•

The Assign Profile tab provides a way to specify only a category of cross section, either Angle, Double Angle, Beam, Column or Channel. Based on the profile that is selected, STAAD.Pro assigns a hard-coded section size without any attempt to design or optimize the section. It just provides a starting point for analysis.

•

The Material checkbox and associated list provide a connection between section properties and materials.

•

Click Close to dismiss the Property dialog.

•

Click the Materials… button in the Properties dialog.

•

The Materials dialog lists the currently defined materials and their values for modulus of elasticity E, Poisson’s ratio, density, and alpha coefficient. Materials are defined in another area of the program. The values cannot be edited in this table, but the dialog provides access to the table for convenient viewing.

•

Click the X in the upper right corner of the Materials window to close it.

•

The Thickness button can be used to assign thickness to surfaces or plates if the model contains any.

•

Click the User Table… button. The User Table button provides access to user-defined section properties tables, if any exist.

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•

A warning box pops up indicating that no user tables were found, and offering to create one.

•

Click Yes to the warning box.

•

Click the New Table button on the Create User Provided Table dialog.

•

The Select Section Type list is used to define the section type: wide flange, channel, angle, etc…

•

The External Table checkbox is unchecked, so the new table will be specific to (and contained within) the current model. If it is checked, the new table will be available for use on future models. If the intent is to reuse the table in other projects, toggle on the External Table checkbox, and provide a file name and path in the File Name field. An example of an application for user tables would be premanufactured building design where steel sections of I-shapes are used, but they may be fabricated out of plates to optimize a design, and therefore are not standard sections listed in the steel tables.

•

Section 5.19 of the Technical Reference manual provides instructions for specifying a user steel table.

•

A sample project illustrating the application of user tables is provided in Example Problem 17 of the STAAD.Pro Examples manual.

•

We will not actually create a new user table at this time.

•

Click the Cancel button to return to the Create User Provided Table dialog.

•

Click the Close button to return to the Main Window.


•

The Modify Section Database command provides another way to access and modify the steel tables. It is accessible from the Tools pull-down menu. It opens the SectionDBManager window, which provides an interface for editing the existing section tables if necessary.

Figure 3. 4 For example, the American steel table provided with STAAD.Pro is based on current AISC tables. Older steel sections many not be listed, and some of the sections that are listed may not be available from local steel mills. Editing the American steel table with the SectionDBManager is a way to introduce an older section in order to analyze an existing structure, or to delete sections that are not in production. Note that if the standard section table is edited, and if the STAAD.Pro model is later sent to another STAAD.Pro user, the modified steel table database file will also need to be provided to run the model correctly. For the American steel table, the file you need to include is AISCSections.mdb, and it is typically located in \SPro2007\STAAD\Sections\. •

We are now ready to assign the selected sections to members of the structure.

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Note: if the model was saved and closed at this point, without actually assigning sections to any of the members, ALL OF THE SECTIONS (W18X35, C12X30, HSST7X4X0.188 and L30308) WOULD BE REMOVED from the list in the Properties dialog when the model is reopened. •

Click on the W18X35 section from the list in the Properties dialog.

•

In the Assignment Method area, select the Use Cursor To Assign option.

•

Click the Assign button in the lower left corner of the Properties dialog. Note that the name of this button changes to Assigning, indicating that we are now in an active assignment mode.

•

The cursor changes to a steel beam shape with a triangle in the upper left corner. Click on each of the two columns with the cursor to assign the W18x35 section to the columns.

•

Click the Assigning button in lower left corner of the Properties dialog to exit the active assignment mode.

•

The label “R1” appears near the center of both columns. This is a reference number that corresponds to the W18X35 section, and it appears just to the left of the section name in the Properties dialog, in a column labeled “Ref”.

•

To display the full section name on the members instead of the reference number, follow the steps below: •

Right-click in the Main Window.

•

Select Labels from the pop-up menu.

•

Click the Sections radio button under the Properties category on the Labels page of the Diagrams dialog.

•

Click OK.


•

Select the C12X30 section from the list in the Properties dialog.

•

Click Select | By Group Name…. The Select Groups dialog opens.

•

Click the line that says G1: _BOTC and leave the dialog open. The bottom chord is highlighted in the Main Window and the Assignment Method automatically changes to Assign To Selected Beams.

•

Click the Assign button, and click Yes in the pop-up message box to confirm. The label “C12X30” appears near each bottom chord segment.

During this process of assigning member properties, take care to: •

Check that only the intended members have been selected.

•

Check that the Assignment Method option in the Properties dialog is properly set to Assign To Selected Beams.

•

Always use extra care when assigning member properties.

•

If properties get mistakenly assigned, it can be very difficult to detect.

•

Take the time to review the settings in the dialogs and to carefully note which members have been selected before assigning properties.

•

Click on the HSST7X4X0.188 section in the Properties dialog to highlight it.

•

Click G2: _TOPC in the Select Groups dialog. The top chord of the structure is highlighted in the Main Window.

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•

Again, leave this dialog open. The Assignment Method defaults to Assign To Selected Beams.

•

Click the Assign button, and then click Yes to confirm. The label “HSST7X4X0.188” appears near each top chord segment.

•

Click on the L30308 section in the Properties dialog.

•

Click G4: _WEB in the Select Groups dialog. The webs are highlighted in the Main Window.

•

Click the Close button. The Assignment Method defaults to Assign To Selected Beams.

•

Click the Assign button, and then click Yes to confirm. The label “L30308” appears near each web member.

•

Right-click in the Main Window, and click Labels… from the pop-up menu.

•

Click References in the Properties category on the Labels page of the Diagrams dialog, and then click OK. The display is neatened up by removing the section labels and replacing them with references to the sections.

•

Note that all members in the model are labeled with a reference number, confirming that all the members now have section properties assigned to them.

•

A quick comparison of the reference numbers in the model to the corresponding sections listed in the Properties dialog confirms that the W section (R1) is assigned to the columns, the channel (R2) to the bottom chord members, the rectangular HSS (R3) to the top chord members and the angle (R4) to the webs.


•

In a more complicated model, or in a three-dimensional model, it may not be so easy to observe that all members have been assigned a section.

•

STAAD.Pro provides a tool to confirm that every member in the structure has been assigned member properties.

•

Click in the Main Window to ensure that no members are currently selected.

•

Click Select | By Missing Attributes | Missing Property. The pop-up dialog indicates that there are no entities with missing properties in this model.

•

Click OK. If any member in the structure did not have a cross section assigned to it, this command would have highlighted those members in the Main Window.

•

Double-click on the column at the right end of the structure. This launches the Query function as demonstrated previously.

•

Click on the Property tab in the dialog that appears, and note that the dialog is now fully populated with the member properties. The Member Query screens are gradually able to present more and more useful information as additional parameters are assigned to the members.

•

Click Close to dismiss the Member Query screen.

•


•


•


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Local Axis System: •


•

Up to this point, we have been considering the components of the model with respect to a global axis system.

•

The location of the nodes was defined with reference to a single point of origin in three-dimensional space.

•

STAAD.Pro also contains a local axis system for each member of the model.

•

Why have a local axis system?

•

First consider a cylindrical structure, such as a tank, with wide flange column sections around the perimeter to provide support for the sides of the tank. In this case, the local axis system is required in order to define the radial orientation of the columns as shown in the figure below.

Figure 3. 5


•

Without a local axis system, there would be no way to describe the orientation of the columns, and STAAD.Pro would have no choice but to assume they are all oriented in the same direction as shown in the figure below.

Figure 3. 6

•

Next, consider modeling wind load on the roof of the structure in the diagram below:

Figure 3. 7 •

To express the wind load on the inclined roof with respect to the global coordinate system, the load would have to be broken down into its X, Y and Z components in the global directions.

•

On the other hand, it would be very easy and convenient to express the wind load on the inclined members with respect to

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a local coordinate system oriented along one of the axes of the members. •

The STAAD.Pro Technical Reference manual, Section 1.5.2, explains the orientation of the local coordinate system for an individual member.

•

The online version of the Technical Reference manual is accessible from Help menu. For demonstration purposes, click Help | Contents… | Technical Reference | General Description | Structure Geometry and Coordinate Systems | Local Coordinate System to see Section 1.5.2, Local Coordinate System.

•

Click the X in the upper right corner of the Help window titled STAAD.Pro 2007 to close it.

•

Refer to the figure below. It is a reprint of Figure 1.6a from the Technical Reference manual.

•

The figure shows the default orientations of the local axes when the global Y-axis is oriented in the vertical (gravity) direction (which is the default in STAAD.Pro).


Figure 3. 8

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•

The note at the bottom of the figure says, “The local x-axis of the above sections is going into the paper.”

•

The local x-axis is a line defined by the two ends of the member.

•

The positive direction of the local x-axis is defined by a line going from the starting end (node A) to the ending end (node B) of the member.

•

To display the axes for the local coordinate system of all the members in the structure, follow the steps below: •

Right-click in the Main Window and select Labels… from the pop-up menu.

•

Toggle on the Beam Orientation checkbox in the Beams category.

•

Toggle on the Show Axes At Org checkbox in the General category, then click OK.

•

Symbols indicating the orientation of the local coordinate system and showing the cross section shape will appear in the Main Window.

•

A labeled, color-coded local coordinate axis system also appears in the Main Window. Its purpose is to provide a key to the colors of the local coordinate axis symbols.

•

Local y = red Local x = blue Local z = green

•

The blue arrow representing the local x-axis always points along the axis of each member in the structure.

•

Notice that the blue arrow (local x-axis) points downwards in the case of the two columns. This is because the columns were drawn from top to bottom.

•

For a refresher on how to confirm the direction that the columns were drawn, see the commentary below:


Click on the left-hand column with the Beams Cursor. Click the Geometry page. The Beam sub-page should automatically be active. Note that the line corresponding to the selected column (Beam 35) is highlighted in the Beams table, and that Node A is node 15, and Node B is node 20. This means member 35 starts at node 15 and ends at node 20. The Nodes table indicates that the Y-coordinate of node 15 is 15.000 ft {5.000 meters} and the Y-coordinate of node 20 is 0.000 ft, confirming that the column starts at the top and ends at the bottom. This was a good review, but remember that in practice the member direction can be confirmed much more easily. Hover the Beams Cursor over the left-hand column until the Beam Ends colors appear. By knowing that green signifies the Node A or starting end and blue signifies Node B or the ending end, this method provides instant confirmation of the member direction. •

Note that the local x-axis for the channels along the bottom chord point to the right on the right side of the structure, and to the left on the left side of the structure.

•

This orientation is due to the fact that the Mirror command was used to create the second half of the structure. A consequence of this situation is that the flanges of the channels are pointing out of the screen on the right side, and into the screen on the left side.

•

We will make use of this mirrored orientation later in the training, but if the intent was to orient all of the segments of the bottom chord the same way, there are at least two different ways to accomplish this is STAAD.Pro.

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Method 1: •

Hold down Control (Ctrl) and click the four members of the bottom chord on the left half of the truss.

•

Click Tools | Redefine Incidence.

•

Select the option to Switch Incidence of Selected Beams in the Redefine Incidence dialog, and then click OK.

•

Note that the four selected members are reoriented so that their x-axis direction and their flanges coordinate with the other bottom chord members.

•

Click Tools | Redefine Incidence again, while the four members are still selected.

•

Choose Switch Incidence of Selected Beams and click OK. This will return the four members to their original “mirrored” orientation.

Method 2: •

The second method to orient all of the segments of the bottom chord the same way is to use a parameter called the beta angle.

•

Beta angle is explained thoroughly in the next section.

•

For now… a few more aspects of the local axis system.

•

In addition to the local x-axis, there is also a local y-axis and a local z-axis. These enable us to obtain results such as major axis bending moment, shear force along the local y-axis, etc...


•

The local y-axis is the one that is normally parallel to the web, and the local z-axis is normally the major axis.

•

The statement above says “normally”, because there is a variant to the local axis system. It occurs when the “SET Z UP” command is specified. The main use for this command would be to adopt a global axis system akin to that used by CAD programs such as MicroStation.

•

Note that when using “SET Z UP”, many of STAAD.Pro’s advanced program options will not be available.

•

The “SET Z UP” option will not be used in this training exercise, and because of the limitations it puts on other program options, it is generally recommended to avoid using “SET Z UP” unless absolutely necessary.

•

The only other cross section in the steel design model that requires consideration in terms of the orientation of its local axis system is the single angle section used in the webs.

•

Angles have local axes that point in awkward directions.

•

By default, STAAD.Pro orients angle members so that the beta angle is equal to zero. The next section provides a better understanding of what this means.

•

Keep this model open for use in the next section.

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3.4

Member Beta Angle •

Ensure that the file named Dataset 3_3.std is still open.

•

Click the General page. The Property sub-page should be active.

•

Click View | 3D Rendering. A rendered 3D view opens.

•

Pan and zoom in to observe the orientations of the channel flanges and the angle legs.

•

Stretch the Beams spreadsheet far enough to be able to see that the Beta column has all zero values at this time. Members have a beta angle of zero by default, unless and until it is set differently.

•

The beta angle is just a term that indicates how the member is oriented about its local x-axis with respect to the global coordinate system.

•

In the absence of any explicit instruction from the user, STAAD.Pro orients a member according to a set of mathematical rules which are best described using the name the “beta equals zero condition”.

•

A member’s beta angle is the angle through which the cross section must be rotated about its local x-axis from its beta = 0 position to arrive at the desired orientation.

•

Section 1.5.3 of the STAAD.Pro Technical Reference manual describes the relationship between the local and global coordinate systems.

•

Figures are provided in Section 1.5.3 of the Technical Reference manual to quickly determine the beta angle to apply for commonly encountered cases.


•

In the case of a channel, the following figure from the Technical Reference manual shows the member orientation for various beta angles.

Figure 3. 9 •

The upper left corner of the figure above shows the local axis system for a channel member.

•

The lower portion of the figure shows member orientation of the channel for beta angles of 0, 90, 180 and 270 degrees for members whose longitudinal axes are aligned with the positive and negative global axis directions.

•

Notice that when the member incidence (direction from end A to end B) is defined in the positive global X direction, for beta = 0, the flanges of the channel point in the positive global Z direction, and when the member incidence is defined along the negative global X direction, the channel flanges point in the negative Z direction.

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•

This situation corresponds exactly to the condition of the bottom chord in the current model.

•

Press and hold the Shift key and click inside the Rendered View window.

•

The “orbit paths” appear representing a path of travel for rotating about each of the three global axes.

•

Press and hold the Shift key again. Place the cursor near one of the orbit paths. Click near the orbit path and hold the mouse button to rotate the Rendered View about one particular axis at a time.

•

Rotate the model and zoom in to the location where the bottom chord member orientations change.

•

Note that the orientations of the channels in the bottom chord of the model coordinate with the orientations shown in the figure below.

Figure 3. 10


•

Close the Rendered View window.

•

Another way to confirm a member’s beta angle is through the use of Query.

•

Double-click on the column at the left end of the truss. The Query dialog opens.

•

The Geometry page is active by default. The beta angle is listed in the lower left corner of the dialog under the Additional Info category.

•

Close the Query dialog.

•

Right-click in the Main Window, and select Labels… from the pop-up menu.

•

Select Beam Numbers in the Beams category, and then click OK. Remember that the “hotkey” for turning on beam numbers without having to open the Labels… dialog is Shift + B.

•

Click the Beta Angle tab on the Properties dialog.

•

Click the Create Beta Angle button.

•

Ensure that the Angle in Degrees option is selected in the Beta Angle dialog.

•

Enter 90 in the input field, and click OK. Note that “Beta 90” now appears in the Beta Angle window indicating that it is an available definition that can be assigned to members. Other Beta Angle definitions can be defined now if they are required.

•

Click on Beta 90 on the Beta Angle tab in the Properties dialog.

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•

Click Use Cursor To Assign in the Assignment Method category.

•

Click the Assign button. The cursor changes to the special Assign Beta Angle Cursor .

•

Click on beam number 1, in the bottom chord, just to the right of center. The beam label indicates β 90.00.

Figure 3. 11 •

Click the Assign button again to exit the assignment mode.

•

Click View | 3D Rendering.

•

Zoom in to observe the orientation of the channel flanges for beam number 1. They now point straight down. In a real structure, there would be no reason to orient one member of a chord differently from the others, but it was done here because it will be instructive when we look at analysis results later on.

•

While the 3D Rendering window is still open, note that the angle sections used for the truss web members are also not oriented in a realistic direction.


•

The beta equals zero condition for the web members orients the local z-axis parallel to the global Z-axis.

•

For fabrication reasons, it is preferable that one of the angle legs be oriented in the XY plane in the real structure.

•

STAAD.Pro provides two built in commands to automatically orient one angle leg parallel to the global Y-axis.

•

Close the 3D Rendering window.

•

Click the Beta Angle tab on the Properties dialog.

•

Click the Create Beta Angle button.

•

The options labeled Angle and RAngle in the Beta Angle dialog both result in an angle orientation with the legs parallel to the global axis.

•

Each steel angle section has a characteristic parameter, α, that relates the section’s principal axis system and geometric axis system.

•

The Angle option rotates a section (90 - α).

•

The RAngle option rotates a section (180 - α).

•

With both commands, the direction of the resulting rotation about the local x-axis is in the positive direction with respect to the right-hand rule. In other words, when the thumb of the right hand points in the positive direction of the member’s local x-axis, the fingers of the right hand curl in the direction of the resulting rotation. (See figure below.)

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Figure 3. 12


•

Click the Angle option, and click OK.

•

A new line of text, “Beta Angle”, now appears in the Beta Angle window.

•

Click on that Beta Angle line of text.

•


•

Click on the _WEB group, and then click Close. The Assignment Method in the Properties dialog will now default to Assign To Selected Beams.

•

Click the Assign button, and click Yes in the pop-up dialog to confirm.

•

Click in the Main Window to deselect the web members. Note that STAAD.Pro places a new entry in the Beta Angle tab: “Beta 45”. This corresponds to 90° - 45° = 45° for equalleg angles.

•

Click on any web member to select it. The line in the Beam Table corresponding to the selected member is highlighted.

•

Drag the Beams table open wide enough to view the column labeled “Beta”. Notice that the Beta Angle for the selected web member is indicated to be 45°. The beta angle for this web member could also be verified by double-clicking it to use the Query function.

•

Click in the Main Window to deselect all members.

•


•

Click on the _WEB group, and then click Close.

•

Click View | 3D Rendering.

•

Zoom in to observe the orientation of the angle legs. Note how the legs are now aligned with the XY plane.

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•

Click the X in the upper right corner of the Rendered View window to close it. An alternate method of assigning a beta angle is to select the member in the Main Window. Then from the Main Menu, click Commands | Geometric Constants | Beta Angle…. The Beta Angle dialog opens. If the To Selection radio button is “grayed out,” it probably means that no members have been selected in the Main Window. If this is the case click the Cancel button and try again. Note that assigning beta angles by this method does not populate the Beta Angle tab with the values that are assigned. This is something to keep in mind if it is important to have the value available to assign easily at a later stage.

•

Sometimes it is not obvious what beta angle is necessary to orient a member in a certain direction.

•

The rules stated in Section 1.5.3 of the Technical Reference manual can be used.

•

But here is an alternative method that involves two steps: 1. Determine the orientation of the member that corresponds to the “beta equals zero condition”. 2. Remember that the beta angle will rotate the member in a positive direction with respect to the right-hand rule.

Determine the orientation of the member that corresponds to the “beta equals zero condition”: •

Either use the diagrams in the Technical Reference manual, or apply the following method.


•

Establish the local x-axis by knowing the starting and ending nodes of the member.

•

Establish the local z-axis by applying the rule that the cross product of the local x-axis and the global Y-axis will result in the local z-axis as shown in the figure below.

Figure 3. 13 •

The only time that this rule cannot be used is when the local x-axis is parallel to the global Y-axis, as in the case of a vertical member such as a column or truss vertical, because it is not possible to obtain a cross product of two vectors that are parallel. In this case, STAAD.Pro adopts the convention that the local z-axis will be oriented parallel to the global Z-axis.

•

Finally, establish the local y-axis by applying the rule that the cross product of the local z-axis and the local x-axis results in the local y-axis. See the figure below for a refresher on cross product rules of operation.

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Cross Product Rules of Operation:

Cross product rules of operation are cyclical in nature:

XxY=Z

YxZ=X

ZxX=Y

and

Y x X = -Z

X x Z = -Y

Z x Y = -X

The following figure is a graphical representation of the cross product relationships among the three axes; X, Y, and Z.

To • • •

• • • •

use the graphic given a cross product in generic format A x B: Find A on the graphic. Move around the circle toward B. Note the direction of movement with respect to the sign convention arrows indicated on the graphic. Clockwise movement indicates that the result will have a positive algebraic sign. Continue in the same direction past B and read the next value as the result, say C. Thus A x B = C in its generic form. Example 1: X x Y = Z Example 2: Y x X = -Z

Figure 3. 14


•

Now apply this procedure to the channel sections assigned to the bottom chord of the model. •

Place the cursor on the bottom chord member just to the left of the truss centerline.

•

The Beam Ends colors light up, showing green at the righthand end of the member and blue at the left-hand end.

•

Based on the Beam Ends colors, the member local x-axis is established as pointing to the left (in the negative global X-direction).

•

Cross the local x-axis with the global Y-axis to establish that the local z-axis points into the page (in the negative global Z-direction).

•

Cross the local z-axis with the local x-axis to establish that the local y-axis points straight up (in the positive global Y-direction).

•

The member orientation has now been completely determined by nothing more than knowing the A and B ends and applying the rules discussed above.

•

Now graphically verify what has just been determined.

•

Click the Spec sub-page of the General page. (This clarifies the view by eliminating the beta angle labels.)

•

Right-click in the Main Window, and click Labels… in the pop-up menu.

•

Click Beam Orientation in the Beams category.

•

Click Show Axes At Org, in the General category, and then click OK.

•

Zoom in on the bottom chord member just to the left of the truss centerline.

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•

Compare the local axes of the member with the colored axis system key at the origin to confirm that the member’s x points left, z points into the page (in the negative global Z-direction), and y points up, as determined above.

•

Now that the full orientation of the member is understood and confirmed, it is easy to determine appropriate beta angles for the member.

•

Remember that the beta angle rotates the member in a positive direction with respect to the right-hand rule.

•

With your right hand, point your thumb in the direction of the member’s x-axis. The natural curl of your fingers indicates the direction of rotation for a positive beta angle.

•

Therefore, to orient the member with flanges pointing down to coordinate with its adjoining neighbor on the right side of the truss centerline, a beta angle of 90° is appropriate.

•

To orient the member with flanges pointing in the positive global Z-direction, a beta angle of 180° is appropriate.

•

For the purposes of this exercise, we will leave the bottom chord members oriented as-is, because it sets the model up to observe some interesting results later when an analysis is performed.

•


•


•



3.5

Assigning Member Specifications •

Open the file named Dataset 3_4.std. Now that we have defined member cross sections and member orientation, we are ready to move to the next item in the Page Control.

•

Click the General page, and then click the Spec sub-page.

•

The Specifications – Whole Structure dialog is used to define member conditions such as: •

Released or partially-released degrees of freedom at either end of the member

•

Member offsets

•

Truss member, cable member, tension-only member or compression-only member

•

Inactive member

•

Reduced section properties due to cracking in concrete members.

•

Click on the Beam button in the Specifications-Whole Structure dialog (from here on we will refer to it simply as the Specifications dialog).

•

The Member Specification dialog opens, and the Release tab is active by default.

•

The operation of the Member Specification dialog remains consistent regardless of which page is being displayed. •

Clicking the Add button adds the specification to the model.

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•

Clicking the Assign button adds the specification to the model AND assigns the specification to the selected members.

•

Unless one or more members is selected before opening the Member Specification dialog, the Assign button remains inactive or “grayed out.”

How to specify member releases: •

•

There are six degrees of freedom in a structural connection or support: •

Three translational degrees of freedom - (δx, δy and δz), and

•

Three rotational degrees of freedom - (θx, θy, and θz).

Member releases are specified about the local axis system. •

FX = axial force

•

FY = shear force along the local y-axis

•

FZ =

•

MX = torsion

•

MY = moment about the local y-axis (the weak axis of a wide flange beam)

•

MZ = moment about the local z-axis (the strong axis of a wide flange beam)

shear force along the local z-axis


Figure 3. 15 •

By default, all six degrees of freedom are fixed, so initially all connections are considered to be moment-resisting connections.

•

If one or more of those forces or moments cannot be transferred by a connection, the force or moment can be released at the appropriate end of the member in the model.

•

Any of the six degrees of freedom at either end of the beam can be fully or partially-released using the Release page.

•

The first step in setting a release is to select either Partial Moment Release or Release in the Release Type category.

•

Based on the setting in the Release Type category, the options become active in either the Partial Moment Release category or the Release category, and the options in the other category are grayed out.

•

To specify a full release, set the Release Type category to Release, and toggle the checkboxes labeled FX, FY, FZ, MX, MY and MZ in the Release category.

•

To specify a spring release, set the Release Type category to Release, toggle the checkboxes labeled KFX, KFY, KFZ, KMX, KMY and KMZ in the Release category, and enter the spring constants for the selected degrees of freedom.

•

To specify a Partial Moment Release, set the Release Type category to Partial Moment Release. Then estimate what

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percentage of the full-moment capacity can be resisted by the connection. •

Enter a decimal value between 0.0 and 1.0 in the MPX, MPY, and/or MPZ fields to specify the fraction of the full moment capacity on the connection that is to be released for the indicated rotational degrees of freedom.

•

Alternatively, the MP option is a means of specifying a partial release for all the 3 moment degrees of freedom (MX, MY and MZ). Using this option, a single factor is applicable to all three. Note that a Partial Moment Release specifies the percentage to be released, not the percentage to be resisted. For example, a value of zero means no release, i.e. full moment restraint. A value of 1.0 means a full release, i.e. no moment restraint. A note to this extent has been placed on the Release tab as a reminder.

•

Note that at any end of a member, for any particular degree of freedom, STAAD.Pro only allows one of the following: full release, partial release, or spring release. It is not permitted to apply more than one simultaneously for a given degree of freedom at a given member end.

How to specify member offsets: •

Click the Offset tab.

•

Offset conditions at the ends of members are specified on the Offset tab in the Member Specification dialog. In the mathematical model, assumptions are made about the structure that do not necessarily reflect the actual conditions on the physical structure. One of these assumptions is


regarding where the START and END locations of members are. Beams and columns, modeled as lines, are assumed to meet at a point in space, whereas in the physical structure, a beam might be attached at the outer surface of the column flange. •

In the figure below, a beam is shown framing into a column. If both are wide flange members, the beam stops at the column flange. This may create a rigid zone at the connection where very little relative deflection will occur between the beam and the column within this zone.

Figure 3. 16 •

Therefore in the physical structure, the beam will behave more nearly as though it spans to the column face as opposed to the column centerline.

•

However, in the mathematical model the length of the beam is treated as though it spans to the centerline of the column.

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•

The difference between these span lengths (the one in the mathematical model versus the one in the physical structure) can be substantial, particularly if the columns have large sections.

•

If the difference in lengths is small, this effect may be able to be ignored, since the results will only be marginally affected.

•

But in the case of a large difference in lengths, the calculated moment at the midspan of the beam may be significantly higher than what will actually occur.

•

One way to avoid over-designing the beam is by using the concept of member offsets.

•

A member offset is a way to declare that the beam Start and/or End faces are a certain distance away from the column centerline.

•

It is another way of saying that the region shown shaded in the figure above is a rigid zone.

•

The length of this offset is equal to the distance from the face of the column flange to the centerline of the column.

•

The offset is in the direction of the local x-axis of the beam.

•

Member offsets may be modeled in any direction relative to either the local or the global coordinate system.

•

Another example of an offset connection is a situation where the centerlines of the connected members do not intersect at a common working point.

•

The figure below shows an example where there is an offset of 9 inches {225 mm} between the beam working point and the brace working point, measured along the column flange.


Figure 3. 17 •

In this case the offset could be modeled several ways, but the easiest would probably be to model the brace with an offset of 9 inches {225 mm} in the negative global Y direction.

•

The member offset dimensions shown in the figure above could be represented in the input file by the following commands: MEMBER OFFSET 1

START

7.0

0.0

1

END

-6.0

0.0

2

END

-6.0

-9.0

Figure 3. 18

0.0 0.0 0.0

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•

Another example that could be modeled using the member offset option is a beam supporting a slab as shown in the figure below.

Figure 3. 19 •

This arrangement might be modeled as plates and beams that connect at the same nodal points, with the center of gravity of the beam offset to accurately model the true geometry.

•

Additional information on the Member Offset specification may be found in Section 5.25 of the STAAD.Pro Technical Reference manual and in Example 7 in the STAAD.Pro Examples manual.

•

Click the Property Reduction Factors tab.

•

This tab provides a method to apply reduced effective section properties to concrete sections to represent the loss of stiffness due to cracking. •

The approach follows recommendations in ACI 318-05, which suggests the use of reduction factors for individual members.

•

Section 10.11.1 of ACI 318-05 provides a list of suggested reduction factors dependent upon the nature of stresses the member is subjected to.


•

Click the Cable tab.

•

This tab is used to declare a member as being a cable. •

Cable members can carry no shear, bending, or torsional forces,

•

This specification requires the user to input either an Initial TENSION or an Unstressed LENGTH. Note that the Cable specification does not imply tensiononly. If members are to be considered tension-only, they must be explicitly defined as such.

•

Click the Truss tab.

•

This tab can be used to declare a member as being a truss member. •

The Truss specification has the effect of stating that the member has no ability to transmit loads through shear, bending or torsion.

•

The Truss specification requires no additional parameters.

•

Click the Tension tab or the Compression tab.

•

These tabs can be used to create tension-only and compression-only members, respectively. •

A Compression-only specification has the effect of making a member inactive under conditions where it would tend to experience tensile forces.

•

A Tension-only specification makes a member inactive under conditions where it would tend to experience compressive forces. These specifications are usually used to overcome certain design-related code restrictions.

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Generally, codes are quite stringent about the KL/r limits of members subjected to compressive forces. If members which potentially might fail this requirement are present in the model, they may be “switched off” with the Tensiononly command to accurately portray their failed status under such compressive loads. •

A compression-only member will be switched off if it starts to experience tensile axial forces.

•

The tension-only and compression-only specifications require no additional parameters.

•

Click the Inactive tab.

•

This tab provides a way to inactivate selected members. •

The Inactive Member specification is ideal for modeling stages of construction of a structure.

•

The full structure is first defined, and members may be selectively inactivated to account for their “absence” at particular stages of construction.

•

Example 4 in the Examples Manual illustrates the usage of this option.

•

The Inactive specification requires no additional parameters.

•

Click the Fire Proofing tab.

•

This tab provides a method to automatically consider the weight of fireproofing material applied to structural steel. •

Two types of fireproofing configurations are currently supported – Block Fire Proofing and Contour Fire Proofing.


•

Click the Imperfection tab.

•

This tab provides a method to apply a camber or drift value to a member to be considered for secondary effects. •

Used to compute an additional loading on the selected imperfect members that are in compression.

•

Works in conjunction with an Imperfection Analysis. Respect is a non dimensional constant used to skip the camber imperfection calculation if the compressive load is small or EI is great or length is short. A combination of these terms is calculated and called EPSILON. If EPSILON is less than the specified value of RESPECT, then the imperfection calculation is skipped for that local direction, for that case, for that member. EPSILONy = Length * SQRT[ (abs(axial load)) / EIz] EPSILONz = Length * SQRT[ (abs(axial load)) / EIy] Member imperfection modifications are only applied to members that are in compression.

•

Close the Member Specification dialog.

•

Assume that the goal is to specify a moment release at the left end of the bottom chord of the truss in the model, where it joins the column (left end of beam number 22).

•

Determine whether the node attached to the column is at the starting end or the ending end of the beam. See the commentary below for four ways to do it: Hover cursor over member and observe green for start at right node and blue for end at left node at column, or Click View | Structure Diagrams | Labels , select Beam Ends in the Beams category, and click Apply,or

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Right-click in Main Window, click Labels…, select Beam Orientation in the Beams category, and click Apply,or Click on member number 22 to select it. Click the Geometry tab. The line for member number 22 is highlighted in the Beams spreadsheet. Note that Node A is indicated as node 14 and Node B is node 15. Compare the X coordinates of nodes 14 and 15 in the Nodes spreadsheet to see that member number 22 starts on the left and ends on the right. •

Double-click member number 22 to activate the member query. Note that the node numbers are listed in the table in the center of the Geometry page. They are listed in order; starting node on top, ending node below it. By observing the X coordinates, it is easy to see that the member spans from left to right in the view where the global X-axis points to the right.

•

With the Beams dialog still open, note that there is a Releases category in the lower right corner.

•

Click Change Releases At End.

•

Make sure that the End radio button is selected in the Location category of the Member Specification dialog.

•

Make sure that the Release radio button is selected under the Release Type category.

•

Click the MX , MY and MZ checkboxes under the Release category, and then click the Assign button.

•

Note that now under the Releases category, MX, MY and MZ appear next to the End label.

•

Click Close.

•

If you changed to the Geometry page to check the beam and node numbers, return to the Spec page by clicking on the


General tab in the Page Control, then click on the Spec subpage tab. •

Click in the Main Window to deselect all members.

•

Note that a small circle now appears at the ending end of member number 22. This symbol is a graphic cue to let you know that there is a release of some type defined there.

•

A common problem at this stage is that the blue circle representing the release appears on top of more than one member.

•

STAAD.Pro has some tools on the View toolbar to help clarify the release:

•

and then press and hold Click the Magnifying Glass icon the left mouse button to see an enlarged view of an area on the Main Window.

•

and then use the left mouse Click the Zoom Window icon button to click and drag a rectangular fence around the area to window in on.

•

Note that after windowing in with the Zoom Window tool, the Magnifying Glass tool remains active.

•

By using a combination of Zoom Window and Magnifying Glass, it should now be possible to verify that the release indicator circle is on the correct member.

•

Click the Magnifying Glass icon again to turn it off, and then click the Display Whole Structure icon

.

•

Assume that the webs of the truss are to be modeled as truss members.

•

Click Select | By Group Name…. The Select Groups dialog opens.

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•

Click the _WEB group, and then click the Close button.

•

Click the Beam… button on the Specifications dialog.

•

Click the Truss tab. Note that the Assign button is active, because the webs were already selected.

•

Click the Assign button. The truss specification is assigned to all web members. Also, Member Truss now appears in the Specification – Whole Structure dialog. This makes the truss specification available to assign to any other members of the model if necessary.

•

Note the checkbox labeled Toggle Specification in the Specifications dialog.

•

When the Toggle Specification checkbox is activated, the Assignment Method works as a toggle to alternately apply and remove the assignment of the selected specification.

•

This makes it possible to remove a specification from a member, that is, to alternately toggle the specification on and off the member by clicking it with the mouse.

•

When Toggle Specification is enabled and a specification in the list is highlighted, clicking on a member the first time assigns the specification to the member; clicking on it again removes the specification.

•

It is recommended to generally work with the Toggle Specification option turned off, and to only turn it on when the function is required. This helps to avoid making unintended specification changes if a member is clicked for some other purpose while the Toggle Specification option is still active.

•

Select Toggle Specification.


•

Ensure that MEMBER TRUSS is selected in the Specification category of the Specification – Whole Structure dialog.

•

Click Use Cursor To Assign in the Assignment Method category.

•

Click the Assign button. The cursor changes to the special Assign Specification cursor that looks like the letters “SP” in a circle.

•

Click the central vertical web member. Note that the “Truss” label disappears from the member.

•

Click on the Highlight Assigned Geometry checkbox in the Specification – Whole Structure dialog.

•

Note that the central vertical web member is no longer highlighted, confirming that its truss specification has been removed.

•

Now click on the central vertical web member once more with the special Assign Specification cursor to restore its truss specification.

•

Turn off the Toggle Specification checkbox when finished using it.

•


•


•


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3.6

Assigning Supports •


•

Click the General page, and then click the Support sub-page.

•

The Supports – Whole Structure dialog (we will refer to it from here on as simply the Supports dialog) is used to define support or boundary conditions for a structure.

•

Click the Create button in the Supports dialog.

•

The Create Support dialog offers separate tabs for each type of support that is available.

Types of Supports: Fixed: •

Click the Fixed tab.

•

At a fixed support, all degrees of freedom are restrained to prevent any translation or any rotation.

•

On the Fixed page of the Create Support dialog, the controls for the six degrees of freedom are “grayed out.”

Pinned: •

Click the Pinned tab.

•

At a pinned support, the three translational degrees of freedom are restrained, but the three rotational degrees of freedom are not.

Fixed But: •

Click the Fixed But tab.


•

A Fixed But support provides checkboxes to individually control the fixity or release of the 3 translational and 3 rotational degree of freedom.

•

In this dialog, F stands for “force”, corresponding to translation and M stands for “moment” corresponding to rotation.

•

A Fixed But support provides the ability to assign a spring constant to any of the six degrees of freedom in lieu of full fixity or full release.

•

Note that if a degree of freedom is fully released by toggling the checkbox on, the associated Define Spring field becomes inactive, or “grayed out.” One example of the use of the Fixed But support type would be to model a roller support that slides in the X direction but does not rotate. This type of support is modeled by toggling on the FX checkbox. This has the effect of fixing rotation in all directions and fixing translation in all directions except X, i.e. it is released for translation in the X direction.

•

Any combination of fully or partially released translational and/or rotational degrees of freedom is permitted.

Enforced and Enforced But: •

Click the Enforced But tab.

•

Perform the same basic functions as the Fixed and Fixed But supports.

•

Different from Fixed and Fixed But in the following ways:

•

First, the Fixed and Fixed But supports cannot handle Support Displacement loading if plates and/or solids are present in the model. The Enforced and Enforced But supports were introduced to handle these conditions.

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•

Second, the Fixed and Fixed But supports restrain certain degrees of freedom when the global stiffness matrix is assembled. By contrast, the Enforced and Enforced But supports actually maintain all degrees of freedom as active in the global stiffness matrix. It just assigns springs with infinitely high stiffness to the supports that are supposed to be restrained in certain directions.

•

If a model does not include any support displacement loads for plates or solids, a Fixed or Fixed But support offers faster calculation speed.

•

Since the program needs to include only those degrees of freedom that are unrestrained, (restrained d.o.f is known to have zero displacement, and hence need not be considered), the stiffness matrix will be smaller.

•

If the model is large, there may be significant reduction in time required to perform the analysis.

Multilinear Spring: •

Click the Multilinear Spring tab.

•

Provides the ability to model situations where the spring constant varies, depending on the magnitude of the deflection.

•

As an example, consider a cantilever beam that can deflect only a limited distance before it encounters an obstruction, such as another structure or a slab or plate.

Figure 3. 20


•

As load is applied to the end of the cantilever in the negative Y direction, it deflects downward.

•

For a deflection between 0 and δ, the magnitude of the displacement is equal to the applied force divided by some spring stiffness constant K1, where K1 represents the amount of force required to displace the “spring” a given unit of length.

•

Once the deflection exceeds δ, the displacement is dictated by some new spring constant K2, where K2 represents the higher stiffness of the supporting material.

•

In other words, once the displacement exceeds δ, it takes a much larger force to achieve an additional unit of deflection of the beam. Another example of a situation that can be modeled effectively with the Multilinear Spring option is a pile, where the resistance varies in a manner that is not linear with displacement.

•

The Multilinear Spring is defined by entering values of displacement versus spring constant in the Multilinear Spring page of the Create Support dialog.

•

Up to 10 values of δ vs. K can be entered in the dialog.

Foundation: •

Click the Foundation tab.

•

A Foundation type of support is also available to model the effect of soil acting as a spring.

•

An example of where it would be useful is in modeling the behavior of a slab on grade where the support for the structure is the soil itself. Foundation Analysis and Design by Joseph E. Bowles (McGraw Hill, Inc.), includes a discussion of the Modulus

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of Subgrade Reaction, a quantity that specifies the amount of force required to displace a unit area of soil by a unit distance. •

Modulus of Subgrade Reaction has units of (Force/Area)/Displacement, e.g. kip/ft 2 /ft {kN/m 2 /m}.

•

In other words, the behavior of the soil is analogous to that of a spring.

•

In a model, the spring constant for the soil at a particular node can be determined by multiplying the subgrade modulus by the influence area of the node in question.

Figure 3. 21 •

For irregularly-shaped or large slabs with many nodes, computing the influence area by hand for each node can become quite tedious and time-consuming.

•

This is where the Foundation support can be useful. STAAD.Pro can calculate all the tributary areas and derive the spring constants automatically.

•

The Foundation support can also be used to manually apply spring constants to discrete spread footings by entering the dimensions of the footing and the Subgrade Modulus.


•

STAAD.Pro provides the ability to have Elastic Mat and Plate Mat foundations behave as compression only springs.

•

Also, there is an option to include in the output file the area that has been used in the calculation of the spring stiffness of each joint used when defining a Plate Mat or Elastic Mat foundation.

•

For more information, see examples 23 and 27 in the STAAD.Pro Examples Manual.

Inclined: •

Click the Inclined tab.

•

The Inclined Support resists displacements along userdefined directions that are not constrained to be parallel to the global axes.

•

An example of the application of an Inclined Support would be the cooling tower shown below. When the cooling tower experiences temperature loads, the force at the supports is radial and circumferential, and not along a global direction. The inclined support is well suited for this situation.

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Figure 3. 22

•

In all other respects, the inclined support is the same as any other support.

Tension/Compression Only Springs: •

Click the Tension/Compression Only Springs tab.

•

As the name suggests, the assignment of this type of support permits only one type of reaction force to develop, either tension or compression, in the selected global direction(s).

•

The note in the dialog is a reminder that “This support requires the earlier assignment of a spring support to the node to which this support would be assigned.”

•

In other words, the Tension/Compression Only Springs support assignment can be thought of as a modification to an existing Fixed But support where a spring constant has been defined.

•

Note that the assignment of Tension/Compression Only Springs triggers an iterative solution if, after any of the cycles of analysis, the direction of the force in the spring is in the “wrong” direction. If this is detected, then the


support will be removed from that direction and a new analysis will be performed. Additional information on the use of the Supports dialog can be found in the STAAD Graphical Environment section of the online help. Clicking on the Help button in the Supports dialog takes you to the appropriate section in the online help manual. This feature is known as contextsensitive help. The method of assigning supports to the structure is very similar to the method used to assign member properties and specifications. Add the supports to the Supports dialog, and then assign them to the structure. •

Assume that the support on the left side of the model is to receive a Fixed support, and the support on the right is to receive a Pinned support.

•

Click the Fixed tab again. Note that an alternate way to access the Support dialogs is to click Commands | Support Specifications | Fixed… from the Menu Bar.

•

Click the Add button. The Fixed support now appears as “Support 2” in the list of supports at the top of the Supports dialog.

•

Click the Create button in the Supports dialog.

•

Click the Pinned tab, and then click the Add button. The Pinned support will now be included as “Support 3” in the list of supports in the Supports dialog.

•

Click the Fixed Support (S2) in the Supports dialog.

•

Click the Use Cursor to Assign radio button under the Assignment Method category.

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•

Click the Assign button, and then click on the bottom of the left column. The fixed support symbol appears at the bottom of the column.

•

Click the Pinned support (S3) in the Supports dialog.

•

Click the bottom of the right column in the model. The pinned support symbol appears at the bottom of the column.

•

Click the Assigning button to turn off the assign mode. It is good practice to turn off assign modes like this to avoid assigning properties to the model unintentionally.

•

In addition to the Fixed and Pinned supports, there is another item called No support in the Supports dialog.

•

This option is used to remove a support that has already been assigned.

•

Unlike the Toggle Specification option discussed earlier, or the Toggle Load option coming up in the next section, there is no Toggle Support command.

•

To remove a support from the model, the No support option is assigned to a particular node by any of the available Assignment Methods.

•


•


•



3.7 Assigning Loads •


•

Click the General page and then click the Load & Definition sub-page.

•

The following separate load cases are to be created: 1. Member load (self-weight). 2. Uniformly distributed live load of 2.0 kip/ft {30 kN/m} acting downward on the bottom chord. 3. Transverse load due to wind forces in the X direction. 4. Load combination: dead load plus live load plus wind load (LC1 + LC2 + LC3)

•

Click on the New button in the Load & Definition dialog.

•

The Create New Definitions/Load Cases/Load Items dialog opens. This will hereafter be referred to simply as the Create New Definitions dialog.

•

The Create New Definitions dialog contains 4 tabs – Definitions, Load Case, Load Items, and Load Envelopes.

Definitions: •

Click the Definitions tab.

•

This tab contains the options used to generate the “DEFINE” block of data in the input file.

•

The “DEFINE” block is required to create Code-specified load cases such as wind, seismic, and snow.

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•

It is also required to generate moving load cases, time history load cases, and pushover loads.

•

The command syntax for these cases is explained in section 5.31 of the STAAD.Pro Technical Reference manual.

Load Case: •

Click the Load Case tab.

•

This tab contains the dialog used to initiate a new load case (primary load, moving load, or load combination) and assign it a case number.

Load Items: •

Click the Load Items tab.

•

This tab contains the dialogs used to add loading data to load cases.

Load Envelopes: •

Click the Load Envelopes tab.

•

This tab contains the dialog used to create load envelopes.

•

These envelopes can later be used for Post Processing.

Creating the First Load Case: •

Click the Load Case tab once again.

•

Leave the Number field set to 1 on the Primary page.


•

Enter Dead Load, in the Title field.

•

The Loading Type list is used to associate the load case with one of the Building Code definitions of Dead, Live, Wind, etc., for the purpose of automatically generating load combinations.

•

The following Loading Types are available:

•

•

Dead

•

Traffic

•

Live

•

Temperature

•

Roof Live

•

Imperfection

•

Wind

•

Accidental

•

Seismic

•

Flood

•

Snow

•

Ice

•

Fluids

•

Wind on Ice

•

Soil

•

Crane Hook

•

Rain Water/Ice

•

Mass

•

Ponding

•

Gravity

•

Dust

•

Push

Select Dead from the Loading Type list. For this exercise, the automatic load combination generator will not be used. So, there is no need to associate the load case with any of these Loading Types. However, there is no harm in doing so, either.

•

Click Add followed by the Close button.

•

Note that the load case number and name now appear in the list at the right end of the View toolbar at the top of the screen. Up until now, this field has been empty.

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Figure 3. 23 •

Note also that the Dead Load case now appears in the Load Cases Details category of the Load & Definition dialog at the right side of the screen.

•

Now that the Dead Load case has been created, loads can be applied to the model and assigned to this case.

•

The only load that will be applied to the Dead Load case is the self-weight of all of the members.

•

At this point, all of the parameters necessary to calculate the self-weight have already been defined (density, cross-sectional area and the length of each member).

•

Click on 1:Dead Load in the Loads & Definition dialog to select it.


Figure 3. 24 •

Click the Add button.

•

The Add New: Load Items dialog contains all of the available load types that can be defined. The Selfweight Load item is automatically selected.

•

The default Direction parameter is Y and the default Factor is -1. These parameters indicate an unfactored load acting in the negative global Y direction.

•


•

Click the Close button to dismiss this dialog.

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•

The Command Tree at the top right hand side should now show the “SELFWEIGHT Y -1” entry under the Dead Load case.

•

Currently, the small graphic in front of the SELFWEIGHT Y 1 expression includes a question mark. This is an indication that STAAD.Pro is expecting this load to be assigned to specific members.

•

Click on SELFWEIGHT Y -1 in the load list in the Load & Definition dialog.

•

Click the Assign To View option in the Assignment Method category of the Load & Definition dialog, and then click the Assign button.

•

Click Yes in the pop-up dialog confirming the assignment.

•

Click the mouse anywhere in the Main Window to deselect all of the members. Note that the small graphic in front of the SELFWEIGHT Y -1 expression no longer includes a question mark. This indicates that the load has been applied to at least one member.

Creating the Second Load Case: •

The second load case will consist of a distributed live load of 1.5 kips per foot {20 kN/m} applied to the bottom chord of the truss.

•

Click on Load Cases Details in the Load & Definition dialog, and then click the Add… button.

•

The load case number automatically increments to 2 in the Add New: Load Cases dialog.

•

Select Live as the Loading Type.

•

Note that the checkbox below the Loading Type becomes active when the Loading Type is set to Live. This controls


whether or not STAAD.Pro is to consider the live load reduction permitted by the Building Code. Some things to remember about Live Load Reduction in STAAD.Pro: •

Only the rules for live load reduction on Floors have been implemented; not the rules for Roofs.

•

Only the rules for live load reduction on Beams have been implemented; not the rules for Columns.

•

Some codes prevent live load reduction for buildings in Group A occupancies. In STAAD.Pro, there is no direct method for conveying to the program that the occupancy type is Group A. So, it is the user’s responsibility to decide when it is or is not appropriate to use the live load reduction feature based on this code provision. STAAD.Pro does not check this condition by itself.

•

Some codes place limits on the amount of reduction that may be applied to structures of certain other use groups such as garages. Again, in STAAD.Pro, there is no direct method for conveying the occupancy of the structure to the program. The user responsibility to decide when it is or is not appropriate to use the live load reduction feature based on this code provision. STAAD.Pro does not check this condition by itself.

•

Live Load Reduction is only applied to the FLOOR LOAD or ONEWAY LOAD types.

•

Leave the live load reduction checkbox unselected for the purposes of this exercise.

•

Enter Live Load in the Title field.

•

Click the Add button, and then click Close.

•

Click on 2:Live Load in the Load & Definition dialog, and then click Add….

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•

Click the Member Load option in the Add New:Load Items dialog, and then select the Uniform Force option. A diagram is provided within the dialog to graphically describe the meanings of the parameters available to define a Uniform Force.

•

The W1 parameter is the load intensity.

•

The parameters d1 and d2 allow the load to be applied only on a portion of the beam (d1 and d2 are both distances measured from the starting end of the member).

•

The parameter d3 can be used to specify a load that is offset from the shear center.

•

The Direction category is used to specify the direction of the load. X, Y, Z indicate the direction in local coordinates; GX, GY, GZ indicate the loads in global coordinates; PX, PY, PZ indicate the loads along the projected length of the member in the corresponding global direction.

•

Note that when loads are indicated to be along the projected length of the member, the parameters d1, d2 and d3 are still measured along the length of the member and not along the projected length.

•

If parameters d1 and d2 are left at their default value of zero, the load will be applied along the full length of the member.

•

Additional information is available in Section 5.32.2 of the STAAD.Pro Technical Reference manual.

•

Enter -2{-30} in the W1 field. The value is negative because the load should act downward, that is, in the negative global Y direction.

•

Leave the parameters d1, d2 and d3 set to their default values of 0 so the load will act at the shear center along the entire length of the beam.


•

Click the GY radio button under the Direction category.

•

Click the Add button followed by the Close button.

•

The expression UNI GY -2 kip/ft {UNI GY -30 kN/m} is listed in the Load & Definition dialog.

•

As with the selfweight load earlier, the small graphic in front of the UNI GY -2 kip/f t {UNI GY -30 kN/m} expression includes a question mark indicating that STAAD.Pro is expecting this load to be assigned to specific members.

•

Click on UNI GY -2 {UNI GY -30} in the load list in the Load & Definition dialog.

•


•

Click _BOTC, and then click Close.

•

Click the Assign to Selected Beams option in the Assignment Method category of the Load & Definition dialog, and then click the Assign button.

•


•

Click the Loads icon on the Structure toolbar to view the uniformly distributed load on the bottom chord.

Creating the Third Load Case: The third load case represents transverse loads caused by wind. •

Click the New button in the Load & Definition dialog. The Create New Definitions dialog appears.

•

Click the Load Case tab, and ensure that the Primary type is selected in the left-hand portion of the dialog. The load case number automatically increments to 3.

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Module 3

•

Select Wind as the Loading Type.

•

Enter Transverse Wind Load along GX in the Title field.

•


•

Click on 3: Transverse Wind Load along GX in the Load & Definition dialog, and then click Add….

•

Click the Nodal Load option in the Add New:Load Items dialog, and ensure that the Node option is selected.

•

Enter 1.2 kips {5 kN} in the Fx field, then click Add followed by the Close button. FX 1.2 kip {FX 5 kN} now appears in the Load & Definition dialog.

•

Click on the FX 1.2 kip {FX 5 kN} expression in the Load & Definition dialog.

•

Click Use Cursor to Assign in the Assignment Method.

•

Click the Assign button. The text in the button will change to “Assigning” as before, and the cursor graphic will change to the special assign nodal loads cursor.

•

Click on each of the six nodes on the left (windward) top chord of the truss, from eave to ridge.

•

Click the Assigning button to toggle the Assign mode off when finished.

•

Click the New… button in the Load & Definition dialog.

•

Note that there is a Wind item on the Definitions tab of the Create New Definitions dialog. We did not use this item when we created the “Transverse Wind Load along GX” load case.


•

To clarify, the Wind item on the Definitions tab is used to enter the parameters necessary to calculate code-specified wind pressures.

•

This method of generating wind loads on a structure would be useful in a situation where there are influence areas such as glass panels taking wind pressure and transferring it to the building frame.

•

When this is the case, the Wind item can be used to instruct STAAD.Pro to automatically calculate wind pressures according to code, and to create the loading condition by applying the pressures to the influence areas on the structure (see Example 15 in the STAAD.Pro Examples manual).

•

In the case of the current example, the wind loads were applied as nodal loads, assuming that the appropriate load magnitudes had already been calculated by other methods.

•

Click Close to dismiss the Create New Definitions dialog.

•

Load icons should be visible on the screen because the Load sub-page of the General page is currently active.

•

Temporarily click to the Support sub-page, and note that the load icons disappear.

•

It is possible to view loads while on other pages like this.

•

To see the load icons on the screen: •

Right-click the mouse inside the Main Window and select the Labels… command from the pop-up menu.

•

Click the Loads and Results tab in the Diagrams dialog.

•

Click OK to acknowledge the warning box that Force results are not available.

•

Click the Loads checkbox, and ensure that the Show Load Arrow checkbox is also selected in the Loads category, and then click Apply.

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Module 3

The load arrows for each of the nodal loads should now be displayed. •

To see the load values: •

Click back to the Labels tab.

•

Click the Load Values checkbox in the Loading Display Options category, and then click OK. The load values will be displayed on the structure.

•

Click back to the Load sub-page in the Page Control.

•

Note the Toggle Load checkbox in the Load & Definition dialog just above the Assignment Method area.

•

This checkbox enables an option to toggle any of the loads on or off.

•

To see this effect: •

Double-click Load Case Details to expand the tree.

•

Click the + symbol in front of 3:Transverse Wind Load along GX.

•

Click FX 1.2 kip {FX 5 kN}.

•

Click the Toggle Load checkbox.

•

Click Use Cursor To Assign in the Assignment Method area, and then click the Assign button.

•

Click on the node at the ridge of the truss, and note that the load is removed from that one node.

•

Click the node again to restore the load.

•

When Toggle Load is turned on, clicking on an entity will alternately assign and remove the load.


•

Click the Toggle Load checkbox again to deselect this option.

•

Click the Assigning button to exit assignment mode.

•

With the expression FX 1.2 kip {FX 5 kN} still selected, click the Edit… button on the Load & Definition dialog.

•

The Edit dialog opens, providing the ability to edit the magnitudes of the components in that particular load.

•

The column headed with the check symbol provides a checkbox for every node in the model that has been assigned the particular load. All of these checkboxes are checked by default.

•

Removing the check from one of these checkboxes will remove the particular load from the corresponding node.

•

The column headed with the light bulb symbol also provides a checkbox for every node in the model that has been assigned the particular load. All of these checkboxes are unchecked by default.

•

Placing a check in any of the “light bulb” checkboxes will highlight the corresponding node in the Main Window. This helps to establish which node is which without having to relate to node numbers.

•

Click the Close button.

•

The Delete… button can be used to delete a selected load.

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Module 3

Creating the Combination Load Case: The next load case is a combination of the three existing primary load cases. This will create a load case that combines the analysis results for the dead, live and wind loads. •

Click the New… button in the Load & Definition dialog.

•

Click the Load Case tab, and then click the Combination option. The Define Combinations item is selected by default. The Load Number is automatically incremented to 4.

•

Enter LC1 + LC2 + LC3 in the Name field.

•

Ensure that the Type category is set to Normal.

•

The General Format category shows how the individual components will be combined. For the Normal Type, the combination will consist of the sum of the individual load components, each multiplied by a factor.

•

The Default factor is currently set to 1, which will be acceptable for the purposes of this example.

•

All three of the existing load cases are currently listed in the Available Load Cases box.

•

Click the double-right arrow button to include each of them with the Default load factor of 1. All three load cases get moved from the Available Load Cases box to the Load Combination Definition box, with factors of 1. Note that load factors could be varied by load case. To apply different load factors for each load case, enter the appropriate factor in the Default field, select the corresponding


load case, and then click the single-right arrow. Then repeat the process for the remaining load cases in the combination. •

Click the Add button, and slide the Create New Definitions dialog out of the way to see that the load combination now appears in the Load & Definition dialog with the reference number 4.

•

It has a blue graphic with the letter “C” for “combination” to differentiate it from the load cases, which have a graphic of the letter “L” in a box in the Load Case Details list.

•

Note also that this fourth load case (the newly created load combination) is also available in the load case list on the View toolbar.

•

Refer back to the Create New Definitions dialog for some additional information on load combination options.

•

Normally the analysis results of individual load cases are combined algebraically. However, there are instances where it may be necessary to use other combination methods.

•

One example of another combination method is the SRSS, or Square Root of the Sum of Squares method. This method of combining loads is often used in the nuclear power industry.

•

STAAD.Pro provides the SRSS combination type for these applications. In fact, STAAD.Pro actually provides the ability to combine loads in a mixed algebraic and SRSS combination.

•

The mixed combination could be created by selecting the SRSS combination type, and then activating and deactivating the checkbox labeled “SRSS Component” as necessary.

•

When the “SRSS Component” checkbox is activated, the selected load cases are added to the load combination in the Square Root of the Sum of Squares method. When the “SRSS Component” checkbox is deactivated, the selected load cases are added to the load combination in the basic algebraic format.

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Module 3

•

The last form of Load Combination is the Absolute Value method. When ABS is the selected combination method, the absolute values of the individual load components are multiplied by the factor in the Default field and then combined algebraically.

•

These tools allow load combinations such as:

or or •

The SRSS or ABS options will not be used for this example problem.

•

More information on combining load case analysis results is provided in Section 5.35 of the Technical Reference manual.

•

Click Close to dismiss the Create New Definitions dialog.

•

Keep the current model open for reference in the next section.


3.8

The Material Page •

Click the Material sub-page of the General page.

•

The Material – Whole Structure dialog opens and lists the common materials that are available to assign to members.

•

All of the members in the Main Window indicate that they are of the Steel material.

•

The Create button in the Material – Whole Structure dialog is available to create a new custom material such as plastic, fiberglass, or a composite material when necessary.

•

It won’t be necessary to create any new materials for this example exercise, but it is good to note that it is there in case it is needed in the future.

•


•


•


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Module 3

-End of Module-

4-1

Analyzing the Model Module

4

The following topics are included in this module. 4.1 Preparing for the Analysis................................................................. 2 4.2 Performing the Analysis................................................................... 10 4.3 How Does STAAD.Pro Generate Results?.................................... 11 4.4 Viewing the Output File.................................................................. 13


4-2

Module 4

4.1

Preparing for the Analysis •

Open the file named Dataset 4_1.std. This Module begins at the point where all of the steps needed to create and load a complete model have been performed. The next step is to perform the analysis, in order to obtain the forces, moments, displacements, support reactions, etc. STAAD.Pro offers various types of analysis methods. The basic type of analysis, known as a linear-elastic analysis, will be performed on this model. This Module demonstrates how to instruct STAAD.Pro to perform a specific type of analysis, and to provide certain types of output. The general workflow process continues to move from top to bottom in the Page Control area. The Analysis/Print page is the next page below the General page.

•

Click the Analysis/Print tab. Three sub-page tabs are displayed in the Page Control area: Pre-Print, Analysis and Post-Print. The Analysis sub-page is active by default. A dialog labeled Analysis-Whole Structure appears in the Data Area and the Analysis/Print Commands dialog pops up on the screen.

•

The Analysis/Print Commands dialog contains the following tabs: •

Perform Analysis – active by default

•

P-Delta Analysis

•

Perform Cable Analysis


•

Perform Pushover Analysis

•

Change

•

Perform Direct Analysis

•

Perform Imperfection Analysis

•

Perform Buckling Analysis

•

The Perform Analysis tab provides access to the standard linear-elastic analysis method.

•

The other analysis methods are advanced topics that are not covered in this Module.

•

The Perform Analysis page contains various print options. •

No Print – none of the Print Options will be included in the output file.

•

Load Data – includes an interpretation of all the load data in the output file.

•

Statics Check –includes a report in the output file that will provide, for each load case: •

The total load acting on the structure.

•

The forces in the X, Y, and Z directions.

•

The moments about the X, Y and Z axes acting at the origin.

•

A support reaction summary.

•

The maximum displacements in the model.

•

The maximum translation in the X, Y and Z directions.

•

The maximum rotations about the X, Y and Z axes.

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Module 4

In a concise form the Statics Check provides an equilibrium check and a maximum displacement summary. The Statics Check output can be used to compare the total loading to the total reactions. These two quantities should be equal in magnitude and opposite in sense. If they are not, there is a problem in the analysis. Do not confuse the Statics Check option with the Statics Load option directly below it.

•

•

Statics Load –includes an equilibrium check at every joint in the structure, instead of the concise check for only support reactions versus applied loading.

•

Mode Shapes – includes a report of frequencies and modes when a dynamic analysis is performed.

•

Both – equivalent to selecting Load Data and Statics Check.

•

All –includes all available Print Options in the output file.

Click the Statics Check option, and then click the Add button. This adds a line at the end of the STAAD.Pro input file that instructs the program to perform an analysis and to include in the output file the information listed above in the description of the Statics Check option.

•

The order of commands in the STAAD.Pro input file is very important.

•

Note the checkbox labeled After Current in the lower left-hand corner of the Analysis/Print Commands dialog.

•

This checkbox influences the location where a new command will be inserted into the STAAD.Pro input file.


•

It refers to the currently selected line in the Command Tree shown in the Analysis – Whole Structure dialog in the Data Area.

•

If left unchecked, a new command will always be added to the end of the STAAD.Pro input file. For instance, a Perform Analysis command must precede a Check Code command in the input file. Assume a Check Code command was inadvertently placed in the input file without a preceding Perform Analysis command. If STAAD.Pro adds new commands to the end of the input file by default, how could a Perform Analysis command be inserted above the line containing the Check Code command? This is where the After Current checkbox is useful.

•

To demonstrate, click the Load Data radio button on the Perform Analysis page of the Analysis/Print Commands dialog, and then click Add.

•

Note that the new command PERFORM ANALYSIS PRINT LOAD DATA is inserted just above the FINISH line in the input file by default.

•

Now click the Close button to dismiss the dialog.

•

Double-click the line that starts with LOAD 2... in the Analysis – Whole Structure dialog. That folder expands to reveal its contents.

•

Double-click the line that says MEMBER LOAD.

•

Click on the line that says UNI GY -2{UNI GY -30}. It becomes highlighted to indicate that this is now the “current” line.

•

Click the Define Commands button.

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Module 4

•

Click the Both radio button.

•

This time, click the After Current checkbox to activate it, and then click Add, followed by Close.

•

The new command, PERFORM ANALYSIS PRINT BOTH, is inserted after the currently selected line in the input file.

•

These commands were only added to demonstrate the function of the After Current option. They should not be left in the input file.

•

Right-click the line that says PERFORM ANALYSIS PRINT BOTH.

•

Click Delete Command in the pop-up menu, and then confirm by clicking Yes. Note that the command disappears from the input file.

•

Right-click the line that says PERFORM ANALYSIS PRINT LOAD DATA, and delete that line, too.

•

Leave the command that says PERFORM ANALYSIS PRINT STATICS CHECK.

•

Click the Pre-Print sub-page tab in the Page Control on the left side of the screen, and then click the Define Commands… button in the Pre Analysis Print – Whole Structure dialog. The Analysis/Print Commands dialog opens. Note the Analysis/Print Commands dialog has different options when it is accessed from the Pre-Print sub-page than when it is accessed from the Analysis sub-page.

•

This dialog is used to include in the output file certain items related to the input data.

•

Click the Material Properties tab, click the Add button, and then click Close.


This places a command in the input file requesting STAAD.Pro to print the material properties of members in the output file. •

Note that the command appears in the Pre Analysis Print – Whole Structure dialog, and that it has a question mark graphic in front of the command. This indicates that the command has not yet been assigned to any members.

•

Click the PRINT MATERIAL PROPERTIES command in the Pre Analysis Print – Whole Structure dialog.

•

Click the Assign To View radio button in the Assignment Method category, and then click the Assign button.

•

Click Yes in the pop-up dialog to confirm the assignment.

•

All members in the Main Window become highlighted, indicating that the command was applied to every member in the model. Note that even if no Pre Analysis Print commands were issued, STAAD.Pro will still echo the input data in the output file. The Pre Analysis Print commands are provided to access information in a nice tabular format.

•

Now, click the Post-Print sub-page tab in the Page Control on the left side of the screen, and then click the Define Commands button. Another Analysis/Print Commands dialog opens with a large number of post-analysis printing options available.

•

Some of the available options to place in the output file include analysis results, joint displacements, support reactions, member forces, member section forces (all 6 forces at 1/8th intervals along the member length), member stresses, etc.

•

Click the Analysis Results tab, and then click Add followed by Close.

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Module 4

The Print Analysis Results command does not need to be assigned to any specific member. It automatically is assigned to every member in the structure. By adding this command, all displacements, forces, and reactions will now be included in the output file. •

The PRINT ANALYSIS RESULTS command now appears in the input file in the Post Analysis Print – Whole Structure dialog.

•

Note that it is always possible to come back later, add more analysis/print commands, and re-run the analysis. In addition, there are other methods of obtaining analysis results beside the output file. For example, the Post Processor, which is covered in detail in another module, offers a variety of ways to view results graphically. It is also used to create customized reports that can include information in both tabular and graphical format.

•

The commands in the Post Analysis-Whole Structure dialog now include: PERFORM ANALYSIS PRINT STATICS CHECK PRINT MATERIAL PROPERTIES PRINT ANALYSIS RESULTS FINISH

•

Note that when the command list is viewed from the Post Analysis-Whole Structure dialog, most of the commands are “grayed out”, and only the PRINT ANALYSIS RESULTS command is in bold text with a green checkmark.

•

The other items are grayed out to indicate that they cannot be modified from the current location in the Page Control. Edits to those items require moving to a different page in the Page Control first.


For example, if it is necessary to modify the edit list of members for the PRINT MATERIAL PROPERTIES command, it requires clicking on the Pre-Print sub-page first. Then the PRINT MATERIAL PROPERTIES command would be in bold text, indicating that it is accessible to modify. •


•


•


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4-10

Module 4

4.2

Performing the Analysis •

Open the file named Dataset 4_2.std. Now it is time to actually perform the analysis.

•

Click Analyze | Run Analysis….

•

A dialog labeled STAAD Analysis and Design displays a series of messages as the analysis proceeds. While the analysis is in progress, a button labeled Abort is provided in the lower right corner. It can be used to stop the processing and abort the run. In the case of this example model, the processing time is so short, that it may be difficult to see the Abort button before it changes to the Done button.

•

When the analysis is complete, STAAD.Pro displays the message: “End STAAD.Pro Run…” and reports the total processing time.

•

Three options are presented in the lower left corner of the dialog: •

View Output File

•

Go to Post Processing Mode

•

Stay in Modeling Mode

•

Click the View Output File radio button, and then click Done.

•

The STAAD Analysis and Design dialog is dismissed and the output file opens in the STAAD Output Viewer.

•

Keep the STAAD Output Viewer window open for reference in the next section.


4.3

How Does STAAD.Pro Generate Results? •

In a linear elastic analysis, a fundamental equation is used to generate the results:

[K] {u} = {P} •

It states that the stiffness K of the structure multiplied by the displacement vector u must be equal to the applied loading vector P in order to satisfy the requirement that the structure is in a state of equilibrium.

•

The stiffness of a structure is a composition of the individual stiffnesses of each member and each degree of freedom in the structure. The simplest case of this concept, a single member with a single degree of freedom, can be illustrated by considering a weight suspended at the end of a spring of stiffness K.

Figure 4. 1 The weight applies a load to the spring, causing it to deflect a distance δ as shown in the figure above. In this particular example, it is easy to solve for the deflection delta. However, even when looking at only a single beam in a

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Module 4

three-dimensional structure model, the problem immediately becomes more complicated. Each beam has six degrees of freedom at each end of the beam; three translational degrees of freedom and three rotational degrees of freedom. So there are twelve degrees of freedom for each beam element, and each degree of freedom has its own stiffness associated with it. There are also coupling effects which have to be taken into account. For instance, when one portion of the structure pushes on another portion, the second portion pushes back, and when one end of a beam moves, the other end moves too, etc… •

All of these stiffnesses must be assembled into a stiffness matrix.

•

The magnitudes of the stiffness factors are known. The stiffnesses are a function of member properties, material properties, member orientation, beta angles, etc.

•

The load values are also known.

•

The only unknown values are the displacements.


4.4

Viewing the Output File •

During the analysis, an output file is produced containing results, warnings and messages associated with errors if any.

•

The output file has the extension .ANL and may be viewed using the STAAD Output Viewer.

•

Use the scroll bar to scroll down through the report.

•

The first section displays any job information that was entered in the Job Info dialog, followed by the input data in a format very similar to the way it appears in the input file.

•

Below that is a list of PROBLEM STATISTICS: number of joints, members and elements, supports, load cases, etc.

•

Following the statistics is information associated with the Statics Check requested with the PRINT STATICS CHECK command.

•

The Statics Check was requested in order to verify that the structure is in equilibrium for the various load cases.

•

For each primary load case, the Statics Check report provides:

•

•

Summary of total applied loads for all 6 degrees of freedom, with moments calculated about the origin of the coordinate system (0, 0, 0).

•

Summary of total reactions from the supports of the structure, with moments calculated about the origin of the coordinate system (0, 0, 0).

•

Maximum displacements (3 translations and 3 rotations) in the structure induced by this load case.

To check equilibrium for a given load case, verify that each of the 3 applied forces and 3 applied moments is equal in

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Module 4

magnitude and opposite in sign to the 3 reaction forces and 3 reaction moments. •

A failure to achieve equilibrium could imply that the analysis results (for a linear elastic analysis) were erroneous. Factors such as instability conditions or improperly applied loads can cause the equilibrium check to fail.

•

It is also important to examine the maximum displacements for two reasons: •

First, to verify that the displacements seem reasonable and do not indicate extreme deflections that could indicate a modeling error, an instability, or a drastically disproportionate member stiffness somewhere in the model.

•

Second, to simply verify that the deformations are within tolerable limits.

•

Following the statics check is the material properties information for members 1 through 35.

•

The next block of data is the analysis results, which includes:

•

•

Joint displacements for every joint

•

Support reactions for every support

•

Member end forces for every member

Finally, a message is printed indicating the end of the STAAD.Pro run. The output report for this very simple structure is 18 pages long. This underscores the need to be judicious when choosing analysis/print commands. It would be very easy to end up with an output report that is hundreds of pages in length, making it difficult to find the desired results.


Bear in mind that the output file is just one method of obtaining output results from STAAD.Pro. The Post Processor, which is covered in detail in a different Module, is specifically for the purpose of observing and reporting analysis results. •

Close the STAAD Output Viewer window by clicking File | Exit. Be careful to select the STAAD Output Viewer’s File menu, not the File menu in the STAAD.Pro main menu.

•


•


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Module 4

-End of Module-

5-1

The Post Processor Module

5

The following topics are included in this module. 5.1 Introduction to the Post Processor.................................................... 2 5.2 Coordinate Systems for Reporting Results ...................................... 3 5.3 Sign Conventions for Reporting Member End Forces ................... 6 5.4 How to Determine if Results are Available ................................... 9 5.5 Activating the Post Processor ......................................................... 12 5.6 Displaying the Displacement Diagram ........................................... 14 5.7 Displacement and Reactions Tables................................................ 19 5.8 Beam Analysis Results .................................................................... 28 5.9 Verifying the Results ....................................................................... 44 5.10 Viewing Results with Member Query.......................................... 48 5.11 Using Structural Tool Tips to View Results .............................. 53 5.12 Labeling the Structure Diagram .................................................... 55 5.13 Individual Control of Labels ......................................................... 62 5.14 Animation ........................................................................................ 65 5.15 Plotting Output from STAAD.Pro ................................................ 69 5.16 Simple Query .................................................................................. 72


5-2

Module 5

5.1

Introduction to the Post Processor •

This module begins at the point where all of the major modeling has been completed using STAAD.Pro’s Pre Processor, analysis instructions have been issued, and the analysis has been performed.

•

The next step is to view the results of the analysis.

•

Structural analysis software can generate hundreds of pages of output results, even for relatively small structures.

•

The STAAD Post Processor is designed to assist in interpreting analysis results and creating well organized reports, complete with tables and supporting graphics.

•

An awareness of coordinate systems and sign conventions used by the program is fundamental to understanding the output.

•

STAAD.Pro incorporates a coordinate system and sign conventions typical to structural engineering and they are presented in the next two sections.


5.2

Coordinate Systems for Reporting Results •

STAAD.Pro produces three major types of output results: • • •

nodal displacements support reactions member end forces

Other types of results involving stresses on plate and solid elements will be discussed later. •

STAAD.Pro’s stiffness matrix is a global stiffness matrix. Member loads that are skewed with respect to the global axis system are resolved into their global components for the purpose of analysis.

•

However, as shown in the table below, when viewing the results of the analysis, member end forces are reported with respect to the member’s local coordinate system.

•

The following convention is used: Result Nodal displacements Support reactions Member end forces

Reference Global coordinate system Global coordinate system Local coordinate system

It is logical and convenient to express nodal displacements and support reactions in terms of the global coordinate system. It is usually logical and convenient to express member end forces with respect to a member’s local coordinate system. •

The following is a brief refresher on establishing the starting end and ending end of a member, and the orientation of a member’s local axis system. Additional information is available in Chapter 1 of the Technical Reference manual.

5-3


5-4

Module 5

Refresher on Local Coordinate System: •

The local x-axis is a line defined by the two ends of the member.

•

The positive direction of the local x-axis is defined by a line going from the starting end (node A) to the ending end (node B) of the member.

•

Each member also has a local y- and local z-axis.

•

The local x, local y, and local z axes are always mutually perpendicular, and conform to the right-hand rule; so local x cross local y equals local z.

•

The local y-axis is normally parallel to the web of a wide flange beam section, and the local z-axis is normally the major axis.

•

The actual orientation of each member’s local coordinate system (within the global coordinate system of the model) is defined by the order in which the member’s end nodes were selected and by any beta angle that may have been assigned to the member. The axes for the local coordinate systems of all members in model can be displayed as follows: Right-click in the Main Window and select Labels… from the pop-up menu, then toggle on the Beam Orientation checkbox in the Beams category and the Show Axes At Org checkbox in the General category, then click OK. Symbols indicating the orientation of the local coordinate system and showing the cross section shape will appear in the Main Window. A labeled, color-coded local coordinate axis system also appears in the Main Window. Its purpose is to provide a key to the colors of the local coordinate axis symbols, where local x = blue, local y = red, and local z = green.


The STAAD.Pro Technical Reference manual contains thorough explanations for the orientation of the local coordinate system for an individual member.

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Module 5

5.3

Sign Conventions for Reporting Member End Forces •

Results for member end forces are reported with respect to the member’s local coordinate system, as mentioned above.

•

The following statement establishes the sign convention used by STAAD.Pro for reporting axial member end forces: An axial force (F x ) at the starting end of a member acting in the positive direction of the local x-axis is considered to be a positive force. Such a force would be pushing into the member, so therefore it would be a compressive force. An axial force (F x ) at the starting end of a member acting in the negative direction of the local x-axis is considered to be a negative force. This would be a tensile force. An axial force (F x ) at the ending end of a member acting in the positive direction of the local x-axis is considered to be a positive force. This would also be a tensile force. Finally, an axial force (F x ) at the ending end of a member acting in the negative direction of the local x-axis is considered to be a negative force. This would also be a compressive force.

•

The following figure and chart summarize the sign convention for axial member end forces:

Figure 5. 1


Axial Member End Forces:

Force In Positive Local x Direction Force In Negative Local x Direction

At Starting End of Member

At Ending End of Member

Positive Sign Compressive Force Negative Sign Tensile Force

Positive Sign Tensile Force Negative Sign Compressive Force

Figure 5. 2 •

Shear forces also conform to the rule that a force in the positive direction of the local axis system is considered to be a positive force, as shown in the figure below.

Figure 5. 3 •

The moments at each end of a member are treated in a similar way in terms of the sign convention.

•

The right-hand rule is used to dictate the positive sense of rotation about each of the local axes. For example, M x , the moment about the local x-axis, is considered a positive torsion if the rotation produces a vector having the same sense as the positive local x direction, and similarly for the other moments.

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•

The following figure from Section 1.19 of the Technical Reference manual illustrates the sign convention for moments about a member’s local axis system.

Figure 5. 4 The moments shown in the figure above all represent positive bending or torsion, since they all coincide with the positive directions of the axes based on the right-hand rule.


5.4 How to Determine if Results are Available •


•

There are two ways to quickly determine if analysis results are available in a model.

•

STAAD Output toolbar button on the File toolbar:

•

Opens the output file in the STAAD.Pro Viewer when current results are available.

•

If toolbar button is “grayed out,” current results are not available.

No Results Available

Results Available Figure 5. 5

If toolbar button is “grayed out,” it could either be because an analysis has not been performed yet, or because something has changed since the last analysis was run, making the previous results invalid. •

Another way to tell whether results are available is to look at the selections in the Mode pull-down menu.

•

Click Mode in the Main Menu, and note that the Post Processing menu option is “grayed out,” meaning it cannot be activated.

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No Results Available

Results Available Figure 5. 6

Again, if the toolbar button is “grayed out,” it could either be because an analysis has not been performed yet, or because something has changed since the last analysis was run, making the previous results invalid. •

Press the esc key twice to close the Mode menu.

•

Even if an analysis has been run on a model, there are conditions that can cause the Post Processing mode to be unavailable. These include: •

Errors encountered during the analysis,

•

Discrepancies between the input file and the output results.

STAAD will try to protect the integrity of the results by deleting the results if any change is made to the input file. For example, suppose an analysis is run, and then changes are made to the model. The program will offer a warning that if changes are made, the Post Processing results will no longer be available. If you confirm that you want to make a change, the program will delete the existing analysis results, and the Post Processing mode will not be available. Even seemingly insignificant things such as opening the input file editor to add a carriage return or a comment will be interpreted as changes to the input file and will cause the output results to be deleted.


Hint: to add a comment to the input file without causing the results file to be deleted, open the input file outside of STAAD.Pro with an external text editor program such as Notepad or WordPad instead of using the STAAD editor. This can be especially helpful on a very large model that would require a large amount of time to re-analyze. •

•

STAAD.Pro will ignore anything on a line preceded by an asterisk (*) in the input file. This can be useful for: •

Creating comments within the input file for record or to help with interpretation.

•

Formatting the input file to offset or draw visual attention to a section of the file.

•

Temporarily disabling portions of the input file that may need to be added back in later.

A STAAD.Pro output file can be identified by the .ANL extension. The output file is just a text file, so it can be viewed with any text editor. If you want to make changes to a model after running the analysis, but you think you might want to keep the original analysis results, there are two options. Either: 1. Create a backup copy of the original output file, and then make revisions as necessary in the original model file, Or, 2. Create a copy of the model using File | Save As, and then make changes to the new model and let STAAD.Pro delete the associated results file created by the Save As operation. (The original model and its results file remain intact.)

•

Keep the current model open for use in the next section.

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5.5

Activating the Post Processor •

With Dataset 5_1.std still open, select Analyze | Run Analysis from the main menu. When the analysis is complete, select the Go to Post Processing Mode radio button in the STAAD Analysis and Design dialog, and then click Done.

•

The Loads page of the Results Setup dialog is used to select the load cases for which analysis results are to be viewed. By default, all the load cases in the project are selected. However, in a large structure with many load cases, it might be very cumbersome to view the results for all load cases at the same time. The Loads page provides a convenient way to work with results from only selected load cases at one time.

•

Regardless of which load cases are initially selected, it is always possible to change the selection later by using the Select Load Case command in the Results menu of the Post Processor.

•

Click the Range tab in the Results Setup dialog. This page can be used to specify particular nodes, members and elements for which analysis results are desired. By default, all members are selected. However, results can be displayed for just the members of a certain group, for the members with a given cross sectional property, or for nodes and beam numbers that fall within a given range.

•

The Increments option is used to specify the number of segments into which a member is divided for printing section forces, displacements, etc.

•

Click the Result View Options tab. This page provides access to STAAD.Pro’s automatic scaling controls.


•

Scale is the relationship between the magnitude of forces and displacements in the real structure and the units used to represent them on graphs and diagrams. Depending on the type of forces, moments, load intensities and displacements represented, the magnitude of the units will vary greatly from member to member. Scaling units are chosen to make diagrams and graphs convey the desired information concisely and in a way that is visually attractive. (More to come on this topic.)

•

STAAD.Pro has the ability to set the scaling controls automatically.

•

Remember that this option is available, but for training purposes, leave the Enable Automatic Scaling checkbox turned off.

•

It is instructional to set the scaling manually in order to demonstrate how to use the scaling commands.

•

Leave all selections in the Results Setup dialog at their default values.

•

Click OK to dismiss the dialog and enter the Post Processing mode.

•

To return to the Results Setup dialog at a later time, pull down the Results menu and click Select Load Case.

•


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5.6

Displaying the Displacement Diagram •

Ensure that the file named Dataset 5_1.std is still open. The Post Processing mode presents a new set of page and subpage tabs in the Page Control.

•

The Displacement sub-page of the Node page should currently be active.

•

When the Displacement page is active, a displacement diagram is shown by colored lines superimposed on the structure.

•

It may not be possible to see any actual displacement of the structure at this time. Instead, the displacement diagram may appear to be superimposed directly on top of the structure without any apparent deflection.

•

The appearance of the displacement diagram depends on which load case is active, and on how the diagram is scaled.

•

The current Load Case is 1:DEAD LOAD as shown in the Load Case list in the View toolbar.

Figure 5. 7 •

The current Load Case is also reported in the Status Bar at the bottom right corner of the screen.

Figure 5. 8


This load case was automatically selected by default. The only force that was applied under this load case was the structure’s own self weight. •

The diagram should be re-scaled to be able to see an exaggerated deflected shape of the structure due to the self weight loading.

•

Right-click the mouse in the Main Window.

•

Click Structure Diagrams… in the pop-up menu.

•

Click the Scales tab in the Diagrams dialog. Note: another way to display the Scales page is by selecting the Scale button on the Structure toolbar (the toolbar names are visible only when the toolbars are floating, not when they are docked). A third way to display the Scales page is by pulling down the Results menu and clicking on the Scales command.

•

Toggle on the Apply Immediately checkbox to view changes immediately. Drag the Diagrams dialog to one side if it is blocking the view of the structure diagram.

•

The Displacement scaling parameter field (under the Result Scales category) is labeled with units of “in per ft {mm per m}.”

•

A setting of 12 means that for every 12 inches {12 mm} of calculated displacement due to the current load case, STAAD.Pro will plot it as a scale 1 foot {1 meter} on the diagram.

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•

It may be that no deflection is visible on the displacement diagram at the current scale.

•

To make the deflection more apparent, click the down arrow to decrease the number in this field.

•

If the scale is reduced far enough, it will be possible to find a scale that makes the deflected shape apparent on the scale of the diagram. The concept here is that in order to increase the exaggeration of the deflected shape relative to the scale of the entire structure, the scale value should be decreased. Remember that the units on the Displacement scale can be thought of as “inches of deflection per scale foot on the diagram”. When thought of this way, it may be more intuitive to decrease the scale to emphasize the deflection. For a given deflection, the deflection diagram shows a larger apparent deflection when the scale is “1 inch of deflection per scale foot on the diagram” than when the scale is “12 inches of deflection per scale foot on the diagram”. Another way of looking at it would be to say if a structure actually deflects 0.01 inch, it can be made to look like a foot of deflection relative to the scale of the diagram by setting the scale value to 0.01; to make 0.001 inches of deflection look like a scale foot on the drawing set the scale value to 0.001, and so on.

•

Set the Displacement scale value to 0.01 in per foot {0.8 mm per m}. As the scale value is reduced, the exaggeration of the deflected shape increases with each click of the scale arrow buttons, because the Apply Immediately option is turned on.


At a scale value of 0.01 inch per foot {0.8 mm per m}, the deflected shape is definitely apparent. •

Scaling works the same for all the different types of diagrams: moments, shears, axial forces, etc. The choice of a scale value is arbitrary. Choose whatever scale value produces a good looking diagram.

•

For any given type of diagram (deflection, axial, moment, etc.) the “ideal” scale value will almost certainly be different, depending on which load case is active.

•

Click on the Loads and Results tab within the Diagrams dialog. Select 2:LIVE LOAD from the Load Case list, and click Apply. A second method of changing to Load Case 2 would be to select 2:LIVE LOAD from the list in the View toolbar, but this method requires the Diagrams dialog be closed first. Changing the load case from the Loads and Results page within the Diagrams dialog makes it convenient to quickly return to the Scales page to rescale the view for the new load case.

•

With the Deflection scale still set at 0.01 inches of deflection per scale foot {0.8 mm per m} on the drawing, the deflected shape is wildly exaggerated. This is because the displacement due to Load Case 2 is so much greater than that for Load Case 1. The scale value will have to be increased to make the deflected shape more reasonable.

•

Click back to the Scales tab in the Diagrams dialog.

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•

Click the up arrow for the Displacement scale to increase the value to 0.2 in per foot {20 mm per m} to adjust the scale for better viewing.

•

See the following commentary to explore the scaling concept a little further. Click back to the Loads and Results tab of the Diagrams dialog. Select 3:TRANSVERSE WIND LOAD ALONG GX from the Load Case list, and click Apply. Click back to the Scales tab in the Diagrams dialog. Click the up arrow for the Displacement scale to increase the value from 0.2 in per foot to 1.0 in per foot {from 20 mm per m to 100 mm per m}, and watch the change in the deflected shape with each click. The point to note here is that the change in deflected shape between a scale of 0.5 and 1.0 {50 and 100} is not nearly as much as the change from 0.2 to 0.5 {20 to 50}. This is because the deflection is really proportional to the inverse of the scale. Scale 0.2 {20} 0.5 {50} 1.0 {100}

Inverse 5 {0.05} 2 {0.02} 1 {0.01}

•

Click the OK button to close the Diagrams dialog.

•

Note that scaling controls only change the appearance of the structure diagram by scaling the way the results are drawn on the diagram. They do not change the results themselves in any way.

•



5.7

Displacement and Reactions Tables •

Ensure that the file named Dataset 5_1.std is still open.

•

Click the Post Processing tab at the top of the Main Window.

•

Click OK to accept the default settings in the Results Setup dialog.

•

The Node Displacements table appears in the Data Area on the right-hand side of the screen.

•

Note that displacements for all the nodes in the model are shown for all four load cases. This is a result of leaving the settings in the Loads page and the Range page of the Results Setup dialog set to All when first entering the Post Processing mode. The alternative would have been to specify a limited number of nodes and/or load cases to display, since, even with only 20 nodes and 4 load cases, the Node Displacements table is quite extensive. For even a moderately sized structure, the ability to limit the range of nodes, beams and load cases for which results are displayed at any given time can be very useful. This function is provided by the Results Setup dialog.

•

Click Results | Select Load Case…, and view the Loads tab.

•

Modify the load list so that only 2 LIVE LOAD remains in the Selected category. (See commentary below for step-by-step instructions.) In the Selected category, select 1 DEAD LOAD, 3 TRANSVERSE WIND LOAD ALONG GX , and

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4 LC1+LC2+LC3 by holding down the Control (Ctrl) key and clicking on each load case. Click the < button to remove the selected load cases. Now, only the 2 LIVE LOAD case remains in the Selected category. •

Click OK.

•

The Node Displacements table now only reports displacements for the 2 LIVE LOAD case.

•

Note that there are two tabs, All and Summary in the Node Displacements table. Each presents node displacement results in a different format, but in both tables, the results presented depend upon the selections made in Results | Select Load Case… | Range, and in Results | Select Load Case… | Loads.

•

The All tab of the Node Displacements table reports translations and rotations for all nodes. The first column grid table gives the node number. The second column lists the load case(s). The following three columns provide the translational displacements in each of the global X, Y and Z directions. The next column gives the magnitude of the resultant displacement. This magnitude is the square root of the sum of the squares of the X, Y and Z displacements.

To the right of the Resultant column are three more columns listing the rotational displacements for the three rotational degrees of freedom.


•

By default, the translational displacements are shown to a precision of three units to the right of the decimal place. See the commentary below for instructions to revise the precision and to change the units used in the Node Displacements table. To change the number of decimal places shown in the Node Displacements table, click View | Options. The Options dialog contains many tabs that provide access to pages of controls used to customize the appearance of the program. Click the Structure Units tab. Under the Dimensions category, note that Displacement units can be set to a variety of common unit systems, and note that the precision used to report displacements can be adjusted by varying the number of digits to the right of the decimal place. Click OK to dismiss the Options dialog. If any changes were made to units or precision, they should now be visible in the Node Displacements table. An alternate method of changing the units of the displayed numbers is to click Tools | Set Current Display Unit…, and then click the Structure Units tab.

•

Modify the load list again so that all load cases appear in the Selected category. (See commentary below for step-by-step instructions.) Click Results | Select Load Case…, and view the Loads tab. Click the category.

>> button to move all load cases to the Selected

Click OK. •

Click the Summary tab at the top of the Node Displacements table.

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•

The Summary page reports maximum and minimum translational and rotational displacements. Subject to the selections made in Results | Select Load Case… | Range and in Results | Select Load Case… | Loads, the Summary page reports maximum and minimum translations and rotations for each degree of freedom, the node where each maximum value occurred, the Load Case that produced each maximum value and the other displacements associated with that particular node and load case. For visual clarity, the extreme values are shown in bold font on the Summary page. The other values in normal font are “associated values”.

•

Note that this table is compatible with Microsoft Excel, as are all the grid tables in STAAD.Pro. Values can be copied and pasted from this table directly into an Excel spreadsheet to work with the data in Excel. To select data to copy to a spreadsheet, either: Click on the top left corner of the table to highlight its entire contents, or Click and drag in the first column to select a subset of the entire table. Note that the usual Windows selection methods are supported; i.e. Shift + click can be used to select multiple contiguous rows, Control (Ctrl) + click can be used to select multiple rows, even if noncontiguous. After the selection is made, right-click, select Copy, go to Excel, right-click and select Paste.

•

There is a second table below the Node Displacements table, labeled Beam Relative Displacement Detail.


•

This table has two tabs used to view relative displacements of beams in different formats. But in both tables, the results presented depend upon the selections made in Results | Select Load Case… | Range, and in Results | Select Load Case… | Loads. Relative displacements are reported in terms of the member’s local coordinate system. They are measured with respect to a chord through the member endpoints, so the relative displacement at the starting end and ending end will always be zero by definition.

•

The All Relative Displacements tab shows relative displacements for all beams. The All Relative Displacements tab shows x, y, z and Resultant relative displacements at the beam’s starting end, ending end, and at a number of intermediate points along the beam’s length. The number of intermediate points to be reported is dictated by the Increments setting, which can be found at Results | Select Load Case…, Range tab, Detail Tables category. When the Increments setting is set to 4, displacements are reported at the beam’s starting end, ¼ point, midpoint, ¾ point, and ending end.

•

Click the Max Relative Displacements tab.

•

This table lists maximum relative displacement values and distances from the starting end of the beam to the locations where the maximum displacements occur. Subject to the selections made in Results | Select Load Case… | Range and in Results | Select Load Case… | Loads, the Max Relative Displacements table provides results for displacements in the local x, y, and z directions as well as a resultant value. In the far right-hand column it reports the ratio of member span length to maximum displacement.

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•

Click the Reactions tab in the Page Control.

•

The Main Window should now show reactions at the two supports, for the current load case.

•

By default, reactions for all six degrees of freedom are plotted on the screen, but the display of reactions can be customized if desired.

•

Click Results | View Value… | Reactions tab.

•

Checkboxes allow individual control over the force and moment reactions to be displayed.

•

Click the Show Line checkbox and click Annotate to toggle the display of the support reactions from tabular to graphical format.

•

Click the Show Line checkbox again to deselect it, and click Annotate, and then click Close.

•

Click Select | Text Cursor. The cursor graphic changes to the special Select Text cursor.

•

Click and drag one of the reaction text boxes on the structure diagram to see how it can be relocated.

•

Click the Beams Cursor return to the normal cursor.

•

Note that the reactions for the moments on the right-hand support are listed as “Free.” This is a result of having a pinned support at the base of the right-hand column.

on the Selection toolbar to

STAAD.Pro uses this “Free” annotation to specifically indicate that that degree of freedom has been released, whereas a 0 value would indicate that the degree of freedom is restrained, but the moment or force for that particular degree of freedom happens to be 0.


In other words, at the right-hand support, the moments are listed as “Free” to indicate that there cannot be any moment at that support, as opposed to simply indicating that there is no moment at that support. •

The Support Reactions table in the Data Area has three tabs, All, Summary, and Envelope, that allow support reactions to be viewed in different forms. In all three tables, the results presented depend upon the selections made in Results | Select Load Case… | Range, and in Results | Select Load Case… | Loads.

•

The All tab displays reactions for all six degrees of freedom, at all nodes, for all load cases.

•

Click the Summary tab. The Summary tab displays the extreme reactions (max and min) for all six degrees of freedom, along with the load case that caused the extreme value, and the other reactions that are associated with that load case. The Summary table will always have twelve lines of data corresponding to max and min of Fx, Fy, Fz, Mx, My, and Mz, regardless of how many nodes or load cases exist in the model or how many nodes are selected in Results | Select Load Case… | Range or in Results | Select Load Case… | Loads.

•

For structures with multiple supports, the Summary table may never report the reactions for some of the supports, if they do not represent extreme values based on the selections made in Results | Select Load Case… | Range, and/or Results | Select Load Case… | Loads.

•

On the Summary table, the column labeled “L/C” indicates the controlling load case for each extreme. The extreme value is shown in bold font, and the associated values are shown in regular font.

•

Click the Envelope tab on the Support Reactions table.

•

The Envelope tab displays results for each node in the model.

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•

For each reported node, the Envelope tab reports the maximum positive and maximum negative reactions for all six degrees of freedom. In addition, it reports the load case that causes the extreme. The Envelope view and the Summary view differ in two ways: First, the Envelope view reports values for all nodes, where the Summary view only reports on the maxima and minima considering all nodes. Second, the Summary view reports the associated reactions from the other degrees of freedom, where the Envelope view does not provide the associated values.

•

Note that the units used to report results such as reactions, displacements, etc. can be changed on the fly. See the commentary below for a step-by-step description. To see how results could be viewed in different unit systems: Click the All tab on the Support Reactions table. Click Tools | Set Current Display Unit…. Click the Force Units page. The Force Units page contains controls for the units used to report the various types of force results. Change the units in the Force category to lb {N}, and adjust the precision to show 0 decimal places. Change the units in the Moment category to lb·ft {N-m}, and adjust the precision to show 0 decimal places. Click OK, and observe the change in the Support Reactions table.

•

The Statics Check Results table provides a tabular presentation of the equilibrium check on the structure.


This is the same information that can be viewed in the Output File by including PRINT STATICS CHECK in the PERFORM ANALYSIS command. However, this table just presents the information in a more concise format. •


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5.8

Beam Analysis Results •

Dataset 5_1.std should still be the current file.

•


•


•

Click the Beam page.

•

The Forces sub-page is used to plot force and moment diagrams on the structure and work with the Beam End Forces grid tables.

•

The tables and the structure diagrams are interactive.

•

Click on the left-hand column in the structure diagram. Note that the corresponding member information becomes highlighted in the Beam End Forces table and the Beam Force Detail table.

•

Click on any other line in either of the two current tables in the Data Area and note that the corresponding member becomes highlighted in the structure diagram.

•

Let’s explore the distinction between the Beam End Forces table and the Beam Force Detail table.

•

To illustrate the difference: •

Make 2 LIVE LOAD the only selected load case. (See commentary below for step-by-step instructions.) Click Results | Select Load Case…. Click the double left arrow to remove all load cases, then click on 2 LIVE LOAD to highlight it, and click the single right arrow to move it to the Selected list. Click OK.


•

Set force units to display zero decimal places. (See commentary below for step-by-step instructions.) Click Tools | Set Current Display Unit… Click Force Units tab. Set the Force item to kip {kN} and the Show dec places value to 0. Click OK.

•

Click the top chord member just to the left of the ridge (member #23).

•

Beam End Forces table:

•

•

Member end force Fx (axial force) at the starting end (node #6) is positive 61 kips {276 kN}.

•

Member end force Fx at the ending end (node #16) is negative 61 kips {276 kN}.

•

Therefore the member is in compression, which makes sense for a top chord member under this type of loading, and the magnitude of the compression is 61 kips {276 kN}.

Beam Force Detail table: •

The value of Fx (axial force) for member #23 is consistently positive 61 kips {276 kN} at all five stations cut along the length of the member.

•

The magnitude of the force is consistent between the two tables. This is as expected.

•

This comparison establishes the sign convention used in the Beam Force Detail table for axial forces: Compressive axial forces are considered positive forces in the Beam Force Detail table.

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•

The Beam End Forces table reports the forces at member ends. Therefore, for a simple truss member, the axial member end forces in the Beam End Forces table at opposite ends of the member should be equal in magnitude and opposite in algebraic sign.

•

The Beam Force Detail table reports beam forces at sections, rather than member end forces. Therefore, for a simple truss member, the axial member forces reported in the Beam Force Detail table are all expected to be of a consistent algebraic sign.

•

Reselect all load cases. (See commentary below for step-bystep instructions.) Click Results | Select Load Case…. Click the double right arrow to re-select all load cases. Click OK.

•

There are three tabs in the Beam End Forces grid table: •

The results presented on each of the tabs in the Beam End Forces grid tables depend upon the selections made in Results | Select Load Case… | Range, and in Results | Select Load Case… | Loads.

•

The All tab displays beam end forces for both ends of all members.

•

Click the Summary tab. This tab reports exactly twelve different conditions consisting of the maximum and minimum beam end forces for all six degrees of freedom, in addition to the load condition that generated the controlling values, and the associated member end forces for all of the other 5 degrees of freedom for that particular loading condition.


•

•

Click the Envelope tab. This tab reports the envelope of member end forces by providing the maximum positive and maximum negative member end forces for all member ends, along with the name of the loading condition that causes the envelope value.

The units used to display results in the Beam End Forces and Beam Force Detail tables can be modified if desired. (See commentary below for step-by-step instructions.) Click Tools | Set Current Display Unit…. Click the Force Units tab in the Options dialog. Use the list boxes to select the desired units for the different types of forces. Adjust the associated precisions as necessary. Click OK, and note the change in the Data Area.

•

The Main Window is currently showing a bending moment diagram for the entire structure, although it may not be obvious.

•

As was demonstrated earlier with the Displacement diagrams, the issue here is one of selecting an appropriate scale.

•

Click View | Structure Diagrams… , then select the Labels tab.

•

In the General category, note the options to Show Axes Window and Show Diagram Info. Ensure that both options are selected and click OK. The equivalent keyboard “hotkey” to Show Diagram Info without leaving the Main Window is Shift + G.

•

Note that these settings provide: •

A coordinate axis system for reference in the lower left corner of the Main Window, and

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•

A line of text in the lower right-hand corner that indicates the Active Load case and the force currently being plotted on the Structure Diagram.

•

Click View | Structure Diagrams… , then Loads and Results tab.

•

Select 2: LIVE LOAD in the Load Case category.

•

Select Bending zz in the Beam Forces category. Note the other forces that are available to be plotted as well.

•

Click the Scales tab, and activate the Apply Immediately checkbox in the upper right-hand corner of the dialog.

•

Set the Bending Z scale to 150 kip·in per ft {50 kN·m per m}, and click OK. (If it is necessary to change the current units system, see the commentary below.) Click Tools | Set Current Display Unit…. Click the Force Units tab in the Options dialog. Use the list boxes to select the desired units for the different types of forces. Adjust the associated precisions as necessary. Click OK. The Structure Diagram should now display a diagram of the bending moments about the local z axis at a scale that makes the diagram clearly readable.

•

To properly interpret a bending moment diagram in STAAD.Pro : STAAD.Pro always draws the bending moment diagram on the tension side of the member.

•

To change the type of diagram that is being displayed:


•

Right-click anywhere in the Main Window and select Structure Diagrams… from the pop-up menu.

•

Click on the Loads and Results tab.

•

Choose the desired type of diagram by placing a check in any of the options for the common types of force diagrams listed in the Beam Forces category. Note that more than one type of diagram can be displayed at one time, and that each diagram can be displayed in a characteristic color on the structure. The colored boxes to the right of each item in the Beam Forces category indicate the color that will be used for each type of diagram. To change any of these colors, just click on the box. A standard Windows color palette opens to offer a variety of color options.

•

To demonstrate, select the Axial forces checkbox in addition to Bending zz .

•

Click the Diagram radio button.

•

Click the color palette box labeled “C” for Compression, select a blue color and click OK.

•

Click the color palette box labeled “T” for Tension, select a green color and click OK.

•

Click OK to dismiss the Diagrams dialog.

•

The Structure Diagram should now show a diagram of Axial forces superimposed on Bending Z moments.

•

Click on the Stresses sub-tab of the Beam page in the Page Control.

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•

The view window will be split into four parts. The topmost window is referred to as a “splitter window”, because it has a “splitter” or separator bar that can be moved from side to side.

•

The window in the lower left-hand corner displays the Whole Structure diagram.

•

Click on beam number 1, the bottom chord member immediately to the right of midspan.

Figure 5. 9 •

The Select Section Plane dialog opens.

•

The left side of the splitter window displays the selected member in 3D.

•

The right side of the splitter window shows the combined stress of the selected member on a cross section view. Combined stress is the algebraic combination of the stresses resulting from FX, MY and MZ. Positive values represent compression, and negative values represent tension.

•

The location of the section is indicated by the yellow rectangle in the left side of the splitter window, and can be adjusted by dragging the slider in the Select Section Plane dialog.


•

Click the Display Corner Stress checkbox in the Select Section Plane dialog.

•

Click and drag the slider in the Select Section Plane dialog, and note that the corner stress values change continually as the slider is moved along the length of the member. The splitter window can show the stress distribution for only one member at a time. The Display Legend checkbox in the Select Section Plane dialog can be used to display the combined stress range and associated color gradient.

•

The Select Profile Point category in the Select Section Plane dialog provides tools to determine combined stresses at specific points on the cross section and to record those values in a table if desired. A Profile Point is defined by its local y-axis coordinate and local z-axis coordinate, and must fall within the outline of the cross section to be valid. Profile Points can either be defined by keying in coordinate values in the Y Point and Z Point fields, or by clicking on the section with the cursor. Once a valid Profile Point has been defined, it appears as a small green dot on the cross section in the right side of the splitter window. The coordinates of the Profile Point and the combined stress value are displayed in the lower left corner of the right side of the splitter window. To save the data for a Profile Point, click the Add Stress to Table button in the lower right corner of the Select Section Plane dialog. The data for all saved points is accessible from the Profile Stress Points tab of the Beam Combined Axial and Bending Stresses table.

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For each Profile Point added to the table, a new line is created in the table, and the following data is saved: • • • • • • •

Beam number Load case number Location of section along length of member Location of point of interest in y-z plane of section Magnitude of axial force Magnitude of both bending moments Combined stress value at point of interest

•

When the Stresses sub-page is active, the Whole Structure diagram in the lower left corner displays the structure with the Beam Stress diagram superimposed on it.

•

If the current scale is not set to view the diagram clearly, see the following commentary. To adjust the scale of the Beam Stress diagram, right-click in the Whole Structure diagram, and click Structure Diagrams… in the pop-up menu. Click the Scales tab, and check the Apply Immediately checkbox in the upper right-hand corner. Verify that the units for the Beam Stress category are currently set to psi {kPa}. (If the current unit system is not displaying Beam Stress in units of psi {kPa}, close the Diagrams dialog temporarily. Click Tools | Set Current Display Unit…. Click the Force Units tab in the Options dialog. Use the Stress list to set the units to psi {kPa}. Click OK. Then return to the Scales tab of the Diagrams dialog as described above.) Set the Beam Stress scale value to 8000 psi per ft {100000 kPa per m}in the Results Scales category. Click OK.


Recall that in order to increase the size of the stress diagram with respect to the structure, the value of the scaling parameter should be decreased. •

Note that the Beam Stress diagram is displayed in two colors to distinguish compressive stress from tensile stress.

•

By default, the compressive stress is shown in red and the tensile stress is shown in blue, but these colors can be modified if desired. See the commentary below for step-bystep instructions. To change the colors used to display compressive stress and tensile stress: Right-click in the Whole Structure diagram, and click Structure Diagrams… in the pop-up menu. Click the Loads and Results tab in the Diagrams dialog. Locate the Stress option in the Beam Forces category. Click the color palette box labeled “C” for Compression, select the desired color and click OK. Click the color palette box labeled “T” for Tension, select the desired color and click OK. Click OK to dismiss the Diagrams dialog.

•

Shifting focus to the Data Area, note the table labeled Beam Combined Axial and Bending Stresses.

•

This table reports combined axial and bending stresses as the algebraic combination of the stresses resulting from FX, MY and MZ.

•

The layout of this table is similar to other results tables in that:

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•

It has different pages to display the combined axial and bending stresses in different formats, and

•

The results presented on the different tabs depend upon the selections made in Results | Select Load Case… | Range, and in Results | Select Load Case… | Loads.

•

The All page shows the stresses for all members in the model, for all load cases.

•

Cross sectional stresses are reported at both ends as well as at multiple intermediate points along the length of each beam. The number of increments used for determining the intermediate data points can be adjusted as follows: Click Results | Select Load Case... . Click the Range tab. Enter the desired number in the Increments field in the Detail Tables category. (Valid range is 2 to 12.) Click OK.

•

The stresses are reported at the four corners of the cross section. The corner numbers STAAD.Pro uses to identify the corners of various typical cross sections are shown in the following figure.


Figure 5. 10 •

The maximum compressive and tensile stresses at each cross section are also reported.

•

Tensile stresses are reported as negative values, and compressive stresses are considered positive. This is consistent with the sign convention for axial forces discussed earlier. For more information on the sign conventions used for reporting member stresses, please see Section 1.19 of the STAAD.Pro Technical Reference manual.

•

Click the Max Stresses tab.

•

The Max Stresses page reports the magnitude and locations of the maximum tensile and compressive stresses for each load case on every member in the model.

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•

The third tab called Profile Stress Points reports stresses at user-defined points on the cross-section as demonstrated earlier.

•

Click the Graphs sub-page.

•

Ensure that 2: LIVE LOAD is still selected in the Active Load list in the View toolbar.

•

Select member number 1 . This is the bottom chord member immediately to the right of mid-span.

Figure 5. 11 •

The corresponding bending moment diagram, shear diagram and axial force graphs for the selected member are displayed in the Data Area on the right side of the screen.

•

The bottom graph is labeled “Fx”, implying axial load. The graph indicates a constant value of -57.3 kips {-261 kN}, which implies tension. Tension makes sense for the bottom chord of a truss subject to 2: LIVE LOAD.

•

The top and middle graphs are currently blank.

•

To interpret why they are blank, display Beam Orientation and the key to the local axis colors. For step-by-step instructions see the commentary below.


Right-click in the blank portion of the Main Window and click Labels… from the pop-up menu. Click Beam Orientation in the Beams category. (Note the keyboard “hotkey” for this option is Shift + O.) Click Show Axes At Org in the General category. (Note the keyboard “hotkey” for this option is Shift + I.) Click OK. •

Note the orientation of the local axes of member number 1. •

(Blue) Local x points to the right on the screen.

•

(Red) Local y points out of the screen.

•

(Green) Local z points down.

•

These orientations are the result of the beta angle of 90° that was applied to this member in the modeling stage.

•

Now note that the top graph is labeled “Mz”, moment about the local z-axis, implying moment about an axis that points straight down.

•

2: LIVE LOAD is a downward-acting load due to gravity, so there should be no moment about a vertical axis in member number 1 as a result of this load case.

•

Therefore a blank “Mz” graph makes sense.

•

Right-click inside the “Mz” graph and click Diagrams… from the pop-up menu. Note that Bending zz is currently selected, corresponding to the display of the “Mz” graph.

•

Click the Bending yy checkbox to view the bending moment in this member due to the applied live load.

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•

Note that it is not necessary to deselect the Bending zz checkbox in order to select Bending yy. This makes it possible to superimpose the graphs of multiple forces at one time. More to come on this topic…

•

Click OK.

•

The top graph is now labeled “My” and “Mz” as a result of having both options selected. The horizontal scale is graduated in units of feet {meters}, and the x-coordinate of the point of maximum moment is automatically indicated for convenience, along with magnitudes of maximum moments. The vertical scale is automatically set to maximize the graph.

•

Right-click inside the “Fy” graph in the middle window, and click Diagrams… from the pop-up menu.

•

To view a more appropriate shear diagram for this member and its current loading, note that the member’s (green) local z-axis is oriented in the direction of the applied load (downward).

•

Click Shear zz, deselect Shear yy, and click OK.

•

The middle graph now displays a shear force diagram labeled “Fz”, which makes sense for the applied loading.

•

Back to the concept of superimposing more than one force on a graph at one time.

•

Assume that the goal is to view the shear force “Fz” superimposed on the bending moment “My” in the graph in the top window.

•

Right-click on the graph in the top window and click Diagrams… from the pop-up window.

•

Leave Bending yy selected, but deselect Bending zz and click Shear zz.


Note that the color swatches indicate the colors that will be used to plot the selected graphs. To change the colors that will be used, click on the swatches to open color palettes for each of the two selected forces, and choose colors from the palettes as demonstrated earlier. •

Click OK.

•

Although both the shear and moment diagrams are being graphed, it is immediately obvious that the inconsistency in the unit scales makes for a very flat shear diagram.

•

Sometimes the appearance of a graph can be improved by changing the force units used to plot the diagram.

•

Change the units for the moment graph to kip·ft {N·m} and note the difference. See the commentary below for step-bystep instructions. Click in the Main Window, so that the Tools option will become available in the Main Menu. Click Tools | Set Current Display Unit…. Click the Force Units tab in the Options dialog. Set the units for Moment to kip·ft {N·m } then click OK.

•

Now both the shear and the moment diagrams are clearly visible on the same graph.

•


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5.9

Verifying the Results •

Ensure that the file named Dataset 5_1.std is still active.

•


•


•

Before exploring any more features for displaying tables, diagrams, etc., let’s take a few minutes to examine some of the results from the steel design project to verify that they make sense.

•

This is an opportunity to confirm that the output from the program is as expected, based on the input provided: geometry, member properties, beta angles, member specifications, etc.

•

Click the Beam page.

•

Click the left-hand column of the structure (member #35). The corresponding row in the Beam End Forces table is highlighted.

•

Set the units for Force to kips {kN} with three decimal places, in order to validate the results. See the commentary below for step-by-step instructions. Click Tools | Set Current Display Unit…. Click the Force Units tab. Ensure that the Force list is set to units of kip {kN}, and use the up and down arrows to show 3 decimal places. Ensure that the Moment list is set to units of kip·ft {kN·m}, and use the up and down arrows to show 3 decimal place. Click OK.


•

Refer to the Beam End Forces table, and look at the results for member 35, for Fx, Load Case 1 DEAD LOAD.

•

Notice that the forces at nodes 15 and 20 are not equal and opposite.

•

This relates back to that fact that the load case under consideration is the self-weight of the structure, and also that the force under consideration is the axial force in a verticallyoriented member.

•

The difference between the two forces is due to the self-weight of the column.

•

Now click the right-hand column with the Beams Cursor.

•

Using only the Beam End Forces table, determine which node is at the top of the column and which is at the bottom.

•

Recall that the support at the bottom of the right-hand column is a pinned support. The node at the bottom of the column will be the one at which there is no moment.

•

Therefore node 11 must be the bottom node. Another way to distinguish the top node from the bottom using only the Beam End Forces table would be to compare the Fx (axial) forces for the self-weight case as described above.

•

Now click the left-most member of the bottom chord of the truss.

•

Again, using only the Beam End Forces table, determine which node is at the left end of the member and which is at the right.

•

Recall that all bending moments were released at the left end of this member.

•

Node 14 indicates at least some non-zero moments, therefore node 15, for which the moment is always zero, must be the node at the left end of the member.

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Verify by double-clicking this member (beam number 22) to open the Member Query dialog. The Releases category indicates releases for MX, MY, and MZ for the End node (which we already know to be the node at the left end). The table of coordinates in the center of the dialog always lists beam nodes in order; starting node in the first line, ending node in the second line. Therefore the ending node is node 15. Therefore node 15 is the left node. This could also be confirmed just by observing that node 15 is the left-hand node based on the X-Coord values in the table, too. •

This is a good way to verify that the program is giving the results we expect.

•

Notice also that the Beam End Forces in the Fx direction do add up to 0 for this member. That is because the self-weight does not act in the Fx direction for this member.

•

Now click member number 1, which is just to the right of mid-span in the bottom chord of the truss.

•

Notice in the Beam End Forces table that this member has moments acting about its Y-axis, where other nearby members have moments acting about their Z-axis.

•

The reason relates back to the fact that member number 1 was assigned a beta angle of 90° for the purpose of seeing how it affected the results.

•

Press Shift + O to turn on Beam Orientation.

•

Press Shift + I to Show Axes At Org (Origin).


•

Most of the bottom chord members are oriented such that their (green) local z-axes are parallel to the global Z-axis. However, member number 1 is unique, because its (red) local y-axis is parallel to the global Z-axis.

•

It now makes sense that vertical forces caused by member selfweight or applied live load would cause bending about the local y-axis of member number 1 due to its beta angle. The results are consistent. The bending forces in this planar structure are all about the same global axis, but since member forces are reported in terms of the members’ local axis system, the program reports bending about a different local axis for the one bottom chord member that has been oriented differently from the others.

•


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5.10

Viewing Results with Member Query •

Ensure that Dataset 5_1.std is still the active file.

•


•


•

Press Shift + O to turn on Beam Orientation.

•

Press Shift + I to Show Axes At Org (Origin).

•

The Member Query function provides a powerful way to view results for individual members.

•

Member Query is accessed by double-clicking on a member of interest. An alternate way to access Member Query is to click on the member of interest, and then click Tools | Query | Member.

•

Double-click on member number 1, the bottom chord member just to the right of mid-span. The dialog that pops up is the same Member Query that is available in the Pre Processing (Modeling) mode.

•

Now that an analysis has been performed, the Member Query dialog is populated with more information than just the original geometry and property data.

•

In addition, analysis results are now available in the Member Query dialog through two new tabs that were not present before: Shear Bending and Deflection. The Shear Bending tab doesn’t literally mean “shear bending”. It is just written that way to save “screen real estate”.


•

Click the Shear Bending tab. This tab provides access to shear and bending results.

•

The top half of the dialog contains a diagram for the selected beam.

•

The type of diagram displayed is controlled with the Selection Type category in the lower right corner of the dialog.

•

Select 2:LIVE LOAD in the Load Case list.

•

Four types of diagrams are available from the radio buttons:

•

•

Bending about local z axis

•

Bending about local y axis

•

Shear force along the local y axis

•

Shear force along the local z axis

Click the Bending-Y radio button. Based on the beta angle of member number 1, the diagram for bending about the local y-axis should be interesting.

•

The bending moment diagram is now displayed. Note that the bending moment diagram indicates values of bending moment at each end, and it provides x coordinates for the two points of inflection.

•

The Dist field directly above the Selection Type category is linked to the slider bar below the beam diagram. Both provide a method to enter the distance from the starting end to a point of interest on the beam.

•

The value of the shear and bending moment at the location of interest is displayed in the boxes labeled Fz and My.

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Note that the labels of these boxes changes based on the selection made with the radio buttons in the Selection Type category. •

A table of distances vs. member forces is provided in the category labeled Section Forces. 13 distance values divide the beam into 12 equal-length segments. The corresponding shear and bending moment at each location is given in the table. The distance values can be edited within this table, and STAAD.Pro will calculate the shear and bending at the distances entered.

•

Click on the Deflection tab in the Member Query dialog.

•

The Deflection page provides access to deflection diagrams and data, and the operation is very similar to the Shear Bending page.

•

Select 2:LIVE LOAD in the Load Case list.

•

The Selection Type category offers radio buttons to specify the direction of interest and to differentiate between Global Deflection or Local Deflection.

•

Select Global Deflection and Y Dir.

•

The diagram indicates downward deflection at each endpoint of the member.

•

This makes sense based on the uniform distributed Live Load in the global –Y direction that causes deflection of the truss as a whole.

•

The diagram also indicates some additional deflection near the mid-span of the member.

•

This represents the deflection of this individual member with respect to its own endpoints.

downward


•

Now select Local Deflection. disappears.

The deflection diagram

This makes sense, because the direction is still set to Y Dir. Due to the beta angle applied to this member, its local y-axis is perpendicular to the gravity direction, so 2:LIVE LOAD causes no deflection about the member’s local y-axis. •

Click the Z Dir radio button.

•

The deflection diagram now indicates a deflected shape that has zero deflection at the endpoints.

•

This makes sense, because it is specifically a Local Deflection diagram, meaning that it reports deflections of the selected member as if the member endpoints had no translation. In other words the horizontal line in the diagram can be thought of as the straight-line chord that connects the two endpoints of the member, and the deflected shape is shown with respect to that straight line.

•

The deflected shape also implies tangents with nearly zero slope at the two endpoints.

•

This is logical due to the assumed continuity of member number 1 with the adjacent bottom chord members.

•

The diagram lies entirely above the horizontal line. Is this contrary to the shape of the Global Deflection diagram?

•

The answer lies in the fact that this diagram is not literally a physical representation of the deflected member, but rather it is a graph of the deflection in the local z direction.

•

When interpreted this way, the positive values in the graph imply deflection in the positive local z direction, which is downward in the model, so the results are consistent.

•

The Deflection tab provides the ability to select the load and to specify a point of interest by its distance from the starting end.

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•

A table of displacement results is provided in the form of displacement versus distance from the starting end. A steel design has not yet been performed for this structure, so at present, the results are based on an analysis of members whose properties have been explicitly specified. If the program had been requested to perform a steel design, a tab labeled Steel Design would be displayed in the Member Query dialog. The Steel Design tab provides access to a page of information on steel design results for the member including critical load, Pass/Fail status, design ratio, design code, governing clause, etc. Similarly, after performing a concrete design, a Concrete Design tab would appear in the Member Query dialog.

•

Finally, the Member Query dialog is modeless, meaning that it can be left open and its focus can be shifted by doubleclicking on another member, at which time it will display the properties and results of the newly selected member.

•

Click Close to dismiss the Member Query dialog.

•

Press Shift + O and Shift + I to turn off the Beam Orientation indicators and the reference axis at the origin.

•



5.11

Using Structural Tool Tips to View Results •

Ensure that the file named Dataset 5_1.std is the currently active model.

•

The model should still be in the Post Processing mode from the previous section.

•

Ensure that the Graphs sub-page of the Beam page is currently active.

•

With the Beams Cursor active, hover the cursor over the column at the left end of the model to see an example of Structural Tool Tip.

•

The Structural Tool Tip, or Bubble Help as it is also called, displays some information about that member.

•

Now that an analysis has been performed on the model, Structural Tool Tips can be used to display certain analysis results.

•

Click View | Structural Tool Tip Options….

•

Assume the goal is to have member end forces displayed in the Structural Tool Tips.

•

To do this, click the Beam item under the Tool list in the Tool Tip Options dialog.

•

Click the + (plus) symbol beside the End Forces option in the Options category to display all of the End Forces options.

•

Click the End Forces checkbox to get a check mark in the End Forces box, the Starting box, and all of the options within the Starting category. Note that toggling the End Forces checkbox automatically toggles the Starting and Ending checkboxes as well.

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•

Click OK.

•

Now, hover the Beams Cursor over any member.

•

Structural Tool Tips now include the member end forces for the currently active load case.

•



5.12

Labeling the Structure Diagram •

Dataset 5_1.std should be the currently active model.

•

Post Processing mode should be active.

•

2:LIVE LOAD should be the active load case.

•

Assume the goal is to display the nodal displacements on the structure diagram.

•

Click the Node page, and then click the Displacement subpage in the Page Control.

•

Click Results | Scale….

•

Click the Apply Immediately checkbox in the upper right corner of the Scales page.

•

Set the Displacement scale to 0.2 inches per foot {20 mm per m} in the Results Scales category, and then click OK. The deflected shape of the model should be more apparent at this scale.

•

Click Results | View Value….

•

This Annotation dialog contains 4 tabs: Ranges, Beam Results, Node and Reactions.

•

The Ranges tab is used to select which beams and nodes will have their results displayed. By default, all the members are selected. However, the Ranges tab can be used to display results for only: •

Members of a certain group,

•

Members with a given cross sectional property, or

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•

Nodes and beams with numbers that fall within a given range.

Notice the “grayed out” option labeled View. If saved views existed in this model (using View | View Management | Save View…), the View option would be active, offering the ability to select all members in a given view for annotation simply by selecting the name of the saved view. The Ranges page is almost identical to the Range page in the Results Setup dialog. •

Click the Beam Results tab.

•

If beam results are desired, this tab can be used to select which types of results will be displayed.

•

Click the Reactions tab.

•

This tab is used to select the degrees of freedom for which reactions will be displayed. The Diagram category provides the option to view reactions in tabular or graphical format. If graphical format is chosen, then scaling controls are available to adjust the appearance of the graphics.

•

Click the Node tab.

•

This tab is used to select the global directions for which nodal displacements will be displayed.

•

Click the Global Y checkbox on the Node page, and then click the Annotate button.

•

Click Close to dismiss the Annotation dialog. If annotation is not displayed: •

Verify that a Node Displacement diagram is currently being shown.


•

Verify that the None radio button has not been selected on the Ranges page of the Annotation dialog.

•

Press Shift + N to turn on node numbers.

•

Press Shift + B to turn on beam numbers.

•

Now that we have decided what to display, let’s explore the options we have to control how things are displayed.

•

Right-click the mouse in the Main Window, and click Labels… from the pop-up menu. We have already seen many examples of how the Labels page can be used to affect how things are displayed on the screen.

•

Click the Loads and Results tab of the Diagrams dialog.

•

This tab can be used to change any of the colors on the diagrams by clicking the color swatch for the function.

•

By specifying characteristic colors for each type of results available, the user can establish at-a-glance recognition of what type of results are being displayed. For example:

•

•

Shear and bending forces can be assigned their own individual colors for each degree of freedom.

•

Tension and compression can be differentiated by colors.

•

Loads, deflections and mode shapes can also be assigned distinctive colors.

Options are available to specify whether the beam forces diagrams are to be hatched, filled with a solid color, or outlined.

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•

Settings such as color options, current display units and precision are saved in an INI file and in the Windows Registry. Therefore: •

When one model is closed and another model is opened, the same settings will be applied to the new file.

•

The display settings on one engineer’s workstation can be completely different from the settings on another engineer’s workstation, even for the same STAAD.Pro model.

•

Click the Cancel button to dismiss the Diagrams dialog.

•

Click View | Options.

•

The Options dialog is used to control the appearance of annotation on the structure diagram such as font, size, position, etc. The use of this dialog to set the appearance of node and beam labels is covered in depth in a different Module.

•

Click the Node Labels tab.

•

This page offers controls that affect the style, alignment, and font used to display node numbers. For example: Click Font. Choose Blue in the Color list. Click OK in the Font dialog. Click Apply in the Options dialog.


Note that the effect is to change the color used to display the node number labels. •

Click the Beam Labels tab.

•

This page offers controls that affect the style, alignment, and font used to display beam numbers and section references. For example: Click Font. Choose Bold Italic in the Font Style category. Click OK in the Font dialog. Click Apply in the Options dialog. Note that the effect is to change the font style used to display the beam number labels.

•

Click the Annotation tab.

•

This page offers controls that affect the style, alignment, and font used to display all of the different types of results annotation that are available. In this sense, “results annotation” pertains to the options offered in the tabs of the Annotation dialog as described above. It includes things like reactions, beam shears and moments, and nodal displacements. There may be a tendency to try to use the Beam Labels and Node Labels tabs to control the annotation of beam and node results. Instead, remember that results annotation settings are controlled from this separate page within the Options dialog, called the Annotation page.

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The separation of these controls was provided so that font (and related display settings) could be used to distinguish between results annotation and other labels on the diagrams. For example: Click Font. Choose 18 in the Size category. Click OK in the Font dialog. Click Apply in the Options dialog. Note that the effect is to change the font size used to display the annotation text, which is currently set to display nodal displacement in the Global Y direction. •

In the upper left corner of the Annotation page is a list box labeled Style.

•

The effect of the two Style settings is to either append a units indicator to the end of every results value, or to not display the units. If the Diagram Info label was turned off in the Labels page, it might be helpful to append the units indicator to all results on the screen. On the other hand, including the units label in the annotation can sometimes cause the structure diagram to become cluttered with too much annotation. In this case it might be preferable to turn the Diagram Info label on, and annotate the structure with the result values only, since the Diagram Info reports the units.

•

Set the Style to 123.4, and then click OK.


•

The structure diagram now shows nodal displacement values for deflection in the global Y direction, and the Diagram Info label indicates that the units are inches.

•


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5.13

Individual Control of Labels •


•


•


•

The Displacement sub-page of the Node page will be active by default.

•

With the various types of annotation that can be added to the structure diagram, the display can become very cluttered.

•

To neaten up the display, certain types of labels can be individually turned on or off.

•

The program allows individual control for: •

beam numbers,

•

node numbers,

•

plate numbers and

•

solid numbers.

•

Four cursors are provided for the purpose of selecting individual labels to turn on or off.

•

These cursors are located on a small toolbar on the left side of the screen called the Labels toolbar.


Figure 5. 12 •

In order to use the Labels Cursors, at least some labels must be turned on, and the program has to be instructed to “Use partial labeling mode.”

•

To turn labels on, right-click in the Main Window, and then click Labels… from the pop-up menu.

•

Click the checkbox to display Beam Numbers in the Beams category.

•

Instructing STAAD.Pro to “Use partial labeling mode” is a two-step process: •

Click the Always Use Current Label Settings radio button near the bottom of the Diagrams dialog.

•

Click the Use partial labeling mode checkbox even further down on the Diagrams dialog. Note that this option is grayed out until Always Use Current Label Settings is selected.

•

Click OK.

•

Click the second cursor on the Labels toolbar, the Turn ON/OFF Individual Beam Label cursor.

•

Now click on any individual beam in the model. Clicking once turns the beam label off, and clicking again turns the label back on.

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•

The normal operation of the Labels cursors may sometimes require redrawing the screen to completely remove a label.

•

If this happens (most notable on vertical members) a shortcut is to roll the wheel on the mouse forward and then backward. This forces a quick redraw of the screen by zooming in and back out.

•

Press the esc key to turn the Labels Cursor off.

•



5.14

Animation •


•

Post Processing mode should be active.

•

Select 1:DEAD LOAD as the active load case.

•

Animation can be used to dynamically display the movement of the structure due to forces acting upon it.

•

It can be a very effective way of displaying and checking the results of an analysis.

•

Animation can often reveal problems with the model. For example if there is no connection between members at a location where a connection was intended, this will become immediately apparent when animation of the deflections is viewed.

•

Click the Animation tab in the Page Control. The Diagrams dialog opens with the Animation page active.

•

Click the Deflection radio button in the Diagram Type category, and then click the Apply button.

•

The structure diagram is now moving, but the deflection may not be visible due to the current scale.

•

Click the Scales tab in the Diagrams dialog.

•

Click the Apply Immediately checkbox in the upper right corner of the dialog.

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•

In the Result Scales category, set the value of the Displacement field to 0.01 inches per foot {0.8 mm per m} using the arrows beside the field. The deflection should be easily visible at this scale.

•

Click the Loads and Results tab.

•

Select 3:TRANSVERSE WIND LOAD ALONG GX in the Load Case list, and then click Apply. The deflection is dramatic at this scale.

•

Click the Scales tab again.

•

Increase the value in the Displacement field to 0.1 inches per foot {8 mm per m}. To review: the concept with scaling in STAAD.Pro is that the scale can be thought of as “number of force units or deflection units per scale unit of length measure on the screen.” Therefore larger scale values result in smaller graphical deflections on the screen, and vice versa. The deflection should be more reasonable at this scale, but the animation may be moving too fast to interpret easily.

•

Click the Animation tab in the Diagrams dialog, and adjust the Target FPS to 5 frames per second.

•

Click Apply and observe the animation. The structure should now deflect and return to its original shape more slowly, but the animation is not smooth.

•

Set the value of the Extra Frames parameter to 20, and then click the Apply button.


This should make the animation appear more fluid and smooth, but slow to complete a full deflection cycle. •

Increase the Target FPS setting to 40 and click Apply.

•

Now set the Extra Frames parameter to its maximum value of 99, and the Target FPS to its maximum value of 99 frames per second. At these settings, the animation will be very smooth, but at the expense of processing time. Not much of an issue for a model of this size.

•

Note that in the current animation, both columns are rotating as rigid bodies, showing no deformation along their lengths.

•

Click the Section Displacement radio button in the Diagram Type category, and then click OK.

•

Now note the difference in the appearance of the deformed columns. The column on the left displays reverse curvature due to the fact that it was modeled as being fixed at the support, and because there is continuity between the top of the column and the top chord member. The column on the right displays single curvature because it is pinned at the support but there is continuity between the top of the column and the top and bottom chord members.

•

To stop the animation, press the esc key twice. To reopen the Animation page, click again on the Animation tab in the Page Control. Another way to access the Animation page is to right-click in the Main Window, select Structure Diagrams… from the pop-

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up menu, and then click on the Animation tab in the Diagrams dialog. A third way to access the Animation page is to pull down the Results menu and select the Animation… command. Using this method, note the icon that looks like a television set to the left of the Animation command in the pull-down menu. When an icon is displayed next to a menu item in a STAAD.Pro menu, it indicates that there is a corresponding toolbar button on one of the STAAD.Pro toolbars that performs the same function as selecting the command from the menu. The Animation toolbar button is located on the Results toolbar, and it provides another convenient way to quickly open the Animation page. Note that the toolbar names are not visible when the toolbars are docked. To find the name of a toolbar, place the cursor over the toolbar at a location where it does not have any buttons, click and hold the left mouse button, and then drag the toolbar out into the Main Window and release the left mouse button. The toolbar will float in the Main Window, and the toolbar name will be displayed. To dock the toolbar again, place the cursor over the toolbar’s title bar, click and hold down the left mouse button, drag the toolbar back to the location where it was originally docked, and then release the left mouse button. •



5.15

Plotting Output from STAAD.Pro •

STAAD.Pro offers a variety of options for plotting output. These different options are explored in detail in a different module, but the following is a brief list of the plotting options that are available. •

The Print Current View option is available from the Print toolbar.

•

Print Preview Current View is also available from the Print toolbar.

•

The Take Picture option is available from the Print toolbar.

When images are captured with the Take Picture option, they then get incorporated into printed output through the Report Setup tool, which is accessible from the Print toolbar as shown below.

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•

The Export View option, also available on the Print toolbar, provides the ability to export a view or the screen to a graphic image file.

•

The Copy Picture option is available from the Edit item in the Menu Bar.

Graphic images captured using the Copy Picture option can be pasted into a program capable of handling graphics such as Microsoft Paint, Adobe Photoshop, etc.


•

Finally, it is possible to capture the display on the screen by pressing the "Print Screen" key or “Shift-Print Screen" depending on the keyboard configuration. Images captured this way will be copied to the Windows clipboard, where they can then be pasted into another graphics program.

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5.16

Simple Query •

Ensure that the file named Dataset 5_1.std is still the active model.

•


•


•

STAAD.Pro has a tool called Simple Query that can be used to search the results for very specific information, such as results that meet a combination of specified criteria. The search results can also be saved so they will be available later if the Report Setup facility is used to prepare a report.

•

To demonstrate the use of the Simple Query feature, let’s assume that the goal is to study vertical deflections of the truss in Dataset 5_1, and to identify any nodes along the bottom chord that deflect 1/2 inch {12 mm} or more under load condition 4, the combination of dead, live, and wind loads.

•

Select the nodes along the bottom chord. See the commentary below for some options. One option would be to choose the Nodes Cursor, and to use the point and click method to select each node individually while holding down the Control (Ctrl) key. Another option would be to view the model from the +Z or –Z direction, and then drag a fence around the bottom chord with the Nodes Cursor.

•

Click Tools | SQL Query | Simple Query .

•

Click the New Query button.

•

Queries consist of logical or conditional statements that filter for desired information.


•

Click on the arrow in the Select Table Type box to see the different types of tables that can be searched with the Simple Query tool.

•

Select Node Tables from the list. This controls what tables will be available to choose from when developing the conditional statement.

•

Click the Node Displacements checkbox. This identifies the specific table that will be used to develop the conditional statement. The checkboxes listed below Node Displacements represent the individual fields that are in the Node Displacements table.

•

Click the checkboxes to select Node No., Load Case, and Y Displacement. This identifies which fields will be included in the results of the query. By default, if no checkboxes are selected, all fields in the table will be included in the results.

•

Click the radio button labeled Where, under the Select Condition category. Several more options will become activated in the Select Condition category.

•

Choose the Load Case option in the Select Field list.

•

Choose the

•

Enter a value of 4 in the Value field.

•

Click the double-right-arrow button Value field.

•

Select the AND command from the small pop-up sub-menu.

= (equals) symbol in the Operator list.

to the right of the

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•

The Select Field, Operator and Value options will be cleared to allow another conditional statement to be entered.

•

Select the Y Displacement option in the Select Field list.

•

Choose the list.

•

Enter a value of -0.5 {-0.012} in the Value field, and then click the Done button.

<= (less than or equal to) symbol in the Operator

Note the need to use the negative value here, because of the sign convention used on downward displacements in the model. Also note that when metric units are used, the default units for displacement in the Simple Query are meters, thus a value of -0.012 must be entered. •

The Select Table and Fields and the Select Condition categories will become gray, indicating that they are now inactive.

•

Click the radio button for Selected Node No. in the Query for category. This indicates that STAAD.Pro is only to consider the currently selected nodes as it processes the query. Currently, the only nodes that are selected are those in the bottom chord of the truss.

•

Click the OK button.

•

The query now appears under the Query Statement category in what is known as SEQUEL syntax.

•

The Query Statement could be edited manually at this point if necessary. Even without knowing SEQUEL syntax, it is easy to modify the query by changing the node numbers, displacement values, logical operators, etc….


•

Click the Execute Query button.

•

STAAD.Pro runs the query and displays the results in a table in the Query Result section. The results indicate that seven nodes (1, 2, 3, 4, 12, 13 and 14) all experienced downward vertical deflections of 1/2 inch {12 mm} or more under load condition 4.

•

There is an obvious difference between a Query and the results of a query. STAAD.Pro allows both to be saved. Depending on the stage of design, if there is reason to think that analysis results are likely to change, it might be wise to save the query, so it could be rerun at a later date.

•

Click the Save Query button.

•

Edit the title to read Deflections One-Half Inch or Greater {Deflections 12 mm or Greater}, and then click OK.

•

The saved query name now appears in the Query List on the left side of the Simple Query dialog. It will be available to rerun at any time in the future.

•

To save a copy of the results just produced by this query, click the Save Query Result button.

•

Enter Bottom Chord Deflections in the Title field. The text entered in the Title field will appear as a title at the top of the query results if the results are printed in a report.

•

The Save Report checkbox will be toggled on by default. If it is toggled off, the query results will not be available after the program is closed and reopened at a later date.

•

Revise the Id to read Bot Chord. The Id is used to assist in identifying the query results if they are to be incorporated into a report.

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•

Click the OK button.

•

The program will save the query result, and it will appear in a list of available report items if the Report Setup facility is used to prepare and print a report.

•

Note that in order to save query results, the query itself must be saved first.

•

Click the Close button to dismiss the Simple Query dialog.

•


•


-End of Module-

6-1

Steel Design Module

6

The following topics are included in this module. 6.1 Introduction to STAAD.Pro Steel Design ....................................... 2 6.2 How to Specify Steel Design Parameters ........................................ 4 6.3 How to Use the Check Code Command....................................... 18 6.4 Checking Steel Design Results ....................................................... 25 6.5 Optimizing Steel Designs................................................................. 30 6.6 Statically Indeterminate Structures .................................................. 34 6.7 Finalizing the Design ....................................................................... 39 6.8 Additional Comments Regarding Design Commands ................... 51


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Module 6

6.1

Introduction to STAAD.Pro Steel Design •

Steel design in STAAD.Pro involves two basic kinds of activities: Code Checking and Member Selection.

Code Checking: •

Check Code is a request to determine if the member properties that the user has provided are adequate to carry the forces that are applied to the members.

•

Used when the user has provided member properties and presumes that those properties are fairly close to what they should be.

•

If members are found to be inadequate in a code check, the user is responsible for finding a new set of members to replace the inadequate ones.

Member Selection •

By contrast, Member Selection is a request to provide an optimum set of members, that is, to indicate what minimum weight cross sections are sufficient to safely carry the design loads.

•

In a Member Selection the program finds the lightest acceptable section, incorporating the specified constraints, such as minimum depth, or sections of a particular profile. For example, if STAAD.Pro is restricted to choose from among W12 sections, it will not look for any W8 sections that might be sufficient.

•

The actual optimization process is to start with the lightest possible section within the specified constraints, and verify whether or not that section is adequate.


•

If it is not adequate, the program goes to the next heavier section and keeps going until it finds the first one that satisfies the code requirements and the specified constraints.

•

If it is unable to find any section that satisfies both the specified constraints and the code requirements, the program will report the last section it tried, and the results of that check, including why that section failed the code check. The sequence of commands for performing a Check Code and those for performing a Member Selection are similar.

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6.2 How to Specify Steel Design Parameters •


•

This model has been constructed and loaded using the STAAD.Pro Pre Processor.

•

Preliminary member sizes have been assigned, and the model is prepared for the design/code checking process.

•

The commands related to design and code checking are added to the input file in the modeling mode of the program.

•

Before adding these commands, let’s first introduce an additional command that is quite useful in certain situations: the Load List command.

•

In the Main Menu bar, select Commands | Loading | Load List.

•

In the Load List dialog, note that the four load cases that are present in this model are listed.

•

The load cases consist of the three primary load cases: Dead, Live, and Wind. The fourth load case is the load combination case: LC1 + LC2 + LC3.

•

It is common to only consider the load combinations, instead of the primary load cases, when performing member design or code checking operations.

•

We can instruct STAAD.Pro to only consider Load Case 4 when performing the design and code check operations by using the Load List command. As another example, assume that we have a model containing both unfactored and factored load combinations.


We could use the Load List command to select the unfactored load combinations, then issue a PRINT SUPPORT REACTIONS command to view the unfactored reactions for foundation design. Then, we could use a second Load List command to select the factored load combinations, and then issue all of the commands related to member design or code checking using LRFD procedures. •

In the Load Cases window of the Load List dialog, select 4: LC1 + LC2 + LC3 .

•

Move this load to the Load List window by selecting the single right arrow button,

•

. Click OK .

Load Case 4 will now be the only load case considered for any commands that are issued hereafter, until another Load List command is issued. View the Input file, and note that the command LOAD LIST 4 has been added at the end of the file, just above the FINISH command.

•

Next, click on the Design tab at the bottom of the Page Control. The Design page is activated.

•

Note that the Design tab logically follows the Analysis/Print tab. This follows the program methodology of suggesting a logical workflow process by the order in which the Page Control tabs are organized.

•

Five sub-page tabs labeled Steel, Concrete, Timber, Aluminum, and Shearwall appear beneath the Design page.

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The Steel page is active by default. In the Data Area on the right, a dialog with the title Steel Design – Whole Structure is displayed. This dialog will be referred to from here on as simply the Steel Design dialog. •

STAAD.Pro offers the choice of designing using many different codes from numerous countries.

•

Access to the different codes depends on which codes were requested when the software was purchased.

•

Click the Current Code list at the top of the Steel Design dialog to view the available codes for steel design.

•

Select the AISC 360-05 code.

Some general discussion about parameters: •

In the lower portion of the Steel Design dialog note the three buttons labeled Select Parameters, Define Parameters and Commands.

•

Click the Define Parameters button.

•

The category window on the left side of the Design Parameters dialog lists all of the available parameters from which to choose.

•

The parameters listed in this dialog are those that are referenced in the various sections of the currently selected design codes.

•

This dialog is used to control the variables and to set values for the different design parameters.


•

All the parameters displayed in this dialog are initially set to default values.

•

In the absence of any other instruction, STAAD.Pro will use the default parameter values shown.

•

One common example of the use of parameters is to correctly set the yield strength of the different members in the model. For instance, in the steel design example, the structure has tubes as the top chord members. Many tubes come in 46 ksi {320 N/mm 2 or MPa} steel, while the majority of wide flanges are 50 ksi {345 N/mm 2 or MPa}.

•

The yield strength affects many of the design equations when solving for section capacities.

•

The FYLD parameter can be used to specify different values of yield strengths for different members.

•

Scroll down through the list of parameters on the left side of the Design Parameters dialog to find the FYLD parameter.

•

Click on FYLD . The right side of the dialog indicates that FYLD is the current parameter, and that it represents the Yield strength of steel, and it provides the default value for the variable.

•

If the Yield strength of steel is shown in some units other than kip/in 2 {N/mm 2 }, change the Length Units to Inch { Millimeter}, and set the Force Units to KiloPound {Newton}. See the step-by-step instructions in the following commentary. Click Close to dismiss the Design Parameters dialog. Click Tools | Set Current Input Units. Click Inch {Millimeter} in the Length Units category.

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Click KiloPound {Newton} in the Force Units category, and then click OK. Click the Define Parameters button once again. Scroll down the list of parameters on the left and find the FYLD parameter. Click FYLD , and note that the value is now reported in units of kip/in 2 {N/mm 2 } with a default value of 36 {248.213}. •

Some other commonly used parameters are the ones which affect slenderness checking; i.e. Kl/r ratio. Effective length factor, K, addresses the end conditions of the columns. The unsupported length, l, represents the distance between two points at which the member is braced against lateral buckling. The radius of gyration, r, is a property of the cross section, expressed as the square root of the moment of inertia divided by the area.

Since r is a function of the member cross section, STAAD.Pro has this value already, and r is not a user-input value. The user does have influence over the values used for K and l. •

For the Y-axis the parameter names are K y and l y ; for the Zaxis, they are called K z and l z .

•

In the absence of any user input, the K values are assigned a default value of 1.0 and the l values are assigned to be equal to the node-to-node member length.


•

It is up to the user to assign the correct K and l values to the members. For example, the columns supporting the truss in the current model might be braced by wall girts at intermediate points, in which case, the value for l could be smaller than the overall length of the member. It is important that the user understand the system of bracing in the model. For example, a member that is braced at a point against buckling in one plane may not necessarily be braced for buckling in the orthogonal plane at that point. Under these conditions, it may be necessary to modify the default value of 1.0 for K in one of the directions.

•

STAAD.Pro has a third parameter called Kx which affects the slenderness calculation for Flexural Torsional Buckling (failure by twisting).

•

A similar set of parameters affects the capacities in bending by specifying unbraced lengths for bending members. Under normal conditions, when a beam bends, one flange is in tension, the other in compression. Compression flanges can buckle, either local buckling or lateral torsional buckling, between points of bracing.

•

Two parameters called UNT and UNB are used to define these unbraced lengths for bending.

•

UNT is the unbraced length for the top flange of the beam, and UNB is the unbraced length for the bottom flange.

•

“Top flange” and “bottom flange” are defined with reference to the orientation of the local axis system.

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•

The flange on the positive side of the major (local x) axis, i.e., in the direction in which the local y-axis points, is the top flange; the flange on the negative side is the bottom flange.

Figure 6. 1 There may be instances where the top flange of a wide flange beam is braced by a deck or slab of some type, precluding any kind of buckling of the top flange; whereas, the bottom flange may be supported at discrete distances. Under this condition, the unsupported length for the top flange will be one value, and the unsupported length for the bottom flange will be another value. These parameters require the application of engineering judgment on the part of the user. •

Parameters can also be applied to assist with deflection checking.

•

The deflection limits in most codes are considered serviceability requirements as opposed to strength or life safety requirements.

•

For this reason, deflections are not automatically investigated when the Check Code command is used, and are not considered when the Member Selection is used.


•

To specifically instruct STAAD.Pro to perform deflection checking, the variables Dff, Dj1 and Dj2 can be specified. In the case of the current steel design example, STAAD.Pro would need input from the user as to what to consider as the “length” of the top and bottom chords of the truss, if a deflection check were to be performed. It can’t determine the length automatically, because those structural elements are represented by a series of individual member segments connected at nodes. The details of all of these parameters are explained in Chapter 2 of the Technical Reference manual. There are also several examples in the Examples manual that illustrate the use of parameters to control the design.

•

Click Close to dismiss the Design Parameters dialog for now.

•

Click the Select Parameters button.

•

Select Parameters is really just a convenience feature, to help configure the display to individual preferences. It does not control any type of program function. It simply offers control over which parameters will be displayed in the Design Parameters dialog.

•

The Parameter Selection dialog is divided into two sides: Available Parameters and Selected Parameters.

•

Items can be moved back and forth between the two sides by using the left and right arrow and double-arrow buttons that are familiar from other similar selection dialogs in STAAD.Pro.

•

To reduce the clutter in the Design Parameters dialog, the Parameter Selection dialog can be used to remove any parameters that will not be used.

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•

Only parameters that are in the Selected Parameters list will be listed in the Design Parameters dialog and will be accessible for use in the model.

•

This makes it more convenient to locate the parameters that will be used on a regular basis.

Selecting specific parameters for the steel design model: The example problem will make use of just a few parameters for illustration purposes. •

Click the double-left arrow to move all parameters from the Selected side to the Available side.

•

Scroll down through the Available list, click on FYLD , and click the single-right arrow side.

•

to move it to the Selected

Repeat for the Ky , Method , and Track parameters, then click OK.

Defining specific parameters for the steel design model: •

Click the Define Parameters button once again. The list of available parameters is now reduced to just the four we specifically selected in the step above.

•

Click FYLD in the short list of parameters.


The model contains wide flanges, channels, angles, and tubes with yield strengths shown in the following table. Member Columns Bottom chord Top chord Webs •

Section Wide flange: W 18 x 35 Channel: C 12 x 30 HSS: 7 in. x 4 in. x 3/16 in. Angle: 3 in. x 3 in. x ½ in.

50 36 46 36

Fy ksi {350} ksi {250} ksi {320} ksi {250}

Enter 50 {350} in the Yield strength of steel field and click Add. Some new lines are added to the input file, and can be seen in the Command Tree in the Steel Design dialog. The new lines include the units change to UNIT INCHES KIP {UNIT MILLIMETER NEWTON}, the reference to the selected AISC code, and a line referring to FYLD 50 {FYLD 350} with a question mark icon. The question mark icon indicates that this particular parameter has not yet been assigned to any members.

•

Enter 46 {320} in the Yield strength of steel field and click Add. It is not necessary to add a value of 36 {250} in the Yield strength of steel field for the channel and angle sections, since this is the default STAAD.Pro value that will be assigned to those members automatically absent any instructions to the contrary.

•

Click the KY parameter tab. (Assume that we have already determined that a value of Ky = 1.2 is appropriate for the columns in this model.)

•

Enter a value of 1.2 in this field, and click Add.

•

Click the METHOD parameter.

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For steel design using the American AISC 360-05 code, it is necessary to specify the design method to be used, LRFD or ASD. The default value is LRFD. •

For this example, select ASD from the list, and click Add.

•

Click on the Track parameter tab. The Track parameter is used to control the amount of detail that is printed in the design output.

•

Click the radio button corresponding to level 1, i.e. maximum detail level, then click Add.

•


•

Note that all of these new lines have been added to the end of the input file by default.

•

If there is ever a need to insert a parameter at a location other than the default end-of-file location, this can be done using the After Current checkbox as described in the commentary below. First, click on the line in the Command Tree that immediately precedes the desired insertion point of the new command. Next, use the Design Parameters dialog to select the new parameter and set its value. Finally, click the After Current checkbox in the Design Parameters dialog and click Add or Assign. The newly added parameter should appear in the Command Tree immediately after the currently selected command.


Assigning specific parameters for the steel design model: •

The question marks displayed to the left of some of the parameters in the Command Tree indicate that those parameters have not yet been assigned to any members in the model. If the model was analyzed at this point, the parameters with the question marks would have no influence on the model. In fact, those lines get skipped, and don’t even get echoed in the output file.

•

In order to make use of these parameters, they must be Assigned to the members to which they apply.

•

FYLD 50 {FYLD 350} applies to wide flange members, which are the columns in the model.

•

In the Steel Design dialog, click FYLD 50 {FYLD 350}.

•

Click Select | By Group Name… | _COL, and then click Close to dismiss the Select Groups dialog.

•

Back in the Steel Design dialog, confirm that the Assignment Method has automatically changed to Assign To Selected Beams, and then click Assign.

•


•

Note that the question mark corresponding to the FYLD 50 {FYLD 350} parameter has been replaced with a green check mark in the Command Tree, indicating that this parameter has been assigned to at least one member.

•

FYLD 46 {FYLD 320} applies to tube members, which are the top chord members in the model.

•

In the Steel Design dialog, click FYLD 46 {FYLD 320}.

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•

Click Select | By Group Name… | _TOPC, and then click Close to dismiss the Select Groups dialog.

•

Back in the Steel Design dialog, confirm that the Assignment Method has automatically changed to Assign To Selected Beams, and then click Assign.

•


•

The KY factor will be assigned to the two columns.

•

Click in a blank area of the Main Window to deselect all members.

•

Click on KY 1.2 in the Command Tree.

•

Click on one of the columns.

•

Press and hold down the Control (Ctrl) key, and then click on the other column .

•

Release the Control (Ctrl) key. Both columns should now be selected.

•

Confirm that the Assignment Method has automatically changed to Assign To Selected Beams, and then click Assign.

•


•

The yellow question mark to the left of KY 1.2 in the Command Tree changes to a green check mark.

•

Note that the METHOD ASD item already has a green check mark. This indicates that this parameter was automatically assigned to every member of the model and no further assignment is necessary for this parameter.

•

Finally, the Track parameter will be assigned to all members in the structure.


•

Click on the TRACK 1 item in the Command Tree list.

•

Click the Assign To View radio button in the Assignment Method category. Click the Assign button.

•


•

All the members in the structure are highlighted and the yellow question mark to the left of the TRACK 1 item changes to a green check mark, indicating that the TRACK 1 design parameter has been assigned.

•

Notice the checkbox labeled Highlight Assigned Geometry immediately below the Command Tree in the Steel Design dialog.

•

This is a useful option for checking that items like parameters, properties, etc. have actually been assigned to the intended members.

•

To demonstrate, make sure the Highlight Assigned Geometry checkbox is toggled on, and then click on FYLD 50 {FYLD 350} and FYLD 46 {FYLD 320} in succession.

•

The member geometry will be highlighted appropriately as the different parameters are selected in the Command Tree.

•


•


•


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6.3

How to Use the Check Code Command •


•

Click the Design tab in the Page Control.

•

Assume the intent is to do a code check for all of the members in the structure.

•

Click Select | By All | All Beams.

•

Click the Commands… button in the lower portion of the Steel Design dialog.

•

The CHECK CODE tab is currently the active tab in the Design Commands dialog. The Assign button will be available, because members are presently selected in the Main Window. The Assign button is convenient because it adds the command of the currently active page to the command list, and it simultaneously assigns the command to all of the currently selected members. This is more convenient than the two-step process demonstrated in the previous section where design parameters were first added to the input file and then assigned to specific members in a separate step. Note that the Assign button would not have been available if the members had not been selected first. This behavior is typical of many dialogs in STAAD.Pro. For these reasons, it is good practice to select the members to be operated on first, and then perform the operation.


•

Click the Assign button to add the Check Code command to the command list and simultaneously assign it to all the members in the model.

•

Click the Close button to dismiss the Design Commands dialog.

•


•

Click the Save button.

•

The STAAD Analysis and Design dialog opens, and a series of messages scroll down the screen as the program runs the analysis. While the analysis is running, the button in the lower righthand corner of the STAAD Analysis and Design dialog is labeled Abort. After the analysis is complete, the label on that button changes to Done. There will now be some new messages in the STAAD Analysis and Design dialog that were not present the first time the analysis was run. These indicate additional operations that were performed, like Performing Steel Design, Finished Design, Creating Design Information File (DGN), etc.

•

The indications that the run was successful are: •

The message **Output Written to File.

•

The presence of an option to Go to Post Processing Mode.

•

The absence of any error messages at the bottom of the STAAD Analysis and Design dialog.

If the program is ever unsuccessful in analyzing the input file and generating results, the Post Processing mode will not be available, as shown in Figure 6. 2 below.

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Figure 6. 2 The program might also display a message like ERROR in Analysis, check Output (ANL) File, if the analysis concludes prematurely, without generating any results. If this ever occurs, open the output file and look for error and/or warning messages that will help to locate the problem.

Figure 6. 3


The STAAD Output Viewer has two panes. If there is any kind of problem in the file, the left pane will display horizontal bars labeled Error or Warning. There may also be a Results bar if the program was able to proceed through the analysis far enough to generate some results. What is the difference between an error message and a warning message? An Error message indicates a condition which must be corrected in order for a successful analysis to be performed. A Warning message indicates that the program encountered an unexpected or abnormal condition, but it was still able to perform an analysis while warning that the output results should be checked carefully. •

Click the View Output File radio button in the lower left corner of the STAAD Analysis and Design dialog, then click the Done button.

•

The Results bar will appear at the top of the left pane of the STAAD Output Viewer.

•

Click on the STEEL DESIGN item under the RESULTS bar in the left pane. It is a link directly to the beginning of the steel design results in the output file.

•

STAAD.Pro CODE CHECKING – (UNIFIED ASD) – indicates the design code selected.

•

The next line indicates the units that are being used to report the results.

•

The results of the code check are reported in this table for each member in the model.

•

The level of detail shown in this table is a function of the Track parameter, which was set to a value of 1.

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•

Note the asterisk beside member 1. This is actually a graphical flag used to denote members that fail the code check.

•

The column headed MEMBER displays the member number.

•

The ST notation indicates that it is a standard section, as opposed to a user-defined section.

•

The column headed TABLE lists the name of the cross section (a C12 x 30 channel in this case).

•

Each of the remaining columns reports two pieces of data. The column headings provide the key to determining what the data represents.

•

First read the top line from left to right.

•

The column headed RESULT provides the overall design result for the member in PASS/FAIL format. In this case the member fails.

•

The column headed CRITICAL COND reports the code reference to the expression that produces the highest ratio for the member. In this example, the CRITICAL CONDITION is created by Clause H1 (axial force plus bending) in AISC 36005.

•

The column headed RATIO provides the controlling utilization ratio for the member (this is essentially a demand/capacity ratio). In this case, RATIO is the term on the left-hand side of AISC 360-05 equation H1-1a or H1-1b.

•

The column headed LOADING indicates the Load Case that produced the controlling ratio.

•

The column headed FX (directly beneath RESULT) indicates the axial force in the member under the controlling Load Case. In this case, it is a tensile force, indicated by the “T” after the force magnitude.


•

Note that this is not necessarily the largest axial force, just the axial force associated with the load case indicated in the LOADING column.

•

The columns headed MY and MZ indicate the bending moments about the local y- and local z-axes, respectively, that are associated with the load case indicated in the LOADING column.

•

The last column headed LOCATION provides the location along the beam where the RATIO is the highest. In this case the value is 0.00, indicating that the critical loading takes place at the starting node of the member.

•

Recall that Member 1 is the only member in the model with a beta angle equal to 90 degrees.

•

The model is a planar structure with no out-of-plane forces acting on it.

•

For Member 1, the local y-axis is oriented parallel to the global Z-axis, because the beta angle is 90 degrees. Based on the applied gravity loading, we would expect bending to take place about this member’s local y-axis.

•

We would expect no bending about Member 1’s local z-axis, since no out-of-plane forces are acting on the structure.

•

For the remaining members, we would expect that bending will take place about their local z-axes since their local z-axes are oriented parallel to the global Z-axis, and we expect no out-ofplane bending to take place about their local y-axes.

•

The box below the table data provides some additional information regarding member slenderness checks and capacities.

•

Click File | Exit in the STAAD Output Viewer window to return to the STAAD.Pro environment.

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•


•


•



6.4

Checking Steel Design Results •


•

In addition to reviewing the output file, there are other facilities available for checking steel design results.

•

Click Analyze | Run Analysis… to be sure analysis results are available and current.

•

When the analysis is complete, click the Stay in Modeling Mode radio button, and then click Done.

Searching for Failed members in Modeling Mode: •

Click Select | By Specification | All Failed Beams. All of the members that are highlighted failed the code check.

•

This command warrants a bit of caution.

•

If the input file does not include any steel design commands, no steel design will be performed and no steel design results will be generated. So, no beams will fail!

•

If that is the case, then executing the command Select | By Specification | All Failed Beams may produce a message indicating that no beams failed.

•

This message can be misleading. If no Check Code command was included in the input file, or if an analysis has not yet been run, the program will not be able to correctly identify failed members.

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Observing Design Results on the Unity Check page in the Post Processor: •

Click Mode | Post Processing .

•

Click OK in the Results Setup dialog to display results for all load cases.

•

Click the Beam tab in the Page Control.

•

Click the Unity Check tab. The Unity Check sub-page was not present until the Check Code command was added.

•

The members in the structure diagram will be color coded and annotated with their controlling ratio values, and the ratios will also appear in the Design Results table. Any member with a ratio value less than or equal to 1 is considered to have passed the code check; a member with a ratio greater than 1 is considered to have failed, hence the term Unity Check.

•

Right-click the mouse in the Main Window, and then click Structure Diagrams… from the pop-up menu.

•

Click the Design Results tab in the Diagrams dialog.

•

The Design Results page provides a way to adjust the colorcoding of members based on the value of their design ratio.

•

Radio buttons allow the user to choose between basing the diagram on Actual Ratios or Normalized Ratios. (The Normalized Ratio is calculated by dividing the Actual Ratio by the specified value of the RATIO parameter.)

•

Click the Show Diagram (Based on Actual Ratio) radio button.

•

The next set of radio buttons allows a choice between a Basic Diagram and a Detailed Diagram.


•

Click the Basic Diagram radio button.

•

In the Basic Diagram option: •

Members are displayed in 4 distinct colors to indicate Not Designed, Pass, Fail, or Extreme Failure.

•

Colors can be changed if desired by double-clicking on them.

•

The default values define Pass as a ratio less than 1, Fail if the ratio is between 1 and 1.5, and Extreme Fail if the ratio is greater than 1.5.

•

These ranges can be customized as desired.

•

It is important to understand that the categories of Pass and Fail on this diagram can be set to have different ranges of values than those used in the calculation engine during the steel design process.

•

In the calculation engine, a Fail status will be reported on any member whose Unity Check value exceeds 1.0 multiplied by the value of the RATIO parameter and multiplied by the OVR parameter (both of whose default values are 1.0).

•

Click the Detailed Diagram radio button.

•

In the Detailed Diagram option: •

Ranges of values can be created for interpreting the design status.

•

By default, the range consists of an equally distributed set of values between the lowest ratio and the highest ratio.

•

The Use Custom Limits checkbox provides a way to create an equally distributed set of values between a user-defined minimum and maximum ratio limit.

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•

The Use Custom Divisions checkbox makes it possible to specify ranges that are not necessarily equally distributed.

•

The colors used to represent the different ranges can be changed as desired by double-clicking on them.

•

In all cases, the scroll box is available for increasing or decreasing the No. of values (number of color-coded value ranges) that are displayed.

•

The Show Values checkbox controls whether or not ratio values appear on the diagram.

•

Click Cancel in the Diagrams dialog to return to the Unity Check page.

Observing Design Results using the member query feature: •

Double-click on Member No. 1 (bottom chord member just to the right of midspan).

•

This dialog continues to get populated with more information as the model is constructed, properties get assigned, and as analysis and design results become available.

•

Now that the analysis has been re-run using some steel design commands, a new page is present.

•

Click the Steel Design tab in the Beam dialog.

•

This Steel Design page displays the same information that was just reviewed in the output file in the previous section.

•

This is an easy way to obtain basic design results for a particular member.

•

The Steel Design page presents the design strength, critical loads, pass / fail status, unity ratio, governing clause of the design code, Kl/r ratio, etc.


•

Click the Close button to dismiss the member query dialog.

Searching the Output File for Failed Members: •

Click the STAAD Output icon

•

Click the Find toolbar button in the upper left corner of the STAAD Output Viewer (it looks like a pair of binoculars).

on the File toolbar.

Another way to open the Search dialog is to pull down the viewer’s Edit menu and select the Find command, or use the shortcut key method of pressing the F key while holding down the Control (Ctrl) key. •

Type the word Fail into the field labeled Find What at the top of the dialog, then click on the Find Next button.

•

The viewer moves to the first instance of the word “Fail” in the output file and highlights it.

•

If the search does not find any instance of the word “Fail” in the output file, the message, “SproView has finished searching” is displayed.

•

Continue to click the Find Next button to find successive occurrences of the word “Fail”.

•

From the current cursor location, the direction of the search can be specified in the Direction category as either Up or Down.

•

Click Cancel to dismiss the Search dialog.

•

Click File | Exit in the STAAD Output Viewer.

•


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6.5

Optimizing Steel Designs •

The next logical step after obtaining the results of the code check is to have STAAD.Pro optimize the design.

•

STAAD.Pro has the ability to select the most economical section in terms of weight that will satisfy the code requirements.

•

Ensure that the file named Dataset 6_3.std is still the active model.

•

Click the Design page tab in the Page Control.

•

The Check Code command that appears in the Steel Design dialog is no longer appropriate, since the goal is now to allow STAAD.Pro to select members that satisfy the code requirements, rather than to just check and report on the assigned sizes.

•

Right-click on the CHECK CODE command, then select Delete Command from the pop-up menu. Click Yes to confirm.

•

Select all members using any preferred method. See commentary below for options. Drag a rubber band line around the entire model with the Beams Cursor, or choose Select | By All | All Beams.

•

Click the Commands button at the bottom of the Steel Design dialog.

•

Click the Select option in the Design Commands dialog.

•

Click the Assign button to simultaneously add the SELECT command to the command list and assign it to all members in the model.

•



•

The green check mark to the left of the SELECT command indicates that the command has been assigned to members in the model. The icon would appear as a yellow question mark instead of a green check mark if the Add button was clicked instead of the Assign button. If this was the case, the Assign To View option could be used to assign the SELECT command to all members in the model.

•

Click File | Save and then click Save in the pop-up warning dialog box to confirm the intent to save the input file with the recent changes.

•

Click Edit | Edit Input Command File.

•

Scroll down through the input file in the STAAD.Pro Editor. Note that the CHECK CODE ALL command has been replaced by the SELECT ALL command.

•

Click File | Exit in the editor’s menu bar to return to the Main Window.

•


•

A dialog pops up with the warning message shown below.

Figure 6. 4 •

Click Yes. The meaning of this warning will be discussed in detail in an upcoming section titled “Statically Indeterminate Structures”.

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•

When the analysis concludes, click the View Output File radio button, and then click the Done button at the bottom of the STAAD Analysis and Design dialog.

•

Click the words STEEL DESIGN under the RESULTS bar. This is a link to go straight to the steel design pages in the output file.

•

Scroll through the steel design results, and note that every member has passed.

•

Note also that nearly every member now has a unique cross section, because no control was provided for the program as it optimized individual members.

•

A more sophisticated optimization technique will be presented in an upcoming section titled “Finalizing the Design”.

•

Click File | Exit in the STAAD Output Viewer.

•

In the Steel Design dialog, note that the MEMBER PROPERTIES AMERICAN folder icon has been expanded in the Command Tree.

•

The new entries in the list (the ones with the question marks) represent the sections that were determined to be the optimized sizes by the SELECT command.

•

The question mark icon is used to indicate that they have not yet been assigned to the model.

•

Don’t be deceived by the fact that the optimized member sizes were just viewed in the STEEL DESIGN section of the output file.

•

Press Shift + X , the hotkey to show member sections on the structure diagram.

•

Note that the sections shown on the structure diagram are still the original sizes that were assigned to the members.


•

There is one additional step to instruct STAAD.Pro to update the model with the optimized member sections. It is accessible from the Post Processing mode, and the command is Results | Update Properties. This command will not be used here, but it will be covered in the upcoming section titled “Statically Indeterminate Structures”.

•


•


•


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6.6

Statically Indeterminate Structures •

In a previous section titled “Optimizing Steel Designs,” a warning message was encountered in the beginning of the analysis.

•

The message indicated that the model contained instructions for Member Selection/Optimization and/or Grouping but that these commands were not followed by an instruction to reanalyze the model.

•

It goes on to say in effect that the analysis results will not be consistent with the new member properties.

•


•


•

Click Yes to acknowledge the warning dialog and allow the analysis to run.

•

When the analysis concludes, click the Go To Post Processing radio button, and then click the Done button.

•

Click OK in the Results Setup dialog to select all four load cases.

•

Click the Beam tab in the Page Control, and then click the Unity Check tab.

•

The Design Results table shows the Analysis Property cross sections that were used in the analysis to obtain the member forces. These are the member sections that we initially assigned to the members of the model.

•

This table also shows the Design Property sections, which are the member sizes chosen using the Select command, and the ratios for each of the Design Property sections.


•

Most of the Actual Ratio values are all less than but very close to 1.0. This is an indication of the efficiency of the selection process. If many members were far below, say, 0.9, it would not be considered to be an efficient, economical design. Occasionally there might be a member with a very low ratio. For example, one of the angles, an L20202 (2 in. x 2 in. x 1/8 in.) has a ratio of approximately 0.52 {0.63}. This is because that angle size is the smallest angle available. In other cases, the efficiency of the design might be governed by the slenderness ratio Kl/r. In that case, the member might appear to be underutilized in terms of its ultimate strength, but that larger cross section is needed to resist buckling effects. Note: there is a provision in some codes that permits members to be designated as secondary members that are not subject to slenderness limits. An example might be a member that is designed to perform in tension, but which might also experience some compression loading. In such cases, the parameter called Main can be used to designate certain members as secondary members, and waive the slenderness check.

•

To understand the warning message that appeared when the Analyze | Run Analysis command was issued, first consider the difference between a determinate structure and an indeterminate structure.

•

A determinate structure is one in which all the forces and reactions in the structure can be found using equations of static equilibrium.

•

Simply by setting the sum of the forces and moments equal to zero, all of the internal forces in a determinate structure can be solved.

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•

In an indeterminate structure on the other hand, there are more unknowns than there are equations of static equilibrium.

•

In order to have a sufficient number of equations to solve for the unknown quantities, additional equations known as Equations of Compatibility must be relied upon.

•

For example, it could be said that, at a point of connection between a vertical column and a horizontal beam, the displacement of the vertical member must be equal to that of the horizontal member.

•

These Equations of Compatibility use relationships between the forces and the displacements, and they depend upon the section properties of the members. Moment Distribution methods for solving indeterminate structures rely on equations that involve the fixed end moments and quantities like E, I, and L.

•

Consider the portal frames shown in the figure below. Both frames have identical geometry, support conditions and external loading, but the member properties are different.


Figure 6. 5 •

These two frames would not be expected to have the same distribution of forces and reactions, due to their differences in stiffness.

•

This points up the other difference between determinate and indeterminate structures; the nature of force distribution and redistribution in an indeterminate structure depends on the section properties of the members.

•

What does all this have to do with the member selection process and the warning message that appeared during the analysis?

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•

When the model was first analyzed, STAAD.Pro used the section properties of the members that were initially specified.

•

From that analysis, it obtained a set of forces and displacements.

•

Those forces and displacements were then used to select some new members that satisfied Code requirements.

•

However, we have not yet given STAAD.Pro the command to reanalyze the model to incorporate the effects of the changes in stiffness as a result of the newly-selected member sizes.

•

If the intent is to use these new members in the final design, the forces that were used to select the members will no longer be valid, because those forces were based upon a completely different set of member properties.

•

In a statically indeterminate model, once the properties are changed, it must be reanalyzed, in order to make the loading consistent with the properties.

•

In the case of this particular model, it also needs to be reanalyzed for another reason. Load Case 1 is based on the self-weight of the members. Since the self-weight of the new members is likely to be different than the self-weight of the original members, the analysis must be re-run to incorporate this change as well.

•



6.7

Finalizing the Design •

Ensure that Dataset 6_4.std is still the current file.

•

To make this design more realistic, the member sizes should be fairly uniform.

•

At present, the Select command has optimized the size of each member individually, so practically every member in the model has a unique cross section.

•

It is obviously not practical to construct a real-world structure this way.

•

Instead, certain parts of the structure should be comprised of members of a uniform cross section.

•

For example, the bottom chord members should probably have a uniform cross section, the top chord members should have a uniform cross section, and similarly for the two columns and the webs.

•

The other issue we have to address is the consistency of the analysis results and the member section properties.

•

Based on the discussion in the previous section, once the program has selected optimum members of a uniform size, the model should be re-analyzed.

•

The forces found in the first analysis will not be valid anymore because of the differences in stiffness and self-weight associated with the member size changes.

•

A second analysis will determine the distribution of the forces in the new members.

•

With the new force values, one more code check can be performed, to confirm that the new members are able to safely bear the forces on the structure.

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•

In other words, to meet these objectives, the program needs to perform multiple analyses. So, the general procedure is: •

Analyze the structure using the initial properties.

•

Perform a Member Selection to optimize the design.

•

Make the sizes uniform – the command to do this must always be preceded by a member selection.

•

Re-analyze the structure for the new member sizes.

•

Perform a Code Check.

•

The commands to perform the analysis and the member selection have already been defined.

•

The next step will be to go back to the Modeling mode, Design page, to tell the program to make the sizes uniform, re-analyze the structure and perform a code check.

•

The command to make the member sizes uniform is called the Group command (see Section 5.48 in the Technical Reference manual).

•

This command should not be confused with commands used in other Modules to create groups, select by group, etc. (see Section 5.16 in the Technical Reference manual).

•

The steel design Group command tells the program to use the same cross section for a given set of members.

•

As noted above, the command to make the member sizes uniform must always be preceded by a member selection.

•

Ensure that the program is in Modeling mode. If not, switch to Modeling mode by clicking Mode | Modeling.

•

Click the Design tab in the Page Control.


•

Highlight the Select command in the Command Tree of the Steel Design dialog, and then click the Commands button in the Steel Design dialog.

•

Toggle on the After Current checkbox at the bottom of the Design Commands dialog. The use of After Current ensures that the next command will be added immediately beneath the command that is currently selected in the Command Tree, instead of defaulting to the position at the very end of the Command Tree.

•

Click the Group item.

•

STAAD.Pro needs direction as to what parameter to use when evaluating a list of members and identifying a “controlling” section. Normally members would be grouped according to the member in the group with the highest weight (i.e. largest cross sectional area). But members can be grouped using other criteria as well. The section with the highest weight may not be the one with the largest section modulus.

•

The Property Specification list on the Group page offers control over what property to use in identifying the controlling member. Options include Ax, Sy or Sz (area or section moduli about the y- or z- axes). For some codes, there is a fourth option called None. Selecting None is the same as selecting Ax as the controlling parameter. Another modifying option is to toggle on the Same As Beam # checkbox. If this option is used, the selected Property

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Specification from the selected beam will be used as the governing property for the group. •

If no selection is made in the Property Specification list the default group method will be used, which is to determine the cross sectional area of the largest member in the group and then assign that size to all members in the group.

•

Select Ax in the Property Specification list.

•

The current model lends itself to four groups: top chord, bottom chord, columns and webs.

•

Ensure that the After Current checkbox is toggled on, click the Add button four times, and then click the Close button to dismiss the Design Commands dialog.

•

Click anywhere in the Main Window to deselect all members. The first GROUP MEMB command will be assigned to the columns.

•

Click on the first Group Memb command in the Command Tree.

•

Toggle on the Use Cursor To Assign radio button in the Assignment Method category.

•

Click the Assign button to activate the Assign mode.

•

Click on one column, then the other.

•

Click on the Assigning button to turn the Assign mode off.

•

Again, click anywhere in the Main Window to deselect all members. The second GROUP MEMB command will be assigned to the truss bottom chord.


•

Click on the second Group Memb command in the list.

•

Click Select | Beams Parallel To | X . The Assignment Method in the Steel Design dialog is now automatically set to Assign To Selected Beams.

•

Click the Assign button, and then click Yes to confirm.

•

Again, click anywhere in the Main Window to deselect all members. The third GROUP MEMB command will be assigned to the top chord.

•

Click on the third Group Memb command in the list.

•

Click Select | By Group Name.

•

Select G2:_TOPC from the Select Groups dialog, and then click the Close button. The Assignment Method in the Steel Design dialog is now automatically set to Assign To Selected Beams.

•

Click the Assign button, and then click Yes to confirm.

•

Again, click anywhere in the Main Window to deselect all members.

•

Assign the fourth GROUP MEMB command to the _WEBS group using this same procedure.

•

Click the Analysis/Print page in the Page Control area.

•

The Analysis/Print Commands dialog opens, with the Perform Analysis tab active.

•

Click Add, then Close.

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•

This adds a second PERFORM ANALYSIS command in the Command Tree of the Analysis dialog.

•

Click the Design page in the Page Control.

•

Click the Commands button in the Steel Design dialog.

•

The Design Commands dialog opens with the CHECK CODE page active.

•

Click Add, then Close.

•

Select the CHECK CODE line in the Command Tree of the Steel Design dialog.

•

In the Assignment Method category, select the Assign to View radio button.

•

Click the Assign button. Note that it is not necessary to re-specify the design parameters. The parameters that were specified previously will remain valid until they are re-specified. The program will continue to use the ASD provisions of the AISC 360-05 code, the K values, FYLD values, the Track parameter, etc., until they are re-specified or until the program reaches the FINISH command.

•


•

Click Save in the Warning dialog that pops up.

•

Check for any error messages in the STAAD Analysis and Design dialog.

•

If the analysis ran successfully, click the Go to Post Processing Mode radio button, and then click the Done button.


•

Click OK in the Results Setup dialog.

•

Now click the Beam page tab, and then click the Unity Check page tab.

•

Look in the Design Results table and note that all of the channels now have the same cross section specified in the Design Property column. The same is true for all of the tube sections, angle sections, etc.

•

Also note that Member 27 failed the Unity Check, with an Actual Ratio value of 1.110. (Note: This is only true if the English dataset is being used. There are no failed members at this point if the Metric dataset is used. For the Metric example, the largest Actual Ratio value is 0.940).

•

As discussed above, this is due to the fact that the member selection process causes significant changes in relative stiffness, and the member forces get completely redistributed when the model is re-analyzed.

•

What options are available in situations where some members have failed after the Check Code command?

•

One option is to perform another design iteration: reselect, regroup, and reanalyze.

•

This process can be iterated over and over until STAAD.Pro converges on a solution.

•

In larger and more complex models, more design iterations may be required in order to converge on a solution.

•

There is a quick way to reduce the number of iterations that may be required by using a STAAD.Pro design parameter called the Ratio parameter.

•

Click Mode | Modeling to return to Modeling mode.

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•

Click the Design page tab.

•

Select all of the members in the model. One quick way to select all members is to click inside the Main Window and use the standard Windows shortcut key combination of Control (Ctrl) + A.

•

Click on the “+” sign to the left of the Parameter 1 folder in the Command Tree.

•

Click the TRACK 1 parameter to make it the current location.

•


•

Scroll down through the list of available parameters, and click on the Ratio tab.

•

The Ratio parameter can be used to specify an upper limit for the ratio of the applied forces to the capacity of the section. Setting this value to something less than 1.0 directs STAAD.Pro to select members with some additional capacity with respect to the code design (or allowable) strength. This builds in a margin of additional strength in the structure that allows it to tolerate the inevitable redistribution of loads that occurs when member stiffnesses change. The resulting design is less sensitive to subtle shifts in load. In this way, an acceptable design will be found with fewer design iterations required.

•

Enter a value of 0.75 in the field labeled Permissible ratio of actual load to section capacity.

•

Toggle on the After Current checkbox.

•

Click the Assign button.


•


•

Scroll down through the list of commands in the Steel Design dialog. Locate the PARAMETER 2 command, just before the CHECK CODE command at the very bottom of the list.

•

Click on the + symbol adjacent to the PARAMETER 2 item to expand the tree.

•

Select the CODE AISC UNIFIED command to highlight it.

•

Re-select all members in the model.

•


•

Click the Ratio item.

•

The value in the edit box labeled Permissible ratio of actual load to section capacity should have defaulted back to 1. This time, leave it at its default value.

•

Toggle on the After Current checkbox.

•


•

Click the Close button. Now when an analysis is run, the Select command will use a ratio of 0.75 and the Check Code command will use a ratio of 1.0.

•

If any member still fails, the analysis could be run again to see if STAAD.Pro will correct the failure based on the redistribution of forces.

•

Another approach would be to go back and change the value used in the Ratio command to something slightly more conservative.

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The Ratio command can also be applied selectively. Several different Ratio commands could be used to specify different ratio values for different members. For example, the ratio for member selection of channels could be set to 0.7, and for selection of angles it could be set to 0.6. STAAD.Pro offers quite a bit of flexibility in this regard. Of primary importance is that the parameters must be set and other operations must be performed in the correct sequence. •


•

Click Save to acknowledge that the model has changed.

•

When the analysis is complete, click the radio button to Go to Post Processing Mode, and then click Done.

•

Click OK to select all load cases if the Results Setup dialog is displayed.

•

Click the Beam page tab followed by the Unity Check sub-tab in the Page Control.

•

Click the Actual Ratio column heading to sort all members by their ratio values. Note that the highest ratio is now 0.895 {0.901}.

•

The recent changes to the input file have corrected the fact that some members were actually very slightly overstressed.

•

It is interesting to note that not all of the members ended up with a ratio less than 0.75, which was the limit used in the SELECT command.

•

This is a good demonstration of how stresses can “creep” after member sizes change and forces redistribute.


•

It is also a good demonstration of wise use of the Ratio values (0.75 to select, 1.0 to check), to eliminate the need to run multiple iterations.

•

A few notes on the use of the RATIO parameter: •

Good practice is to use values between zero and 1.0 with the RATIO parameter.

•

Resist the temptation to use RATIO to account for increases in allowable stresses that may be permitted in some codes.

•

In addition to modifying the allowable stresses, RATIO has the effect of acting as a multiplier on allowable KL/r slenderness ratios. This makes RATIO very effective in building some conservatism into a design when it is used with values less than 1.0, but makes it technically incorrect if used with values greater than 1.

•

If there is a need to acknowledge allowable overstresses (other than what is already built into modern load combinations), then STAAD.Pro provides the OVR parameter.

•

Good practice would be to use the OVR parameter with values greater than 1.0 to account for allowable stress increases.

•

Select the STAAD Output icon, the output file.

•

Click the first STEEL DESIGN line under the RESULTS bar to go straight to the steel design pages in the output file.

•

Note that members 1 and 4 fail during the member selection routine.

, from the toolbar to view

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•

They “fail” because their unity check values exceed the 0.75 limit placed by the RATIO command.

•

The warning message, “TRIAL FAILS FOR MEMBER x. FOLLOWING IS LAST RESULT OF TRIAL”, indicates that STAAD.Pro performed a code check for all channel sections in the database, and none were satisfactory. The results that are reported are for the last section that was tried. In this case, the last section tried (i.e. the heaviest channel section) is a C15x50.

•


•


•



6.8

Additional Comments Regarding Design Commands Additional design commands available: •


•

Click the Design tab, followed by the Steel sub-tab in the Page Control.

•

Click the Commands button in the Steel Design dialog.

•

Note the option labeled Select Optimized.

•

“Optimized” in this context means that the program will automatically iterate twice, without the need for the user to manually specify the repetitions with Select and Perform Analysis commands.

•

The commentary below describes the Select Optimized command in greater detail. It is good to be aware that the command exists, as it may have an application under special circumstances. However, good practice generally dictates manually specifying an iterative “analyze-design-reanalyzecheck” process as described above. When the Select Optimized command is issued the following steps are taken: CHECK CODE ALL, then modify ratios, then SELECT ALL, then PERFORM ANALYSIS, then SELECT ALL. There are some limitations to what the Select Optimized command can handle. In a file with a lot of difficult conditions, for example a file that includes specifications such as Member Tension, Member Cable, Multilinear springs, Tension-only springs, etc., STAAD.Pro may report that it is unable to optimize the model. Also, the Select Optimized command only executes one additional iteration. It does not cause the program to iterate

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endlessly, until it converges to a solution to some n th degree of precision. •

The Select Weld command instructs STAAD.Pro to pick a weld size for moment resisting connections (frame connections).

•

The Select Weld Truss command should be used for pure axial conditions where STAAD.Pro does not have to design for shears and moments.

•

Take Off and Member Take Off commands can be used to generate a Bill of Materials for a model, including a report of the weight of each member. Both commands perform the same basic function, but the Member Take Off command provides a higher level of detail in the output file.

•

The Fixed Group command is an alternate to the Group command. Fixed Group is used with the Select Optimized command, in the same way that Group is used with the Select command.

•

No changes have been made to the model named Dataset 6_5.std.

•


•


-End of Module-

7-1

Finite Element Modeling Module

7

The following topics are included in this module. 7.1 Introduction to Finite Element Analysis .......................................... 2 7.2 How to Create Finite Elements ....................................................... 12 7.3 How to Create Plates with Nodes Off-Grid ................................. 18 7.4 Mesh Generation ............................................................................... 20 7.4.1 Using Structure Wizard to Generate a Mesh ............................. 21 7.4.2 Creating a Mesh From a “Super-Element” ................................ 26 7.4.3 How to Use the Mesh Generation Cursor ................................. 29 7.4.4 Using the Editor to Create a Mesh ............................................ 37


7-2

Module 7

7.1

Introduction to Finite Element Analysis •

Beams and columns are modeled with line-type entities.

•

Modeling walls, roofs, slabs and other surface components requires an area-type entity capable of distributing load in more than one direction.

•

This entity is known as a finite element.

•

In a finite element analysis, a wall or a slab is modeled by an assemblage of small parts consisting of triangles or quadrilaterals.

•

STAAD.Pro documentation uses the terms “finite elements” and “plates” interchangeably.

•

The difference between a beam and a plate relates to their abilities to distribute loads.

•

A load that is applied to a beam can really go in only two directions, towards one end, or the other as indicated graphically in Figure 7. 1 below.

Figure 7. 1 •

By contrast, in a plate, there is more than one path for the load to flow as indicated graphically in Figure 7. 2 below.


Figure 7. 2 •

A plate can be 3-noded (triangular) or 4-noded (quadrilateral).

•

The thickness of a plate may be different from one node to another.

•

All nodes of a 4-noded plate must lie in the same plane. If four nodes do not lie on one plane, use two triangular elements.

•

STAAD.Pro includes another type of entity called a Surface element, which inherently is a mesh of plate elements. Surface elements are not covered in detail in this Module.

•

Another finite element available in STAAD.Pro is a solid element, or cube. Solid elements will not be used in this training. The eight-noded solid element, or cube, is shown in Figure 7. 3 below.

Figure 7. 3

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Solid elements are normally used only in situations where the thickness of the object being modeled is large in proportion to the lateral dimensions. By collapsing various nodes together, an eight-noded solid element can be degenerated to forms with four to seven nodes, as shown in Figure 7. 4 below.

Figure 7. 4 •

In a structure where the ratio of the smallest lateral dimension to the thickness is less than 10, it is generally advisable to model that structure using solid elements, as indicated graphically in Figure 7. 5 below.

Figure 7. 5 Why Use a Mesh? •

When analyzing a beam, if the displacements at the ends are known, the displacements at intermediate points can be determined using secondary analysis techniques like the moment-area method.


Figure 7. 6 •

In a plate, there are no equations to determine the displacement at some arbitrary point within the 3 or 4 corners of the element.

•

It is impossible to accurately model the behavior of a slab using just a single element.

•

Displacements can only be determined at the nodes (corners) of finite elements, and stresses can only be accurately determined at the center of an element.

•

So, to solve for displacements at interior points of a slab, or to determine the deformed shape along the edges of a slab, the slab must be modeled using a series of plate elements, such that the points of interest become nodes of the elements.

•

To determine stresses at points of interest, one must interpolate values between the centers of adjacent elements.

•

Consider a slab supported by a frame, and assume that under load it had a deflected shape similar to the shape shown in Figure 7. 7 below.

Figure 7. 7

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•

In order to obtain deflection information along the indicated edge, it would be necessary to know the deflections at the points of maximum deflection, at the end points, and at a few intermediate points, as shown by the X’s in the figure.

•

The more data points there are, the more accurately the deflected shape can be modeled.

•

On the other hand, it would be undesirable to have too many points, since it would make the structure too cumbersome to analyze.

•

Judgment must be exercised in selecting the number of elements used to model a slab in order to balance accuracy with modeling efficiency.

•

Another situation in which more than one plate element would be needed to model a slab would be when the stresses are to be determined in a slab subject to some type of point loading.

•

At points of application of concentrated loads, it is typically desirable to model many elements in order to determine the stress distribution in the slab caused by the concentrated load.

•

So, rather than just a single element or a few elements, a series or matrix of finite elements is often needed to accurately model the behavior of a wall or slab.

•

This series of elements is commonly referred to as a mesh.

•

Once a mesh has been created, incorporated into a model and used as a basis for further developing the model, it can be difficult to go back later and change the size (i.e. the ‘density’) of the mesh.

Some suggestions that may help determine required mesh size: •

Try to predict the approximate deflected shape of the structure, and envision the number of nodes that would be required to


provide a reasonably accurate indication of that deflected shape. For example, a simply supported plate deflects like a bowl. Envision the deflected shape that would be revealed if longitudinal and transverse sections were cut through the point of maximum deflection. The shape would be parabolic, similar to the deflected shape of a beam. How many points does it take to accurately represent a deflected shape of that type? Probably a total of seven points would be a minimum. Seven points would imply six elements along the length of the beam. Thus a six-by-six grid of elements seems like a minimum for this plate. If the edges of the element are fixed or monolithic with a concrete beam, the deflected shape is more like an inverted hat. In this case, nine or more points may be required to accurately represent the deflected shape. That would imply eight or more elements in that direction. •

Finer meshes may be needed in the vicinity of any concentrated forces in order to visualize the deflected shape or the stresses at that location. One rule of thumb for determining the number of nodes to be modeled around a point load is to start by envisioning a circular area around the concentrated load. Divide that circle into 30° pie-shaped segments. This implies 12 triangular elements around a circle whose center is the location of the point load.

•

A finer mesh should be considered around any holes in a plate, based on engineering judgment.

•

Again, there are no hard-and-fast rules for how many elements to use.

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Module 7

Guidelines for Element Shape: •

The shape of the individual elements is important in order to obtain good results from the finite element analysis.

•

Optimum shape for a quadrilateral element is a square.

•

•

The more a quad plate deviates from a square towards a rectangular shape, the less accurate the results become.

•

The same effect holds true as the corner angles of a quadrilateral plate deviate from 90 degrees.

•

The best results are obtained when the ratio of the element’s longest side to its shortest side is no greater than 2:1. In no case should the ratio exceed 4:1.

•

As a general rule for quadrilateral plates, internal angles of plate elements should be kept between 60 and 120 degrees. Internal angles in excess of 180 degrees are not allowed.

In the case of triangular elements, the ideal shape is an equilateral triangle. •

•

As a general rule for triangular plates, internal angles should be kept as close to 60 degrees as possible.

Figure 7. 8 below, taken from Section 1.6 of the STAAD.Pro Technical Reference manual, shows examples of well-formed and poorly-formed plates.


Figure 7. 8 How to address poorly shaped plates in a model: •

The problem can usually be solved by breaking a badly shaped plate into two or more plates that have a better shape.

•

For example, a badly shaped quadrilateral plate can often be broken into two triangular plates that will have better shapes.

Figure 7. 9 •

Since plates cannot have curved sides in STAAD.Pro, circular structures must be modeled using a series (i.e. mesh) of triangles or quadrilaterals.

•

One way to model circular plates in STAAD.Pro is to draw them using a radial grid.

•

Because the distance between grid points gets larger toward the outside of a radial grid, it is possible to end up with elements near the outer edges that are very long and narrow as shown in the figure below.

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Figure 7. 10 •

When the ratio of the element’s longest side to its shortest side exceeds 4:1, the results of a finite element analysis become questionable, or even impossible to obtain.

•

The figure below shows a method of creating elements so they get smaller towards the center but retain the same approximate proportions between the sides. This is a recommended procedure to avoid receiving error messages or inaccurate results when performing an analysis on a radial structure.

Figure 7. 11


•

Consider all of these things when estimating how many divisions a mesh should have to generate a successful finite element model.

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7.2 How to Create Finite Elements •

Click File | New from the Start Page.

•

Use the following settings in the New dialog: Space frame Length Units: Foot {Meter} Force Units: KiloPound {KiloNewton} File Name: My Dataset 7_0 In the Location field, STAAD.Pro indicates the location where a new file is to be saved. To change the location, click the button with three dots in it, browse to the desired location, and click OK.

•

Click Next.

•

Select Add Plate, and then click Finish. STAAD.Pro opens the Main Window with a grid and the Snap Node/Plate dialog active. This environment looks similar to the grid used earlier to draw beams. The controls for the grid are identical. The only difference is that the Plates Cursor is active, and drawing on the grid produces plates instead of beams.

•

Click the cursor at 4 successive points in a clockwise or counterclockwise direction to experiment with drawing a quadrilateral plate.

•

Toggle off the Snap Node/Plate button in the Snap Node/Plate dialog.

•

STAAD.Pro draws a 4-noded element, automatically closing the polygon from the last node you picked back to the first node.


•

The hot spot concept is the same for plates as it is for drawing beams. The ending node for the last plate becomes the beginning node for the next plate, unless the Control (Ctrl) key is pressed to move the hot spot.

•

It is essential to draw the nodes of a plate element in either a clockwise or counterclockwise sequence.

•

Although STAAD.Pro will allow a plate to be drawn in a sequence that is not clockwise or counterclockwise, a plate defined in this manner will be “warped” and will cause errors when the analysis is run.

•

The geometry shown in Figure 7. 12 below represents an attempt to draw a plate without drawing the nodes in consecutive order, clockwise or counterclockwise. The figure shown below is not two triangular plates, because there is no node where the diagonal lines cross. Instead it is a folded or “warped” rectangular plate.

Figure 7. 12 •

Plates should not be defined in this manner, even though the program does not prohibit nodes from being selected this way. Notice that the Plates Cursor is now automatically activated by STAAD.Pro, based on our decision to Add a Plate.

•

Double-click on the plate just drawn.

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Module 7

•

An element query dialog opens, just as it does for beams and nodes. It provides: •

Node coordinates

•

Lengths of the sides

•

Plate area

•

The Property Constants page does not contain any information at this point, because properties have not yet been defined.

•

More information will appear in the element query dialog as the model is constructed.

•

When the model is completed and the analysis has been run, additional tabs will appear in this dialog for displaying results such as stresses, displacements, etc.

•

Click Close to dismiss the dialog.

•

The Plates Cursor can be used to select plates, copy and paste them, etc. Sometimes there is a noticeable delay when trying to select a plate. This can be caused by the amount of calculation required by the program, to determine if the click point is a point on the surface of a particular element. If this happens, try clicking another location within the same plate.

•

Tool tip help, or “bubble help”, is also available for plates. Hover the Plates Cursor over the plate. A window displaying some information about the plate will pop up next to the Plates Cursor. The amount and type of information displayed by the tool tip help is controlled by selecting the Structural Tool Tip Options command from the View pull-down menu.

•

Click Geometry | Plate in the Page Control.


•

Two tables labeled Nodes and Plates are displayed in the Data Area on the right side of the screen. These tables are analogous to the Nodes and Beams tables for structures composed of linear elements.

•

The Nodes table provides the XYZ coordinates for each node in the model.

•

The Plates table contains a listing of the plates in the model, and their incidences, that is, the nodes at their corners A, B, C and D.

•

The order in which the nodes are listed follows the order in which they were added to the grid.

•

The significance of this order is that it establishes the local coordinate system for the plate.

•

This local coordinate system makes it possible to discuss the stresses on an individual element without having to resolve those stresses with respect to the global coordinate system.

•

Consider the plates with nodes at the corners labeled A, B, C and C as shown in Figure 7. 13 below. The orientation of the local coordinate system axes for plates is determined as follows: 1) The local x-axis is defined to be parallel to the vector pointing from node A to node B. 2) The cross-product of vectors AB and AC defines a vector parallel to the local z-axis of the plate, i.e., Z = AB x AC. The local z-axis is always normal to the plate surface. 3) The cross-product of vectors Z and X defines a vector parallel to the local y-axis, i.e., Y = Z x X. (Both the X and Y axes lie in the plane of the plate.)

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Module 7

4) The origin of the axes is at the center (average) of the 4 node locations (3 node locations for a triangle).

Figure 7. 13 •

The side of the plate from which the z-axis points in the positive direction is considered to be the “top” of the plate.

•

The locations of nodes A, B, C and D are dependent solely on the order they are picked (or typed in the editor) when defining the plate element. Therefore, the orientation of the local axis system is also solely dependent on the order in which the plate corners are selected.

•

Orientation of the plate’s local z-axis determines which surface of the plate is considered the “top” and which is the “bottom.” Note that in the normal process of modeling with plates, it is common to end up with plates in various orientations. To address this, and provide some consistency to the orientation of logical groups of plates, STAAD.Pro provides a tool called Commands | Geometric Constants | Plate Reference Point… This tool can be used to reorient plates as desired.

•

Additional information on creating plate elements, and details on the theoretical basis of STAAD.Pro finite elements are


provided in Section 1.6.1 of the STAAD.Pro Technical Reference manual. Creating Triangular Plates: •

Click Geometry | Snap Grid/Node | Plate | Triangle.

•

Click at three locations on the grid to create a three-noded plate element.

•

Click Snap Node/Plate to toggle it off.

•

Using the Plates Cursor just drawn.

•

Notice that triangular plates can be selected just like rectangular plates.

•


, click on the triangular plate

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7.3 How to Create Plates with Nodes Off-Grid Suppose the goal is to create a plate with a node that is not located at a grid point. Suppose for example that one of the plate corners must be 0.7 feet {0.7 meters} to the right (i.e. in the positive X direction) of an existing grid point. How can this be done? •

Ensure that the Snap Node/Plate button is toggled on. If the Snap Node/Plate dialog is not still open, click Geometry | Snap Grid/Node | Plate | Quad.

•

Press and hold the Control (Ctrl) key. This method allows nodes to be placed without connecting them with plate edges.

•

Click at the four corners of a new plate using the grid.

•

Release the Control (Ctrl) key.

•

Click the Snap Node/Plate button to toggle it off.

•

Select the Nodes Cursor, and then click on the node in the upper right corner to select it.

•

Click Geometry | Move… | Joint.

•

Enter 0.7 in the X field, and then click OK.

•

Click Yes in the pop-up dialog offering the option to split members if the moved node happens to fall on an existing member.

•

Click Geometry | Snap Grid/Node | Plate | Quad.

•

Click the checkbox to Snap to existing nodes too in the Snap Node/Plate dialog.


This is necessary in order to snap to the node that was just shifted off the grid. •

Click on the four newly added nodes to draw the plate.

•

Click the Snap Node/Plate button to toggle it off.

•


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7.4

Mesh Generation •

Suppose a model contains some nodes that define the corners of a wall that is to be represented with a series of finite elements.

•

Such a series or matrix of coplanar finite elements is often referred to as a mesh, and the process of creating a series or matrix of elements is known as mesh generation or meshing.

•

An earlier section demonstrated how to create additional nodes between existing grid points, then draw in the plates from node to node. That is what one might call a “brute force” method for generating a mesh.

•

Fortunately STAAD.Pro offers four alternative methods that are much more convenient and much less labor-intensive. • • • •

•

Structure Wizard method Super-element method Mesh Generator method STAAD.Pro Input Editor method.

These methods will be discussed in detail in the following sections to illustrate four different methods to create a 20 ft x 40 ft {6 m x 12 m} rectangular mesh.


7.4.1

Using Structure Wizard to Generate a Mesh •

The Structure Wizard offers a library of numerous prototype models whose dimensions can be specified parametrically to quickly create a variety of structures. The Structure Wizard can be used to generate plate elements by selecting from several available prototypes, including: • • • • • • •

•

Polygonal Plate With Holes Circular Plate With Holes Quad Plate Cylindrical Surface Spherical Surface Cooling Tower Hyperbolic Paraboloid Shell

Delete any elements in the current model by using the following sequence: Plates Cursor Control (Ctrl) + A to select all members. Delete key to delete all selected members. OK to confirm intent to delete all members. Yes to confirm intent to delete all orphan nodes.

•

Click Geometry | Run Structure Wizard.

•

Verify that the Prototype Models option is selected.

•

Select Surface/Plate Models in the Model Type list. Icons representing the available prototype models for plate-type structures appear in the left pane of the Structure Wizard window. Three prototype structures at the top of the left pane may be used for generating a planar mesh: •

Polygonal Plate With Holes

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Module 7

• •

Circular Plate With Holes Quad Plate

The Quad Plate prototype is well-suited to parametrically define a mesh for a 4-sided plate. •

Double-click the Quad Plate icon.

•

The Select Meshing Parameters dialog provides the following parameters to control the mesh generation: • Corners category: to input the X, Y, and Z coordinates of the four corners A, B, C and D of the plate. Quadrilateral elements would probably be preferred if the plate takes the form of a square or rectangle. If the internal angles of the plate or the length of its opposite sides varies significantly, then triangular elements would probably be the best choice to obtain plates that are properly shaped for the best finite element analysis results. • Element Type category: to choose whether to mesh the quadrilateral surface using triangular elements or quadrilateral elements. • Divn. column: to specify the number of divisions to create along the AB, BC, CD and DA sides. The minimum and maximum limits of number of divisions on each side are 1 and 100 respectively. Two opposite sides may have a different number of divisions. However, if the number of divisions for two opposite sides is different, and if Quadrilateral elements are being used, then the sum of all divisions must be an even number. • Bias column: to create divisions of varying lengths if desired.


If the goal is to create equal divisions along the length of a side, keep the Bias parameter set to its default value of 1. Figure 7. 14 below shows an example with 5 divisions along line BC. Moving from B toward C, the divisions vary from 1 unit long to 5 units long. A mesh with this spacing could be created by specifying the Bias for that side as 5.

Figure 7. 14 Note that the Bias value may also be negative. When negative biasing is specified, the side is divided so that the first division length is the value of the biasing times the last division length. •

The current example is to create a 20 ft x 40 ft {6 m x 12 m} rectangular mesh as shown in Figure 7. 15 below.

•

The geometry must be defined either in clockwise or counterclockwise order to avoid a warped plate.

Figure 7. 15

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Module 7

•

Enter the values in the Select Meshing Parameters dialog as shown below to produce a 10 x 20 mesh of 2-foot {0.6-meter} square plate elements.

Figure 7. 16 •

Leave the Element Type category set to Quadrilateral.

•

Click Apply. A graphical representation of the plate appears in the right pane of the Structure Wizard window. Note that any of the parameters can be revised by doubleclicking on the graphic to re-open the Select Meshing Parameters dialog, or by right-clicking on the graphic and selecting Change Property from the pop-up menu. The effect of changing various parameters can quickly be viewed and evaluated by observing the resulting prototype model in the right pane of the Structure Wizard.

•

Select File | Merge Model with STAAD.Pro Model, click Yes to confirm and OK to finish. By using any combination of the available prototype models, a wide range of structure geometry can quickly be modeled and transferred into the main STAAD.Pro model.


Additional information on using the Structure Wizard to model slabs may be found in Section 2.3.6.16 of the STAAD.Pro Graphical Environment manual. •


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7.4.2

Creating a Mesh From a “Super-Element” •


•

Click Geometry | Snap/Grid Node | Plate | Quad. The grid and the Snap Node/Plate dialog are displayed, and the Plates Cursor is activated.

•

Click the Edit… button in the Snap Node/Plate dialog to modify the settings for the Default Grid.

•

In the Plane category of the Default Grid pop-up dialog, select the X-Y radio button. The grid changes to the orientation of the X-Y plane, which will be appropriate for modeling a wall.

•

In the Construction Lines category, set the parameters as follows: X lines: 20 on the Right with 2 ft. {0.6 meter} spacing. Y lines: 10 on the Right with 2 ft. {0.6 meter} spacing.

•

Click OK. The Default Grid dialog is dismissed, and the grid is displayed in the Main Window.

•

Check to be sure that the Snap Node/Plate button is still turned on, that is, that the Snap mode is active.

•

Click on grid locations in the following order: 0, 0, 0, 20, 40, 20, 40, 0 {0, 0 , 0, 6 , 12, 6 , 12, 0}

•

Snap Node/Plate button to toggle it off.


•

The resulting 20 ft. by 40 ft. {6 m x 12 m} plate is a “superelement” that represents the overall size of the mesh.

•

to select it. When Click the plate with the Plates Cursor the edges highlight to confirm that it is selected, click the right mouse button anywhere in the Main Window. A pop-up menu is displayed.

•

Click on Generate Plate Mesh.

•

Choose the Quadrilateral Meshing option and click OK.

•

The coordinates for the corners automatically appear in the Select Meshing Parameters dialog.

•

Node A is the first node that was clicked to define the plate, Node B is the second one, etc.

•

Leave the Bias parameter in all four fields set to its default value of 1, so that each side will be divided into equal proportions creating equal length elements.

•

Set the Division parameters as follows to produce a 10 x 20 mesh of 2 ft. by 2 ft. {0.6 m x 0.6 m} elements: AB: 10 BC: 20 CD: 10 DA: 20

•

Apply to mesh the plate. Click on the toolbar button that looks like a question mark as shown in the figure below.

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Figure 7. 17 The Structural Diagram Info dialog opens and displays statistical information about the model. In this case, it is useful to confirm that a total of 200 plates exist in the model. •

The Generate Mesh command is an excellent way to generate a mesh from a triangular or quadrilateral surface, but it cannot be used for figures with five or more sides.

•

The next section presents another method for generating meshes that allows a mesh to be created from a super-element of any shape.

•



7.4.3

How to Use the Mesh Generation Cursor •


•

First we will demonstrate how the Mesh Generation Cursor can be used to create exactly the same 20 ft. by 40 ft. {6 m x 12 m} mesh as we created above. Then we will explore how the Mesh Generation Cursor can be used to generate meshes in figures with five or more sides.

•

Select Geometry | Snap/Grid Node | Plate | Quad

•

Select Edit… in the Snap Node/Plate dialog to modify settings for Default Grid as follows: X-Y plane X Constr. Lines: 20 on the Right with 2 ft. {0.6 m} spacing. Y Constr. Lines: 10 on the Right with 2 ft. {0.6 m} spacing. OK.

•

Be sure that the Snap Node/Plate button is still turned on, i.e. snap mode is active.

•

Press and hold Control (Ctrl) key while clicking on grid locations in the following order: 0, 0, 0, 20, 40, 20, 40, 0 {0, 0 , 0, 6 , 12, 6 , 12, 0} to create nodes only. Then release the Control (Ctrl) key.

•

Snap Node/Plate button to toggle off snap mode.

•

Click back in the Main Window and then press Shift + K to highlight nodes.

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As an alternative to the SHIFT + K “hotkey”, nodes can also be highlighted by the following sequence: Right-click on the screen, Select the Labels command from the pop-up menu, Toggle on the Node Points checkbox from the Labels page of the Diagrams dialog, Then click OK. •

Geometry | Generate Surface Meshing to activate the Mesh Generation Cursor.

•

Click the cursor on nodes in the following order: 0, 0, 0, 20, 40, 20, 40, 0, 0, 0 {0, 0 , 0, 6 , 12, 6 , 12, 0 , 0, 0}. Clicking back on the starting node instructs STAAD.Pro to close the figure designating the boundary of the mesh. Another option is to click the four nodes at the corners of the plate and then right-click the mouse instead of clicking back on the starting node.

•

Quadrilateral Meshing , OK The Select Meshing Parameters dialog opens with the coordinates for the corners already filled in. Node A is the first node that was clicked to define the plate, Node B is the second one, etc. The Bias parameter is available if the divisions to be created are NOT all equal. See the example in section 7.7.1 above. A bias value of 1 results in equal-length divisions.

•

Set the Division parameters as follows to produce a 10 x 20 mesh of 2 ft. by 2 ft. {0.6 m x 0.6 m} elements: AB: 10 BC: 20 CD: 10 DA: 20


•

Set Element Type to Quadrilateral, and then click Apply to mesh the plate.

•

The result is a 10 x 20 mesh of 2 ft. by 2 ft. {0.6 m x 0.6 m} elements identical to the mesh created in the previous section.

•

Now let’s explore STAAD.Pro’s ability to generate meshes in figures with five or more sides using the Mesh Generation Cursor.

•


•

Ensure that the Snap Node/Plate dialog is still open and that the Snap Node/Plate mode is active.

•

Hold down Control (Ctrl) and click on 6 different grid locations to place 6 unconnected nodes to serve as the vertices for a new plate.

•

Release Control (Ctrl) and toggle off Snap Node/Plate button.

•

Click back in the Main Window and then press Shift + K to highlight nodes.

•

Select Geometry | Generate Surface Meshing to activate the Mesh Generation Cursor.

•

Click each of the 6 nodes in a clockwise or counterclockwise order.

•

Right-click the mouse after the 6 th node to close the polygon.

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Notice that the Define Mesh Region dialog is similar to the dialog that Structure Wizard displays when the Polygonal Plate With Holes option is selected. The Boundary item in the tree view shows the corner nodes and associated XYZ coordinates of the super-element. It also shows the number of divisions, that is, the number of elements to be created along each side of the polygon, as well as the Bias value as described in section 7.7.1. These numbers can be edited directly in this table. •

Note the HOLES item in the tree in the Define Mesh Region dialog. This is used to enter the data to create holes in the plate. For this exercise, no holes will be added, but if holes were required, the process would be as outlined in the following commentary. If holes are to be added, the procedure is as follows: Click on the item labeled HOLES beneath Boundary item in the tree view. Two new icons appear just above the tree view. Click the Add New Hole icon

.

A new item labeled Hole 1 appears beneath the HOLES item in the tree view. Additional tabs will appear for each new hole that is added. The upper right cell of the Define Mesh Region dialog contains a list to select the Region Type, i.e. the shape of the hole to add.


Figure 7. 18 The input cells change based on the selected Region Type, to offer context-appropriate options for defining holes with different geometries. For the purposes of the example, leave the Region Type set to its default of Polygon. Each row in the table is used to enter the coordinates of one vertex of the current hole. To add new rows to the table, click on the Add New Row icon .

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Figure 7. 19 If it becomes necessary to delete a row, use the Delete Row icon

.

Enter coordinates for each vertex of the hole, moving around the hole in a clockwise or counterclockwise order. Finish the hole definition by reentering the starting vertex coordinate to form a closed boundary for the hole. Once all of the vertices of a given hole have been entered in coordinate form, click back on the item in the tree view labeled HOLES. The Add New Hole tool becomes available if it is necessary to enter data for additional holes. There is also a tool to Delete Holes as shown below, in case it becomes necessary.


Figure 7. 20 Once the data for all of the holes has been entered, the workflow process continues as described below this commentary. Note that holes can also be created in the mesh simply by selecting elements with the Plates Cursor and deleting them, but this method can only be used after the elements have actually been generated. •

Click OK. With this 6-sided shape the program did not display an option to generate either a polygonal mesh or a quadrilateral mesh. That is because STAAD.Pro automatically determined that this 6-sided shape was not a good candidate for quadrilateral meshing, therefore it did not offer that option. However, if only 4 nodes had been picked with the Mesh Generation Cursor before clicking back on the starting node, even if those 4 nodes did not define a rectangular shape,

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STAAD.Pro would have offered the option of either a polygonal mesh or a quadrilateral mesh. Suppose that the current mesh represents a mat foundation, and that the next step is to generate spring supports for all nodes. Imagine how tedious it would be to calculate the spring constant for each one of these! In that situation, the Elastic Mat or Plate Mat Support command comes in very handy. All that is required is to provide the Modulus of Subgrade Reaction. STAAD.Pro calculates the tributary areas and K values automatically. •



7.4.4

Using the Editor to Create a Mesh •

Actions performed in the GUI to build a model have the effect of adding new commands to the STAAD.Pro input file.

•

Click Edit | Edit Input Command File and then click Save.

•

Notice the JOINT COORDINATES and ELEMENT INCIDENCES SHELL sections that have been automatically generated by the use of the Mesh Generation Cursor in the previous section.

•

It is also possible to modify the input file directly, rather than doing it indirectly through the GUI.

•

In some situations, this may be the easiest and most efficient way to add commands or geometry to the input file. This concept holds true for meshes also.

•

Users who are familiar with the command syntax may find that this is the fastest and easiest way to create meshes.

•

The STAAD.Pro Technical Reference manual, Section 5.14 contains a complete description of the commands available for generating meshes.

•

Several examples illustrating how to create meshes using the Input File Editor are presented in the STAAD.Pro Examples manual. See Example Problem No. 9, No. 19 and No. 20.

•

Click File | Exit in the STAAD Editor window to return to STAAD.Pro.

•

Click File | Close to return to the new Start Page.

•


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-End of Module-

8-1

Concrete Design Module

8

The following topics are included in this module. 8.1 Concrete Design Example Problem .................................................. 2 8.2 Defining Model Geometry ................................................................. 4 8.3 Defining Element Properties .............................................................. 6 8.4 Adding the Supports ........................................................................ 11 8.5 Defining Beam – Slab Monolithic Action....................................... 13 8.6 Defining the Slab ............................................................................. 16 8.7 Tools for Viewing Plates................................................................. 20 8.8 Plate Orientation and Local Coordinate System ............................ 21 8.9 Defining Plate Properties ................................................................. 27 8.10 Plate Element Specifications .......................................................... 29 8.11 Assigning the Loads ....................................................................... 32 8.12 P – Delta Analysis ........................................................................... 37 8.13 Providing Analysis Instructions ..................................................... 43 8.14 Running the Analysis ..................................................................... 45 8.15 Viewing the Results ....................................................................... 46 8.16 Reinforced Concrete Design .......................................................... 49 8.17 Understanding Concrete Design Results ....................................... 59 8.18 Additional Concrete Modeling Examples ..................................... 65


8-2

Module 8

8.1

Concrete Design Example Problem •

The kind of entity used to model a beam or a column is a linetype entity that cannot be used to model a slab.

•

STAAD.Pro offers an array of tools for creating plate elements. This module will explore how these tools can be used to effectively model the behavior of a real-world structure.

•

A simple table-like concrete structure will be modeled, such as one that might be used for a bus shelter, for example.

Figure 8. 1 •

This structure will consist of a combination of beams, columns and a slab. For illustration purposes, various types of cross sections will be used for the columns to show how different concrete cross sections can be created.

•

The structure will be a 16-foot by 20-foot {5-meter by 6meter} rectangular slab supported by beams on all four sides. The beams are in turn supported by four 12-foot {4-meter} tall columns at each corner.


Figure 8. 2 •

Two columns will be 18-inch {450 mm} diameter circular sections, and two will be 16-inch {400 mm} deep by 20-inch {500 mm} wide rectangular sections.

•

The beams will be 20 inches {500 mm} square, and the slab will be 8 inches {200 mm} thick.

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8.2

Defining Model Geometry •

Click New Project in the Project Tasks area on the Start Page.

•

Select Space frame.

•

Name the file My Concrete Example.

•

Set Length Units to Foot {Meter} and Force Units to KiloPound {KiloNewton}.

•


•

Click the Open Structure Wizard checkbox.

•

Click the Finish button.

•

Click File | Select Units in the Structure Wizard main menu. Ensure that the units are set to Feet {Meters}, and click OK.

•

Select Frame Models from the Model Type list.

•

Double-click on the Bay Frame icon.

•

In the Select Parameters dialog, enter the values as shown in the following figure {For metric units, Length = 5 m, Height = 4 m, and Width = 6 m}:

Figure 8. 3


•

Click the Apply button.

•

Note the location of the coordinate axis tripod in the righthand pane of the Structure Wizard window. This is the reference location on the prototype model.

•

When the prototype is merged with the STAAD.Pro model, if nothing is done to change this location, the prototype will be placed in the STAAD.Pro model such that this reference location coincides with the origin of the global coordinate system.

•

Click File | Merge Model with STAAD.Pro Model in Structure Wizard’s main menu.

•

Click Yes to confirm the intent to merge. The Paste Prototype Model dialog is used to specify the location in the global coordinate system at which the prototype model is to be inserted into the STAAD.Pro model. For this exercise, leave the values in this dialog set to 0 to insert the reference point of the prototype model at the origin of the global coordinate system.

•

Click the OK button to complete the merge.

•


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8.3

Defining Element Properties •

Open the file named Dataset 8_1.std. The next step is to assign properties to the beam and column elements in the model. All beams in this model will have square cross sections with the depth and width equal to 20 inches {500 mm}. Two of the columns will be rectangular in cross section, 16 inches {400 mm} wide by 20 inches {500 mm} deep. The other two columns will be of circular cross section, 18 inches {450 mm} in diameter.

•

Since the dimensions of all beam and column properties are defined in units of inches {millimeters}, it is more convenient to set the input units to inches {millimeters}. See commentary below for step-by-step instructions. Click Tools | Set Current Input Unit…. Click the Inch {Millimeter} radio button in the Length Units category. Click OK.

•

Click the General page tab in the Page Control. The Property sub-page is active by default.

•

Click the Define button in the Properties-Whole Structure dialog. The diagram on the Circle page indicates that the value YD represents the diameter of the circular section. Since the current input units are set to inches {millimeters}, the label “in {mm}” is shown just to the right of the YD field.

•

Enter 18 {450} in the YD field.

•

Leave the Material checkbox toggled on, and leave the Material list item set to Concrete.


This will ensure that STAAD.Pro assigns default material constants for concrete to these members. •

Click the Add button. The 18-inch {450 mm} circular concrete section is added to the list in the Properties-Whole Structure dialog.

•

Click the Rectangle tab. The diagram shows that YD represents the depth of the member, and ZD is the width.

•

Enter 20 {500} in the YD field and 16 {400} in the ZD field.

•

Keep the Material checkbox toggled on, and leave the Material list item set to Concrete.

•

Click the Add button. A Rect 20.00x16.00 Concrete {Rect 0.50x0.40 Concrete} section is added to the list in the Properties-Whole Structure dialog. The last section to be added is for the beams.

•

Enter 20 {500} in the YD field and 20 {500} in the ZD field on the Rectangular page to define the section for the beams.

•

Keep the Material checkbox checked, and keep the Material list item set to Concrete.

•

Click the Add button. A Rect 20.00x20.00 Concrete {Rect 0.50x0.50 Concrete} section is added to the list in the Properties-Whole Structure dialog.

•


•

Click in the Main Window, and then press Shift + B to turn on the Beam Numbers. The circular cross-section applies to the two columns in the rear of the structure; that is, members number 2 and 3.

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•

Click the Cir 18.00 CONCRETE {Cir 0.45 CONCRETE} item in the section list in the Properties - Whole Structure dialog.

•

, press and hold the Control Using the Beams Cursor (Ctrl) key, and then click on members number 2 and 3 to select both rear columns. Note that the Assignment Method in the Properties – Whole Structure dialog automatically changes to Assign To Selected Beams.

•


•

Click Yes in the pop-up dialog to confirm the assignment.

•

Click the Rect 20.00x16.00 CONCRETE {Rect 0.50x0.40 CONCRETE} item in the section list.

•

Using the Beams Cursor , press and hold the Control (Ctrl) key and then click on members 5 and 6 to select both front columns.

•


•

Click Yes to confirm the assignment of the column section to the selected members.

•

Reference numbers should now be visible on all four columns. They correspond to the cross section property reference numbers listed in the Ref column in the Properties – Whole Structure dialog.

•

If reference numbers are not visible on the columns, they can be turned on by following the steps in the commentary below. Right-click in the Main Window. Select the Labels command from the pop-up menu. Locate the Properties category on the Labels page of the Diagrams dialog.


Toggle on the References checkbox, and then click OK. •

Click on 1 Cir 18.00 {1 Cir 0.45} in the first line of the Section list on the Properties - Whole Structure dialog.

•

The member numbers of the members to which that property is assigned are shown in the field at the bottom of the dialog.

•

Ensure that the Highlight Assigned Geometry checkbox is checked. It is located just beneath the Properties list in the Properties – Whole Structure dialog.

•

When this checkbox is toggled on, and a property is selected in the Properties list, the members that have been assigned that property are highlighted in the Main Window. The next step is to assign the square cross section to the perimeter beams.

•

Click the Rect 20.00x20.00 CONCRETE {Rect 0.50x0.50 CONCRETE item in the properties list.

•

Set the view to the Front view to make it easy to select all beams at once. See step-by-step-instructions in the commentary below. Click View | Orientation… . Click the Front button, and then click Apply. The main view changes to the Front view. Click Close. A quick alternative way of switching to the Front view is to click the View from +Z toolbar button toolbar.

•

on the Rotate

Click and drag a rubber band line around the horizontal members in the Front view using the Beams Cursor.

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•

to switch back to the Click the Isometric View button isometric view and confirm that all beams are selected. Note that the Assignment Method in the Properties – Whole Structure dialog has automatically set itself to Assign To Selected Beams.

•

Click the Assign button, and then click Yes to confirm. The square concrete cross section property is assigned to all beams. Now all beams and columns have properties assigned to them.

•


•


•



8.4

Adding the Supports •

Open the file named Dataset 8_2.std. All four columns in the model are to have fixed supports at their bases. The general process here is to create, or Add, a fixed support to the model, and then Assign it to the bases of each of the columns.

•

Click on the Support sub-page tab of the General page in the Page Control.

•

Click the Create button in the Supports – Whole Structure dialog.

•

The Fixed page is active by default.

•


•

The fixed support is added to the list in the Supports-Whole Structure dialog.

•

Click on Support 2 in the Supports-Whole Structure dialog to highlight it. The Assign button in the dialog changes from an inactive (“grayed-out”) status to an active status.

•

Confirm that the Assignment Method category is automatically set to Use Cursor To Assign.

•

Click the Assign button. It turns white and changes to say Assigning, and the Support Cursor is activated.

•

Click at the bases of the four columns to assign the fixed support to each one.

•

Click the Assigning button once again to turn off the support assigning mode and deactivate the Support Cursor.

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•


•


•



8.5

Defining Beam – Slab Monolithic Action •

This example raises an important aspect of modeling with plates. When a plate shares a boundary with a beam, how can the condition be modeled to ensure that the beam and the plate behave monolithically in the model?

•

If the beams were defined as going between the columns, and the slab was meshed on top of them, then the beams and the slab would only be connected at the four corners.

•

In order to guarantee monolithic behavior, the beams must be subdivided at exactly the same points as the slab, and those nodes must be common to the incidences of the beams and the slab elements. If this is done correctly, then there will be sharing of loads and stiffness at those points.

•

This will ensure that a load from the slab will be transmitted from the slab into the beams, and through the beams into the columns.

•

STAAD.Pro has a feature that will facilitate this process. It appears in the View | Options… | Tolerance menu in the form of the checkbox titled Split member if new node is added on the member as shown in the figure below.

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Figure 8. 4 •

When this checkbox is selected, if a meshed slab is modeled on top of a beam model, STAAD.Pro will automatically split the beam and create a node at any location where a slab node falls directly on the beam. This feature can save a considerable amount of work, since it relieves the user of having to perform these repetitive steps.

•

Similarly, if a super-element is created and meshed on top of an existing beam element, the beam will automatically be split when the meshing takes place.

•

Note that the beam must be created first, and then the mesh dropped onto it in order for STAAD.Pro to be able to split the member and coordinate the nodes.

•

If a plate mesh is created first, and then the beam is added afterwards, the beam will not be split automatically.

•

In this instance, another feature called Break Beams at Selected Nodes can be used.


•

While not as powerful as the method described above, the Break Beams at Selected Nodes feature can still significantly reduce the effort involved in manually breaking up beams when the intent is to model beam – slab composite action.

•

It can be located by clicking Geometry | Break Beams at Selected Nodes.

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8.6

Defining the Slab •

Open the file named Dataset 8_3.std. The instructions in this section will add the plate elements to the model. The sequence of operations presented in this Module does not necessarily follow the recommended workflow process in STAAD.Pro. In reality, the creation of the plate elements would typically occur immediately after the creation of the beam and column elements, and before the assignment of section properties. However, for training purposes, it is more convenient to present the material in the order outlined in this Module.

•

Note in the lower right-hand corner of the Status Bar that the current input units are set to kip-in {kN-mm}. For the following exercise, it may be more convenient to set the input units to Foot {Meter}. See commentary below for step-bystep instructions. Click Tools | Set Current Input Unit…. Click the Foot {Meter} radio button in the Length Units category. Click OK.

•

Since the four corner points along the top are already defined, the mesh generation cursor can be used to define the slab.

•

Click Geometry | Generate Surface meshing.


Figure 8. 3 •

Click on the first corner point A, and then click on the other three corner points B, C and D with the Mesh Generation Cursor. Select the nodes in clockwise order around the perimeter of the slab to stay consistent with the dataset model.

•

Finally, click again on the starting point A. When the starting point is clicked the second time, it indicates to STAAD.Pro that the “loop has been closed” and that the area to be meshed has been completely defined. An alternative would be to right-click the mouse to signify that the boundary is complete.

•

STAAD.Pro opens a dialog labeled Choose Meshing Type. STAAD.Pro recognizes that a figure with four sides has been defined, so it offers the choice of either Polygonal or Quadrilateral meshing. Since the figure is rectangular, it is a good candidate for a quadrilateral mesh.

•

Click the Quadrilateral Meshing radio button, and then click the OK button.

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Module 8

•

The corner labels A, B, C and D in the Select Meshing Parameters dialog correspond to the successive points used to define the extent of the slab.

•

Corner A is the first corner that was clicked when the mesh was defined. B is the second corner clicked, etc…

•

Set the Divn. parameters as indicated in the figure below:

Figure 8. 4 •

Click the Apply button.

•

The mesh is automatically generated and displayed in the Main Window.

•

Press the escape key to deactivate the Mesh Generation Cursor.

•

Press Shift + K to turn on node point labels.

•

Press SHIFT + N to turn on node numbers. By specifying only 4 divisions for the 16-foot {5 meter} sides and 5 divisions for the 20-foot {6 meter} sides, the resulting mesh consists of 4-foot square {1.25 meter by 1.2 meter rectangular} elements. For more accurate results, the model would probably warrant more divisions. It is hard to obtain an accurate picture of the


deflected shape of the model with only 5 or six data points on a side. However, as a learning exercise, this simple model will suffice. It will keep the screen from getting cluttered and make the model easy to work with. •

Click on one of the beams with the Beams Cursor

•

The beam segments can be selected in individual 4-foot {1.25 or 1.2 meter} lengths, and the beam segments start and end at the plate corners. This confirms that they have been meshed, that is, that they have been broken into segments that coincide with the nodes of the plate elements.

•


•


•


.

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8.7

Tools for Viewing Plates •


•

Right-click anywhere in the Main Window and select Structure Diagrams… from the pop-up menu. The Diagrams dialog opens with the Structure page active.

•

Toggle on the checkbox labeled Fill Plates/Solids/Surface under the View category. This will “paint over” the surface of the plate elements, making them easier to read graphically.

•

In addition, toggle on the checkbox labeled Shrink, and verify that the value in the associated field is 10%. This will reduce the size of the plates and beams with respect to the nodes to which they connect. Doing this distinguishes the plates from the beams, and makes it easier to view the connectivity more clearly.

•

Click OK.

•

Click the Geometry page tab, and then click the Plate subpage tab.

•

Click on any one of the rows in the Plates table and notice that the corresponding element becomes highlighted.

•

Right-click in the Main Window, and then select New View… from the pop-up menu.

•

Select the Create a new window for the view radio button, and then click OK.

•

The single element that was highlighted in the Plates table is displayed in the new window. This can be a handy way to clearly display just one element.

•



8.8

Plate Orientation and Local Coordinate System •

With the model named Dataset 8_4.std still open, right-click inside the new view window showing the single plate element.

•

Select the Labels command from the pop-up menu.

•

Under the Plates category on the Labels page, toggle on the Plate Orientation checkbox, and then click OK.

•

The local x, y and z axes are drawn on the plate.

•

Why is the local axis system oriented with the z-axis pointing downward? The answer relates to STAAD.Pro’s convention for orienting the axes of a plate element as reviewed in the commentary below. (See also Section 1.6.1 of the STAAD.Pro Technical Reference manual.) Consider the plates as shown in the figure below with nodes at the corners labeled A, B, C and D. The orientation of the local coordinate system axes for plates is determined as follows: 1) The local x-axis is defined to be parallel to the vector pointing from A to B. 2) The cross-product of vectors AB and AC defines a vector parallel to the local z-axis, i.e., Z = AB x AC. The z-axis is normal to the plate surface. 3) The cross-product of vectors Z and X defines a vector parallel to the local y-axis, i.e., Y = Z x X. (Both the X and the Y axes lie in the plane of the plate.) 4) The origin of the axes is at the center (average) of the 4 node locations (3 node locations for a triangle).

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Figure 8. 5 • The orientation of a plate’s local axis system is dictated solely by the order in which the corner nodes for the plate are specified. For the single plate currently being displayed in the new view, the incidence order of the nodes can be determined by looking at the corresponding row in the Plates table. In the example below, the nodes are specified in the order 10, 13, 19 and 17.

Figure 8. 6 Consider nodes 10, 13, 19 and 17 to be A, B, C and D respectively. It is now easy to confirm that STAAD.Pro has drawn the local x-axis parallel to vector AB. The vector AC points from node 10 to node 19.


Use the right-hand rule to take the cross product of vector AB and vector AC to define a vector parallel to the local z-axis. The z-axis is normal to the plate surface. Envision a screw with right-hand threads, oriented perpendicular to the plane defined by the vectors AB and AC. If the screw was rotated in the direction from vector AB to AC, it would move downwards. Therefore, vector z, the local z-axis for this plate, points downward. Alternatively, consider closing vector AB into vector AC with the fingers of the right hand. The right thumb will point downward, confirming the direction of the resulting crossproduct vector, z.

Figure 8. 7 • In STAAD.Pro, the side of the plate from which the z-axis points in the positive direction is considered to be the “top” of the plate.

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The “top” surface of the plate in the figure above is actually facing downward, and the “bottom” surface is facing up. This situation could lead to a lot of confusion if a reinforced concrete design was being performed, as STAAD.Pro reports the steel reinforcement required with respect to the local top and local bottom of the element. With an “upside-down” orientation of a plate like this, it would be very easy to lose track of the actual orientation, and place reinforcing steel on the wrong face. • To avoid confusion, many people find it desirable to coordinate the local top with a global top. In other words, to have the local z-axis for all (horizontal) plates pointing upward (parallel to global Y-axis). • That way, when a vertical loading is applied, it is easy to understand which direction the load is acting with respect to the plates’ local coordinate system. • There is a simple way to do this in STAAD.Pro. • Click the X in the upper right corner of the window with the single plate to close that window and return to the Main Window with the entire structure. • Right-click in the Main Window. Select Structure Diagrams… from the pop-up menu. The Diagrams dialog opens with the Structure page active. • Toggle off the Fill Plates/Solids/Surface and Shrink checkboxes. • Click the Labels tab. • Toggle on the Plate Orientation checkbox, and then click OK. • It is now clear that the local z-axis is oriented downward for all plates in the current model.


• Activate the Plates Cursor if it is not already active. Select all plates in the structure. • Click Commands | Geometric Constants | Plate Reference Point…. The Plate Reference Point tool can be used to rearrange the incidences of plates such that their local z-axes point in the general direction of some point above the top of the structure. This can be done by entering the coordinates of a reference point and then specifying whether the local z-axes are to point toward or away from the reference point. • Enter a value of 1000 in the Y field of the Point category. • Select Towards Ref. Point in the Local Z Axis category. Since the plates were selected before entering this dialog, the Assign category defaults to the To Selection option. • Click OK. • STAAD.Pro revises the incidences in the Plates table. The plate orientation symbols now indicate that the local z-axis of all plates is pointing up. A new view was created earlier with just a single plate. It is worth noting that if the same plate was viewed again, the node numbers and orientations would be no different. The change in the “top” orientation of the plate is affected by altering the order in which the nodes are listed in the Plates table. To see this effect, compare the figure below with Figure 8. 6 above.

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Figure 8. 8 Before the Plate Reference Point command was used, the nodes were listed in clockwise order from Node A to Node D. Now they are listed in counterclockwise order. As a result, the zaxis points upward instead of downward. •


•


•



8.9

Defining Plate Properties •

Open the file named Dataset 8_5.std. The next step is to assign properties to the plate elements in the model. The slab will be 8 inches {200 mm} thick.

•

Since the plate thickness is defined in units of inches {millimeters}, it is more convenient to set the input units to inches {millimeters}. See commentary below for step-by-step instructions. Click Tools | Set Current Input Unit…. Click the Inch {Millimeter} radio button in the Length Units category. Click OK.

•

Click the General page tab in the Page Control. The Property sub-page is active by default.

•

Click the Thickness button in the Properties – Whole Structure dialog. The Plate Element Thickness page allows the flexibility of defining a different thickness at each node, if necessary.

•

Enter a value of 8 inches {200 mm} in the Node 1 field. Note that STAAD.Pro automatically populates the other three node thickness fields with the same value.

•

Leave the Material checkbox toggled on, and leave the Material list item set to Concrete. This will ensure that STAAD.Pro’s default material constants for concrete are assigned to the plate elements.

•


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•

Highlight the Plate Thickness CONCRETE property in the structure properties list. Since every plate in the model is going to receive the 8-inch {200 mm} plate thickness, there is no need to use a cursor to assign the thickness property to the plates.

•

Toggle on the Assign To View radio button in the Assignment Method category, and then click Assign .

•

Click Yes in the pop-up dialog to confirm. The reference number shown on all plates confirms that the 8inch {200 mm} thickness property has been assigned.

•


•


•



8.10

Plate Element Specifications •


•

Click the General page tab, and then click the Spec sub-page tab.

•

Click the Plate button in the Specifications – Whole Structure dialog.

•

The Release tab (active by default) can be used to specify releases for nodes that define plates in the same way that releases can be assigned to beams. Releases can be applied to one or more of the six degrees of freedom at any node. This is not a feature that is needed very often, but it is there in case it is needed.

•

Click the Ignore Inplane Rotation tab. This tab can be used to add the specification called Ignore Inplane Rotation. •

STAAD.Pro normally takes into consideration in-plane rotation of plate elements. In other words, plates are assumed to have some inherent flexibility.

•

This means that the length of the diagonals connecting opposite corners of a wall would change slightly as a force is applied to the corner of the wall as shown in the figure below.

Figure 8. 9

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•

If the wall was considered a rigid body, however, the length of the diagonals connecting opposite corners of the wall would remain the same.

•

If the goal is to model the wall to behave as a rigid body, the Ignore Inplane Rotation specification can be used. This feature is not used very often. One potential use would be to compare STAAD.Pro’s analysis results with those of another structural analysis program that ignores in-plane rotation by default.

•

Click the Plane Stress tab. This tab can be used to add another specification called Plane Stress. •

A Plane Stress specification means that a plate can only carry an axial force. It cannot resist any component of force acting perpendicular to the plane of the plate.

•

Normally a steel or concrete plate has some amount of stiffness to carry bending loads. However, STAAD.Pro can be instructed to completely ignore the bending stiffness by specifying the plate as a Plane Stress element.

•

Bear in mind that using the Plane Stress specification on a structure like the slab in the current model can lead to “loss” of loads such as self-weight, because, for “Plane Stress” elements, the out-of-plane shear action and the bending degrees of freedom are switched off. One application of this specification is for modeling some soft material like cloth or a balloon skin.

•

Click the Ignore Stiffness tab. This tab can be used to add another specification called Ignore Stiffness. •

The Ignore Stiffness specification is provided to handle special types of load situations such as pressures over zones.

•

The Ignore Stiffness specification enables entities to be modeled purely for the purpose of transmitting loads, but not for any contribution of stiffness to the model.


One application of this specification is for the facade of a building. Glass panels are usually present over such regions, and bear the brunt of wind forces. The stiffness of such panels is typically ignored in a structural analysis. The Ignore Stiffness specification makes it possible to model plates that represent the facade, and to use them as a convenience for applying wind loads to the structural frame, without considering any stiffness from those particular plates when the analysis is run. •

None of these additional specifications will be used in the current model.

•

Click Close to dismiss the Plate Specs dialog.

•


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8.11

Assigning the Loads •

Ensure that the file named Dataset 8_6.std is the active model. The next step is to assign loads to the structure.

•

Look at the right end of the Status Bar at the bottom of the STAAD.Pro window, and note that the current input units are set to kip-in {kN-mm}. Input units of inches {millimeters} are not very convenient for specifying loads.

•

Set the length input units back to feet {meter}. Step-by-step instructions are provided in the commentary below. Click Tools | Set Current Input Unit…. Click the Foot {Meter} radio button in the Length Units category of the Set Current Input Units dialog. Click OK.

•

Click the General page tab, and then click the Load & Definition sub-page tab in the Page Control.

•

Click the New button in the Load & Definition dialog.

•

The Create New Definitions/Load Cases/Load Items dialog contains 4 tabs – Definitions, Load Case, Load Items, and Load Envelopes.

•

The commentary below presents some review on terms related to loads in STAAD.Pro. Definitions: •

Click the Definitions tab.


•

This tab contains the options used to generate the “DEFINE” block of data in the input file.

•

The “DEFINE” block is required to create Code-specified load cases such as wind, seismic, and snow.

•

It is also required to generate moving load cases, time history load cases, and pushover loads.

•

The command syntax for these cases is explained in section 5.31 of the STAAD.Pro Technical Reference manual.

Load Case: •


•

This tab contains the dialog used to initiate a new load case (primary load, moving load, or load combination) and assign it a case number.

Load Items: •

Click the Load Items tab.

•

This tab contains the dialogs used to add loading data to load cases.

Load Envelopes: •

Click the Load Envelopes tab.

•

This tab contains the dialog used to create load envelopes.

•

These envelopes can later be used for Post Processing.

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Load Case 1 Load Case 1 consists of a vertical load over the full surface of the slab. The magnitude of the load is 400 lb. per square foot {20 kiloNewtons per square meter}, acting downward. •


•

Type the name Pressure Load in the Title field.

•

The Loading Type category can be left at the default value of None for this exercise, because the automatic load combination generation facility will not be used. There is no need to associate this load case with any load types.

•

Click the Add button, but do not close this dialog yet.

•

Click on 1: Pressure Load in the Load & Definition dialog. This is the way to tell STAAD.Pro that the next load item will be added to the load case entitled 1: Pressure Load.

•

Click the Load Items tab in the Create New Definitions/Load Cases/Load Items dialog. All the available load types are displayed here.

•

Click the Plate Loads category tab. The Pressure on Full Plate tab is selected by default.

•

Enter a value of -0.4 kip/ft 2 {-20 kN/m 2 } in the Load category. (Note the minus sign.)

•

The Local Z radio button is selected by default in the Direction category. In this particular case, choosing Local Z or GY (global Y) has the same effect, since Local Z points in the global Y-direction.

•



•

The expression PR –0.4 kip/ft2 {PR -20 kN/m2} appears under 1: Pressure Load in the Load & Definition dialog. The question mark in front of the expression indicates that it has not been assigned to any elements yet.

•

This load case will be assigned to specific entities after all the load cases have been created.

Load Case 2 Load Case 2 consists of a 600 pound {3 kN} horizontal load that might cause the structure to sway. •

Click the Load Case tab in the Create New Definitions/Load Cases/Load Items dialog. Note that STAAD.Pro automatically increments the Number of the load case.

•

Type the name Lateral Load in the Title field.

•

Leave the Loading Type box set to None since there is no need to associate this load case with any code-based load types.

•


•

Click on 2: Lateral Load in the Load & Definition dialog.

•

Click the Load Items tab in the Create New Definitions/Load Cases/Load Items dialog.

•

Click the Nodal Load category tab. The Node tab is selected by default.

•

Enter a value of 0.6 kips {3 kN} in the Fx field, and then click the Add button. The expression FX 0.6 kip,ft {FX 3 kN,m} appears under 2: Lateral Load in the Load & Definition dialog.

•

Click the Close button to dismiss the Create New Definitions/Load Cases/Load Items dialog.

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The next step will be to assign the two new load cases with specific entities. •

Click the expression PR -0.4 kip/ft2 {PR -20 kN/m2} in the Load & Definition dialog.

•

Click the Assign To View radio button, and then click Assign.

•

Click Yes in the pop-up dialog to confirm. The next step is to assign the second load case to just a single node on the structure, so that the load will create a torsional deflection pattern, and the structure will twist in plan view.

•

Click the expression FX 0.6 kip,ft {FX 3 kN,m} in the Load & Definition dialog.

•

Click the Use Cursor To Assign radio button followed by the Assign button. The Assign button becomes active, and the label changes to say Assigning, indicating that the Loads Assignment Cursor has been activated.

•

Press Shift + N to display node numbers.

•

Click on node 3 to assign the 0.6 kip {3 kN} load to the top of the column.

•

Click the Assigning button to toggle off the Loads Cursor. It is important to remember to turn off the Assigning mode after assigning loads, to avoid unintentionally assigning loads by clicking in the structure for some other purpose later on.

•



8.12

P – Delta Analysis •

Consider a column of length L that has two concentrated loads applied at the top of the column: a vertical load P and a horizontal load H.

•

According to a linear elastic analysis, the reactions at the base of the column for these two loads will be a vertical reaction of magnitude P, a horizontal reaction of magnitude H and a moment equal to H*L as shown in the figure below.

Figure 8. 10

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•

This is to say that the result of Loads A and B acting simultaneously is equivalent to the result of Load A plus the result of Load B.

•

This logic represents a linear combination, which can be created in STAAD.Pro using the Define Combinations tab.

•

This method of load combination could be more accurately termed “result combination”, because it does not truly analyze a combined load case. It simply instructs the program to combine the results of multiple load cases.

•

The implicit assumption with this type of load combination is that the effect of the combined loading is equivalent to the sum of the effects of the individual loads.

•

This may or may not be a valid assumption, and it warrants consideration on the part of the design professional.

•

The linear-elastic type of analysis is not permitted with some design codes, including the ACI code. There is an extra effect called the P – Delta effect which must be taken into account when designing according to the ACI code.

•

In a real structure, the horizontal force H might be caused by a wind load or earthquake load, causing the column to deflect a distance Δ. The taller the column, the greater the distance Δ for a given force H.

•

The vertical force P might represent a dead load or a live load. So, in reality, these load cases would act simultaneously, not independent of each other.

•

During this simultaneous action of the two loads, while the column is deflecting due to the action of the horizontal load, the position of the vertical load P shifts a distance Δ so that the vertical load, instead of acting axially along the column, now induces a moment reaction at the base of the column equal to P * Δ.


•

The total moment reaction at the base of the column is now (H * L) + (P * Δ) as shown in the figure below. However, the additional component of moment, P * Δ, is not apparent in a linear –elastic analysis.

Figure 8. 11 •

When considering the equations of static equilibrium, the quantity (P * Δ) is not actually seen in the “applied load” side of the equation, but appears in the reaction side of the equation.

•

This is a linear – inelastic analysis. In this type of analysis, it is not correct to simply take the combination of the results of Load A plus the results of Load B.

•

The results of Load A just give a reaction P.

•

The results of Load B just gives a reaction H * L.

•

Looking at these two load cases in isolation, the P – Delta effect never becomes apparent.

•

It is only when these two load cases act simultaneously that the P – Delta effect is produced. Consequently, the traditional

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linear-elastic load combination, where results are just added up, is not going to reveal the P – Delta value. •

The ACI code indicates that in the design of a column, the slenderness effect can be accounted for using two different methods.

•

One method is called the moment magnifier approach, which uses some code-based equations to approximate these second order effects.

•

The other method is to perform a P – Delta Analysis.

•

The next step in the example model will be to create a third load case that is a combination of the first two load cases.

•

In this example, an alternate method of combining loads will be used, one that correctly accounts for the P-Delta effect by applying the horizontal and vertical loads simultaneously.

•

There are actually a couple of ways to achieve this in STAAD.Pro.

•

One way would be to put both loads in a single load case, instead of creating separate load cases for the horizontal and vertical loads, as was done in this model.

•

Although it is possible, this is not a very convenient method, because of all the different load cases that would be required to correctly model all of the required load combinations.

•

This method would also be undesirable from the standpoint that it is often necessary to evaluate a structure for individual load cases as part of the overall structural evaluation/design. Combining multiple forces into each load case would make this evaluation impossible.

•

Instead of requiring all the loads on the structure to be jumbled into a single load case in order to carry out a P – Delta Analysis, STAAD.Pro provides another type of primary load that “looks like” a load combination.


•

It is called a Repeat Load, and it is a primary load where the program is instructed to create a new load case whose constituents are derived from the various existing load cases with any necessary load factors applied to them.

•

Using the Repeat Load command is a two-step process. First, a new Repeat load case must be created, and then the constituent load cases and their respective factors must be identified and associated with the new Repeat Load case.

•

Click on Load Cases Details in the Load & Definition dialog, and then click the Add button.

•

A Repeat Load is actually a primary load, and the Primary tab is active by default in the Add New:Load Cases dialog.

•

Type the name Loads 1 + 2 in the Title field.

•

Leave the Loading Type set to None by default, since this new load case will not be associated with any code-based load types.

•

Click the Add button, but do not close this dialog yet.

•

Click on the expression 3: Loads 1 + 2 in the Load & Definition dialog. This is the way to tell STAAD.Pro that the next component is to be added to this load case. Note that the Add New:Load Cases dialog automatically changes to the Add New:Load Items dialog.

•

Click the Repeat Load tab in the Add New:Load Items dialog. The Repeat Load tab contains two items: Repeat Load and Reference Load. The Repeat Load item is active by default. The left side of this dialog lists the existing Available Load Cases. The right side displays the Repeated Load Definition.

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Loads can be moved back and forth between the Available Load Cases on the left and the Repeated Load Definition on the right using the arrow buttons. The Factor field is available to apply factors to individual load cases that comprise the Repeated Load Definition. •

Click on 1: Pressure Load in the Available Load Cases list.

•

Click the single right arrow button to move the load to the Repeated Load Definition list.

•

Since the design will be based on the ACI code, the loads should be factored.

•

Apply a dead load factor of 1.2 in the Factor field.

•

Click on 2: Lateral Load in the Available Load Cases list.

•

Click the single right arrow

•

Enter a Factor of 1.6, and click the Add button.

•


button.

The new Repeat Load case is shown in the Load & Defintions dialog. The syntax is load case 1 with a factor of 1.2 load case 2 with a factor of 1.6. •

Remember to always use the Repeat Load specification, rather than the Load Combination specification, any time a P – Delta analysis is to be performed.

•


•


•



8.13

Providing Analysis Instructions •

Open the file named Dataset 8_7.std. The next step is to issue the analysis instructions.

•

Click on the Analysis/Print tab in the Page Control.

•

Click on the PDelta Analysis tab in the Analysis/Print Commands dialog.

•

The PDelta Analysis page includes a field labeled Number of Iterations, and a field labeled Converge.

•

If a Number of Iterations, n is specified, STAAD.Pro will iterate n times.

•

An alternative to specifying a Number of Iterations is to use the Converge option. See the following commentary for additional information about the Converge option, but take special note of the “word of caution” below. When the Converge checkbox is selected, STAAD.Pro will continue to iterate and compare joint displacements with a convergence displacement tolerance. The default convergence displacement tolerance is equal to the maximum span of the structure divided by 120. Note that this default value was not intended to suggest an “optimum” value. It was merely put in place to allow the engineer to apply his or her own value based on engineering judgment. To specify a different value for the convergence displacement tolerance, use the SET DISPLACEMENT f command in the input file. Refer to section 5.5 of the Technical Reference manual. The Converge command has the option of specifying a maximum number of iterations, “m”. If “m” is specified, the analysis will stop after that iteration even if convergence has

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not been achieved. If convergence is achieved in less than “m” iterations, the analysis is terminated. •

A word of caution about the use of the CONVERGE option: it is possible that a model using the CONVERGE option may have 2 early iterations with results close enough to be deemed converged. However, if the same analysis was changed to not use CONVERGE but instead to specify many more iterations, occasionally buckling would be detected. Experience shows that it generally takes 5 to 35 iterations to reach buckling failure. So in this day and age where computing power and speed is so abundant, good practice dictates avoiding the use of the CONVERGE feature and instead using the option to set the Number of Iterations high enough to prove that the structure is stable for a given load case.

•

Enter 35 in the Number of Iterations field.

•

Leave all other options at their default settings, and click the Add button to add the P – Delta Analysis command to the input instructions.

•

Click the Close button to dismiss the Analysis/Print Commands dialog.

•


•


•



8.14

Running the Analysis •


•

The model is now ready to analyze.

•


•

The program should be able to run the analysis and generate results. The message Analysis Successfully Completed should appear in the lower portion of the STAAD Analysis and Design dialog, followed by some messages indicating that the program created some results files.

•

Click the Go to Post Processing Mode radio button, and then click Done.

•

Click OK to accept the three load cases shown in the Selected list on the Results Setup dialog.

•


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8.15

Viewing the Results •

Ensure that the file named Dataset 8_8.std is the active model.

•

Click on the Plate page tab in the Page Control. This tab is only present in models that contain plates. It provides options for viewing various types of stress results for plates.

•

Plate stress results tables are displayed in the Data Area.

•

The Diagrams dialog opens with the Plate Stress Contour page active.

•

This dialog is used to display a plate stress contour diagram on the structure. A stress contour is a diagram which shows the variation of stress – for a selected stress type – over the selected set of elements.

•

The Load Case list can be used to select the load case for the stress contour.

•

Set the Load Case field to 1: PRESSURE LOAD.

•

The Stress Type list can be used to select the type of stress contour to display. A description of the different types of plate stresses reported by STAAD.Pro appears in Section 1.6.1 of the STAAD.Pro Technical Reference manual. Stress Type

Description

Max Absolute

Larger of the absolute values of SMAX & SMIN (Force/unit area)

SQX, SQY

Shear stresses (Force/unit length/thickness)


SX, SY, SXY

Membrane stresses (Force/unit length/thickness)

MX, MY, MXY

Bending moments per unit width (Moment/unit length)

SMAX, SMIN

In-plane principal stresses (Force/unit area)

TMAX

Maximum in-plane shear stress (Force/unit area)

VON

Von Mises stress

TRESCA

Tresca stress, where:

TRESCA = MAX[ |(Smax-Smin)| , |(Smax)| , |(Smin)| ] Global Moment (or Stress)

Moment (or stress) about a specified global axis

Base Pressure

Base pressure for a mat-type foundation (Force/unit area)

The in-plane Principal stresses (SMAX and SMIN), the maximum in-plane shear stress (TMAX), the Von Mises stress (VON), and the Tresca stress (TRESCA) are available for the top and bottom surfaces of the elements. Also, the maximum Von Mises stresses and Tresca stresses can be plotted. Please refer to Section 1 of the STAAD.Pro Technical Reference manual for additional information. •

Click the Stress Type list, then select Max Absolute stress and click OK. This is the larger of the absolute values of SMAX and SMIN.

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•

The stress contour is plotted on the structure.

•

The various types of plate stress values are also available in tabular format in the Plate Centre Stress table and the Plate Corner Stress table in the Data Area.

•

The tables contain a list of stresses, element by element, for each load case.

•

A summary page lists the maximum stresses for each load case. There is also a page for Global Moments.

•



8.16

Reinforced Concrete Design •

Ensure that the file named Dataset 8_8.std is the active model.

•

Click Mode | Modeling to return to STAAD.Pro’s Modeling mode.

•

Click the Design page tab in the Page Control. Note that the Design tab logically follows the Analysis/Print tab. This follows the program methodology of suggesting a logical workflow process by the order in which the Page Control tabs are organized.

•

Click on the Concrete sub-page in the Page Control.

•

Note the Current Code list in the top right corner of the Concrete Design – Whole Structure dialog. It offers the choice of designing using many different codes.

•

Make sure that Current Code is set to ACI.

•

Click the Select Parameters button. Note that all of the concrete design parameters currently appear in the Selected Parameters list on the right-hand side of the Parameter Selection dialog. These are all of the parameters associated with a standard reinforced concrete design, such as: compressive strength of concrete, yield strength of reinforcing steel, clear cover along the bottom, sides and top of beams, etc.

•

The Parameter Selection dialog is a convenience to control which concrete design parameters will be listed and available for use when the Define Parameters button is used.

•

Since we will only need a small subset of the available parameters, we can reduce the length of the list of parameters in the Design Parameters list.

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•

Click the double-left arrow to temporarily move all parameters to the Available Parameters list.

•

Press and hold the Control (Ctrl) key, and then click on the following parameters in the Available Parameters list: Depth, Maxmain, Reinf, and Track.

•

Release the Control (Ctrl) key, click the single-right arrow to move all four selected parameters to the Selected Parameters list, and then click OK. Note that Fc – Compressive strength of concrete was not one of the selected parameters. The STAAD.Pro default value of 4,000 psi {27.58 MPa} will be used for this example. Likewise, the yield strength parameters for main and secondary reinforcing were not selected. The default value of 60 ksi {413.69 MPa} will be used for these parameters. It is only necessary to assign a parameter to a member(s) if the value of the parameter differs from the default value. Otherwise, STAAD.Pro will just use the default value.

•


•

The Design Parameters dialog lists only the four parameters we selected in the previous step. The general procedure is to select a tab to define the desired parameter, enter the appropriate value in the field, Add that parameter to the model, and then Assign the parameter to the appropriate elements.

•

The DEPTH tab is active by default. This is the tab that is used to specify the Depth of cross section to be used in beam design.

•

Note that the units are currently set to ft {m}. It would be preferable to use units of inches {mm} when specifying parameters of this type.


•

Change the length input units to inches {millimeters}. Refer to the following commentary for step-by-step instructions. Click the Close button to dismiss the Design Parameters subdialog. Click Tools | Set Current Input Unit…. Click the Inch {Millimeter} radio button, and then click OK.

•

Click the Define Parameters button once again, and note that the units for the DEPTH parameter are now in inches {mm}.

•

The DEPTH parameter can be used to specify the rebar location in a beam, if the rebar is not in the default location assumed by the program. For instance, a beam may be deeper than structurally necessary due to architectural or detailing reasons. In this case, it is convenient to specify the actual beam dimensions so that the self-weight is calculated correctly, but the actual dimensions may not be representative of the actual rebar location for a beam like this. The Depth command could be used in a case like this to indicate to STAAD.Pro that it should consider the depth to be shallower than the overall dimensions when the design is performed. Note that this parameter specifies the value that is traditionally referred to as “h” in concrete design, not “d”. The “d” value will be calculated by deducting the clear cover (and stirrup rebar size if applicable) from the YD dimension of a concrete beam, or from the depth specified by the Depth command, if it is used.

•

Enter a value of 16 inches {400 millimeters} in the DEPTH field, and then click Add.

•

Click MAXMAIN.

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•

This parameter defines the maximum permissible rebar size for main reinforcement.

•

Enter a value of 8 {25} in this field to limit the maximum bar size to #8 {25 mm}, and then click Add.

•

Click the REINF tab.

•

This parameter is used to distinguish between Tied and Spiral column reinforcing. The default is Tied, but the current model has both rectangular (tied) and round (spirally reinforced) columns.

•

Click the Spiral Column radio button, and then click Add.

•

Click the TRACK tab.

•

This parameter is used to select the level of detail to be provided in the output.

•

Click the (2) radio button corresponding to the highest level of output detail, and then click Add, followed by Close.

•

The newly added parameters appear in the Concrete Design – Whole Structure dialog (simply referred to as the Concrete Design dialog from this point forward). They are preceded by question marks in the list, implying that they have been Added, but not yet Assigned.

•

Click the DEPTH 16 {DEPTH 400} parameter. This is intended to apply to all beams around the perimeter of the slab.

•

Click Select | Beams Parallel to | X . The beam segments on two sides of the model are selected.

•

Click Select | Beams Parallel to | Z. The beam segments on the other two sides of the model are added to the selection. Note that the Assignment Method is automatically set to Assign To Selected Beams.


•


•

Click Yes to confirm the assignment. The parameter is assigned to the four perimeter beams. Note that the Edit List in the Concrete Design dialog contains more than just four beam numbers, because the perimeter beams were segmented into many elements. Note also that the DEPTH 16 {DEPTH 400} parameter no longer has a question mark in the Concrete Design dialog, because the parameter has now been Assigned to some members in the model.

•

Click the MAXMAIN 8 {MAXMAIN 25} parameter. This is intended to apply to all members in the model.

•


•

Click Yes to confirm the assignment. All beam and column elements in the model are highlighted, indicating that all have been assigned the MAXMAIN 8 {MAXMAIN 25} parameter.

•

Click the REINF 1 parameter, and then click inside the Main Window.

•

Press Shift + X , the hotkey to turn on member sections. This helps to identify the two circular columns in the rear of the structure.

•

Verify that the Assignment Method is set to Use Cursor To Assign by default, and then click Assign . The cursor changes to the special “SP” in a circle to indicate that it is in ready to assign the parameter.

•

Click on the two circular columns with the Cir 18.00 {Cir 0.45} labels.

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They become highlighted as they are clicked, and the member numbers 2 and 3 should appear in the Edit List at the bottom of the Concrete Design dialog. •

Click the TRACK 2 parameter. This is intended to apply to all members in the model.

•


•

Click Yes to confirm the assignment. All beam and column elements in the model are highlighted again, indicating that all have been assigned the TRACK 2 parameter. This completes the assignment of Design Parameters. The next step is to add the actual concrete design commands to the model.

•

Click the Commands button in the Concrete Design dialog.

•

The Design Commands sub-dialog contains tabs labeled Design Beam, Design Column, Design Slab/Element and Take Off.

•

The Design Beam tab is active by default. The Design Beam tab is used to add the command for performing reinforcement calculations for flexure, shear and torsion (Mz, Fy and Mx).

•


•

Click the Design Column tab. The Design Column tab is used to add the command for designing for biaxial bending moments and axial force (My, Mz and Fx). The output will consist of the reinforcing steel requirement and bar arrangement where applicable.

•



•

Click the Design Slab/Element tab. The Design Slab/Element tab is used to add the command for designing individual plate elements for two-way flexural moments (Mx and My).

•


•

Click the TAKE OFF tab. The TAKE OFF tab is used to add the command to tabulate and print the total volume of concrete and weight of reinforcing steel for beams, columns and elements that are designed.

•


•

Click Close to dismiss the Design Commands dialog.

•

Note that the four new commands appear in the Command Tree in the Concrete Design dialog. The next step is to Assign the appropriate design commands to the appropriate members/elements. For the purposes of this example, and to limit the quantity of output, the Design commands will only be Assigned to one representative beam, column, and slab element.

•

Click the DESIGN BEAM command in the Concrete Design dialog.

•

Click the Assign To Edit List radio button in the Assignment Method category.

•

Enter beam number 4 in the Edit List, and then click Assign. This selects the beam segment highlighted in the figure below for design.

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Figure 8. 12

•

Click the DESIGN COLUMN command.

•

Verify that the Assignment Method category is set to Use Cursor To Assign.

•

Click Assign , and then click on member number 2 as shown in the figure below.

Figure 8. 13 Member number 2 is highlighted, and the question mark changes to a checkmark in front of the DESIGN COLUMN command.


•

Click the Assigning button once again to turn it off. This button says Assigning when it is active and Assign when it is inactive.

•

Click the DESIGN ELEMENT command in the Concrete Design dialog.

•

Verify that the Assignment Method category is set to Use Cursor To Assign.

•

Click Assign , and then click on plate number 37, the element in the front corner as shown in the figure below.

Figure 8. 14 Plate number 37 is highlighted, indicating that the Design Element command has been Assigned to it. •

Click the Assigning button once again to turn it off.

•

Verify that the Highlight Assigned Geometry checkbox is checked on the Concrete Design dialog. When this checkbox is selected, STAAD.Pro highlights all members/elements that have been assigned the currently selected parameter.

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This provides a quick visual way to verify that the recent assignments have been made correctly. •

Click on DESIGN BEAM, DESIGN COLUMN, and DESIGN ELEMENT commands in the Concrete Design dialog one at a time. As each command is highlighted in the list, the corresponding members in the model are highlighted in the Main Window. The CONCRETE TAKE command is a little different. It had a checkmark in the Command Tree as soon as it was Added, because it automatically applies to all concrete members. It cannot be Assigned to specific members. Because it is not explicitly Assigned, no members are highlighted in the Main Window if the CONCRETE TAKE command is clicked.

•


•


•



8.17

Understanding Concrete Design Results •


•

Click Analyze | Run Analysis…. The STAAD Analysis and Design dialog appears, and scrolls through several messages indicating the status of the analysis. One of the last lines in the list of messages indicates “Creating Design information File (DGN)…” This is the indication that STAAD.Pro has actually performed design calculations as requested by the recently added DESIGN commands.

•

Click the View Output File radio button, and then click Done.

•

Scroll down in the Output File and locate the line that says, “PROBLEM STATISTICS”.

•

Just below this is a block of 35 lines of text that say, “++ Adjusting Displacements”. This is evidence of the 35 iterations requested by the PDELTA 35 ANALYSIS command.

•

Continue to scroll down in the Output File and locate the line that says, “BEAM NO. 4 DESIGN RESULTS – FLEXURE PER CODE ACI 318-05.” The design of beam number 4 starts on this page and continues to the next.

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•

The first line of data in the beam design output echoes the beam dimensions and material properties.

Figure 8. 15 •

The next section provides geometric information about the layer of rebar that occurs near the bottom of the beam. See the itemized descriptions corresponding to the numbered items in the figure below.

Figure 8. 16 1 – Rebar Level number – starting with bottom layer first. 2 – Height from the bottom of the beam to the centroid of the rebar at this level. 3 – Number and size of rebar required by design. 4 – Starting location of the rebar at this level, measured from the starting node of the beam.


5 – Ending location of the rebar at this level, measured from the starting node of the beam. 6 – Indication as to whether or not the rebar at this level is considered to be fully-developed (as with a standard hook or full development length projection) at the start (STA) and end (END) of the rebar. •

Below the line of geometric data pertaining to the first layer of rebar is a dashed box. It contains the design information for the first layer or rebar including: •

Magnitude and location of design moment

•

Critical load case

•

Rebar area requirements

•

Rebar spacing data

•

Development length

•

A single line of text below the dashed box reports the cracked moment of inertia at the location of the design moment.

•

Subsequent levels of rebar are described in the same manner. In this beam, there is negative moment at the starting end, so there is a second level of rebar required near the top of the beam as shown in the figure below.

Figure 8. 17 Note that this second level of rebar is being designed for a critical negative moment of 24.18 kip-ft {34.99 Kn-m}, which

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occurs at 0.00 ft {0 mm} from the starting end. This negative moment drops off quickly, because the rebar is terminated approximately 3’-7” {1113 mm} from the starting end of this segment of the beam. •

The next section of output presents the shear design for the starting end and the ending end, followed by diagrams of the elevation view and three sections through the beam.

•

The diagrams schematically show the top and bottom longitudinal reinforcement and the stirrups.

•

The next section provides design output for the column.

•

Material and geometric properties are listed first.

Figure 8. 18 •

This is followed by bar configuration details.

Figure 8. 19 •

And finally the interaction diagram and data.


Figure 8. 20 •

The design summary for the plate element follows next.

Figure 8. 21

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•

And the final piece of output is the concrete take-off.

Figure 8. 22

•

Click File | Exit in the STAAD Output Viewer main menu to return to the Main Window.

•

No changes have been made to the current file in this section, so it can be closed without saving.

•


•



8.18

Additional Concrete Modeling Examples •

Click Help | Contents in the Menu Bar.

•

Double-click Getting Started on the Contents tab.

•

Double-click Tutorial 2.

•

Tutorial problem 2 provides step by step instructions on creating, analyzing and performing concrete design for a portal frame.

•

Double-click Application Examples on the Contents tab.

•

Double-click American Examples.

•

The STAAD.Pro Examples manual contains several example models that illustrate finite element analysis applied to various real-world reinforced concrete structures.

•

Example No. 8 illustrates concrete design performed on a space frame structure, including computation of reinforcement for the beams and columns. Secondary moments on the columns are obtained through the means of a P – Delta analysis.

•

Example No. 9 is another space frame structure that includes frame members and finite elements (plates). The plates are used to model floor slabs and a shear wall. Concrete design is performed on one of the elements.

•

Example No. 10 shows how to model a water tank which is subjected to hydrostatic pressure as the tank is filled.

•

Example No. 18 demonstrates the calculation of principal stresses on a finite element.

•

Example No. 23 illustrates how to generate spring supports for a slab on grade.

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•

Example No. 27 deals with a mat foundation subjected to loads that cause a partial uplift.

•

The STAAD.Pro Examples manual is written in a very concise format. Its purpose is not to illustrate the use of the graphic interface. Instead, each example explains, line by line, the input file commands that are needed to correctly model the proposed scenario.

•

This format thoroughly explains the purpose for each command, step by step, while presenting the entire example scenario in only a few pages of text.

•

These examples also illustrate the most economical, efficient use of the input command language. They provide an in-depth understanding of how the program operates.

•

Many times in this training course, actions that took many pages of text and numerous pictures and diagrams to describe could very easily be replicated with two or three lines of input command language.

•

The graphic interface is STAAD.Pro’s “front end.” The input command file is its “backbone.” Developing an understanding of the relationship between these two aspects of the program will lead to a real mastery of STAAD.Pro.

-End of Module-

9-1

Exercise Problems Module

9

The following topics are included in this module. 9.1 Exercise Problem One........................................................................ 2 9.2 Exercise Problem Two ....................................................................... 4 9.3 Exercise Problem Three ..................................................................... 6 9.4 Exercise Problem Four ..................................................................... 11 9.5 Exercise Problem Five ..................................................................... 17 9.6 Exercise Problem Six ....................................................................... 23


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9.1

Exercise Problem One Create the geometry of the structure shown in the figures below.

Isometric View of entire structure The supports and dimension lines are shown for information only.


Dimensions of one of the side trusses Hints: •

In the Run Structure Wizard option of the Geometry menu, create a Pratt Truss with the overall dimensions shown above.

•

Bring it into the main drawing.

•

Delete the unwanted members.

•

Split the cross members at the bottom, and connect them at the split points.

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9.2

Exercise Problem Two Create the geometry of the structure shown in the figure below.

Isometric View of entire structure The supports and dimension lines are shown for information only. Hints: Method 1: •

In the Geometry menu, select Snap/Grid Node – Beam. Set the plane of the grid to XZ.

•

Draw the outer triangle of the bottom level. Split the 2 members at their midpoints, and add a beam between the 2 new points.


•

Use Geometry | Translational Repeat to create the upper triangle. Remember to switch on Link Steps to connect the 2 levels using vertical members.

•

Using Geometry | Add Beam, draw the diagonals.

•

Split the diagonals and connect them at the split points.

•

Using Geometry | Add Beam, draw the remaining members.

Method 2: •

In the Geometry menu, select Snap/Grid Node – Beam. Set the plane of the grid to XY. Calculate the angle of the vertex of the bottom triangle, and set the angle of the plane to be half that value about YY.

•

Draw one of the vertical side faces of the structure. Use Geometry | Circular Repeat – Copy mode to create the other face. Remember to switch on Link steps while circular repeating.

•

Add the rest of the members, and split and connect as necessary.

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9.3

Exercise Problem Three Create the model of the structure shown in the figures below, and assign the following data. BASIC DATA FOR THE STRUCTURE ATTRIBUTE

DATA

Member Properties

W12x26 for all members

Material Constants

E, Density, Poisson – Default value for steel

Supports

Fixed supports as shown

Loads

2 primary load cases as shown. Load case 3 should combine 1 & 2, with a factor of 1.

Analysis Type

Linear Static (PERFORM ANALYSIS)

Results

Produce a report containing the following items. •

Support Reactions for load 3.

•

Bending Moment Diagram for load 3 with the maximum values annotated.

•

Node deflection diagram for load 3 with the resultant values annotated.


5.50m

3.00m

9-7

4.50m 6.00m

5.50m

5.00m

4.50m

5.50m

5.50m

3.00m

5.50m

5.00m

5.00m

5.00m

5.50m

Y X

Z

Isometric View of structure


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Connection data: Moments MY and MZ released Note: At junction points where horizontals, verticals and bracing members meet, it is sufficient for this exercise to apply the releases only on the horizontal members.


1.6 kN/m 3.19 kN/m

3.05 kN/m 3.05 kN/m

1.6 kN/m

Load 1: Distributed Member Loads

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1.50 kN/m

3.00 kN/m

1.50 kN/m

Y X

1.50 kN/m

3.00 kN/m

Z 1.50 kN/m

Load 2: Lateral forces along global X


9.4

Exercise Problem Four Create the model of the steel tower shown in the figures below. Perform the analysis, followed by a member selection, re-analysis, and a code check on the members to determine if they pass the AISC ASD code requirements.

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Components of the structure in detached views


BASIC DATA FOR THE STRUCTURE ATTRIBUTE Groups

DATA 3 groups to be formed. _VERTICAL, _HORIZONTAL, _BRACING

Member properties

Vertical Members: W10x49 Horizontal Members: W8x28 Bracing Members: L3x3x1/4 Single Angle

Material Constants

Modulus of Elasticity: 30 000 ksi {207 000 MPa} Density, Poisson : Default value for steel

Additional Member Specifications

Bracing members to be declared TRUSS type.

Supports

Pinned Supports as shown in earlier figure

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ATTRIBUTE Load Case 1

DATA Equipment Load 2 kips {9 kN} concentrated force at midpoint of roof-level beams. Use the Member Load – Concentrated force option to do this.



DATA Walkway Live Load 300 pounds/ft {4.4 kN/m} distributed load on intermediate level beams

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DATA Load in X direction on windward face 1.2 kips {5 kN} as shown

Load Case 4

Case 1 + Case 2 + Case 3 (LOAD COMBINATION type)

Analysis Type

Linear Elastic (PERFORM ANALYSIS)

Steel Design Parameters

Yield strength of steel : 40 ksi {275 MPa}

Steel Design Operation

Perform a member selection for the entire structure

Grouping

Group members after selection according to their group names

Reanalyze Check Code

Perform a code check for the entire structure


9.5

Exercise Problem Five The concrete frame shown in the figures below should be modeled and analyzed. Following the analysis, perform a concrete design for the beams, columns and slab per the ACI 318 code as explained below.

Isometric View

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Y X

Z

Beams and Columns in the Structure (Dark lines)


Y X

Z

Roof slab as 5ft X 5ft {1.5m x 1.5m} finite elements (shaded region)

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BASIC DATA FOR THE STRUCTURE ATTRIBUTE Cross Section Properties

DATA Interior Columns (30 ft {9 m} tall): Circular, 28 in {700 mm} diameter Exterior Columns (20 ft {6 m} tall): Rectangular, 36 inch {900 mm} (YD) x 30 inch {750 mm} (ZD) Beams: Rectangular, 36 inch {900 mm} (YD) x 24 inch {600 mm} (ZD) Plate Thickness: 8 inches {200 mm}

Material Constants

Modulus of Elasticity, Density, Poisson : Default value for concrete

Additional Member Specifications (Releases, Offsets, etc.)

None (Program defaults)

Supports

Fixed Supports as shown in earlier figure

Loads

Load Case 1: Dead Load – Selfweight Load Case 2: Live Load – Pressure load on plates, 200 lbs/sq.ft {9.5 kN/m 2 }acting globally downward Load Case 3: Wind Load in X direction on roof – 200 lbs/sq.ft {9.5 kN/m 2 } acting in positive global X direction (on both slopes) Load Case 4: Combination Case – Case 1 + Case 2 + Case 3 (Use REPEAT LOAD)

Analysis Type

PDelta


Concrete Design: •

Design the beam shown

•

Design the columns shown

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•

Design the element shown


9.6

Exercise Problem Six The tower shown below is supported by six cables. Analyze the structure for 3 load cases, as explained.

Isometric View

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Cable Connection levels


Typical segment in elevation

Typical segment in isometric view

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Plan view of typical level

Details of typical level


BASIC DATA FOR THE STRUCTURE ATTRIBUTE Member Properties

DATA All components of tower : Pipe section 24 in {600 mm} OD, 22 in {550 mm} ID Cables : 1 sq.in {650 mm 2 } cross section area

Material Properties

Default values for steel

Cable Initial Tension

3000 lbs {13.3 kN}

Loads

Load Case 1: Wind Load – 100 lbs {445 N} at each node on windward face Load Case 2: Ice Load – 50 lbs per foot {730 N/m} on each horizontal member Load Case 3: Load 1 + Load 2

Analysis Type

Linear Static

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-End of Module-

STAAD.Pro Standard Training Manual - Bentley Institute.pdf

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