BS5950 - Connections Handbook

CSC Fastrak ™

Structural steelwork analysis and design

.cscworld.com/fastrak

CONNECTIONS

Connections Documentation page 2

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Friday 4 January 2013 – 15:49

Disclaimer

Disclaimer

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CSC (UK) Ltd does not accept any liability whatsoever for loss or damage arising from any errors which might be contained in the documentation, text or operation of the programs supplied. It shall be the responsibility of the customer (and not CSC)

• to check the documentation, text and operation of the programs supplied, • to ensure that the person operating the programs or supervising their operation is suitably qualified and experienced,

• to ensure that program operation is carried out in accordance with the user manuals, at all times paying due regard to the specification and scope of the programs and to the CSC Software Licence Agreement.

Proprietary Rights

CSC (UK) Ltd, hereinafter referred to as the OWNER, retains all proprietary rights with respect to this program package, consisting of all handbooks, drills, programs recorded on CD and all related materials. This program package has been provided pursuant to an agreement containing restrictions on its use. This publication is also protected by copyright law. No part of this publication may be copied or distributed, transmitted, transcribed, stored in a retrieval system, or translated into any human or computer language, in any form or by any means, electronic, mechanical, magnetic, manual or otherwise, or disclosed to third parties without the express written permission of the OWNER. This confidentiality of the proprietary information and trade secrets of the OWNER shall be construed in accordance with and enforced under the laws of the United Kingdom. Fastrak documentation: © CSC (UK) Ltd 2012 All rights reserved.

Trademarks

Fastrak software: © CSC (UK) Ltd 2012 All rights reserved.

Fastrak™ is a trademark of CSC (UK) Ltd TEDDS® is a registered trademark of CSC (UK) Ltd Orion™ is a trademark of CSC (UK) Ltd The CSC logo is a trademark of CSC (UK) Ltd HOOPS™ is a trademark of Tech Soft 3D Autodesk and Revit are registered trademarks or trademarks of Autodesk, Inc., in the USA and/or other countries. Microsoft and Windows are either trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries. Acrobat® Reader Copyright © 1987-2012 Adobe Systems Incorporated. All rights reserved. Adobe and Acrobat are trademarks of Adobe Systems Incorporated which may be registered in certain jurisdictions. All other trademarks acknowledged.

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Disclaimer

Table of Contents


Help System Overview . . . . Customising Connections . How do I set preferences? .

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. . . How do I control Connections’ interface components? . Working with Projects . . . . . . . How do I create a new project? . . . . . How do I open an existing project? . . . . How do I close a project? . . . . . . How do I save a project with the same file name? . . How do I save a project with a new file name? . . How do I edit the project details? . . . . Working with Connections . . . . . . How do I add a new connection to a project? . .

. . . . . . . . . . . . . How do I add a new connection of the same type to a project? . How do I modify the reference details for a connection? . . How do I modify the configuration of a connection? . . How do I copy a connection? . . . . . . How do I delete a connection? . . . . . . How do I edit the basic connection details? . . . . How do I perform the design? . . . . . . How do I view a design’s results? . . . . . Working with Views . . . . . . . . How do I control the view in the connection Definition window?

Working with Reports .

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. . . . . . . . . . Exporting information from Fastrak Connections . . How do I return information to the Building Designer? . How do I set up a page header or page footer? . How do I set up a report page? . . . . How do I control the contents of a report? . . How do I view a report? . . . . . How do I export a report to Microsoft Word? . . How do I export a report to a pdf file? . . . How do I print a report? . . . . . How do preview a report? . . . . . How do I control the printer used to create a report?

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Table of Contents

BS5950 Connections Design Handbook Connection Modelling in Building Designer 26 Introduction. . . . . Data Sources . . . . Connection Types . . . . Generating Connections . . Editing Connections . . . Viewing Results and Creating Output

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Simple Connections 30 .

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Scope . . . . . Limitations and Assumptions. Limitations . . . Assumptions . . .

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Connection Types . . Steel Grades . . . Notches . . . . Connecting Element Geometry Bolts . . . . Design Forces . . . Tie forces . . . .

Limitations and Assumptions. General Limitations . . General Assumptions . .

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Additional Assumptions and Limitations for Toe Plate Connections

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Moment Connections 38 .

Connection Types Steel Grades . End Plates . . Bolts and Welds . Stiffeners . . Design Forces .

Column Splices 46

Hollow Section Connections 48 Practical Applications .

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Checking a Hollow Section Connection .

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Connection configurations . Steel sections . . .

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Column Bases 51 Limitations and Assumptions

General Limitations and Assumptions . . . . Limitations and Assumptions specific to Simple Bases . Limitations and Assumptions specific to Moment Bases .

Analysis 57 Global analysis . . Connection analysis .

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Additional Design Considerations 58 Accidental Limit state . Structural Integrity . Fire Limit State . Serviceability Limit State

Sign Conventions 60

References 61


Chapter 1 : Working With Fastrak Connections

Help System

Chapter 1

Working With Fastrak Connections

Overview The main sections in this document are listed below. The links take you to the initial topic for that section. Major topics

• • • • • • •

Overview Customising Connections Working with Projects Working with Connections Working with Views Working with Reports Exporting information from Fastrak Connections

Customising Connections These topics tell you how to customise the Fastrak Connections interface, both by preferences which you can set, and also by the components you can add-to, or remove-from the interface. The links below detail all the available topics in this section. Related topics

• How do I set preferences? • How do I control Connections’ interface components?

How do I set preferences? 1. Pick File/Preferences… 2. Use the various pages of the Preferences property sheet to tailor the way that you and Connections work together.

How do I control Connections’ interface components? You can switch various elements of the Fastrak Connections interface on and off at will. When you install Fastrak Connections the toolbars, status bar, workbook and project workspace are all shown. We would recommend that you do not turn these off on a long term basis since they provide much useful information and are the quickest way to access many features. However, you may want to switch one or more off momentarily to increase the area available for a graphical display.



To hide a toolbar 1. Pick View/Toolbars»Toolbar Name (where Toolbar Name is the name of the toolbar you want to switch off). Note

Toolbars which are already switched off will not have the name in the list.

icon against their

To show a toolbar 1. Pick View/Toolbars»Toolbar Name (where Toolbar Name is the name of the toolbar you want to switch on). Note

Toolbars which are already switched on will have the in the list.

icon against their name

To set the position of a toolbar 1. Grab the toolbar by its handle (a vertical bar to its left for a horizontal toolbar, or a horizontal bar at its top for a vertical toolbar) and drag the toolbar to its new location. 2. If you place the toolbar over an edge of the main Connections window, then it will dock to that edge. To change the shape of a floating toolbar In order to change the shape of a toolbar it must not be docked against an edge of the Connections window. 1. Position the cursor over an edge of the floating toolbar, and you will see that the pointer changes to a representation of two arrows. 2. Click and hold the left mouse button and drag in the direction of the arrows. 3. The toolbar will change shape in a series of steps, to accommodate the buttons that it contains. Once you have achieved the shape that you require release the mouse button. To hide the status bar 1. Pick View/Status Bar. Note

If the status bar is already switched off it will not have the name in the menu.

icon against its

To show the status bar 1. Pick View/Status Bar. Note

If the status bar is already switched on it will have the in the menu.

To hide the workbook 1. Pick View/Workbook.

icon against its name


Note


If the workbook is already switched off it will not have the name in the menu.

icon against its

To show the workbook 1. Pick View/Workbook. Note

If the workbook is already switched on it will have the in the menu.

icon against its name

To hide the project workspace 1. Pick View/Project Workspace or click the workspace. Note

icon at the top-right of the project

If the project workspace is already switched off it will not have the against its name in the menu.

icon

To show the project workspace 1. Pick View/Project Workspace. Note

If the project workspace is already switched on it will have the its name in the menu.

icon against

To set the position of the project workspace 1. Grab the project workspace by its handle (the title bar at the top of the project workspace pane) and drag it to its new location. 2. If you place the project workspace over an edge of the main Connections window, then it will dock to that edge.

Working with Projects These topics relate to the way in which you can work with projects in Fastrak Connections. The links below detail all the available topics in this section. Related topics

• • • • • •

How do I create a new project? How do I open an existing project? How do I close a project? How do I save a project with the same file name? How do I save a project with a new file name? How do I edit the project details?

How do I create a new project? 1. Pick File/New Project… (

).



2. Enter the Project Details (the Job No. is required, the other information is optional) and then click OK. 3. Pick the Type of the first connection that your project is to contain and enter its Reference. Once you have done this click OK. 4. You will see a dialog which allows you to define the detail of the connection. Use its various pages to do so and then click OK. 5. Your new project opens and you will see the Connection Definition window for the first connection it contains.

How do I open an existing project? 1. Pick File/Open Project… (

).

2. Navigate to the folder which contains the project you want to open, then either: • click the file name, and then click Open, or

• double click the file name. How do I close a project? 1. Pick File/Close 2. If the project has not changed in any way since you last saved it, then it will close immediately. 3. If the project has changed, then you will be asked if you want to save it. The options you have are: • Yes — save the project1 and then close it,

• No — close the project losing any unsaved changes, • Cancel — abort the closing of the project, leaving it open. How do I save a project with the same file name? 1. Pick File/Save (

).

2. If you haven’t saved the project before, then you will see the Save As dialog. a) Use this dialog to navigate to the folder into which you want to save the project, enter the File name you want to use for the project and then click Save. 3. If you have saved the project before, then this option simply updates the saved file to take account of any changes. Footnotes 1. If you have never saved the project, then Connections will allow you to specify the folder and file name under which it is to be saved. If you have saved the project previously (so that it has a folder and file name), then Connections will automatically save the project under the existing path and file name.



How do I save a project with a new file name? 1. Pick File/Save As… You will see the Save As dialog which automatically shows the folder and file name under which the project is currently saved. 2. If necessary navigate to the folder into which you want to save the project and/or enter the new File name you want to use for the project and then click Save.

How do I edit the project details? You set the initial project details as you create a new project. If you want to change these later, this is easily done. 1. Pick File/Project Details… and you will see the Project Details dialog together with the current information which is defined for this project. 2. Make any changes that are necessary, and then click OK to close the dialog.

Working with Connections The links below detail all the available topics in this section. Related topics

• • • • • • • • •

How do I add a new connection to a project? How do I add a new connection of the same type to a project? How do I modify the reference details for a connection? How do I modify the configuration of a connection? How do I copy a connection? How do I delete a connection? How do I edit the basic connection details? How do I perform the design? How do I view a design’s results?

How do I add a new connection to a project? 1. Pick Connection/New Connection… to see the New Connection dialog. 2. In this dialog choose the type of connection that you want to create, enter the Reference details of the connection and then click OK. 3. You will see a dialog which allows you to define the detail of the connection. Use its various pages to do so and then click OK. 4. A new window will be added to your project showing your new connection, and a corresponding entry will be added to the Project Workspace.



How do I add a new connection of the same type to a project? Fastrak Connections assumes that the projects you create will contain more than one of any particular type of connection. Once you have created a new connection, you can create more connections of the same type instantly. 1. Pick Connection/New xxx1 Connection… or click the icon for the connection type from the Connections toolbar. Note

The icon in the toolbar changes to show that relating to the type of connection you last created. These are detailed below.

Icon

Connection type Beam-column moment connection Beam-beam moment connection

Column base connection Beam-column simple connection Beam-beam simple connection

2. You will see a dialog which allows you to define the detail of the connection. Use its various pages to do so and then click OK. 3. A new window will be added to your project showing your new connection, and a corresponding entry will be added to the Project Workspace.

How do I modify the reference details for a connection? 1. There are two methods which you can use to change the connection reference: a. Ensure that a window relating to the connection whose reference you want to change is active and then pick Connection/Reference… ( ) b. Right click over the reference that you want to change in the Project Workspace and then pick Reference… from the context menu. 2. Enter the amended Reference details for the connection and click OK.

How do I modify the configuration of a connection? 1. There are two methods which you can use to change the connection configuration: Footnotes 1. Where xxx is the type of the connection you last created.



a. Ensure that a window relating to the connection whose reference you want to change is active and then pick Connection/Edit Connection… You can also pick the appropriate icon from the toolbar. Note

The icon in the toolbar changes to show that relating to the current type of connection. These are detailed below.

Icon

Connection type Beam-column moment connection Beam-beam moment connection

Column base connection Beam-column simple connection Beam-beam simple connection

b. Right click over the reference of the connection whose configuration you want to change in the Project Workspace and then pick Edit Connection… from the context menu. 2. You will see the Connection Configuration dialog appropriate to this type of connection. Make the changes that you require and then click OK.

How do I copy a connection? 1. There are two methods which you can use to create a copy of an existing connection: a. Make sure that the connection you want to copy is the active one, and then click Connection/Copy from the menu. b. Right click the column reference in the project workspace and then choose Copy from the context menu.

How do I delete a connection? 1. There are two methods which you can use to delete a connection: a. Make sure that the connection you want to delete is the active one, and then click Connection/Delete from the menu. b. Right click the column reference in the project workspace and then choose Delete from the context menu.



How do I edit the basic connection details? 1. Right click the connection reference in the project workspace and then choose Edit Connection… from the context menu. 2. Use the various pages of the Connection Properties sheet to change the connection’s details, then click OK to set them.

How do I perform the design? 1. Pick Connection/Check Connection… (

) and you will see the results immediately.

How do I view a design’s results? 1. Pick Connection/Check Connection… (

).

2. If the design is current (that is nothing has changed since the last design), then you will see the results immediately. 3. If the design is not current then it will be performed while you wait (which in practice means that you will see the results immediately on most modern systems).

Working with Views The topics relate to the ways in which you can control views of your connections in Connections. The links below detail all the available topics in this section. Related topics

• How do I control the view in the connection Definition window?

How do I control the view in the connection Definition window? Fastrak Connections provides a whole range of options which allow you to control the view in the Connection Definition window. You can use a range of standard views, or you can rotate the view to any orientation you require. You can also zoom and pan the view so that you can see just what you need. You can navigate through the most recent views you have defined quickly and easily. To use a standard view 1. Simply use one of the methods below to choose the standard view that you want to see. a. Pick View/Options»View Name (where View Name is the name of the standard view you want to see).



b. Click the appropriate icon from the Connection Details View toolbar.

Icon

View from: Front Top Left Back Bottom Right South-West South-East North-East North-West

To rotate the view If none of these standard views is appropriate, then you can rotate the connection to get to just the view you require. 1. Simply right-click and hold over the connection in the Connection Definition window, and move the mouse to perform the rotation. 2. Once you have achieved the view you require simply release the mouse button. To zoom into an area 1. Pick View/Options»Zoom Area. 2. Move the mouse pointer over one corner of the area into which you want to zoom. 3. Click and hold the left mouse button and drag to the diametrically opposite corner of the same area. 4. Release the mouse button and the display will zoom to show this area. To zoom on the display centre 1. Click and hold both mouse buttons. 2. Move the mouse pointer down to zoom in-to the centre of the display or up to zoom out-from it. 3. Alternatively if you have a mouse with a wheel you can rotate the wheel to zoom in or out on the centre of the display.



To pan the view? 1. Simply click and hold the middle mouse button or mouse wheel 1over the Connection Definition window, and move the mouse to pan the display. 2. Once you can see the part of the view that you require simply release the mouse button. To navigate through views 1. Simply use the buttons of the View toolbar to navigate through the views you have defined in the Connection Definition window.

Icon

Action Show the first available view Show the previous view Show the next view Show the last available view

Note

These buttons perform different functions in the Report window.

Working with Reports Once you have defined your connections you can create a wide range of reports, many of which you can tailor extensively to meet your, or your customer’s, specific requirements. The links below detail all the available topics in this section. Related topics

• • • • • • • •

How do I set up a page header or page footer? How do I set up a report page? How do I control the contents of a report? How do I view a report? How do I export a report to a pdf file? How do I export a report to Microsoft Word? How do I print a report? How do preview a report?

How do I set up a page header or page footer? The header and footer are tables which appear at the top and bottom respectively of every page of your report. You can define the number of rows and columns in the tables, the widths of the column, and you can also merge cells to increase the available size, for instance to accommodate your company logo.

Footnotes 1. You must have a mouse with a middle button or wheel to use this option.



Once your table layout is complete you can determine which information appears in each cell, and define the appropriate details. 1. Pick File/Report View Setup»Report Define Header… and you will see the Edit Header Layout dialog, or pick File/Report View Setup»Report Define Footer… and you will see the Edit Footer Layout dialog. 2. Once your settings are complete click OK to close the dialog. How do I set the horizontal alignment of a cell? 1. Right click the cell in the table. Note

The current alignment setting for the cell is shown below the table.

2. Pick Horizontal Alignment/Left, Horizontal Alignment/Right, or Horizontal Alignment/ Centre from the context menu that appears. 3. The cell in the table shows the new alignment. How do I set the vertical alignment of a cell? 1. Right click the cell in the table. Note

The current alignment setting for the cell is shown below the table.

2. Pick Vertical Alignment/Top, Vertical Alignment/Bottom, or Vertical Alignment/ Centre from the context menu that appears. 3. The cell in the table shows the new alignment. How do I join cells? 1. Left click and hold over the top left most cell that you want to join. 2. Drag down and to the right and you will see a rectangle that follows the mouse pointer. 3. When the rectangle encompasses the cells that you want to join release the mouse button. Note

The lines between the cells are removed, however the cell field names are maintained. However when cells are joined it is only the information referred to by the top left hand most field that is displayed in the header.

How do I unjoin cells? 1. You can rejoin cells in a different combination as detailed above. 2. Alternatively you can right click over the top left hand most field name in the group of joined cells and then pick Unjoin from the context menu that appears. How do I add a row? 1. Click Add a row to add a row to the bottom of your table. How do I add a column? 1. Click Add a column to add a column to the right of your table.



How do I delete a row? 1. Right click over the row that you want to delete. 2. Pick Delete row from the context menu that appears. How do I delete a column? 1. Right click over the column that you want to delete. 2. Pick Delete column from the context menu that appears. How do I set the column width? 1. Click Columns… and you will see the Column Widths dialog. 2. Pick the column whose width you want to set, and then define the appropriate details in the fields at the bottom of the dialog. The options are as follows: Fixed — The width of the column is fixed at the value you specify, the options are: Percent — The column takes up the specified percentage of the total page width. mm — The column is the specified number of millimetres wide. If you use this option, then you must ensure that the total column widths fit within the printable area of the page. Residual — The column takes up the remaining width not required by the other columns in the table. You can only define one column which has its Type set to Residual. How do I determine which information shows in which cell? 1. Click on the variable that you want to place in the cell from the list of Fields. 2. Click on the field to set the field to show that variable’s name. Note

When cells are joined it is only the information referred to by the top left hand most variable name that is displayed in the header.

How do I define the information for a variable? 1. Click Edit fields… to see the Edit Fields dialog. 2. Pick the field from the list of the Available Fields, and then define the appropriate data in the Field Settings part of the dialog. How do I add a new variable or delete one that I previously added but no longer require? 1. Click Add/Remove fields… 2. To add a new field type in the field name that you want to use (this must be different from any existing field name), and then click Add. 3. To delete a field that you don’t require pick the field from the list of Available Fields, and then click Remove.



How do I set up a report page? 1. Pick File/Report View Setup»Report Print Options… and you will see the Report Settings dialog. 2. Use the various pages of this dialog to set the fonts for the various paragraph styles used in the report, to set the margins you want to use and the options that you want to use for the tables within your report. 3. Once your settings are complete click OK to close the dialog.

How do I control the contents of a report? 1. Pick File/Report Contents… ( ) and you will see the Report Content dialog. This allows you to control the content of your report for each connection in your project as detailed below. Included — If you check this item, then this connection will be included in the report. If you don’t check this item, then the connection in its entirety will be excluded from the report irrespective of the other settings on the line. Diagram — Check this item to include a diagram of the connection in the report, uncheck it and the diagram will not be included. Summary — If you check this item, then the connection design status information will be included in the report. This simply tells you which is the critical combination for the design (that with the worst utilisation ratio for any check. Basic Details — This option allows you to control the reporting of the basic connection details. These include (among other things) the details of the section size(s), cleat details, end-plate details… … These obviously depend on the type of connection. Report Level — This setting allows you to control the amount of information that you wish to include in your report on the design for the connection. These range from None to Full, and progressively include more information about the design. 2. Once you have made your settings click OK to create and see the report.

How do I view a report? 1. Once you have defined the content of the report it will be automatically created for you. If you have closed the report window, and you want to view the report again, then pick File/ Report Connection Items ( ) and the report will be generated and shown on your screen. You can tailor the way in which the report is shown to achieve a result which enables you to best view the details you require. 2. Once you can see the report you can choose to export it to TEDDS, export it to Microsoft Word, or print it to produce a hard copy.



To navigate through a report 1. You can navigate through the report by using the buttons of the View toolbar.

Icon

Action Show the first page of the report Show the previous page of the report Show the next page of the report Show the last page of the report

Note

These buttons perform different functions in the connection Definition window.

How do I export a report to Microsoft Word? 1. Set up your report so that it contains the information you require. 2. Pick File/Export report to Word… ( ). Word will open and you will see a dialog which allows you to control the formatting of the report. Make the settings that you require, and then click OK. Note

At this point, if your report runs to many pages, you may see the message “Because there is a large amount of input data, the document must be saved periodically during the import process. If you do not wish to save the document select Cancel”. If you click OK, then you should immediately see the Word Save As dialog so that you can specify the name under which the file will be saved. Sometimes you will not see this dialog, and after a short delay you will see a Server Busy dialog instead! Don’t panic, this just means that Word is waiting for you to give the file name, it’s just that you can’t see the Save As dialog as it is hidden by another window. Simply click Switch to… to bring Word to the front of all other windows, you will then be able to see the Save As dialog. Now enter the file name and click OK to continue with the export process. This is a known issue with Word.

3. After a delay while the export process completes you will see the report in Word.

How do I export a report to a pdf file? 1. Set up your report so that it contains the information you require. 2. Pick File/Export report to PDF. The report will be created immediately, and you will see a dialog asking if you want to view the file. 3. If you do click Yes.



How do I print a report? 1. Set up your report so that it contains the information you require. 2. Pick File/Print… (

). You will see your system’s normal Print dialog.

3. Make the settings you require and then click OK.

How do preview a report? 1. Pick File/Print Preview and you will see a preview of your report.

How do I control the printer used to create a report? 1. Pick File/Print Setup… you will see your system’s normal Print Setup dialog. 2. Make the settings you require and then click OK.

Exporting information from Fastrak Connections The topics below relate to exporting information from Fastrak Connections. The links below detail all the available topics in this section. Related topics

• How do I return information to the Building Designer?

How do I return information to the Building Designer? This option is only available when you have defined a connection in Building Designer, and transferred it from there into Fastrak Connections in order to work on it. 1. Manipulate the design in Fastrak Connections until you have achieved a result with which you are satisfied. 2. Pick Connection/Return Connection to Building Designer to return the connection’s details back to that application.

CSC Fastrak ™

Structural steelwork analysis and design

.cscworld.com/fastrak

HANDBOOK CONNECTIONS



Chapter 2 : Introduction


BS5950 Connections Design Handbook

Chapter 2

Introduction This Engineer’s Handbook describes your BS5950 Fastrak Connections application. This is design software which allows you to design simple, moment, hollow section and column base connections. Simple Connections — transfer vertical shear only, Moment Connections — transfer vertical shear and major axis moment, Column Splices — continuity splices in simple construction, Hollow Section Connections 1 — welded hollow section connections of certain configurations including connections with I or H section chords. principally for use in truss work, Column Bases — simple and moment resisting bases including soil bearing pressure and concrete base design. Unless otherwise stated all calculations are in accordance with the relevant sections of BS 5950-1: 2000 and the design models for connections draw heavily on the series of publications from the Steel Construction Institute that cover the design of connections – the so-called Green Books.(Ref. 1),(Ref. 2) All Hollow Section Connection calculations are in accordance with the relevant sections of BS EN 1993-1-8:2005 with the exception of those connection configurations that are not covered by this publication {see the Theory and Assumptions Chapter for more details}. You may find the references quoted later in this document a useful source of information. The following advice is written principally from the point of view of operating connection design from within Building Designer. Where necessary any important factors with regard to the operation of the stand alone application are noted.

Footnotes 1. For the current release there is no integration between the hollow section connections and the Building Designer model.


Chapter 3

Chapter 3 : Connection Modelling in Building Designer

Connection Modelling in Building Designer

Introduction The definition and check of connections is an intrinsic part of Fastrak Building Designer – all data associated with a particular connection is held within the building model. All connections can be opened within Building Designer where they can be modified and refined before saving the data back to the model. Alternatively one or many connections can be passed out to Fastrak Connections where, again, they can be modified and refined and then passed back to Building Designer. Note that certain details (for example the section sizes of the connecting members) cannot be modified since this would affect other parts of the building model. As a further alternative Fastrak Connections can be run as a stand-alone application and the connection data entered in isolation.

Data Sources Whilst all connection data is held in the building model, the source of such data is several fold. This includes,

attributes certain data can be set to be used during the definition of the connections e.g. beam to beam simple connections are to be fin plates,

derived data the building model already holds such items as the section size and grade of the members that are that are to be connected and the design forces,

default data when the connections within the building model are set up by Fastrak, intelligent defaults are used that can establish a part or full solution to the connection configuration,

added data any individual connection can be edited to improve or add to the connection configuration e.g. stiffeners can be added to moment connections.

Connection Types Simple Connection Building Designer will attempt to configure a simple connection at the end of any Simple Beam, Composite Beam or General Beam that is pinned. The word attempt is used since there are some configurations of member and connection that are beyond the scope of the current release, for example, if the supporting beam is not an I-section or the supported beam frames in at a steep angle.



Simple connections can be end plates, fin plates and (double) angle cleats. During definition of your building model a set of Connections Attributes can be established such that by preference, for example, beam to column web connections are end plates and are designed for the minimum tie force requirement of 75 kN. The defaults for these attributes are: • beam to beam - fin plate with one line of bolts,

• beam to column flange - end plate, • beam to column web - end plate, • beam to hollow section column -fin plate.1 When a particular type of connection is established by Building Designer in the model, for example, a fin plate for beam to beam connections, the default settings for bolt size and number, fin plate thickness and so on, are such that the subsequent check of this connection should under normal circumstances give a Pass. This happens because simple connections are more about detailing than design, that is a well detailed simple connection will usually be adequate in design. This has been underpinned in Building Designer by careful selection of the defaults to ensure that the Recommended Details and standard connections contained in the Green Book on simple connections (SCI P212)(Ref. 1) are followed. This all means that as a designer, once you have selected the type of connecting element for a particular situation, for example a fin plate for beam to beam connections, Building Designer will provide robust and well detailed simple connections for the majority of the building. It is likely then that only a few connections will not be adequate. These can be displayed to you on the main building graphic and you can then interactively adjust the connection type or configuration to establish an adequate detail. Examples of connections where you need to make such changes might be: • a heavily loaded beam that might require two lines of bolts, or

• a shallow beam where the default bolt pitch has to be decreased in order to increase the number of bolts.

Moment Connection Building Designer will attempt to configure a moment connection at the end of any General Beam that has a Moment Connection or is fully fixed at the appropriate end. The word attempt is used since there are some configurations of member and connection that are beyond the scope of the current release e.g. if the supporting column is not an I or H-section or the supported beam frames into another beam. Moment connections can be established at beam to I- and H-section column flanges, and at beam to beam on end e.g. apex type connections. All are formed using bolted end plates in the current release. Beam to column moment connections can be single- or double-sided. There are no Connections Attributes associated with moment connections in Building Designer. Hence, during definition of your building model only the essential data and a number of basic defaults are set up for each moment connection. Essential data includes section size of the members joined and their design forces. Basic defaults include such items as

Footnotes 1. In the current release end plates and angle cleats are prohibited from use with hollow sections.



one pair of M20 Grade 8.8 bolts top and bottom of the connection with 20 mm thick end plates. It is necessary therefore for you to 'open' each individual connection and enter such data as, • additional tension and shear bolts,

• extensions to the end plate, • stiffeners, • haunches. Obviously at the same time you can also adjust the default values e.g. change from 20 mm thick end plate to 25 mm thick.

Column Splice Building Designer will attempt to configure a column splice at the end of any Simple Column where a splice position has been specified in the Floors tab of the Column Properties dialog. The word attempt is used since there are some configurations of member and connection that are beyond the scope of the current release, for example, if the column section is not an I-section or if the column is specified as a General Column. There are two types of column splice: • bearing splice - load is transferred in bearing directly or through a division plate,

• non-bearing splice - load is transferred through the bolts and splice plates. Bearing splices being simpler are generally preferred, particularly for heavily loaded connections. In Building Designer this type is therefore the default. As with simple connections, default settings for bolt size and number, plate thickness and so on, are chosen such that the subsequent check of this connection should under normal circumstances give a Pass.

Hollow Section Connection Building Designer will not configure any hollow section connections in the current release. Hollow section connections can therefore only be checked when running Fastrak Connections as a stand-alone application.

Column Base Building Designer will attempt to configure a column base at the lower end of any Simple Column or General Column at any level where a support has been defined in the model.

Generating Connections Once the building model has been designed, you can click on the Update Connections icon. This will create and load all the connections in the model and display them in the Connections-3D window.



Editing Connections You may prefer to adjust the connections inside Building Designer or you can send one or more connections to the stand-alone application. In either case the data you have added or modified is saved in Building Designer. You can see whether your connection configuration looks sensible by right clicking on the connection in the Connections window - this displays a 3D graphic of the connection in its own window. You can adjust each of the connections individually and design them as you proceed or once you are content with the layout of all of them you can click the Check Connections icon. You can use the Show/Alter State icon to view which have passed and which have not.

Viewing Results and Creating Output Results of your connection design can be viewed on the screen. The input, diagrams, and design results can be incorporated into a report by sending the connection or selection of connections out to Fastrak Connections. From there you can control exactly what you wish to see in the report. Connection components for example bolts, welds, stiffeners are not listed in the Material Listing report.


Chapter 4

Chapter 4 : Simple Connections

Simple Connections

Scope Simple connections are by definition pinned connections and transfer vertical shear only.

Connection Types For design to BS 5950, simple connections can be one of four types – end plate, fin plate (double) angle cleat or toe plate. These are termed connecting elements. In the case of fin plates and the leg of the angle cleat to the supported beam, a double line of bolts can be specified. Any of these connecting elements can be provided for beam to beam, beam to column flange and beam to column web connections provided that both the supported beam and the supporting column or beam is an I- or H-section. In the current release, only fin plates can be used to connect to hollow section columns. Toe Plate Connections A Toe Plate connection comprises: • a partial or full depth flexible end plate welded to the end of the supported beam

• a pre-formed fitting comprising a fin plate welded with a full strength weld to a further flexible end plate (the toe plate)

• the pre-formed fitting is then welded in place with a full strength weld to the supporting beam web with placement welds to the i/s face of the flanges

• the connection can be single sided or can be on both sides of the supporting beam. To keep the connection parameters within the scope of the simple connection design philosophy, the component parts are chosen so as to comply with the recommendations given in the Green Book on simple connections (SCI P212).(Ref. 1) The design model for the Fin Plate is based on that given in SCI P212.



The design model for the Flexible End Plate and the Toe Plate is based on that given in SCI P212.

Steel Grades Supporting and supported members and their connecting elements are limited to S275 and S355 grade steels – there are a number of semi-empirical rules in the design models that preclude the use of S460 grade steels.

Notches For beam to beam connections a notch length can be defined that suits the width of the supporting beam flange – this must be the same on both sides of the supporting beam. For each side a notch depth at the top and bottom of the supported beam can be defined – these can be different top and bottom and, different on each side. For convenience standard notch lengths and depths are defaulted and via the Set Standard Notches button you can recover these if you have changed something but wish to get back to the standard values1. Notch details also appear on beam to column connections but changing the default values from zero has no effect. To avoid notching in beam to beam connections a fin plate can be selected to ensure that the supported beam and the fin plate are joined outside of the flanges of the supporting beam. This will usually create a long fin plate for which certain additional checks are required and are carried out by Fastrak Connections.

Footnotes 1. Note that in the stand-alone application if you change the notch details and subsequently change the details of the connection, for example the section size, the default notch length and depth are reinstated.



Connecting Element Geometry Connecting elements can be of different types on each face of the supporting beam or column although those either side of a beam or column web have some design restrictions – see Design Checks. Beams can frame in at different levels or can be aligned (in beam-to-beam connections) with the top flange, bottom flange or centre line of the co-joined members.

Bolts A wide range of bolt grades and sizes can be defined and, by default, their layout (end and edge distance, pitch and gauge) meet the Recommended detailing practice given in SCI P212 (Check 1). The number of bolts is defaulted to meet the standard connections contained therein. Similarly, weld sizes for use with fin plates and end plates are the standard values. For angle cleats the default bolt layout is the same in both legs but you can select different layouts in each leg if required. You are able to adjust all these defaults but you are advised to do so with care.

Design Forces The design forces for simple connections are shear in the plane of the web of the supported beam and where appropriate tie forces. A set of these can exist for each design combination and these are established from the analysis of the building model as a whole (or entered independently in the stand alone application). You can edit the design forces, delete and add load combinations and these changes will be reflected in the design of the connection immediately following the changes. However, all these changes will be lost if you subsequently use the Update Connections function in Building Designer.

Tie forces Tie forces must be considered in the design. For details of how these forces are calculated refer to the later section Accidental Limit state

Limitations and Assumptions General Limitations The following limitations apply: • single angle cleat as connecting elements are excluded,

• a double line of bolts in end plates and in the leg of an angle cleat to the supporting member are excluded,

• in a beam to column web connection where the supported beam flange is wider that the internal dimension between the flanges of the supporting column, in practice a flange strip would normally be called for. Such flange strips are not included in the current release and so you must judge whether they might influence the results from Fastrak,

• similarly where the bottom flange of a beam on one side of a connection might interfere with the bolts on the other (deeper) side of a connection a snipe or flange strip is often used in practice. Such snipes and flange strips are not included in the current release and so you must judge whether they might influence the results from Fastrak,

• channel section and hollow section beams are excluded, • plated section beams, Westok beams and Fabsec beams are excluded,



• sections with unequal flanges are excluded. This covers not only plated section beams that have unequal flanges but also Slimflor beams and asymmetric Slimflor beams,

• connections to concrete filled hollow section columns are excluded, • where more than one beam connects to the face of the supporting member, Building Designer cannot form the connection. Where a component is excluded, for example channel section beams, Building Designer will not create a connection to that beam. In addition, where a connection would otherwise be created on one face of the supporting member but on another side a connection cannot be created then no connection at all will be created. For example, no connection will be created in the case where a channel section edge beam connects to a column on one face and an I-section connects to another face.

General Assumptions Essentially the assumptions in Fastrak Connections are those inherent in the design models for simple connections given in SCI P212(Ref. 1). However, a number of specific assumptions are made as given below. Internal forces in the supporting member from the applied loading that it carries are assumed not to influence the connection design. For example, the axial force in a column from floors above is assumed not to affect significantly the performance or behaviour of the connection. Similarly, where simple connections and moment connections are connected to the same column it is assumed that the forces imparted by the one do not influence the other. A typical example might be moment connections to the column flanges with simple connections to the column web. Not only are the designs independent but also the detailing. Hence. in this example any stiffening required by the moment connections are assumed not to interfere with the simple connections framing into the web. Any shear force out-of-plane of the beam web (minor axis shear force) is assumed not to influence the connection design. Similarly any axial force in the supported beam (other than due to tying action for structural integrity) is assumed not to be significant. In the Design Options off the Design menu in Building Designer, you can specify limits for these forces below which you believe the design will be unaffected. If Building Designer detects forces greater than these limits, the design will still proceed but the connection will be given a Warning status and the value of these forces will be given in the results. The default values for these limits are: • minor axis shear – 0.5 kN,

• axial force – 1.0 kN, • major axis moment – 1.0 kNm • minor axis moment – 0.1 kNm. The two moment limits are included even though simple connections are modelled in the analysis as pins. This is because the analysis model is a mathematical model and as such during the back substitution process very small moments that are effectively zero from an engineering point of view may exist mathematically.



Where connected beams are not orthogonal to the supporting member, Building Designer takes the following approach (see also Global analysis), • where all angles are less than a given lower limit, then the angles are ignored and the design proceeds as if the members do connect orthogonally,

• where any angle is greater than a given upper limit, then Building Designer creates the connection but the design is not performed and the connection is given a Beyond Scope status,

• where one angle lies between the upper and lower limit, then the angle is ignored, the design proceeds as if the members do connect orthogonally and the connection is given a Warning status,

• where more than one angle lies between the upper and lower limit, then Building Designer creates the connection but the design is not performed and the connection is given a Beyond Scope status. In all cases the angle can be viewed either in the design results (on the Notes page) or by editing the connection. The upper and lower limits are, • lower limit for slope, skew and rotation –  0.5°,

• upper limit for slope and skew –  10°, and • for rotation –  5°. The definitions of slope, skew and rotation are depicted in the figure below.

Slope

Skew

Rotation

For beam to beam connections in Building Designer, the top flanges of the supported and supporting beam are assumed to align. However, within the building model beams can be given an alignment relative to its cardinal points – the default is at the centre of the top flange. Any changes that you make to the cardinal points are not reflected in the simple connection design. For example if you set the cardinal point of a supported beam to the centroid of the section and connect this to a supporting beam with the cardinal point set as the centre of the bottom flange, the simple connection design will assume, still, that the top flanges align. Similarly, in beam to column connections the centre lines of beams and the column are assumed to node. However, within the building model both the column and the beams can be set off-grid. Any changes you make that set beams or columns off-grid will not be reflected in the simple connection design. For example, you might offset the beams on the edge of the building towards the outer face of the column to suit cladding details. Nevertheless, the simple connection design will assume, still, that the beams and the column node on the centre lines.



There are likely to be a number of positions in the building where braces connect to columns at the same position as a simple connection joining beams to the same column. The brace force is assumed to be transferred directly to the column and hence in the model has no influence on the force distribution in the connections. Similarly, the detailing of the brace end connection is assumed not to affect the configuration of the simple connections at the end of the co-joined beams.

Additional Assumptions and Limitations for Toe Plate Connections Toe Plate Connection force transfer mechanism In the Fastrak Toe Plate Connection model, the force transfer mechanism is taken as: • The line of shear transfer (supported beam end reaction) is taken to be at the face of the web of the supporting beam. This is equivalent to the flexible support method used in the design of fin plates.

• There is no torsion in the supporting beam. • The fin plate, toe plate and the end plate are all designed for the resulting moment Fv* a where a = the distance from the face of the web to the junction between the toe plate and the end plate.

• To ensure that there is sufficient rotational capacity in the connection for it to be considered as "simple", only Mode 1 failure [Complete End Plate Yielding] will be allowed. If other failure modes become critical the following parameters can be adjusted so that Mode 1 becomes the critical failure mechanism:

• • • • •

Bolt gauge Bolt pitch Bolt diameter Bolt end distances Toe plate/end plate thickness

• All of the bolts are used in both tension and shear - there are no dedicated shear bolts. • The compression zone is limited to the beam flanges with the centre of rotation taken as the mid thickness of the thinner flange.

• No plate stiffeners are allowed to the toe plate or to the beam end plate since these would be counterproductive as the model "forces" Mode 1 failure in these plates.

• The only stiffener allowed in the model is in the extension of an extended toe plate. Additional Limitations for Toe Plate Connections The following limitations are imposed which are additional to those implicit in SCI P212. • The top of the top flange of the supporting beam is to be flush and level with the top of the top flange of the supported beam.

• • • •

Only 2 bolts will be allowed in each row. Only one row of bolts can be placed in the toe plate extension. The toe plate, fin plate and flexible end plate are to be the same steel grade. The minimum depth of the toe plate is equal to the depth of the supporting beam + the leg length of the weld between the outside flange of the beam and the toe plate.

• The minimum depth of the end plate is equal to 0.6 x the depth of the supported beam.



• The maximum depth of the supported beam that can be used is 2 x the depth of the supporting beam.

• The minimum depth of the supported beam than can be used is 0.5 x the depth of the supporting beam.

• The connection can only accept positive bending moments and the associated shears. • The minimum bolt clearance dimension from centre-line of the bolt to the nearest steel face that is used in the software is 1.25 x bolt hole diameter.

Design Checks The design checks for simple connections are given in SCI P212. To assist you, the results displayed in Fastrak are given the title of each check in P212, for example: Check 5 – Supported beam – capacity at notch. The design models in P212 are primarily based on standard connections meeting orthogonally with, in the case of beam to beam connections, top of steel aligned. For such connections the design models are clearly laid out in P212 and so no additional explanation is given here. However, Fastrak Connections covers a somewhat broader spectrum and so additional points of note are given below. For each of the connections there are Recommended Detailing Requirements in SCI P212. These are recognized as good practice and you should comply with these whenever possible. If you select an item or value that is beyond these standards, you will find that the particular entry appears orange to give you a visual warning that you are stepping outside of good practice.1 There are strict limitations on the use of fin plates both in SCI P212 and in Fastrak Connections. These relate to edge and end distance, bolt size and grade, fin plate or web thickness, minimum projection and maximum lever arm between topmost and lower-most bolts in the fin plate. These restrictions are necessary to ensure ductile behaviour and adequate rotation capacity of the connection. Both these properties are essential for a simple connection to act as a pin. Fastrak Connections allows you to contravene these when specifying the connection but will fail the connection in design. Supported and supporting members do not always meet orthogonally – the assumption in Fastrak Connections is that they do. For very small angles, these are likely to be less than the normal tolerance on layout and out-of-plumb and so can safely be ignored. For slightly larger angles, the affect on the design is likely to be only nominal and so, in most cases, might be ignored. For significant angles, assuming that nevertheless they are still orthogonal may not be sufficiently accurate and hence may be unconservative. More information on the treatment of non-orthogonal connections is given in Limitations and Assumptions.

Footnotes 1. If the item or value is not acceptable or not feasible to achieve e.g. the edge distance for the bolts is less than the minimum requirement of BS 5950-1: 2000 then the text or value appears red and you cannot exit the dialog.



Supported and supporting beams in beam to beam connection do not always align with their top flanges and across a column web beams may be at different levels. Fastrak covers such situations in one of two ways. • Where the configuration of the connection either side of a web is not achievable in practice then you are allowed to accept the data and leave the dialog but no design is possible until the discrepancy has been corrected (the offending detail will also appear red on the connection graphic). An example would be where two end plates connect either side of a column web and the bolt gauge is different each side.

• Where the configuration is achievable, Fastrak will carry out the design calculations. However as mentioned earlier, since the design models in SCI P212 are based on alignment of supported beams, these calculations are extrapolations of the norm. You should therefore treat the design results of such connections with care. Supported beams either side of a beam or column web do not have to be the same type. For angle cleat one side and end plate the other side, the supporting web is checked in the normal way. However, for fin plate to one side and end plate or angle cleat the other side, there is no rigorous design model for the connection as a whole. Hence, the supporting beam web is checked for each side of the connection independently. No account is taken of any interaction between the two different connection methods on the web resistance. Fastrak reports the relevant check twice once for each connection type (SCI P212: Check 10). The standard end plate connections in SCI P212 are 8 mm and 10 mm thick and are welded to the web only. Full depth end plates up to 12 mm thick with a full profile weld can be treated as simple connections – see SCI P212: Check 1. You can select thicker end plates and this will result in a Warning status for the connection. In all cases the design model and Fastrak do not take account in design of any weld to the beam flange. Where a supported beam is unrestrained and is notched, this can have a significant influence on the effective length of the beam for lateral torsional buckling. This is one situation where there is a direct impact of the connection configuration on the design of the beam. This is covered by SCI P212: Check 7. In Fastrak you can specify that the beam is unrestrained. However, in the current release the calculations for this check are not implemented. Consequently, this check is always reported with a Warning status if you specify that the beam is unrestrained. You are expected to carry out your own hand calculations. If you have responsibility for the connection design but not for the member design then it is important to ensure that the designer responsible for the beam design is informed of the impact of the connection configuration on his beam design. In the stand alone application, on the Beam Details property page there is an opportunity to enter the Length (span) of the supported beam. In the building model this value is set to zero and cannot be changed. Any value specified is used only to determine whether in the case of fin plates attached to beams deeper than 610 mm that the span/depth ratio is less than 20. This is a requirement to ensure adequate rotation capacity in fin plates attached to deep beams – see SCI P212: Check 1 for fin plates. If the span/depth ratio is greater than 20 the connection will be failed in the design.


Chapter 5

Chapter 5 : Moment Connections

Moment Connections

Scope Moment connections are by definition able to transfer moment as well as vertical shear. The design is also able to deal with axial force in the beam member if present. Fastrak Connections checks only the strength of moment connections. Stiffness, ductility and rotation capacity can be important characteristics in some situations. Your attention is drawn to Clause 2.4.2.5 of BS 5950-1: 2000 and Section 2.5 of the Green Book on moment connections (SCI P207).(Ref. 2)

Connection Types Moment connections can be one of three types - single-sided beam to column flange, double-sided beam to column flange and beam to beam. They are formed using bolted end plates that can be flush or extended top and/or bottom. Haunches can be defined below the supported beam and can be either,

• a section cutting -cut from the same size as the beam, same size as the column or from any (valid) section that you select or,

• built up from plates - a plate size (width and thickness) is required for the web and flange plates. Where a section cutting is defined, you are provided with a button to calculate 'Max Depth' of the haunch based on the length of the haunch, slope of the beam and section size selected for the haunch. In beam to column moment connections the column and the individual beams can be assigned a 'level' within the connection application. This is not reflected in the building model.

Steel Grades Columns, beams and end plates that make up you connection can be S275, S355 and S460 grade steels. Care should be exercised when selecting S460 grade steel since the original Green Book on moment connection design (SCI P207) was written with S275 and S355 steel in mind and there may be limited availability of plate in this grade.

End Plates A range of standard width and thickness of plates is provided from which the end plate can be selected. Flush end plates are given a 'projection' above and below the connection whilst for extended end plates it is necessary to define the extension (above and/or below).



Bolts and Welds A wide range of bolt grades and sizes can be defined and, by default, only one pair of 'tension' bolts and one pair of 'shear' bolts are provided. You can add bolts individually or use the Generate Regular Bolt Layout button. In either case you need to go to the Combinations page and click on the appropriate Bolts column to set which of your additional bolts should be used in tension and which in shear. You need to do this for each design combination. Welds to the beam flanges, beam web and to the haunch if appropriate are all defaulted to 8 mm fillet welds. You should adjust these both in terms of size and type (a butt weld might be more appropriate) to suit the particular application.

Stiffeners Stiffeners in moment connections are often required and a wide range is provided,

rib usually relatively short stiffeners that are used principally to improve column flange bending capacity,

full depth often required to resist compression particularly where the column is a UB section,

shear these can be diagonal, K or 'Morris' types and may be required to assist the web panel shear capacity,

web plate help both compression and shear capacity of the web panel and have the advantage that they do not interfere with any beams framing into the web,

cap plate can be provided for other purposes e.g. to connect parapet posts but if present will usually assist flange bending, and compression in 'reverse' bending combinations,

flange plate these are 'loose' flange plates i.e. they are not fully welded to the flange - they are usually tack-welded to keep them in place during transport and erection. They assist flange bending,

extension plate for an extended end plate connection the extension can be relatively weak in bending and this vertical stiffener will improve the capacity. It is essential when there are two rows of bolts in the extension. Note that incorporating stiffeners is expensive in fabrication terms and most can interfere with other members framing into the same area. It is often economic to avoid stiffeners by increasing the section size (of the column and possibly the beam) or deepening the haunch. This may also avoid detailing issues and improve erection efficiency.



Design Forces The design forces for moment connections are shear in the plane of the web of the beam, moment in the same plane and where appropriate axial force in the beam. Tie forces are not included. For haunched connections, the moment at the 'sharp end' of the haunch can be entered - due to the length of a typical haunch this can be significantly less than that at the connection interface. This moment is used to check the capacity of the beam web at that position. A set of these design forces can exist for each design combination and these are established from the analysis of the building model as a whole (or entered independently in the stand alone application). You can edit the design forces, delete and add load combinations and these changes will be reflected in the design of the connection immediately following the changes. However, all these changes will be lost if subsequently you use the 'Update Connections' function in Building Designer.

Limitations and Assumptions Limitations The following limitations apply:

• • • • •

fully welded moment connections are excluded, section types other than I- and H-sections cannot be used in moment connections, moment connections into the column web are not be permitted, the section size either side of a beam to beam moment connection must be the same, where beam to beam moment connections are formed between beams at different angles, the connection is assumed to be symmetrical - see figure,

• the projecting portion of an extended endplate both above and below is limited to have no more than two rows of bolts,

• where the projecting portion of an extended endplate either above or below has two rows of bolts, an extension stiffener must be provided,

• all components have only one value of design strength, py, taken as the lower of the two values based on flange thickness and web thickness. However, a built-up haunch will have a value of py for the haunch web and another for the haunch flange.

• when checking stiffeners in conjunction with, say, a web, the lower of the two values of py is used. This particularly affects S275 stiffeners used in conjunction with S355 sections.

• where more than one beam connects to the face of the supporting member, Building Designer cannot form the connection. Where a component is excluded e.g. channel section beams, Building Designer will not create a connection to that beam. In addition, where a connection would otherwise be created on one face of the supporting member but on another side a connection cannot be created then no



connection at all will be created. For example, no connection will be created in the case where a plated section beam connects to one flange of the column and an I-section connects to another face.

Assumptions Essentially the assumptions in Fastrak Connections are those inherent in the design model for moment connections given in SCI P207.(Ref. 2) However, a number of specific assumptions are made as given below. It should be noted that, in principle, the design model in SCI P207 is for moment connections with axial load and not axially loaded connections with moment. Internal forces in a column from the applied loading that it carries are assumed not to influence the connection design. For example, the axial force in a column from floors above is assumed not to affect significantly the performance or behaviour of the connection. Similarly, where moment connections and simple connections are connected to the same column it is assumed that the forces imparted by the one do not influence the other. A typical example might be moment connections to the column flanges with simple connections to the column web. Not only are the designs independent but also the detailing. Hence, in this example any stiffening required by the moment connections is assumed not to interfere with the simple connections framing into the web. Any moment or shear force out-of-plane of the beam web (minor axis moment and shear force) is assumed not to influence the connection design. In the Design Options off the Design menu in Building Designer, you can specify limits for these forces below which you believe the design will be unaffected. If Building Designer detects forces greater than these limits, the design will still proceed but the connection will be given a Warning status and the value of these forces will be given in the results. The default values for these limits are, • minor axis shear - 0.5 kN

• minor axis moment - 0.1 kNm Where the members of a moment connection are skewed or rotated relative to each other, Building Designer takes the following approach (see also Global analysis), • where both the skew and rotation angles are less than a given lower limit, then the angles are ignored and the design proceeds as if the angles were zero,



• where either angle is greater than a given upper limit, then Building Designer creates the connection but the design is not performed and the connection is given a Beyond Scope status,

• where one angle lies between the upper and lower limit, then the angle is ignored, the design proceeds as if the angle is zero and the connection is given a Warning status,

• where both angles lie between the upper and lower limit, then Building Designer creates the connection but the design is not performed and the connection is given a Beyond Scope status. In cases where the angle is above the lower limit, the angle can be viewed in the design results (on the Notes page). The upper and lower limits are, • lower limit for skew and rotation -  0.5 deg

• upper limit for skew -  5 deg, and for rotation -  2.5 deg For double sided beam to column moment connections and for beam to beam moment connections in Building Designer, the top flanges of the beams are assumed to align. However, within the building model beams can be given an alignment relative to its 'cardinal points' the default is at the centre of the top flange. Any changes that you make to the cardinal points are not reflected in the moment connection design. For example in a double sided beam to column moment connection if you set the cardinal point of one beam to the centre of the top flange and the cardinal point of the other beam as the centre of the bottom flange, the moment connection design will assume, still, that the top flanges align. The design will consider that the connection is double sided even though in this case the two connections should be treated as single sided. A similar situation occurs when the beams have the same cardinal point but the beams are defined on two separate grid lines that are close together. In this case Building Designer will create two separate single sided connections even though the grid lines may be only a few millimetres apart! Note that for this reason in the stand alone application if you specify 'levels' for the two beams that would effectively mean that they should be treated as two separate single sided connections, Fastrak Connections will still consider them as double sided. In beam to column moment connections the centre lines of the beams and the column are assumed to 'node'. However, within the building model both the column and the beams can be set 'off-grid'. Any changes you make that set beams or columns off-grid will not be reflected in the moment connection design. It is likely that when transferring significant moment, anything but the very smallest of offsets would invalidate the design model.

Design Checks The design checks for bolted moment connections are given in SCI P207. The design models in P207 cover I- or H-section beams to the flange of I- or H-section columns with or without haunches. They can be single or double-sided. For such connections the design models are clearly laid out in P207 and so no general explanation is given here. You are reminded that, in principle, the design model in P207 is for moment connections with axial load and not axially loaded connections with moment. However, Fastrak covers a somewhat broader spectrum and so additional points of note are given below.



SCI P207 was written in 1995 and so reflected the then current British Standard, BS 5950-1: 1990. However, Fastrak uses the latest British Standard, BS 5950-1: 2000 which incorporated a number of changes that affected connection design. These are, in brief, • modification to the buckling check for unstiffened column webs in compression,

• modification to the configuration of the stiffened column web and to the design force that it must resist,

• changes to the requirements for weld design - both calculation of resistance and the force for which it should be designed. The standard formulae for bearing and buckling of the unstiffened column web assume that the column flange at the point of compression is effectively held against both, • rotation relative to the web,

• lateral movement relative to the other flange. Where this is the case the effective length of the unstiffened or stiffened web is taken as 0.7L. However, this may not always be the case. Fastrak always assumes lateral restraint to the flange but you are provided with a means to select whether rotational restraint is present or not. In the latter case, you can adjust the effective lengths for the top and bottom of the connection (since they may be different) - the default value is 1.0 L. A similar provision is made for the stiffened capacity. The centre of rotation of the connection is assumed always to be the intersection of the centre-line of the compression flange with the outside face of the column flange. This position is assumed irrespective of whether some of the beam/haunch web is taken into account in resisting the compression force at that level. Similarly for a stiffened extended end plate the centre of rotation of the connection is not allowed to be within the stiff extension - no guidance exists on how far within the extension the centre of rotation can be placed and so in the meantime the conservative approach is adopted. Whilst the centre of rotation is kept constant, the centre of compression is allowed to move. This is the case when you request that the beam flange bearing check takes account of some of the beam web in its resistance calculation. In this case, the lever arm for each individual bolt is adjusted to take account of the movement of the centre of compression. When a connection contains a haunch, there is a compressive force at the level of the haunch flange/end plate intersection which can be derived from the equilibrium condition of the potential resistances of the components of the connection at that interface. In the conventional approach contained in SCI P207, all this force is assumed to 'pop out' of the flange at the sharp end of the haunch. A more accurate, more logical and less conservative approach is to use the equilibrium condition at the sharp end of the haunch under the moment at that point. Using this approach the forces at the sharp end can be resolved to give a force acting perpendicular to the web of the beam. The unstiffened or stiffened resistance of the beam web is checked against this force. You can see from the Combinations page of the connection input dialogue that the moment used to determine the equilibrium condition at this point is termed, "Moment (Sharp End)". Note that whilst within Fastrak Building Designer, the moment, shear and axial force at the connection interface are automatically entered into the design combinations, the moment at the sharp end is not. You will have to interrogate the bending moment diagram for the individual beam members to establish the value of the moment at the sharp end and enter this



directly. Also note that the effective length of the unstiffened or stiffened beam web is dependent upon the restraint conditions of the flange in a similar manner to that described above for the column web. There are a number of points associated with stiffener design, as follows, • In positive bending, for a full depth stiffener to be effective in compression, it must be placed with its centre-line within the stiff bearing length of the haunch flange or beam bottom flange. In negative bending, for a full depth stiffener or cap plate to be effective in compression, it must be placed with its centre-line within the stiff bearing length of the beam top flange.

• It is assumed that for a tension stiffener to be effective in generating the yield lines around the bolts, the gross depth of the stiffener should be at least 75 % of the outstand of the column flange or end plate. Where this is not the case a warning is issued.

• Stiffeners may optionally be defined 'fitted to root'. This means that the corner of the stiffener is shaped to fit tightly into the root radius of the section. This facilitates the weld runs being taken around the corner of the stiffener. In the normal situation the corner of the stiffener is chamfered so that it clears the root and in this case the weld run must stop at this position. The implication for design is that in the normal situation the length of weld used to calculate its resistance is based on the dimension of the stiffener less two leg lengths of weld (see Clause 6.8.2 of BS 5950 1: 2000). However, where the stiffener is 'fitted to root' only one leg length need be deducted.

• A number of options exist for the detailing of cap plates. Normally a cap plate will sit on top of the column and be welded one side (inside) or both sides. The choice between these two weld details is given to you. The full depth stiffener at the base of a connection is usually assumed to be 'fitted'. Suitable details for the cap plate can be made such that a cap plate also can be assumed to be fitted. Hence, you are provided with the choice of assuming that a cap plate is fitted or unfitted. In the former case, in compression, the weld size will be determined whereas in the latter case only nominal welds are required. In both cases in reverse bending the weld is checked for any net tension force. The weld between the haunch flange and the beam flange is required to resist the force derived from the equilibrium condition at the 'sharp end' of the haunch (in the same manner as described earlier for the beam web in compression). Advantage is taken of the increased depth of the section at this point due to the presence of the two flanges (haunch and beam) in determining the force available to enter the haunch flange. This is resolved into the direction of the haunch flange to provide the design force for the weld. Similarly, the force that continues past the sharp end in the beam flange is used to design the haunch web to beam flange weld. For double sided connections, all checks e.g. column flange bending, beam web tension but excluding web panel shear are carried out for each side of the connection separately. Equilibrium for each side is then established but ignoring column web shear capacity. This is achieved by reducing the number of bolts or their contribution as appropriate until equilibrium is reached. The moment capacity allowing for axial load is then calculated and the net effect of the forces on the connection compared with the web panel shear capacity. This first equilibrium condition is based on bolt row capacities (termed 'potential resistance' in SCI P207). Where the applied moments would not generate these capacities as forces i.e. the applied moment is << the moment capacity, then use of the bolt row capacities can produce significantly conservative or significantly unconservative answers. Consider a case in which



one applied moment is close to the capacity and the other is approaching zero. If both of the applied moments are of the same sign then the value used to compare with the web panel shear capacity is the difference of the two bolt row capacities. In reality the connection with the low applied moment will have only a small force in the bolt rows and hence, a much larger net effect when combined with the other side and compared with the web panel shear capacity. This net effect could be larger than the web panel shear capacity and thus require redistribution of the bolt row forces to an extent where that side would fail. Thus, using capacities of bolt rows could show the connection to pass whereas the use of bolt row forces could show the connection to fail. Having established the first equilibrium condition ignoring shear, there are two main outcomes when the web panel shear capacity is taken into account. If the utilization ratio for both sides is greater than 1.0, then check whether the limiting condition for shear is satisfied. If shear is not limiting i.e. Pv is greater than or equal to the right hand side of the limiting condition for same or opposite sign moments as appropriate, the base set of forces is correct. If shear is limiting, then use the existing routines to redistribute the bolt forces until the limiting condition is satisfied. This will have the effect of making the failed utilization ratios worse for one or both sides. The procedure for the existing routines is described below. Thus, when the utilization ratio for both sides is greater than 1.0 and shear is limiting, then the number of bolts or their contribution must be reduced until the appropriate limiting condition is satisfied at which point the connection as a whole is in equilibrium. A bolt or part of a bolt's contribution is removed, • from the side whose ratio of Mc/Mm is the greater.

• from the other side if on one side there is only one bolt remaining • successively from each side as a proportion of the bolt force when there remains only one bolt on both sides Each time a bolt is removed the moment capacity is recalculated for each side to determine from which side next to remove a bolt or part bolt. The appropriate limiting condition is then re-evaluated. The process continues until the limiting condition is satisfied. The final moment capacity for each side is determined from the resulting bolt force distribution. If the utilization ratio for both sides is not greater than 1.0, then for each side the bolt row capacities that make up the moment capacity need to be converted into bolt row forces consistent with the applied moment. For the side under consideration, if the utilization ratio is greater than 1.0, then no conversion of capacities to forces can be made. Otherwise, remove a bolt or part of a bolt's contribution until the moment capacity equals the applied moment or until there is only 1%, say, of the bolt force remaining. The last requirement is to prevent all bolts being completely removed, as this would give zero capacity.


Chapter 6

Chapter 6 : Column Splices

Column Splices

Scope Splice connections in simple construction are designed to transfer axial and shear forces from the upper column to the lower column via bolted splice cover plates. Only nominal moments are catered for in the design rules. There are two types of column splice:

• bearing splice - load is transferred in bearing directly or through a division plate, • non-bearing splice - load is transferred through the bolts and splice plates. A wide range of bolt grades and sizes can be defined and, by default, their layout (end and edge distance, pitch and gauge) meet the Recommended detailing practice given in the Green Book on simple connections (SCI P212) - column splices (Check 1). The number of bolts is defaulted to meet the standard connections contained therein. The design forces for column splices are axial force, shear and nominal moment in the plane of the web of the column and where appropriate tie forces. A set of these can exist for each design combination and these are established from the analysis of the building model as a whole (or entered independently in the stand alone application). You can edit the design forces, delete and add load combinations and these changes will be reflected in the design of the connection immediately following the changes. However, all these changes will be lost if you subsequently use the Update Connections function in Building Designer. Tie forces must be considered in the design. For details of how these forces are calculated refer to the later chapter Accidental Limit State.

Limitations and Assumptions Limitations Historically, splices were positioned just above floor level (so as to avoid the beam - column connections). Typically at 500mm above floor level, they could be assumed in simple multi-storey construction not to be moment resisting. However, as a consequence of CDM regulations, splices are now more often positioned at around 1.2m above floor level, (to allow for ballustrading to be fixed around the floor perimeter at construction stage and also to facilitate the fixing of the splice itself). When positioned in this way, the splice is more likely to be located where significant p-delta buckling moments arise within the column. The assumption that the splice is not moment resisting may therefore no-longer be valid. In this case you are forced to take account of the p-delta moments as per clause 6.1.8.2 of BS:5950: Part 1. This is beyond the scope of the Fastrak Connections application. The following limitations also apply:

• moment splices are excluded

Chapter 6 : Column Splices


• • • •

channel section and hollow section columns are excluded, plated section columns are excluded, sections with unequal flanges are excluded, a double line of bolts in flange plates are excluded.

Where a component is excluded, for example hollow section columns, Building Designer will not create a connection to that column.

Assumptions The assumptions in Fastrak Connections are those inherent in the design models for column splices given in SCI P212. However, a number of specific assumptions are made as given below. Internal forces in the supporting member from the applied loading that it carries are assumed not to influence the connection design. Similarly, where simple connections or moment connections are connected to the column it is assumed that the forces imparted do not influence the column splice connection. Any major or minor axis moment (other than nominal) is assumed not to influence the connection design. In the Design Options off the Design menu in Building Designer, you can specify limits for these forces below which you believe the design will be unaffected. If Building Designer detects forces greater than these limits, the design will still proceed but the connection will be given a Warning status and the value of these forces will be given in the results. The default values for these limits are: • major axis moment – 2.5 kNm

• minor axis moment – 1.0 kNm.


Chapter 7

Chapter 7 : Hollow Section Connections

Hollow Section Connections

Practical Applications You can use Fastrak Connections to check a welded connection made up of known hollow section sizes to determine whether it is able to carry the specified loading. Certain configurations including connections with I or H section chords are also permitted. Hollow section connections are most typically used in tubular trusses. Despite the fact that the internals are fully welded to the chords, this type of connection behaves as if it were pinned at the final stage of loading i.e. at Ultimate Limit State. This is due to the relatively thin walls of the hollow sections and the large deformations that such connections can sustain. They can, of course, also be designed to resist significant moments so that Vierendeel action can be generated. If the truss is designed first, then due to the efficient way in which hollow sections carry the applied forces (mainly axial), relatively small, very thin walled sections can be found to be adequate. Later, it may be found difficult to justify the connections between such minimum weight members and stiffening may be required. Since most of the work and hence cost is in the preparation and welding of the member ends then attempting to minimise the section size is counter productive. When using the software it is best to be prepared for some iteration in the analysis/design process i.e. guess the member sizes for the truss analysis, being generous on the sizes selected, check the connections, update the analysis/design model and check the member sizes.

Checking a Hollow Section Connection In the typical procedure below items in brackets [ ] are optional. 1. Launch Fastrak Connections 2. Create a new project giving the project name [and other project details] 3. Select Hollow Section Connection from the New Connection dialog 4. Use the Configuration page of the Welded hollow section dialog to select the Welded connection type from the pull down menu {note that when a K or KT connection is selected there is an option to define either the gap between the braces or the eccentricity of the connection - check the Gap govern input box to define the gap gi, or leave blank to define the eccentricity ei}. 5. Use the Sections page of the Welded hollow section dialog to select the section sizes and grades together with other parameters appropriate to the connection type selected. {See the Scope Chapter for a description of error messages and limitations} 6. Use the Combinations page of the Welded hollow section dialog to specify the loadings for which the connection is to be checked. The load values are to be entered as factored loads and each load combination should form consistent load sets i.e. be contemporaneous loads.



7. When all the required input data has been entered and all errors resolved, the typeface of the page tabs will change to normal colour and the OK button will become active. Click this button to proceed with the connection check.

As you are defining the data for your connection Hollow Section Connection checks to ensure that the data is valid. If a particular value is not valid, then it will be shown using a colour of your choice in the dialog. If you allow the cursor to rest over the error you will see a tip telling you the acceptable range of input using the format: Value must lie in interval <{lower bound}, {upper bound}>{units}. For example an angle range of 30o to 90o would be displayed as "Value must lie in interval <30, 90>". Until all the information within the dialog is valid you will not be able to save the dialog since OK will be dimmed. Although checking in this way prevents you from defining an invalid connection, there are many of the specified validity checks that cannot be trapped in this way and in these cases, when you check the results you will see a failure message in the Range of Validity tab in the results viewer. Each failure message is self explanatory. You should take careful note of the failure and change the connection parameters to correct the problem. If there are other problems with the connection, then you will see a warning message in the results viewer. You should take note of any such warnings and take the action that you deem appropriate.

Scope Fastrak Connections will determine whether a hollow section connection is able to carry the specified forces and moments.



The software does not design or check the design of welds between the component members of the connection. In this context, reference should be made to the provisions of BS EN 1993-1-8:2005(Ref. 3) Section 7.3 Welds.

Connection configurations The following configurations are covered in the current release of the application:

Hollow Section Chords • Y connection {a T connection is checked as a Y connection with the angle between the brace and the chord set to 90o}

• X connection • K connection • KT connection I or H Section chords • Y connection {a T connection is checked as a Y connection with the angle between the brace and the chord set to 90o}

• X connection • K connection Steel sections Hollow Section Connection can check connections made up of an international range of steel sections for many different countries.

Theory and Assumptions The definitive guides for the design of welded hollow section connections are those published by CIDECT and CORUS (Ref. 4) (Ref. 7) (Ref. 8) with further CORUS publications (Ref. 5) (Ref. 6) adding to the guidance available. The publication of BS EN 1993-1-8:2005 (Ref. 3) means that, for the first time, guidance for the design of welded hollow section connections is incorporated into a British Standard.

Design The methods employed to check the design of welded hollow connections are consistent with BS EN 1993-1-8:2005 with the following exceptions: 1 KT connections use the methodology outlined in the CORUS publication Design of SHS welded Joints: Supplement No.2 (Ref. 5) 2 K connections in which the loads in the brace members act in the same sense {both compression or both tension} use the methodology outlined in the CORUS publication Design of SHS Welded Joints: Supplement No.3 (Ref. 6)

Chapter 8 : Column Bases

Chapter 8


Column Bases Column base connections can be simple bases, moment bases and stiffened moment bases.. Fastrak Connections will check the base plate size and thickness, the shear resistance of the base, the size of the foundation bolts, and the size and type of any welds that are required. For stiffened moment bases the design will also check the size and thickness of any stiffening that is provided and the welds required to connect the stiffeners to the other parts of the column base. Graphics are used to display the base plate in its current state. You can therefore graphically see the base that you are defining and the results that the design process has achieved. This allows you to see the effects of any modifications that you make, instantly on the screen. Note

Simple Bases and Moment Bases adopt quite different design models. You will find that a Moment Base with a very small moment will not result in the same design as a Simple Base (zero moment) carrying the same axial load. You should therefore judge whether the moment is negligible for each such design. If it is you can design a Simple Base, otherwise a Moment Base design will be appropriate.

Limitations and Assumptions The limitations and assumptions for column base connections are as follows:

General Limitations and Assumptions The following points are of note:

Base Plate • When calculating the compressive capacity of the base Fastrak Connections uses the compressive stress fcbg = 0.6 * fcu where fcu is the minimum value for the bedding material or the concrete base. If fcbg is greater than 15 N/mm2 then special controls are required at site in the placing of bedding materials and so an appropriate warning message is given. A similar approach is adopted for the fire condition, but in this case Fastrak Connections uses the compressive stress fcbg = 0.8 * fcu and applies no upper limit. Note

In either case if the User value has been specified this will be used irrespective of its value relative to the strength of the concrete or the bedding material.



Bolts and Anchorage • If you are defining an un-reinforced column base with uplift, then you can now check that the base is satisfactory against bolt pull out. Fastrak Connections will calculate the shear capacity of the cone of concrete subtended at an angle of 45° from the bottom of the foundation bolt. This will be checked against the pull out force in the bolt.

• The conical surface around an individual bolt will overlap with that of an adjacent bolt when the dimension between them is less than 2 times the embedded length. When this occurs the compound area is treated as a hopper.

• In both cases the surface area is assumed to fall within the concrete and is therefore not truncated by the edge of the concrete base. If the cones or the hopper are truncated by the edge of the concrete additional hand calculations may be necessary in order to validate the design.

• SCI P207(Ref. 2) gives alternative methods for calculating the punching shear perimeter when the base is remote from, or close to a single free edge. Fastrak Connections adopts a more comprehensive approach where the punching shear perimeter is affected by the presence of any free edge or end.

• Fastrak Connections does not hold any details about the reinforcement which is included in the concrete base. You must therefore enter the area of tension reinforcement that is provided directly.

• When Fastrak Connections is checking for clashes between adjacent bolts, bolts and steel faces or bolts and steel edges it includes the clearances for form G washers plus an arbitrary allowance of 10mm in the calculations. If any bolt fails these clearance checks, then it is shown in red on the graphical display. The line relating to the bolt on the input property sheet is also shown in red.

Shear • For resistance to horizontal shear loads the available options are: • Friction alone • Bearing on bolts (for both adjustable or non-adjustable bolt types) • Friction and bearing on the bolts combined • Bearing on a shear key • Friction and bearing on the shear key combined • For Bearing on Bolts shear transfer: • You can specify the contribution of bolts to the shear resistance of the base. This is limited to the maximum contribution that can be provided for non-adjustable bolts.

• The length factor is calculated by applying the factor to the diameter of the bolt. The maximum allowable value is for a bearing length 3.0 times the bolt diameter to be used in the shear capacity calculation. The default value of the factor is 1.0.

• The Bearing Stress factor is applied to the lower of the fcu values for the concrete or bedding material. The maximum allowable value is for a factor of 2.0 to be used in the shear capacity calculation. The default value of the factor is 1.0.



• For Direct Shear Key shear transfer the capacity of the shear key is calculated using the formula vh-shearkey = Lsk * Dsk * factorconc_strength * fcu The allowable range for the above concrete strength factor is 0.10 to 2.00, with the default value being 0.80.

Welds • When Fastrak Connections distributes bolt forces to the inside of a flange or web, the design assumes that the weld is adequate to resist these forces. No specific calculations are performed to check this assumption. If you doubt this assumption, then you should produce hand calculations to prove that the assumption is valid.

• For a partial penetration plus superimposed fillet weld Fastrak Connections always takes the gap as being 3 mm Note

A figure of a partial penetration plus superimposed fillet weld is given on page 102 of SCI P207.

Limitations and Assumptions specific to Simple Bases For simple bases Fastrak Connections follows the procedures given in SCI P212 - Joints in Steel Construction. Simple Connections.(Ref. 1) The following points specific to simple bases are of note: • For the E ffec tive A rea Method the design strength of the base plate is determined from the steel grade and base plate thickness. The value is not limited to the maximum value of 270 N/mm2 as detailed in SCI P212.

• For simple bases with positive axial loads (compression bases) Fastrak Connections allows bolts to be placed inside the column flanges. All other cases with bolts inside flanges (simple bases with tension or moment bases with tension or compression) are beyond the scope of the program and therefore Fastrak Connections will show an error condition for these designs.

• Since these bases do not resist moment, the column can only be symmetric on the base plate. However if uplift occurs on the base this can now be taken by any bolt configuration:

• 1 or 2 rows outside each flange, • 1 or 2 rows inside each flange, • one row each side of each flange. Limitations and Assumptions specific to Moment Bases For moment bases Fastrak Connections follows the procedures given in SCI P207 - Joints in Steel Construction. Moment Connections.(Ref. 2) The following points specific to moment bases are of note: • SCI P207 recommends that the extent of the compression stress block is limited to two thirds of the distance from the compression edge of the base plate to the tension bolts. Fastrak Connections does not impose this limit allowing the compression stress block to



jump to the centre-line of the tension bolts and then if necessary to increase further until the edge of the base plate is reached. However in this case the moment capacity of the base is calculated from the magnitude of the compression stress block and its eccentricity from the centre line of the column base (i.e. there is no tensile contribution to the capacity of the column base from the holding down bolts). A similar situation can arise if the applied moment is small, resulting in the bolt force being negative (i.e. compression). In this case Stress block 2 shown below is assumed. The following diagrams showing the various limits and stress blocks may aid your comprehension. stress block 0 – rectangular

L4

c

L1

L2

c

2c + t

X Increases as compression area increases



stress block 1 – tee

L4

L1

CL Column

L2

c c

c

2c + t

X Increasing



stress block 2 – H

CL Column

c c

c

2c + t

where

p yp c = t p  ---------------3  f cbg

2c + t

1-2

• You can only specify a positive eccentricity. If you need to investigate a base with a negative eccentricity, then you will need to define a mirror image of the base.

• For the compression and tension zones the bolts can be placed both outside and inside the flanges in the following configurations:

• 1 or 2 rows outside each flange, • 1 or 2 rows inside each flange, • one row each side of each flange. • Different numbers of bolts can be defined in each bolt row, Bolts are therefore only included where they can be used.

Chapter 9 : Analysis

Chapter 9


Analysis

Global analysis Connection forces are established from a global analysis of the building as a whole. All the connection types included in Fastrak have a limited set of design forces for which the connection can be designed, for example simple connections are designed for the appropriate beam end reaction (see the simple connections Scope). Non-design forces are identified and, where their value is greater than a given limit, they are displayed to you in the results along with a Warning status. The given limits are defined on the Force Limits – Connections page of the Design Options dialog available from the Design menu. The forces from the global analysis are treated in the following manner for the different connection types, • simple connections are designed for the shear in the plane of the beam web perpendicular to the centre line of the beam. For sloped connections this force is not resolved into the plane of the supporting member. For rotated connections the connecting element is assumed to be rotated by an equal amount and so no resolution of forces is necessary (although any out-of plane shear is ignored).

• moment connections are designed for the in-plane moments and forces, that is major axis moment, shear in the plane of the beam web and axial force. Design forces for sloped connections are resolved into the plane of the supporting column. For skew and rotated beams there is no resolution of moments and forces into the plane of the supporting column.

• column bases are designed for the axial force at the base of the column, the shear in the plane of the column web and where appropriate the moment at the base of the column. Bases are assumed to be orientated to the column’s major and minor axes and hence there is no requirement to resolve the force when the column is rotated. Columns can only be sloped in the pane of the web and the bottom stack axial force and shear are resolved into vertical and horizontal forces in the base. Where the global analysis includes second-order (P-Delta) effects the Ultimate Limit State design forces will include these effects also. However, for column bases the design forces for soil bearing pressure calculations are taken from an elastic global analysis of the unfactored loadcases without second-order effects.

Connection analysis The analysis of the connection itself is normally carried out by determining a rational set of load paths through the components of the connection. This is inherent in the design models adopted. The design models are based closely on those given in the series of Green Books(Ref. 1), (Ref. 2) with extrapolation and addition where necessary to facilitate analysis/design of a wider range of connections.


Chapter 10

Chapter 10 : Additional Design Considerations

Additional Design Considerations

Accidental Limit state Structural Integrity The necessity for tying is a matter of regulation and requirements are included in BS 5950-1: 2000. The April 2007 amendment to BS 5950 includes an adjustment to the tie force that is dependent on the number of storeys in the structure. Since the number of storeys in a building can vary and some ‘levels’ in a building are not ‘floors’ e.g. mezzanine. Fastrak will establish the number of storeys from the number of levels set to be ‘Included’ on the Levels dialogue of the Building menu. Note that the uppermost level will be included irrespective of the setting of the Included check box. Currently only simple connections and column splices are checked for tie forces if applicable. In the building model you are able to set simple connection attributes to allow for tying in one of three ways,

• no tie force -this member does not form part of the tying system, • minimum tie force - regulations permit only nominal tying of the building (75kN) • vertical reaction - full tying requirements are necessary and the tie force is taken to be, MAX(n x reaction, 75kN) where n is the reduction factor for number of storeys. For 5 storeys and above n = 1.0, for 4 storeys, n = 0.75, 3 storeys, n = 0.5, 2 storeys, n = 0.25 and 1 storey, n = 0.0 In the latter case if a member does not support a floor but simply acts as column tie or masonry restraint for example under normal stage loading (that is at the Ultimate Limit State), there may be no reaction and hence the tie force will be set to the minimum. Where design for tie forces is required, Fastrak adopts the following approach: • for simple connections to a column flange or to hollow sections, the connecting elements and the column are designed for the tie force in the supported beam,

• for simple connections to a column web the connecting elements are designed for the appropriate tie force whereas the web is designed for the difference in the tie forces (if any),

• for simple connections to a beam web the connecting elements are designed for the appropriate tie force. However, there is no design model for the tying resistance of a beam web. Hence, Fastrak does not carry out any calculations for the beam web and reports a Warning status against the relevant check (SCI P212: Check 14). Note that edge beams and internal beams where there is net tie force across the web are not designed for the out of plane bending that the application of the tying might infer. This is the correct interpretation and so there is no requirement for either Fastrak or for you independently to carry out such checks.

Chapter 10 : Additional Design Considerations


Fire Limit State The elevated temperature behaviour of connections in fire is not within the scope of Fastrak. However, when portal frame structures are in boundary conditions there is a requirement for the base to resist the overturning moment that is part of the frame design model.[7]

Serviceability Limit State Since pre-loaded bolts are not within the current scope of Fastrak there are no specific serviceability requirements for the connections themselves. Note that the serviceability requirements for the building as a whole (that is deflections) depend on the behaviour of moment connections being sensibly rigid


Chapter 11

Chapter 11 : Sign Conventions

Sign Conventions The following sign conventions apply for your Connections application.

Simple Connections Conventions • positive shear down,

• tie force is positive. Moment Connections Convention • positive moment induces tension in top flange,

• positive shear down, • positive axial into connection. Column Bases Convention looking at the column with face A on the right. • positive moment clockwise,

• positive shear from face C to A, • positive axial into base. Hollow Section Connection Adopts the compression +ve sign convention adopted by BS EN 1993-1-8:2005. The rules are therefore: • Forces inducing axial compression in members are +ve

• Forces inducing axial tension are -ve The connection diagram on the configuration page of the connection dialogue box illustrates this convention with all joint member forces shown as acting in a positive sense. It should be noted however that in certain K and KT joint configurations, no design solution is available when brace forces act in the same sense.

Chapter 12 : References

Chapter 12


References

Simple Connections The connection calculations are performed in accordance with the following reference. 1. Joints in Steel Construction. Simple Connections. SCI/BCSA 2002. Publication P212.

Moment Connections The connection calculations are performed in accordance with the following reference. 2. Joints in Steel Construction. Moment Connections. SCI/BCSA 1995. Publication P207.

Hollow Section Connections 3. British Standards Institution. Eurocode 3: Design of Steel Structures - Part 1-8: Design of Joints. BS EN 1993-1-8:2005 4. The Corus Group. Design of SHS Welded Joints. CT16:1000:UK:08/2005 5. The Corus Group. Design of SHS Welded Joints: Supplement No 2. 6. The Corus Group. Design of SHS Welded Joints: Supplement No 3. 7. CIDECT. Design Guide for Rectangular Hollow Section (RHS) Joints under Predominantly Static Loading. Verlag TUV Rheinland Gmbh ISBN 3-8249-0089-0 8. CIDECT. Design Guide for Circular Hollow Section (CHS) Joints under Predominantly Static Loading. Verlag TUV Rheinland Gmbh ISBN 3-88585-975-0

Column Base Connections 9. W I Simms and G M Newman. Single storey steel framed buildings in fire boundary conditions. SCI

BS5950 - Connections Handbook

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