ETABS-Example-RC Building _Equivalent Special Seismic

Modeling, Analysis & Design of RC Building Using ETABS (Metric Units) ACECOMS, AIT

Table of Content Objective

5

Problem

5

Step by Step

12

1. Start Model with Template

12

2. Define Material Properties

14

3. Define Member Sections

15

4. Draw the Members

20

5. Define Load Cases and Assign Loads

50

6. Define Mass Source

61

7. Define the Design Codes

62

8. Assign Rigid Diaphragm and Mesh the Frame

64

9. Add Load Combinations

66

10. Set Analysis Options

68

11. Run Analysis

69

12. Run Concrete Frame Design and View the Results

70

13. Run Shear Wall Design and View the Results

75

14. Check Story Drift

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ETABS Tutorial Example

ACECOMS, AIT

Objective To demonstrate and practice step-by-step on the modeling, analysis and design of 10 story RC building by static lateral force procedure.

Problem Carry out analysis, and design of 10 story RC building as shown in following details using UBC-97 static lateral force procedure.

3D View

Modeling, Analysis & Design of RC Building

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Plan View (Unit in m)

BASE – STORY 4

STORY 5 – STORY 8


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STORY 9 – STORY 10

Elevation View


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Elevation View of Elevator Shaft


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Material Properties for Concrete (Unit in kg and cm)

Section Properties Member

Dimension

Beam – B1 (width x height)

30 x 60 cm

Beam – B2 (width x height)

40 x 80 cm

Column – C1

40 x 40 cm

Column – C2

50 x 50 cm

Slab

Thickness = 15 cm

Shear wall

Thickness = 20 cm


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Story Height Data Story

Height

Typical Story

3.00 m

Static Load Cases Load Name

DEAD

LIVE

Load Type

Details

Value

-

Dead Load

Self Weight of Structural Members Calculate automatically using Self Weight Multiplier in ETABS Uniform Load on Slabs: (Finishing + Partition Load)

0.20 t/m2

Reducible Live Load

Uniform Load on Slabs: (Use Tributary Area: UBC97)

0.25 t/m2

Wind Load Cases (UBC97) Load Case Parameter

Wind Direction

WINDX

WINDY

X

Y

Wind Speed

70 mph

Exposure Type

B (Suburban area)

Importance Factor

1 (Building normal importance)


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Static Lateral Force Parameters (UBC-97) Parameter

Values

Seismic Zone

2A

Seismic Zone Factor

0.15

Soil Profile Type

SD

Remark Table 16-I (UBC-97)

Overstrength Factor

6.5

Dual Systems Concrete Shear Walls with Concrete IMRF Table 16-N (UBC-97)

Importance Factor

1

Table 16-K (UBC-97)

Ct

0.02

Section 1630.2.2 (UBC-97)

Eccentricity Ratio

0.05

Section 1630.6 (UBC-97)

Static Lateral Force Case Load Case Name

Direction and Eccentricity

% Eccentricity

EQX

X Dir + Eccen. Y

0.05

EQNX

X Dir - Eccen. Y

0.05

EQY

Y Dir + Eccen. X

0.05

EQNY

Y Dir - Eccen. X

0.05


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Step by Step 1. Start Model with Template Step 1-1: Select Working Unit and Start New Model using Template Start up screen of ETABS, select working unit to be “ton-m” at drop-down menu on the bottom-right of screen and click on New Model button to start new model using template

Note: Click the Default.edb button. This means that the definitions and preferences will be initialized (get their initial values) from the Default.edb file that is in the same directory as your ETABS.exe file. If the Default.edb file does not exist in this directory then the definitions and preferences are initialized using ETABS built-in defaults. You should create your Default.edb file such that you most commonly click this button. In some cases you may want to click the Choose.edb button and specify a different file from which the definitions and preferences are to be initialized. For example, a certain client or project may require certain things in your model to be done in a certain way that is different from your typical office standards. You could have a specific .edb file set up for this client or project which could then be used to initialize all models for the client or project. This will allow setting of the repeatedly used preferences. Click the No button if you just want to use the built-in ETABS defaults.


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Step 1-2: Specify Grid and Story Dimension Specify grid dimension and story dimension as shown in figure below. Select “Grid Only” option to add the structural objects later.

Step 1-3: Save the Model The grid system has been created as parameters specified from previous steps. Go to File >> Save, and save the file.


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2. Define Material Properties Step 2-1: Change Working Unit Change working unit to “kg-cm” and go to Define >> Material. Click “Add New Material” button to add the new concrete material.

Note: You may select “N-mm” or “Kip-in” or whatever unit to input material properties. Step 2-2: Specify the Material Properties Specify material properties of concrete (fc’ = 240 ksc) as shown in the figure below.


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3. Define Member Sections Step 3-1: Define Frame Section for Beam (30 cm x 60 cm) Go to Define >> Frame Sections and select on “Add Rectangular” from second drop-down menu. Enter beam section properties for B1 as shown in figure below.


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Step 3-2: Define Frame Section for Beam (40 cm x 80 cm) Select on “Add Rectangular” from second drop-down menu. Enter beam section properties for B2 as shown in figure below.


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Step 3-3: Define Frame Section for Column (40 cm x 40 cm) Select on “Add Rectangular” from second drop-down menu. Enter column section properties for C1 as shown in figure below.


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Step 3-4: Define Frame Section for Column (50 cm x 50 cm) Select on “Add Rectangular” from second drop-down menu. Enter column section properties for C2 as shown in figure below.


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Step 3-5: Define Area Section for Slab (15 cm thk.) Go to Define >> Wall/Slab/Deck Sections and select on “Add New Slab” from drop-down menu. Enter slab section properties as shown in figure below.

Step 3-6: Define Area Section for Wall (20 cm thk.) Select on “Add New Wall” from drop-down menu. Enter wall section properties as shown in figure below.


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4. Draw the Members Step 4-1: Change View to Plan View and Change Working Unit to “Ton-m” Activate left window by clicking on left window area, click on Set Plan View button and select “STORY1”. Change working unit to “Ton-m”

Step 4-2: Draw Columns at Story 1 button, select the property of column in “Properties of Object” dialogue. Click on Window the grid intersections from Grid A4 to H1.


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Step 4-3: Draw Beams at Story 1 button, select the property of beam in “Properties of Object” dialogue. Click on Window the grid intersections from Grid A4 to H1.


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Step 4-4: Draw Slabs at Story 1 button, select the property of slab in “Properties of Object” dialogue. Click on Window the grid intersections from Grid A4 to H1.


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Step 4-5: Set Building View Options Click on

button, set the building as shown in the figure below.


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Step 4-6: Assign the Beam Section (B2) Select the beams along Y-direction. Go to Assign >> Frame/Line >> Frame Section, and assign “B40x80” section as shown in the figure below.


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Step 4-7: Mesh the Slabs Select all the slabs and go to Edit >> Mesh Areas. Enter the number of meshes as shown in the figure below.


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Step 4-8: Draw the Wall Click on Rubber Band Zoom button to zoom plan view at shear wall location. Go to Draw >> Draw Point Objects, enter “Plan Offset X” in “Properties of Object” dialogue and click 4 nodes as shown in figure below.


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button and select the property of wall in “Properties of Object” Click on dialogue. Draw the wall segments from node to node as shown in figure below.


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Go to Select >> by Area Object Type, and select wall to select the walls.

Go to Edit >> Replicate, and replicate mirror about the line as shown in the figure below.


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Step 4-9: Delete the beams on the wall Select the beams on the walls and delete them.


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Step 4-10: Draw the Beams Connecting to the Wall Click on button and select “B40x80” in “Properties of Object” dialogue. draw the beams connecting the columns and the walls.


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Step 4-11: Change the Stiffness Modifiers Select the beams connecting to the wall. Go to Assign >> Frame/Line >> Frame Property Modifiers, and change the torsional stiffness as shown in the figure below.


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Step 4-12: Mesh the Floor between the Core Walls Select the floor between the core walls. Go to Edit >> Mesh Areas, mesh the floor at the intersection with wall segments as shown in the figure below.


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Step 4-13: Delete the Floor inside the Core Walls Select the floor inside the core walls and delete them as shown in the figure below.


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Step 4-14: Draw Developed Elevation Definition Go to Draw >> Draw Developed Elevation Definition, type “H1” in the Developed Elevation Name and click “Add New Name”. Click “OK” and draw the line as shown in the figure below.


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Do the same step as above for other developed elevations of core walls as shown in the figure below.

H2

V1

V2

V3

H1


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Step 4-15: Make the Openings in Walls Go to Select >> Select Area Object Type, and select “Wall”. Go to View >> Show Selection Only.


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Click on

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and select “H1” and click “OK”.

Go to Select >> by Area Object Type, and select wall.

Go to Edit >> Mesh Areas, and mesh the walls as shown in the figure below..


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Click on Rubber Band Zoom button to zoom elevation view “H1”. Delete the wall segments for openings as shown in the figure below.

Do the same step as above for elevation “H2” and delete the wall segments for openings.


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Step 4-16: Assign Pier Labels and Spandrel Labels Click on and select “2” and click “OK”. Select the walls and go to Assign >> Shell/Area >> Pier Label, select pier name “P1” and click “OK” as shown in the figure below.


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and select “H1” and click “OK”. Click on Rubber Band Zoom button Click on to zoom elevation view at shear wall location. Select the walls at the left side and go to Assign >> Shell/Area >> Pier Label, type pier name “P2” in the Pier Name Box. Click “Add New Name” and then “OK” as shown in the figure below.


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Select the walls above the opening and go to Assign >> Shell/Area >> Spandrel Label, select spandrel name “S1” and click “OK” as shown in the figure below.


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Perform the same steps as above to assign the pier label and spandrel as shown in the following figure.


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Step 4-17: Replicate the Floor Click on button, select “STORY 1” and change to plan view as shown in the figure below. Go to View >> Show All.


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Select the members by windowing and go to Edit >> Replicate. Select from STORY 2 to STORY 10 in “Story” tab and replicate as shown in the figure below.


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Step 4-18: Delete the Members Click on button, select “STORY 5”. Select and delete the members as shown in the figure below.

Repeat the above step for STORY 6, 7 and 8.


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Click on button, select “STORY 9”. Select and delete the members as shown in the figure below.

Repeat the above step for STORY 10.


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Step 4-19: Assign the Columns Click on

and select “1” and click “OK”. Select the columns as shown in the

figure below.


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Go to Assign >> Frame Line >> Frame Section, and select C50x50 and click “OK”.

Repeat the above steps to assign the columns in Elevations 2, 3 and 4.


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Step 4-20: Assign the Supports Click on button, select “BASE” and change to plan view as shown in the figure below. Select the points by windowing as shown in the figure below.

Go to Assign >> Joint/Point >> Restraints (Supports), and restrained all DOFs as shown in the figure below.


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5. Define Load Cases and Assign Loads Step 5-1: Define Load Cases Go to Define >> Static Load Cases, modify the “LIVE” Load as Reducible Live Load as shown in the figure below.

Add “SDL” Load as Superimposed Dead Load as shown in the figure below.


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Add “WX” Load as Wind Load as shown in the figure below.

Modify the “WX” Load as shown in the figure below.


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Add “WY” Load as Wind Load as shown in the figure below.

Modify the “WY” Load as shown in the figure below.


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Add “EQX” Load as Quake Load as shown in the figure below.

Modify the “EQX” Load as shown in the figure below.


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Add “EQNX” Load as Quake Load as shown in the figure below.

Modify the “EQNX” Load as shown in the figure below.


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Add “EQY” Load as Quake Load as shown in the figure below.

Modify the “EQY” Load as shown in the figure below.


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Add “EQNY” Load as Quake Load as shown in the figure below.

Modify the “EQY” Load as shown in the figure below.


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Step 5-2: Define Special Seismic Load Effects Go to Define >> Special Seismic Load Effects, and enter the parameters to consider in special seismic design as shown in the figure below.

E = ρ Eh + Ev (30-1) Em = Ω0 Eh (30-2) E = the earthquake load on an element of the structure resulting from the combination of the horizontal component, Eh, and the vertical component Ev Eh = the earthquake load due to the base shear, V, as set forth in Section 1630.2 or the design lateral force, Fp, as set forth in Section 1632 Ev = the load effect resulting from the vertical component of the earthquake ground motion and is equal to an addition of 0.5 Ca ID to the dead load effect, D, for Strength Design, and may be taken as zero for Allowable Stress Design In this case Ca = 0.22, 0.5 Ca I = 0.5 x 0.22 x 1 = 0.11 Ω0 = the seismic force amplification factor that is required to account for structural overstrength, as set forth in Section 1630.3.1


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ρ = Reliability/Redundancy Factor as given by the following formula ρ = 2 – 20 / (rmax x sqrt(AB)) (30-3) = 2 – 6.1 / (rmax x sqrt(AB)) (For SI) rmax = the maximum element-story shear ratio. For a given direction of loading, the element-story shear ratio is the ratio of the design story shear in the most heavily loaded single element divided by the total design story shear. For any given Story Level i, the element story shear ratio is denoted as ri. The maximum element-story shear ratio rmax is defined as the largest of the element story shear ratios, ri, which occurs in any of the story levels at or below the two-thirds height level of building.


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Step 5-3: Assign the Loads Go to Select >> by Area Object Type, select “Floor” as shown in the figure below.

Go to Assign >> Shell/Area Loads >> Uniform, and assign Live Load of 0.25 t/m2 as shown in the figure below.


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Click on to reselect the floor areas. Go to Assign >> Shell/Area Loads >> Uniform, and assign “SDL” Load of 0.2 t/m2 as shown in the figure below.


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6. Define Mass Source Step 6-1: Define Mass Source Go to Define >> Mass Source, and add the mass from loads as shown in the figure below.


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7. Define the Design Codes Step 7-1: Define Design Code for Concrete Frame Design Go to Options >> Preferences >> Concrete Frame Design, change the Design Code


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Step 7-2: Define Design Code for Shear Wall Design Go to Options >> Preferences >> Shear Wall Design, change the Design Code


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8. Assign Rigid Diaphragm and Mesh the Frame Step 8-1: Assign Rigid Diaphragm Go to Select >> by Area Object Type, and select “Floor”.

Go to Assign >> Shell/Area >> Diaphragms, select “D1” and click “OK”.


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Step 8-2: Mesh the Frame button and go to Assign >> Frame/Line >> Automatic Frame Click on Subdivide, select the second option as shown in the figure below.


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9. Add Load Combinations Step 9-1: Add Load Combinations Go to Define >> Add Default Design Combos, and add the default combinations as shown in the figure below.

button and go to Design >> Concrete Frame Design >> View/Revise Click on Overwrites, change Element Type to Sway Intermediate as shown in the figure below.


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Step 9-2: Special Seismic Data Go to Define >> Special Seismic Load Effects, and select no to include Special Seismic Design Data as shown in the figure below.


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10.

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Set Analysis Options

Step 10-1: Set Analysis Options Go to Analyze >> Set Analysis Options, and set the Dynamic Parameters as shown in the figure below.


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11. Run Analysis Step 11-1: Run Analysis Go to Analyze >> Run Analysis or click on Run Analysis button analysis. ETABS will display deformed shape of model when analysis complete.


to start

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12. Run Concrete Frame Design and View the Results Step 12-1: Run Concrete Frame Design Go to Design >> Concrete Frame Design >> Start Design/Check Structure.


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Step 12-2: View the Results Click on figure.

button, and set up the building view options as shown in the following


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Activate the left window and Click on button, select “STORY 1”. Change the working unit to “kg-cm”. Go to Design >> Concrete Frame Design >> Display Design Info, select design output as shown in the following figure.


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Right click on the member to view the design details.


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Beam Reinforcement

Column Reinforcement

Top Reinforcement

Minor Shear Reinforcement

2

2 Shear Reinforcement

3

Major Shear Reinforcement

3

Longitudinal Reinforcement Bottom Reinforcement


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13. Run Shear Wall Design and View the Results Step 13-1: Run Shear Wall Design Go to Design >> Shear Wall Design >> Start Design/Check Structure.


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Step 13-2: View the Results Click on figure.

button, and set up the building view options as shown in the following


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Activate the left window, click on button and select “H1”. Click on Rubber Band Zoom button to zoom elevation view at shear wall location. Right click on the pier to view the design details.


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ACECOMS, AIT Reinforcement Details in Pier


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Go to Design >> Shear Wall Design >> Display Design Info, select design output as shown in the following figure.


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ACECOMS, AIT Reinforcement Details in Spandrel


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Note: Typical Detailing of Shear Wall


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14. Check Story Drift P-∆ Effects In general, P-∆ effects need not be considered when the stability coefficient (θ) defined as the ratio of secondary moments to primary moments, is less than or equal to 0.1. The stability coefficient (θ) for a given story can be computed from the following equation: θ = Px ∆ / (Vx hsx) Px = total unfactored gravity load at and above level x ∆ = seismic story drift Vx = seismic shear force between levels x and x-1 hsx = story height below level x From ETABS, ∆ / hsx is extracted from diaphragm drift of ETABS results. Px is extracted by section cut. V is extracted from story shear. Compute θ and if θ < 1, P-∆ effects needs not be considered. In Seismic Zones 3 and 4, P-∆ effects need not be considered when the story drift (∆) is less than or equal to 0.02hsx / R. Story Drift Limitations According to 1630.10, story drifts shall be computed using the maximum inelastic response displacement (∆M), which is an approximation of the displacement that occurs when the structure is subjected to the design basis ground motion: ∆M = 0.7 R ∆S ∆S is the design level response displacements. For structures with a fundamental period (T) less than 0.7 seconds, the calculated story drift using ∆M shall not be exceed 0.025 times the story height. For structures


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with T greater than or equal to 0.7 seconds, the story drift shall not exceed 0.020 times the story height. From ETABS, Calculated story drift is determined by multiplying the diaphragm drift into 0.7 x R.


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ETABS-Example-RC Building _Equivalent Special Seismic

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