Rc bldg. modeling & analysis

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 82

ETABS Tutorial Example ACECOMS, AIT
Modeling, Analysis & Design of RC Building 5/83
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

Plan View (Unit in m)
BASE – STORY 4
STORY 5 – STORY 8

STORY 9 – STORY 10
Elevation View

Elevation View of Elevator Shaft

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

Story Height Data
Story Height
Typical Story 3.00 m
Static Load Cases
Load
Name
Load Type Details Value
Self Weight of Structural Members
Calculate automatically using Self
Weight Multiplier in ETABS
-
DEAD Dead Load
Uniform Load on Slabs:
(Finishing + Partition Load)
0.20 t/m2
LIVE
Reducible
Live Load
Uniform Load on Slabs:
(Use Tributary Area: UBC97)
0.25 t/m2
Wind Load Cases (UBC97)
Load Case
Parameter
WINDX WINDY
Wind Direction X Y
Wind Speed 70 mph
Exposure Type B (Suburban area)
Importance Factor 1 (Building normal importance)

Static Lateral Force Parameters (UBC-97)
Parameter Values Remark
Seismic Zone 2A
Seismic Zone Factor 0.15 Table 16-I (UBC-97)
Soil Profile Type SD
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

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.

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.

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.

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.

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.

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.

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.

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.

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
Click on button, select the property of column in “Properties of Object” dialogue.
Window the grid intersections from Grid A4 to H1.

Step 4-3: Draw Beams at Story 1
Click on button, select the property of beam in “Properties of Object” dialogue.

Step 4-4: Draw Slabs at Story 1
Click on button, select the property of slab in “Properties of Object” dialogue.

Step 4-5: Set Building View Options
Click on button, set the building as shown in the figure below.

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.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

Do the same step as above for other developed elevations of core walls as shown
in the figure below.
H1
H2
V1 V2 V3

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

Click on 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..

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.

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.

Click on and select “H1” and click “OK”. Click on Rubber Band Zoom button
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.

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.

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

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.

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.

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.

Click on button, select “STORY 9”. Select and delete the members as shown in
the figure below.
Repeat the above step for STORY 10.

Step 4-19: Assign the Columns
Click on and select “1” and click “OK”. Select the columns as shown in the
figure below.

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.

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.

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.

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

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

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

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

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

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

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

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.

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

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

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.

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

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

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”.

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

9. Add Load Combinations
Step 9-1: Add Load Combinations
Go to Define >> Add Default Design Combos, and add the default combinations
Click on button and go to Design >> Concrete Frame Design >> View/Revise
Overwrites, change Element Type to Sway Intermediate as shown in the figure
below.

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.

10. 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.

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

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.

Step 12-2: View the Results
Click on button, and set up the building view options as shown in the following
figure.

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.

Right click on the member to view the design details.

Beam Reinforcement Column Reinforcement
2
3
Shear
Reinforcement
Bottom
Reinforcement
Top
Reinforcement
2
3
Minor Shear
Reinforcement
Major Shear
Reinforcement
Longitudinal
Reinforcement

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.

Step 13-2: View the Results
Click on button, and set up the building view options as shown in the following
figure.

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.

Reinforcement Details in Pier

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

Reinforcement Details in Spandrel

Note: Typical Detailing of Shear Wall

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

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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