Seismic Analysis &
Design of
10 Story RC Building
(Modal Response Spectra Analysis)
Using ETABS
(Metric Units)
ACECOMS, AIT
Table of Content
Objective
5
Problem
5
Step by Step
11
1. Open Existing Model and Unlock Model
11
2. Delete Existing Seismic Static Load Case
14
3. Define Response Spectrum Function
15
4. Specify Response Spectrum Cases
17
5. Run Analysis
21
6. View Modal Analysis Results
24
7. View Results for Response Spectral Analysis
27
8. Run Concrete Frame Design and View Results
36
9. Run Shear Wall Design and View Results
42
ETABS Tutorial Example
ACECOMS, AIT
Objective
To demonstrate and practice step-by-step on modal
response spectra analysis and design of 10 story RC
building.
Problem
Carry out modal response spectra analysis, and
design of 10 story RC building as shown in following
details based on IBC2000.
3D View
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
5/52
ETABS Tutorial Example
ACECOMS, AIT
Plan View (Unit in m)
6.00 m
6.00 m
6.00 m
6.00 m
2.00 2.00 2.00
2.00 2.00 2.00
6.00 m
6.00 m
BASE – STORY 7
6.00 m
6.00 m
6.00 m
6.00 m
2.00 2.00 2.00
2.00 2.00 2.00
6.00 m
6.00 m
STORY 8 – STORY 10
6/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Elevation View
Material Properties for Concrete (Unit in kg and cm)
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
7/52
ETABS Tutorial Example
ACECOMS, AIT
Section Properties
Member
Dimension
Beam (width x Height)
30 x 60 cm
Column
50 x 50 cm
Slab
Thickness = 15 cm
Shear wall
Thickness = 20 cm
Story Height Data
Story
Height
Typical Story
3.00 m
Story at base of building
4.00 m
Static Load Cases
Load
Name
DEAD
LIVE
8/52
Load Type
Dead Load
Reducible
Live Load
Details
Value
Self Weight of Structural Members
Calculate automatically using Self
Weight Multiplier in ETABS
-
Uniform Load on Slabs:
(Finishing + Partition Load)
0.20 t/m2
Uniform Load on Beams:
(Wall Load)
0.50 t/m
Uniform Load on Slabs:
(Use Tributary Area: UBC97)
0.25 t/m2
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Modal Response Spectra Parameters (IBC2000)
Parameter
Values
Note
Damping
0.05
For RC building
Modal Combination
SRSS
Directional Combination
SRSS
Site Class
E
Response Acceleration
for Short Period (Ss)
0.45
Response Acceleration
for 1 Second (S1)
0.18
Site Coefficient of
Response Acceleration
for Short Period (Fa)
1.86
Table 1615.1.2 (1)
Site Coefficient of
Response Acceleration
for 1 Second (Fv)
3.26
Table 1615.1.2 (2)
Maximum Response
Acceleration
for Short Period (SMS)
0.84
SMS = Fa x SS
(Equation 16-16)
Design Response
Acceleration
for 1 Second (SM1)
0.59
SM1 = Fv x S1
(Equation 16-17)
Design Response
Acceleration
for Short Period (SDS)
0.56
SDS = (2/3) x SMS
(Equation 16-18)
Maximum Response
Acceleration
for 1 Second (SD1)
0.39
SD1 = (2/3) x SM1
(Equation 16-18)
Table 1615.1.1
(Soft Clay)
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
9/52
ETABS Tutorial Example
ACECOMS, AIT
Wind Load Cases (UBC97)
Load Case
Parameter
Wind Direction
10/52
WINDX
WINDY
X
Y
Wind Speed
90 mph
Exposure Type
B (Suburban area)
Importance Factor
1 (Building normal importance)
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Step by Step
1. Open Existing Model and Unlock Model
Step 1-1: Open Existing Model
Start up screen of ETABS, click on Open button
file from previous example.
or go to File >> Open and find
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
11/52
ETABS Tutorial Example
ACECOMS, AIT
Step 1-2: Save As to New File
Go to File >> Save As and specify new file name.
12/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Step 1-3: Unlock Model
Click on Unlock Model button
Click on “OK” to confirm to unlock the model and delete all analysis results
Note: ETABS has locked the model automatically from previous. Model has to be
unlocked first before do any modification by clicking on Unlock Model
button
. ETABS will delete all analysis and design results after unlock.
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
13/52
ETABS Tutorial Example
ACECOMS, AIT
2. Delete Existing Seismic Static Load Case
Step 2-1: Delete Existing Seismic Static Load Case
Go to Define >> Static Load Case, select “EQXA” and click on “Delete Load”
Repeat this step to delete “EQXB”, “EQYA” and “EQYB”
14/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
3. Define Response Spectrum Function
Step 3-1: Add New Response Spectrum Function
Go to Define >> Response Spectrum Function and select “Add IBC2000
Spectrum” from drop-down menu.
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
15/52
ETABS Tutorial Example
ACECOMS, AIT
Step 3-2: Enter Response Spectrum Function for IBC2000
Specify response spectrum function for IBC2000 as shown in figure below
16/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
4. Specify Response Spectrum Cases
Step 4-1: Add New Response Spectrum Case
Go to Define >> Response Spectrum Cases and click on “Add New Spectrum”
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
17/52
ETABS Tutorial Example
ACECOMS, AIT
Step 4-2: Specify Response Spectrum Case Data for “EQX”
Enter response spectrum case data as shown in figure below
Note: ETABS will treat response spectrum case as unfactored seismic load (E) in
ACI load combination for RC frame and shear wall design but response
spectrum load from IBC2000 is factored load then “Scale Factor” in
response spectrum case should be divided by load factor (1.4) to change
from factored load to unfactored load.
18/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Step 4-3: Add and Specify Response Spectrum Case for “EQY”
Repeat Step 4-1 and Step 4-2 for response spectrum case (“EQY”)
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
19/52
ETABS Tutorial Example
ACECOMS, AIT
Step 4-4: Deactivate Special Seismic Load Effect
Go to Define >> Special Seismic Load Effect and select “Do Not Include Special
Seismic Design Data”
20/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
5. Run Analysis
Step 5-1: Set Dynamic Analysis Parameters
Go to Analyze >> Set Analysis Options, select “Dynamic Analysis”, click on “Set
Dynamic Parameters” and specify dynamic analysis parameters as shown in figure
below
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
21/52
ETABS Tutorial Example
ACECOMS, AIT
Step 5-2: Start 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.
Note: ETABS will lock the model automatically from undesired changes. Model
will be unlocked by clicking on Unlock Model button
. ETABS will delete
all analysis and design results after unlock.
22/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Step 5-3: Check Error from Analysis Run Record
Go to File >> Last Analysis Run Log and scroll down to check error message.
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
23/52
ETABS Tutorial Example
ACECOMS, AIT
6. View Modal Analysis Results
Step 6-1: Display Mode Shape in 3D View
Select 3D view window, go to Display >> Show Mode Shape or click on Show
and select desired mode.
Mode Shape button
To view deformed shape in animation, click on “Start Animation”.
Note: Time Period of current mode shows at top of 3D window
24/52
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
ETABS Tutorial Example
ACECOMS, AIT
Step 6-2: Display Modal Displacement at Particular node
Right click on desired node to display modal displacement at current mode shape
Seismic Analysis & Design of 10 Story RC Building (Modal Response Spectra)
25/52
