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ETABS Example RC Building Seismic Load _Time History_

Seismic Analysis &
Design of
10 Story RC Building
(Time History Analysis)

Using ETABS
(Metric Units)
ACECOMS, AIT

yg

0.3

0.2

0.1

0
0
-0.1


-0.2

-0.3

2

4

6

8

10

12



Table of Content
Objective

5

Problem

5

Step by Step

11

1. Open Existing Model and Unlock Model

11

2. Delete Existing Seismic Load Case

14

3. Define Time History Function

15

4. Specify Time History Cases

18

5. Run Analysis

23

6. View Modal Analysis Results

26

7. View Time History Analysis Results

29

8. Run Concrete Frame Design and View Results

38

9. Run Shear Wall Design and View Results

48



ETABS Tutorial Example

ACECOMS, AIT

Objective
To demonstrate and practice step-by-step on time
history analysis and design of 10 story RC building.

Problem
Carry out modal time history analysis, and design of
10 story RC building using ELCENTRO time history
data.

3D View

Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)

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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

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

Elevation View

Material Properties for Concrete (Unit in kg and cm)

Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)

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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

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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 (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

ELCENTRO Time History Function

ELCENTRO Time History

Ground Accerelation Normalized by g

0.3

0.2

0.1

0
0

2

4

6

8

10

12

14

16

18

-0.1

-0.2

-0.3

-0.4

Time (Sec)

Note: Use Built-in Time History Data in ETABS located at “Time History Functions”
subfolder in main folder that ETABS has been installed (normally at
C:\Program Files\Computers and Structures\ETABS\Time History Functions)

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ETABS Tutorial Example

ACECOMS, AIT

Wind Load Cases (UBC97)

Load Case
Parameter

Wind Direction

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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 (Time History Analysis)


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

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ETABS Tutorial Example

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Step 1-2: Save As to New File
Go to File >> Save As and specify new file name.

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


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 analysis. 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.

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ETABS Tutorial Example

ACECOMS, AIT

2. Delete Existing Seismic Load Case
Step 2-1: Delete Existing Seismic Load Case
Case A: File from First Example (Equivalent Lateral Force)
Go to Define >> Static Load Case, select “EQXA” and click on “Delete Load”
Repeat this step to delete “EQXB”, “EQYA” and “EQYB”

Case B: File from Second Example (Modal Response Spectra Analysis)
Go to Define >> Response Spectrum Case, select “EQX” and click on “Delete
Spectrum”. Repeat this step to delete “EQY”

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

3. Define Time History Function
Step 3-1: Add New Time History Function
Go to Define >> Functions >> Time History, select “Function from File” and click
on “Add New Function”.

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ETABS Tutorial Example

ACECOMS, AIT

Step 3-2: Locate ELCENTRO Time History Data
Click on “Browse”, select “Files of type” to “All files (*.*)” and locate file named
“ELCENTRO”
(normally at “C:\Program Files\Computers and Structures\ETABS\Time History
Functions”)

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

Step 3-3: Display “ELCENTRO” Time History Function
Select “Time and Function Values” and click on “Display Graph”.

Note: To view coordinate of each point on graph, move cursor over this graph,
location of current point over cursor on graph will display as red dot and
coordinate of cursor is shown at bottom of graph. From above graph found
that total time is 12 sec.

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ETABS Tutorial Example

ACECOMS, AIT

4. Specify Time History Cases
Step 4-1:Add New Time History Case
Make sure that current working unit is “Ton-m” by checking in drop-down menu at
right-bottom of page. Go to Define >> Time History Case and click on “Add New
History”

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

Step 4-2: Specify Time History Case for “EQX”
Specify time history case as shown in figure below

Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)

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ETABS Tutorial Example

ACECOMS, AIT

Note:
1. Output time step size should be set such a way that the peak amplitude
points on the time history function are not missed. (0.1 sec for this example)
2. Because the values along Y axis of time history function as specified in step
3 are normalized by ground acceleration (g), the scale factor will be value of
g (9.81 in metric unit).
3. This scale factor can also be used to increase or decrease the time history
magnitude for difference soil condition, site location…etc.
4. Total analysis time = Total time history function + 5 time of building period in
first mode (for damping = 0.05).
= 12 + 5 x 1.2 = 18 sec
5. Number of output time steps = Total analysis time / Output time step size

ELCENTRO Time History

Ground Accerelation Normalized by g

0.3

0.2

0.1

0
0

2

4

6

8

10

12

14

16

18

-0.1

-0.2

-0.3

Output time step size
Total analysis time

-0.4

Time (Sec)

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


ETABS Tutorial Example

ACECOMS, AIT

Step 4-3: Specify Damping for “EQX”
Click on “Modify/Show” and enter “Damping for all Modes” as shown in figure below.

Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)

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ETABS Tutorial Example

ACECOMS, AIT

Step 4-4: Specify Time History Case and Damping for “EQY”
Repeat Step 4-1 to 4-3 to add “EQY” Time History Case as shown in figures below

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


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 (Time History Analysis)

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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 accidental or undesired
changes. Model will be unlocked by clicking on Unlock Model button
.
ETABS will delete all analysis and design results after unlock.

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Seismic Analysis & Design of 10 Story RC Building (Time History Analysis)


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.

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