Challenge

Project 1_Comparative study of different storey buildings for Seismic forces

GGanesh Patil11 Jul 2022

Aim - To do comparative Analysis of different storey buildings for Seismic forces

Introduction:

1) ETABS is an engineering software product that caters to multi-story building analysis and design

2) Modeling tools and templates, code-based load prescriptions, analysis methods and solution techniques, all coordinate with the grid-like geometry unique to this class of structure.

3)Basic or advanced system under static or dynamic conditions may be evaluated using ETABS.

4)For a sophisticated assessment of seismic performance,modal and direct-integration time-history analyses may couple with p-Delta and Large Displacement effects.

5)Different building geometries behave differently when induced bt the same seismic forces.

6)Hence,it is very important to properly understand the response of buildings related to their structural configuration for a safer design approch.

7)Therefore in this project, we have modeled different buildings with varying geometries using ETABS.

8)Furthermore, their responses are analyzed with the help of the software and the results

are then compared to graps an understanding of the structural behavior of buildings with different storeys.

Structural Element Sizes - For Building type A

Beams - 300x400 mm
Columns - 400x400 mm
Slab - 150 mm

Material Properties

Grade of concrete - M30
Grade of steel Reinforcement Bars - Fe 415
Dead Load on beams from infill wall - 10kN/m
Live load on floor - 3kN/m2 (Assume same for roof floor also)

Procedure:

For Building type A

Step1:

Open the ETABS software from desktop icon
Once software is open click on new model

Step2:

Once you click on new model
A model Initialization setting will open
Select metric SI units
Select section database Indian
Select Steel Code IS 800-2007
Select Concerete design code IS 456-2000

Step3:

Once you click okay
A following dialogue box of grid setting will open
In New Model Quick templates under grid dimensions select the custom grid spacing

Once you click on custom grid spacing
Click on display grid data as spacing

Step4:

In New Model Quick templates under Story dimensions
Select the custom story data and then click edit data.

Now input the storey details
As given in question and Story1 was selected as the Master story
Click on okay.

Step5:

Once you click on okay
A plan and 3D view of model is created in model space

Step6:

Now we have to define the materia properties
click on define click on material properties

Add New material as Concrete
Select Grade of concrete M30
Standard as Indian
Click OK

The remaining data is as per IS Code

Step7:

Similarly we have to define the material properties for steel
Click on define
Click on material properties
Select New material as Rebar
Select Grade of Steel HYSD Grade Fe415
Standard as Indian
Click on Ok

The remaining data is as per IS Code

Material properties is added

Step8:

Now we have to define the section properties (Column and beam)
Click on define
Select Section properties
Click on Frame Section

Click on concrete Rectangular

Click on add new property
Give property name Beam 300x4000
Material type M30
Section shape Concrete Rectangular
Depth 400 mm
Width 300 mm

Click on Modify/show Rebar
Select M3 Design only (Beam)
Select the rebar materials as HYSD Fe415 in both the direction
Click on ok

Similarly we have to follow the same steps for Column also.
Property name Column 400x400mm
Material M30
Depth 400
Width 400
Click on modify/show Rebar
Select M3 Design Only (Column)
Select the Reabr material as HYSD Fe415 in both the direction
Click on Ok

Step9:

Now we have to define slab properties
click on define
Select section properties Select Slab properties
Click on slab section
Give property name Slab150
Slab Material M30
Modeling type Membrane
Type Slab
Thickness 150 mm

Step10:

Now we have keep the 3D view also to see the properties
Now we have to add the columns and beams
Click on Quick Draw Column option
Select the column properties which we have defined earlier
Draw the columns at the grids as shown in below
Note that All stories option should be selected which is at the bottom

Similarly we have to draw beams also
Select quick draw beam option
Select beam properties which we have defined earlier
Draw the beam as shown below

Step11:

Now we have to add slabs
Select wuick draw floor
Draw the slabs as shown below

3D view after assigning the material and section properties

Step12:

Now we have to assign the loads
Select Define
Click on load patterns
Define load pattern dialogue box will open
Add the following loads and select the IS code for seismic case as IS -1893

Step14:

Now we have t apply the live loads
In Assign menu select shell loads
Click on Uniform loads
Load pattern as Live load
Load - 3kn/m2

We can see that floor loads has been assigned to all the floor

Now we have to assign wall load for beams
Select assign
Click on frame loads Uniformly distributed loads
Select load pattern as wall
Apply 10kn/m load

Load has been assigned

Step15:

Now we have to assign Mass source for modal calculations
Click on Define menu
Select mass source options
Mass source dialogue box will open
Add the loads
Dead load 1
Wall 1
Live load 0.25 ( Because we only considered some fraction of live load in calculation of seismic weight)
So, live load upto 3Kn/m2 : 25%

Above 3Kn/m2 : 50%

Step16:

Now we have to assign load combinations
Forthat click on define menu
select load combinations
load combination box will open
Click on add default Design Combos

Step17:

Now we have to assign Diaphragm
Click on assign
Select shell Select Diaphragm
select D1
Click on apply

Click on Ok
A diaphragm has been assigned

Step18:

Now we have to create a Model Analysis
Click on Define
Select Modal cases
Click on Modify
Load Case Name - Modal
Load case type-Eigen
Mass Source Which we have already defined
Click on Ok

Step 19:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 20:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 21:

Now we have to check the mock as per: IS 1893.
For that click on Display Show tables:

For Building Type - D

Step 1:

For Building type 8 we don't need to follow the same steps
Just make a copy of building A and Save it as Building B

Step 2:

Edit the Story data as follows- (which are given)

5-rory building
Farm 300mm x 400 mm
Column: 400mm x 400 mm
Grade M3D-FA 419.
Brick wall load kN/m
Live load 8 KN/m2

Step 3:

Click on new file, go to edit – story and grid data.

Click on the modify story data option

Then right-click on the top story and select the add story option

Set the height and the number of storeys you want to odd.

In our case, we need to add 3 more floors to convert our 2story building into a 5 story one.
Also, make sure to make each story similar to the master story created in Model A.

Click on okay

A 3D view of 5 storey model

Step 4:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 5:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 6:

how we have to check the mock as per is 1893.
For that click on Display – Show tables

For Building Type-C (G+5 with column orientation in X-direction)

Step 1:

For Building type C we just need to edit the Column Orientation
Just make a copy of building B and Save it as Building C

Step 2:

Edit the Story data as follows - (which are given)

5-story building
Beam: 300mm x 400 mm.
Column: 550 mm x 300 mm
Grade M30-Fe 415.
Brick wall load = 10 kn/m
Live load 3 KN/m^2

Step 3:

Edit the Column Size and Orientation
Click on Edit - Column section
Click on Define-section properties -frame section.
Select the previously created column for building A and B.
Click on the modify/show properties option.
Rename the column as 550mmx300mm.
Enter the depth and width of columns
So, select the column section
Then Click on assign

Select Local axis-rotate it by 90 degrees.
This way, all the columns shall be oriented in the X-direction meaning 550mm laying down in the x direction.

Step 4:

Once you click on Ok
The columns will be oriented in X direction

Step 5:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 6:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 7:

Now we have to check the mode as per IS 1893.
For that click on Display - Show tables

For Building Type -D (G+5 WITH COLUMN ORIENTATION IN THE Y DIRECTION)

Step 1:

For Building type D we need to edit the Column Orientation
Just make a copy of building C Save it as Building D

Step 2:

Edit the Story data as follows - (which are given)

5-story building
Beam: 300mm x 400 mm
Column: 300 mm X 550 mm
Grade M30-Fe 415.
Brick wall load = 10 kn/m
Live load 3 KN/m^2

Step 3:

In this model, we don't need to edit the column dimensions other than the column orientation.
The sizes of the column will remain the same
But we have to shift the column orientation from X to Y direction.
Then, select the column section
Click on Assign - Select the local axes and bring the origin back to 0.

Therefore, all the columns shall be oriented in the Y-direction.

Step 4:

Once you click on Okay
The columns will be oriented in Y direction

Step 5:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 6:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 7:

Now we have to check the mode as per IS 1893
For that click on Display – Show tables

For Building Type-BUILDING "E" (G+10)

Step 1:

We have to create a New Model

For that make a copy of Model D and save it as Model E

Step 2:

Edit the Story data as follows-(which are given)

10-story building
Beam: 300mm x 400 mm
Column Bottom 5 (600 mm x 600 mm
Top 5 400 x 400 mm)
Grade M30-Fe 415
Brick wall ion= 10 kn/m
Live load 3 KN/m^2

Step 3:

Once you save the Model D as Model E
Edit the storey and add & more storey just like previously we have done

Step 4:

Now we have to add the Different column section properties
For Bottom storey-600mm x 600 mm
For Top Storey-400mm x 400 mm
And the properties in Column section
Define Section-Frame Section and Add the properties

Step 5:

so go to Visualise setting
Select only Columns
Untick the beams and columns
So it will be easy for us

Step 6:

Now we have to assign the properties to the bottom storey
For that we have to set the limits for bottom floors and top floors
for that go to Edit - Set building limits

The set building limit option in ETABS allows you to view only the floors that you need to work on.
Hence, first set the firm to bottom 3 select at column sand assign and assign them the required column section
Similarly repeat the procedure for the remaining top columns and complete with the model.
Column 600 mm x 800mm has been assigned to bottom storey

Set the building limits to Top floors

Column properties has been assigned to the model

Step 7:

Before Run Analysis we have to check the model
Click an Analyse
Click on Check Model
A structure is verified without any error and Model has been checked

Step 8:

Now Click on Run Analysis
Once the analysis is done you see the deform shaped as below

Step 9:

Now we have to check the mode as per is 1893
For that click on Display-Show tables

For Building Type-BUILDING "H" (G+25)

Step 1:

We have to create a New Model
For that make a copy of Model G and save it as Model H

Step 2:

Edit the Story data as follows-(which are given)

25 story building
Beam: 300mm x 400 mm
Column (600 mm x 800mm)
Brick wall loop-10 Kn/m
Live load 3 KH/m^2

Step 3:

Once you save the Model as Model H
In this mode we don't need to edit too much
We just need to change the Column properties as (800mm x 800mm) which is uniform

Step 4:

Only we have to edit that Column Size
As it has Uniform Column Size (800 mm x 800mm)
Properties are already added in section properties

Step 5:

So go to Visualise setting
Select only Columns
Untick the beams and
So it will be easy for us columns

Step 6:

Now we have to assign Column to the model
Select all the column from Select Object type - Column
Select the properties (800mmx 800 mm)
Click on Okay.

Column properties has been assigned to the model.

Step 7:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure la verified without any error and Model has been checked

Step 8:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 9:

Now we have to check the mods as per is 1893.
For that click on Display-Show tables

For Building Type-BUILDING J (+25)

Step1:

We have to create a New Model

For that make a copy of Model H and save it as Model J

Step 2:

Edit the Story data as follows-( which are given) )25-story building )
Beam: 300mm x 400 mm.
Column: (300 mm X 800 mm)
Grade M30 - Fe 415.
Brick wall load-10 kn/m

Live load 3 KN/m^2 (increased the load by 10%)

= 3 x 10%

= 0.3

Therefore, total Live Load = 3.3 kn/m

In case of Mass Source Take the live load as 0.50

Live load 0.50 (Because only considered some fraction of Live load in calculation of seismic weight)
So live load, upto 3 Kn/m2 - 25%

Above 3 Kn/m2 - 50%

Step 3:

Model J is similar to the Model H
So we do not have to edit the anything regarding properties
Only we have to increase the Live Load by 10%.
For that Select the Slab-Select Object type - Slab 150

Step 4:

Now we have to edit the Load
For that Cilek on Assign Shell Loads - Click On Uniform Load
Click on Replace the Existing Load
Enter the load -3.3 kn/m2

Check If load is applied or not

Step 5:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 6:

Now Click on Run Analysis
Once the analysis is done you will see the deform shaped as below

Step 7:

Now we have to check the mode as per IS 1893.
For that click on Display-Show tables

For Building Type-BUILDING "K"

Step 1:

Step 2:

Edit the Story data as follows - (which are given)
25-story building
Beam: 300mm x 400 mm
Column: (800 mm x 800 mm)
Grade M30 - Fe 415
Brick wall load=10 kn/m

Live load 3 KN/m^2 (increased the load by 20%)

= 3 x 20%

= 0.6

Therefore, total Live Load = 3.5 kn/m
In case of Mass Source - Take the live
load as 0.50 viii) Live load - 0.50 (Because we
only considered some fraction of Live
load in calculation of seismic weight
So live load, upto 3 Kn/m2 - 25%

above 3 kn/m2 - 50%

Step 3:

Model K is similar to the Model J
So, we do not have to edit the anything regarding properties.
Only we have to increase the Live Load by 20%
For that Select the Slab Select Object Type-Slab 150

Step 4:

Now we have to edit the Load
For that Click on Assign - Shell Loads
Click On Uniform Load
Click on Replace the Existing Load
Enter the load-3.6 Kn/m2

Stop 5:

Before Run Analysis we have to check the model
Click on Analyse
Click on Check Model
A structure is verified without any error and Model has been checked.

Step 6:

Now Click on Run Analysis
Once the analysis is done you will
see the deform shaped as below

Step 7:

Now we have to check the mode as per IS 1893,
For that click on Display-Show tables

Results-All the 10 buildings were modelled and analysed successfully.

A] Effect of stiffness on T: Compare fundamental nature periods of building E&F as well as G & H.

Why id there a marginal or significant difference in the fundamental natural periods?

Model Type	No of Stories	Column configuration	Results	Conclusion
Building E	10	Upper 5 stories = 400x400 mm Bottom 5 Stories = 600x600 mm		As we could see that by changing the column sizes there will not be any effect on Natural period, it remains Same
Building F	10	Column Size = 600x600mm Uniform throught Building		As we could see that in Building H has uniform column section but it has more natural time period
Building G	25	Column Sizes Bottom 10 story (800x800 mm) Upper 10 story (600x600 mm) Top upper 5 story (400x400 mm)		Where as building G has large column at its base and reduces as we go higher level. But it has less natural time period as compared to H = ___
Building H	25	Column size = 800x800 mm Uniform throught Building		So we can conclude that providing larger size of column at base and reducing the size at higher level will reduces the Natural time period

B] Effect of mass on T: Compare fundamental natural periods of buildings H,J and K. Have the buildings become more flexible or stiff due to change in mass

Model Type	No of stories	Percentage increase in Load (Mass)	Result	Conclusion
Building H	25	Load is taken as 3KN/m2		As we could see that time period is increase as we increase the load or mass
Building J	25	Load Increase by 10% (3.3kn/m2)		Therefore time period is directly proportional to the mass of the building
Building K	25	Load Increase by 20% (3.6kn/m2)

C] Effect of building Height on T: How does the fundamental natural periods of Buildings A,B,F and H change with change in building height?

Model Type	No of stories	Height of Building	Results	Conclusion
Building	2	7.5 m		As we could see that the height of the building increases the natural time period is also increases Therefore, the natural period 'T' is also directly proportional to the building height
Building B	5	16.5 m
Building F	10	31.5 m
Building H	25	46.5 m

D] Effect of column orientation on T: How does the fundamental natural periods of building B, C and D change with change in column orientation?

Model Type	No of dtories	Column orientation	Results	Conclusion
Building B	5	Equal in Both Direction 400x400 mm		As we could see that when column is orientad in X and Y direction in Time period
Building C	5	In X direction 550x300 mm		So we can say that in Y direction Lateral Displacement is more as compared to X direction
Building D	5	In Y direction 300x550 mm

E] Effect of flexural stiffness of structural elements on mode shapes: Compare fundamental mode

shape of building B in two situations when the flexural stiffness of beams relative to that of adjoining columns is very small versus it is large

Model Type	No of stories	Flexural stiffness of beam	Results	Conclusion
Building B	5	100%		If you decrease the flexural stiffness of beams,the overall flexural strenght of the beam is also going to reduce which increase the Natural period of time
Building B	5	10%

F] Effect of Axial Stiffness of vertical Members on mode shapes: Compare the fundamental mode shape of building H in two situations when the axial cross-sectional area of columns is very small versus when it is large.

Model Type	No of stories	Axial Stiffness of Columns	Results	Conclusion
Building H	25	100%		As we axial stiffness of columns decrease, the fundamental natural period of the building increases regardless of its structural geometry
Building H	25	10%

G] Effect of degree of fixity at column bases on mode shape: Compare the fundamental mode shape of Building B in two dituations when the base of columns is pinned versus when it is fixed.

Model Type

No of stories

Base support

Result

Conclusion

Building B

Pinned

As we can see that in pinned support natural time period is more as compared to fixed support.

Therefore fixed support will provide more resistance as compared to pinned support

Fixed

Project 1_Comparative study of different storey buildings for Seismic forces

Ship work like this
in your own course.

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Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.