Project 1_Comparative study of different storey buildings for Seismic forces

AIM

Comparative study of different storey buildings for Seismic forces

INTRODUCTION

ETABS is an engineering software that is used for multi-story building analysis and design. 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.

Here we are modeling and analyse different storey building using ETABS

Here we are modelling 2,5,10 and 25 story building with different column sizes.The editing of the modelled building using editing options in the ETABS

We are finding

Factors influencing the dynamic characteristics of a building

Factors influencing the Natural Period of a building

Factors influencing the Mode shape of oscillations

PROCEDURE

Step 1:Open ETABS software

Open a new model

Step 2:Select Custom grid spacing

Select ‘edit grid data’

Step 3:Select story data

Select edit story data

Step 4:Select story 3, Delete the story

Step 5:Select story 1 make it master story

Make all other stories similar to story 1

Step 6:From define tab select material property

Add M30 concrete and HYSD415 rebar

Step 7:From define tab select section properties

Then select Frame sections -Add new sections

Add columns and beam

Step 8:From define tab select section properties

Select slab sections

Add new property

Add slab properties

Step 9:Select define

Select load patterns

Add load patterns

Step 10:Select define

Select mass sources

Add mass and mass multipliers

Step 11:From define select load cases

Step 12:From define select load combinations

Add load combinations

Step 13:Select quick draw columns

Select all stories

Select the column size

Step 14:Select quick draw beams

Select all stories

Select the beam size

Step 15:Select the master story(story 1)

Select similar story

Select Quick draw floor

Step 16:From select option-properties-select beam

Select all beams

Step 17:From assign tab-select frame load-distributed

Assign load to beams

Step 18:Assign -select shell load -select uniform

Step 19:Select all slabs

Assign-shell-Diaphragms

Step 20:Select ‘Run analysis’

Save it as model A

Step 21:Save the file as Model B

Step 22:From edit

Select edit stories and data

Click on modify

Modify the stories to 5 story

Step 23:Run analysis

Step 24:Save the file as Model C

Click on define

Section properties -frame sections

Select column c400x400

Edit the column to c550x300

Step 25:Select the column

Assign -frame-local axes

Set angle to 90 degree

Step 26:Run analysis

Step 27:Save the file to model D

Step 28:Select the column

Assign -frame-local axes

Set angle to 0 degree

Step 29:Run analysis

Step 30:Save the file as model E

Step 31:From edit

Select edit stories and data

Click on modify

Modify the stories to 10 story

Step 32:Click on define

Section properties -frame sections

Select column C550x300

Edit the column to C600x60

Add 400x400 column

Step 33:Click on set display option

Unselect beam and floors

Step 34:Select the view

Select set building view

Select bottom story as story 6

Step 35:Select all columns in the view

assign -Frame-section property

Select 400x400 column

Select the view

Select set building view

Select bottom story as base

Step 36:Run analysis

Step 37:Save the file as model F

Step 38:Click on set display option

Unselect beam and floors

Step 39:Select the view

Select set building view

Select bottom story as story 6

Step 40:Select all columns in the view

Assign -Frame-section property

Select 600 x 600 column

Step 41:Select the view

Select set building view

Select bottom story as base

Step 42:Run analysis

Step 43:Save the file as model G

Step 44:From edit

Select edit stories and data

Click on modify

Modify the stories to 25 story

Step 45:Click on define

Section properties -frame sections

Select column C600x600

Edit the column to C800x800

Add 600x600 column

Step 46:Click on set display option

Unselect beam and floors

Step 47:Select the view

Select set building view

Select Top story as 25

Bottom story 21

Step 48:Select all columns in the view

Assign -Frame-section property

Select 400 x 400 column

Step 49:Select the view

Select set building view

Select Top story as 20

Bottom story 11

Step 50:Select all columns in the view

Assign -Frame-section property

Select 600 x 600 column

Step 51:Run analysis

Step 52:Save the file as model H

Step 53:Click on set display option

Unselect beam and floors

Step 54:Select all columns

Assign -Frame-section property

Select 800 x 800 column

Step 55:Run Analysis

Step 56:Save the file as model J

Step 57::Assign -select shell load -select uniform

Select Live load

Add the value as 3.3

Step 58:Run Analysis

Step 59:Save the file as model K

Step 60::Assign -select shell load -select uniform

Select Live load

Add the value as 3.6

Step 61:Run Analysis

RESULTS

1)Model period and frequencies of

Building E,F,G,H

Criteria	Model	Analysis result	Conclusion
Effect of stiffness on time period	Building-E (with varying column size)	1.73 s.	Here the uniform column size and varing column size have no significant difference in their fundamental time period But for higher stories varing column size is more stable than uniform column size
	Building-F (10 story with uniform column size)	1.73 s.
	Building-G (25 story with varying column size)	4.17 s.
	Building-H (25 story with uniform column size)	4.41 s.

2)Model period and frequencies of

Building H,J,K

Criteria	Model	Analysis result	Conclusion
Effect of mass on time period	Building-H (25 story with uniform 3.0kN/m2 imposed load)	4.41 s.	There is no significant change in time period.For change in the imposed load, but mass dirctly propotional to the lateral force
	Building-J (25 story with uniform 3.3kN/m2 imposed load)	4.42 s.
	Building-K (25 story with uniform 3.6kN/m2 imposed load)	4.43 s.

3)

Model period and frequencies of

Building A,B,F,H

Criteria	Model	Analysis result	Conclusion
Effect of building height on time period	Building-A (2 story)	0.50 s.	It is clear that time period varying according to the height of the building. The time period is directly proportional to the height of the building.
	Building-B (5 story)	1.03 s.
	Building-F (10 story)	1.73 s.
	Building-H (25 story)	4.41 s.

4)

Model period and frequencies of

Building B,C,D

Criteria	Model	Analysis result	Conclusion
Effect of column orientation on time period	Building-B (All floors column size C400X400)	1.03 s.	The deflection of building D will be higher in X direction than Y The deflection of building C will be higher in Y direction than X
	Building-C (All floors column size C550X300 while oriented in X-direction.	1.14 s.
	Building-D (All floors column size C300X550 while oriented in Y-direction.	1.12 s.

5)

Model period and frequencies of

Building B and Building B with Flexural stiffness of beams close to nil (Zero inertia)

Select Define-section properties-Frame sections

Select the beam section and modify the section

Criteria	Model	Case	Analysis result	Conclusion
Effect of Flexural Stiffness of structural elements on mode shapes.	Building-B	Flexural stiffness of beams close to nil (Zero inertia)	2.63 s.	It is clear that Flexural stiffness play a significant role in time period,as it changes the value is doubled
		Full Flexural stiffness of beams (regular)	1.03 s.

6)

Model period and frequencies of

Building H and Building H with Axial cross section for columns is close to nil (Zero axial area)

Select Define-section properties-Frame sections

Select the beam section and modify the section

Criteria	Model	Case	Analysis result	Conclusion
Effect of Axial Stiffness of vertical members on mode shapes.	Building-H	Axial cross section for columns is close to nil (Zero axial area)	5.99 s.	It is significant that the Axial Stiffness have a vital role in the time period of the building
		Full axial cross section for columns (Regular)	4.41 s.

7)

Model period and frequencies of

Building B and Building B with Fixed column support

Go to plan view -Select Base

Select the all the joint-Select Assign

Select joint -Select Restraints

select the fixed-Then Analyse

Criteria	Model	Case	Analysis result	Conclusion
Effect of degree of fixity at column base on mode shape.	Building-B	Column support pinned (regular)	1.03 s.	The time period have significant change in pinned and fixed conditions The more the fixity of the column the lesser it gets difflected
		Column support Fixed.	0.943 s.