Project 1_Comparative study of different storey buildings for Seismic forces

Aim & Introduction

To create the 25 storey building and then we have to analyse the building by using the ETABS

Know how to extract different seismic responses for the structure

How to easily alter certain properties in an ETABS model

Know the factors influencing the dynamic characteristics

Know the factors influencing time period of building

Know the factors influencing Mode shape of building

10 ETABS models (preferably in e.2k format exported ) & All relevant screenshots of the procedure

Comparison of Analysis results for each of the criteria

Identifying the reason for the influences and reporting them ( preferably in tabulation )

Procedure

Factors influencing the Natural period of building

Structural Element Sizes

Beams 300 * 400 mm

Coloumns 400*400 mm

Slab 150 mm thick

Material properties

Grade of concrete M30

Grade of steel reinforcement Bars FE 415

Loading

Dead load on beams from infill wall 10 kN/m

Live load on floor 3 kN/m^2

Buildings are assumed to be pinned at base

Effect of stiffness on T : Compare to the fundamental natural periods of buildings E & F as well as G & H. why is there marginal/significant difference in the fundamental natural periods

Effect of mass on T : Compare to fundamental natural periods of buildings H,J & K have the building become more flexible/stiff due to change in mass

Effect of building height on T : How does the fundamental natural periods of buildings A,B,F & H change with change in building height

Effect of Coloumn Orientation on T : How does the fundamental natural periods of buildings B,C & D change in coloumn orientation

Open the ETABS model in the menu and then click the modal information

Display units - Steel section Database - Steel Design Code - Concrete Design Code

And then select the grid option and then the storey option in ETABS

select custom Database - Display grid data - Enter the values in the grid box

Set the X- coordinate and then the Y- Coordinate in the Grid system Data

Assume the beam ,coloumn,slab sizes and thickness in the property box

For cretating beam size Define - Material property - Assume the selected size of beam, coloumn, slab in the property box

For creating the slab sections go to the frame sections and enter the slab size

After the creation of slab coloumn beam property we have to create the coloumn in the grid by using the tools in the property box

Click coloumn in the box and then select the coloumns in the grid view

By using the replicate option we have create the coloumn quickly in the grid view

After the creation of coloumn we have to create the beam

Click coloumn in the box and then select the beams in the grid view

By using the replicate option we have create the beams quickly in the grid view

After the creation of coloumn and beam in the drawing we have to create the slab in the grid view

While creating the coloumn and beam make sure it for all stories if it is not in all stories click the option as all stories at the bottom of toolbar

Click slab in the box and then select the slabs in the grid view

By using the replicate option we have create the slab quickly in the grid view

The use of replicate option is not necessary for the creation of the slab

And then save the model and then create the 5 storey building in the ETABS

The same process is for the 5 storey building

Edit - Edit the grids and stories in the property box

And the enter the number of stories in the box and then click OK

By changing the coloumn size

Define -Material properties- Assign the coloumn detailing and then change the coloumn size

For changing the coloumn axix Assign-Frame-Local axes and then change the angle

We have to create the 10 storey building with two different coloumn sizes

Assume the beam ,coloumn,slab sizes and thickness in the property box

For cretating beam size Define - Material property - Assume the selected size of beam, coloumn, slab in the property box

For creating the slab sections go to the frame sections and enter the slab size

In this we have to create the 25 storey building we already created 10 storey building wehave to edit the grids

Edit grid & storey - Add 16 number of storey and then 25 storey created

We have to create the 3 different coloumn sizes in the moda

C600*600

C800*800

C400*400

We have to select M30 as the grade

Fe415 as the reinforcement

Creating the coloumn size as 800 *800 mm

ter the creation of slab coloumn beam property we have to create the coloumn in the grid by using the tools in the property box

Click coloumn in the box and then select the coloumns in the grid view

By using the replicate option we have create the coloumn quickly in the grid view

Criteria	Modal	Analysis result
Effect of stiffness on Time period	Building E (10 storey with varying coloumn size ) Building F (10 storey with Uniform coloumn size )	1.73s 1.71s
Effect of stiffness on Time period	Building G (25 storey with varying coloumn size ) Building H (25 storey with Uniform coloumn size )	4.09s 4.13s
Effect of mass on Time period	Building H(25 storey with 3 kN/m^2 impose load) Building J(25 storey with 3.3 kN/m^2 impose load) Building K(25 storey with 3.6 kN/m^2 impose load)	4.38s 4.41s 4.42s
Effect of Building height on Time period	Building A(2 storey) Building B(2 storey) Building F(2 storey) Building H(2 storey)	0.5s 1.05s 1.71s 4.38s
Effect of Coloumn orientation on Time period	Building B(All floor Coloumn size 400*400) Building C(All floor Coloumn size 550*300)Oriented in X-Direction Building D(All floor Coloumn size 300*550)Oriented in Y-Direction	1.05s 1.132s 1.103s

Criteria	Modal	Case	Analysis Results	Conclusion
Effect of Flextural stiffness of structural elements on Mode shapes	Building B	Flextural stiffness of Beams close to nil(Zero inertia) Full Flextural stiffness of Beams(Regular)	2.61s 1.05s
Effect of Axial stiffness of Vertical members on Mode shapes	Building H	Axial cross section for Coloumns is close to nil(Zero axis area) Full Axial cross section for Coloumns(Regular)	5.63s 4.38s
Effect of degree of fixity at Coloumn base on Mode shapes	Building B	Coloumn support period(Regular) Coloumn support(Fixed)	1.05s 0.958s