Project 1_Comparative study of different storey buildings for Seismic forces

Project 1_Comparative study of different storey buildings for Seismic forces

 

AIM : Comparative study of different storey buildings for Seismic forces

 

INTRODUCTION : There are 10 project of different story building (A, B, C, D, E, F, G, H, J, K).

 

Factors influencing the dynamic characteristics of a building

    Buildings oscillate during earthquake shaking. The oscillation causes inertia force to be induced in the building. 

    The intensity and duration of oscillation, and the amount of inertia force induced in a building depend on features of buildings, called their dynamic characteristics, in addition to the characteristics of the                  earthquake shaking (beyond the control of an engineer) itself. 

    The important dynamic characteristics of buildings are modes of oscillation and damping (assumed constant in most practical cases). A mode of oscillation of a building is defined by associated Natural Period             and Deformed Shape in which it oscillates. 

    Every building has a number of natural frequencies (how many?), at which it offers minimum resistance to shaking induced by external effects (like earthquakes and wind) and internal effects (like motors fixed        on it).  

    Each of these natural frequencies and the associated deformation shape of a building constitute a Natural Mode of Oscillation. 

    The mode of oscillation with the smallest natural frequency (and largest natural period) is called the Fundamental Mode; the associated natural period T1 is called the Fundamental Natural Period.

    Regular buildings held at their base from translation in the three directions, have two fundamental translational natural periods, Tx1 and Ty1, associated with its horizontal translational oscillation along X and Y        directions, respectively, and one fundamental rotational natural period Tθ1 associated with its rotation about an axis parallel to Z axis. 

 

 

Factors influencing the Natural Period of a building

 

 

 

 

       Effect of stiffness on T: Compare fundamental natural periods of buildings E & F as well as G & H. Why is there a marginal or significant difference in the fundamental natural periods? 

 

 

       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? 

 

       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?

 

 

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

 

 

 

Factors influencing the Mode shape of oscillations

    Mode shape of oscillation associated with a natural period of a building is the deformed shape of the building when shaken at the natural period. Hence, a building has as many mode shapes as the number of        natural periods. 

    For a building, there are infinite numbers of natural period. But, in the mathematical modeling of building, usually the building is discretized into a number of elements. The junctions of these elements are            called nodes. Each node is free to translate in all the three Cartesian directions and rotate about the three Cartesian axes. Hence, if the number of nodes of discretization is N, then there would be 6N modes of      oscillation, and associated with these are 6N natural periods and mode shapes of oscillation. 

   Effect of Flexural Stiffness of Structural Elements on mode shapes: Compare fundamental mode shape of Building B in two situations when flexural stiffness of beams relative to that of adjoining columns is           very small versus when it is large. 

 

 

 

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

 

   Effect of Degree of Fixity at column bases on mode shape: Compare fundamental mode shape of Building B in two situations when base of columns is pinned versus when it is fixed.

 

 

Building A

Given,

2 storey building 

number of bay 

X direction 4,  Y direction 3

size of beam 400X400mm 

 

step 1) open the etabs software and go for new model 

 

 

then set units and press ok in intialization optionn

 

step 2) set grid spacing and custom storey data from quick templet 

 

first go to edit custom grid spacing 

set no. of bay and spacing between two grids and press ok 

 

now storey data 

 

our building frame are created 

 

step 3) go to material proprty from define 

add new material of concrete M30 and steel fe 415

 

step 4) now going for section 

add column frame and beam section according to given size and material 

 

 

step 5) go for slab section 

add 150mm thick membrane slab with M30 grade concrete 

 

step 6) go for load patterns 

click on load patterns option from define

now we add load for wall

and earthquake in X and Y respectively 

 

step 7) go for mass source 

add 1 for dead load and wall 

and 0.25 for live load 

 

step 8) now go for load cases 

 

step 9) create load combination 

 

step 10) now go for column modelling 

clickm on draw column option 

change working plane as all stories

 

 

step 11) beam modelling 

go to quick draw beam change working plane as all storey 

and draw the beam to take a cursor between two grids

 

step 12) slab draw 

go to quick draw slab 

draw only for storey one and two 

 

 

step 13) assign loads 

select beam properties from beam 

to select beams 

 

now assign loads on slabs 

select slab from select option 

then assign slab load from assign 

assign 10Kn/m as live load

 

step 15) diaphragms property 

select all the slabs from select option 

and assign diaphragms 

 

step 16) run analysis 

after complition of modelling part run the analysis 

 

 

 

Building B 

 

Given,

5 storey building 

number of bay 

X direction 4,  Y direction 3

size of beam 400X400mm 

 

step 1) open the etabs software and go for new model 

 

 

then set units and press ok in intialization optionn

 

step 2) set grid spacing and custom storey data from quick templet 

 

first go to edit custom grid spacing 

set no. of bay and spacing between two grids and press ok 

 

now storey data 

 

our building frame are created 

 

step 3) go to material proprty from define 

add new material of concrete M30 and steel fe 415

 

step 4) now going for section 

add column frame and beam section according to given size and material 

 

 

step 5) go for slab section 

add 150mm thick membrane slab with M30 grade concrete 

 

step 6) go for load patterns 

click on load patterns option from define

now we add load for wall

and earthquake in X and Y respectively 

 

step 7) go for mass source 

add 1 for dead load and wall 

and 0.25 for live load 

 

step 8) now go for load cases 

 

step 9) create load combination 

 

step 10) now go for column modelling 

clickm on draw column option 

change working plane as all stories

 

 

step 11) beam modelling 

go to quick draw beam change working plane as all storey 

and draw the beam to take a cursor between two grids

 

step 12) slab draw 

go to quick draw slab 

draw only for storey one and two 

 

 

step 13) assign loads 

select beam properties from beam 

to select beams 

 

now assign loads on slabs 

select slab from select option 

then assign slab load from assign 

assign 10Kn/m as live load

 

step 15) diaphragms property 

select all the slabs from select option 

and assign diaphragms 

 

step 16) run analysis 

after complition of modelling part run the analysis 

 

 

 

Building C

 

Given,

5 storey building 

number of bay 

X direction 4,  Y direction 3

size of beam 550X300mm 

 

step 1) open the etabs software and go for new model 

 

 

then set units and press ok in intialization optionn

 

step 2) set grid spacing and custom storey data from quick templet 

 

first go to edit custom grid spacing 

set no. of bay and spacing between two grids and press ok 

 

now storey data 

 

our building frame are created 

 

step 3) go to material proprty from define 

add new material of concrete M30 and steel fe 415

 

step 4) now going for section 

add column frame and beam section according to given size and material 

 

assign the loacal axis at X direction

by giving 90degree rotation 

 

 

step 5) go for slab section 

add 150mm thick membrane slab with M30 grade concrete 

 

step 6) go for load patterns 

click on load patterns option from define

now we add load for wall

and earthquake in X and Y respectively 

 

step 7) go for mass source 

add 1 for dead load and wall 

and 0.25 for live load 

 

step 8) now go for load cases 

 

step 9) create load combination 

 

step 10) now go for column modelling 

clickm on draw column option 

change working plane as all stories

 

 

step 11) beam modelling 

go to quick draw beam change working plane as all storey 

and draw the beam to take a cursor between two grids

 

step 12) slab draw 

go to quick draw slab 

draw only for storey one and two 

 

 

step 13) assign loads 

select beam properties from beam 

to select beams 

 

now assign loads on slabs 

select slab from select option 

then assign slab load from assign 

assign 10Kn/m as live load

 

step 15) diaphragms property 

select all the slabs from select option 

and assign diaphragms 

 

step 16) run analysis 

after complition of modelling part run the analysis 

 

 

 

 

Building D

 

Given,

5 storey building 

number of bay 

X direction 4,  Y direction 3

size of beam 300X550mm 

oriented along y direction 

 

step 1) open the etabs software and go for new model 

 

 

then set units and press ok in intialization optionn

 

step 2) set grid spacing and custom storey data from quick templet 

 

first go to edit custom grid spacing 

set no. of bay and spacing between two grids and press ok 

 

now storey data 

 

our building frame are created 

 

step 3) go to material proprty from define 

add new material of concrete M30 and steel fe 415

 

step 4) now going for section 

add column frame and beam section according to given size and material 

 

assign the loacal axis at X direction

by giving 90degree rotation 

 

 

step 5) go for slab section 

add 150mm thick membrane slab with M30 grade concrete 

 

step 6) go for load patterns 

click on load patterns option from define

now we add load for wall

and earthquake in X and Y respectively 

 

step 7) go for mass source 

add 1 for dead load and wall 

and 0.25 for live load 

 

step 8) now go for load cases 

 

step 9) create load combination 

 

step 10) now go for column modelling 

clickm on draw column option 

change working plane as all stories

 

 

step 11) beam modelling 

go to quick draw beam change working plane as all storey 

and draw the beam to take a cursor between two grids

 

step 12) slab draw 

go to quick draw slab 

draw only for storey one and two 

 

 

step 13) assign loads 

select beam properties from beam 

to select beams 

 

now assign loads on slabs 

select slab from select option 

then assign slab load from assign 

assign 10Kn/m as live load

 

step 15) diaphragms property 

select all the slabs from select option 

and assign diaphragms 

 

step 16) run analysis 

after complition of modelling part run the analysis 

 

 

BUILDING E (G+ 10 )

Column sizes :

for top 5 storeys: C 400X400

 Column sizes

for bottom 5 storeys: C600X600

 

PROCEDURE : 

 In this model, we need to add up 5 more storeys to our model.

In addition, we also need to assign different column sizes on different floors.

 we'll first save the ETABS file for building D as a new model for building E.

Then, edit the story data as we have done for our previous models in ETABS.

Then, we need to add two new column sections with the required directions and assign them at appropriate floors in our model as specified.

STEP 1

Add 5 more story in previous structure 

so that go to the Edit option 

click on Edit Story And Grid System 

one dialogbox is open 

from that click on Modify Story Data option 

add 5 story there shown below 

refresh it and then click OK 

click ok 

STEP 2 

Check the wall load and floor load of the structure 

click on Display shell load assign 

select the load pattern as live load 

click on APPLY and ok 

again click on Display Frame Load Assign 

select the load pattern as wall load 

Click on Apply and then OK . 

 

STEP 3 

Change the column size as 600x600

so that click on Define tab 

then Section properties 

then Frame section 

select the c550x300 

then click on Modify section 

one dialogbox is open shown below 

give the property name as c600x600 

give the depth as 600 

and width as 600 

click OK . 

Then Add one more new column size 400 by 400

so that click on Add new proprties 

give the name as c400x400

then width of column as 400

depth as 400

Click OK 

STEP 4 

Select the column only 

for that hide the beam and floor 

click on set view point tab 

and unselect the beam and floor and then click ok 

click ok

 

STEP 5 

Select the column from floor 6 to 10 

so that , click on view tab 

Then click on Set Building view Limits 

one dialogbox is open 

from that select the Top story as Story 10

and base story as story 6

then click ok . 

3D VIEW : 

Select the all columns 

then click on Assign tab 

then click on Frame and then click on Section Properties 

one dialogbox is open 

select the c400x400 and then click on APPY and then ok 

3D VIEW 

 

STEP 5 

Then checked for diaphragms 

so that select the slab first 

go to the select option 

then click on properties and slab section 

one dialogbox is open 

click on seect and then close it . 

then click on Assign tab 

then click on shell 

and then diaphragms 

one dialogbox is open 

click on Appy and then OK 

 

STEP : 6 

RAN ANALYSIS 

RESULTS : 

 

 

BUILDING F (G+10)

Throughout the structure having same columns size 

no need to much editng in the previous structure 

jast change the column size from story 6 to 10 as 600x600

PROCEDURE : 

STEP 1 

Hides the beams and floor 

so that click on Set Display Option 

and just unselect the Beams and floor 

click on Apply and then OK 

3D VIEW : 

STEP 2 

Select the columns from story 6 to 10 

so that click on View tab 

Set Building LImets  

then one dialogbox is open 

from that click on 

tao story as 10 story and 

base story as 6 story 

click on OK 

STEP 3 

Change the columns size as 600x600

so that jast select the columns 

click on Assign tab 

then click on Frame and then Section Properties 

then one dialogbox is open 

from that click on c600x600 columns 

click on APPLY AND THEN OK .

Then click on view tab 

then click on Set Building View Limets 

one dialogbox is open 

from that select the top story as 10 story 

and bottom as base 

click ok . 

3d view : 

STEP 4 

Again select the beams ad floors 

click on Set Display Option 

open dialogbox is open 

from that click on Beam and slab 

and then click ok 

3d VIEW : 

STEP 5 

Check for diaphergram 

so first select the slab 

click on Select the tab 

and click on Properties 

then Slab section 

one dialogbox is open 

select the slab150

and then closed it . 

Then click on Assign tab 

click on Shell and the diaphergrm 

one dialogbox is open 

click on D1 

Then click on APPLY  and then OK .

 

STEP 6

RUN ANALYSIS : 

 

RESULTS : 

 

 

 BUILDING G (G+25)

Columns for top 5 stories: C400X400

Columns for middle 10 stories: C600x600

Columns for bottom 10 stories: C800x800

 

PROCEDURE : 

 we need to add 15 new stories and assign different column sizes on different floors.

We can follow the exact procedure that has already been explained for the previous project to create this model by editing building F. The same 

STEP 1 

Click on File manu 

then click on Save As then give the fine name as BUILDING G 

STEP 2 

Add more 15 story in previous story 

so that click on Edit 

then click on Edit Story And Grid System Data option 

one dialogbox is open 

from this click on Modify /Show Story data 

again one dialogbox is open 

from that add more 15 story 

click ok 

click ok 

click ok .

 

STEP 3 

check the live load and wall loads of the structure 

Check Live load : 

click on Display Shell Load Assign 

one dialogbox is open 

select the load pattern as Live load 

click on Apply and then OK . 

Check wall load 

so that click on Display Frame Load Assign tab 

one dialogbox is open 

select the load pattern as wall load 

click on Appy and then OK 

 

STEP 4 

define columns 

c400x400

c600600

c800x800 . 

so that click on Define tab 

then Frame section 

one dialogbox is open 

create a new column 

c800x800

click on OK . 

STEP 5 

Apply different size of columns for each story 

so that click first hide the beams and floors of the structure . 

click on Set Display View tab 

unselect the beam and floors option 

click on Apply and then OK . 

 

STEP 6

Click on assign tab 

then click on Frame and then Section Properties 

one dialogbox is open 

select the c400x400

click on Appy and then OK .

3D VIEW : 

 

Middle 10 story provided with column size as 600x600

again click on View option 

then click on Set Building Limets option 

one dialogbox is open 

select the top story as story 20

and bottom story as story 11

click on OK . 

then click on Assign tab 

then click on Frame and then Section Properties 

one dialogbox is open as shown below 

 

again click on View Option 

click on set building view limets 

then Make visible beam and slab of the structure 

click on Set Display Views Option 

and select the Beam and Slab Option 

and then click on OK.

STEP 7 

CHECK for diaphragms 

first select the slab 

click on Select tab 

then again click on Select and then properties , next is slab section 

one dialogbox is open 

from that click on Slab150

click on Select and then closed it 

click on Assign tab 

the click on Shell and then Diaphragms 

one new dialogbox is open 

from that select D1 

click on APPLY and the OK 

 

STEP 8 

RUN ANALYSIS 

 

RESULTS  : 

 

 

BUILDING H  (G-25)

All column size is 800x800

PROCEDURE : 

First click on File option 

then click on Save as 

Give the file name as BUILDING H 

and the save it 

STEP 2 

First hide the Beam and floor 

and the click on APPLY and the OK 

STEP 3

Assign all columns as 800x800

so that first select the columns 

then click on Assign tab 

then click on Frame and then section properties 

one dialogbox is open 

From that click on c800x800

click on APPLY and Then OK .

STEP 4 

Select the beam and slab 

so that click on set display option 

then select the beam , floor and diaphragms option 

click on APPLY and then OK . 

 

STEP 5 

RUN ANALYSIS : 

RESULTS : 

 

 

 

BUILDING J (G+25)

IN THIS CASE INCREATSE THE 10 % IMPOSED LOAD MEANS LIVE LOAD 

PROCEDURE : 

STEP 1 

Select the all the slab 

click on Select tab 

then click on select tab then section properties and slab section 

one new dialogbox is open 

from that click on Slab150

then click on Select and then closed 

STEP 2 

Increase the 10 % of live load 

so that click on Assign tab 

then shell load 

then click on Unifom 

one dialogbox is open 

give the load as 3.3

then click on APPLY and then ok 

STEP 3 

RUN ANALYSIS : 

RESULTS : 

 

 

BUILDING K (G+25)

In this case the increase the mass of the building by 20 persent imposed load means live load . 

PROCEDURE : 

STEP 1 

Click on File tab 

then click on Save as give the file name as BUILDING K 

And then save it . 

STEP 2

Increase the live load by 20 persent 

click on Select tab 

then again click on Select and then properties and 

then slab section .

one dialogbox is open 

select the Slab150

 

select it and then closed it . 

 

STEP 3

Assign load 

so that click on Assign tab 

then click on Shell load 

then click on Uniform 

one new dialogbox is open 

from that select the load pattern as live load 

then give the load 3.6 

click on APPY and then ok 

STEP 4 

RUN ANALYSIS :

RESULTS : 

 

 

RESULTS : 

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
		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
		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	5	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

 

• BUILDING A 
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• BUILDING B
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• BUILDING C
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• BUILDING D 
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• BUILDING E 
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• BUILDING F 
• 

 

• BUILDING G 
• 

 

• BUILDING H 
• 

 

• BUILDING J
• 

 

• BUILDING K
•