Modelling of 25 storey building with the specified properties using ETABS

AIM-

Model a 25 storey building on ETABS

with structural properties as specified

below. Ground floor or plinth floor level

can be taken at a height of 1.5 metres

from the base. Each of the successive

25 storeys has a storey height of 3 metres.

 

INTRODUCTION -

ETAB OR ETABS they meaning are same .

it is extendended 3d analysis of building 

system.

it is engineering software product .

-that caters to multistorey building 

design and analysis .

-ETabs offers  single user interface.

-to perform modelling .

analysis , design , and reporting .

 

 

PROCEDURE -

-STEP :1 

-Open etabs 

-click on new mode l

and  choose use built in setting with option .

-set display unit is metric SI  as per 

requirement .

-then click ok .

-new dialouge box will apper .

-select custom grid spacing and 

then select edit grid data 

-new dialouge box will appear 

then enter x grid data at a distance 

of 4 meter distance .

-

-click ok 

-then select custom story data 

and select edit story data .

-add story up to 25 

and give input plinth height is 1.5 m .

-and all other story height as 3m .

-

-then make story 1 as master stroy 

and all other storey similar to 1 

 

-then our building model is generated .

-

 

 

 

 

STEP -2 

Select material properties 

select define from that select 

 material properties .

-new window will apeear and 

from that select  add new  new material.

-

-new windows will appear  now 

define materiakl type  concerete 

and grade  M30 .

 

-Similar define rebar  property .

-

 

 

 

go to define tab , select section properties 

and from that select frame properties .

 

-new window will appear , in that 

select add new property .

 

 

-then select rectangular  concerete 

section , rename it as B 300X400

-Change the property as  M30 

AND  changed the size  as B 300 X 400 

 

-Similar add column section properties .

 

-then go to define select section property .

from that select slab section .

 

-new windows appear 

rename it slab 150 , modelling type 

as membrane and changed thickness 

as 150mm .

 

 

 

 

 

 

 

 

-Draw structural members .

for frist select mode as all stories 

at right bottom corner .

 

-then select quick draw column 

and changed property as  C 800X800

 

-Place the column at every intersection 

of grid 

-then select quick draw column /beam.

-changed property as  B 300X400

-PLACE beam at all grids .

-now we need to changed mode as similar 

stories at bottom of window .

-in order to avoid slab placement 

in plinth level .

-

-select  quick draw floor /slab and 

draw slab sections

 

-select assign and click on joint select 

pinned support 

-fix pin support at base .

 

 

 

 

 

 

 

CLICK  on define from that select 

the load pattern .

-define load like  dead load , live load 

brick wall load  and earthquake load

in  x  direction and eccentric earthquake 

load  in position  x and  -x and 

same load in  y  direction also 

mention  is code of respective load .

 

-click on modify lateral load 

set range from base to 25th 

storey , changed direction 

and eccentricity , seismic  zone 

factor as 1.25 and time period 

as .5 sec .

 

-do same for all earthquake loads .

 

 

 

STEP

ASSIGN LOADS 

-to assign loads , select similar stories 

at bottom of windows 

-then select members .

-after go to assign tab > shell load .>

uniform 

-A new window will appear in that 

select live load and give value as 3 kn/m^2

-click on apply 

--then select all story at the bottom 

of the windows and select all beam

under select tab .

 

-after that do assign tab > frame load 

.distributed .

 

-enter value 10 kn/m2

 

-go to mass source from define tab.

 

modify mass source and check specified 

load pattern .

-add load pattern and assign the model.

ok .

 

 

 

 

STEP 

DEFINE LOAD CASES .

 

-Click ok .

-go to define >load combination .

 

-click on add default design combos 

and select conecrete frame design .

 

ok.

 

-frist select slab .

then go assign tab ,select shell 

and click  on diaframe created sucessfully .

-check model , modelled structure varified 

without warning and errors .

-then go analysis tab and run analysis .

 

 

RESULT -

MODAL 1  TIME PERIOD =4.435 SEC.

MODEL 2 TIME PERODE =4.408

 

• Display--> show tables-->analysis result-->structure output >modal information > modal participation mass ratios
• From the table the natural time period for mode 1 and torsional DOF are noted as follows

 

• Tx1= 4.435 seconds, Ty1=4.408 seconds= and Txy1=3.303 seconds
• So from the results it is clear that the torsional time period is less than two translational time
• period is less than two translational time period as required by IS 1893 provision Table 5
• When we add the three mode mass ratios we get 0.8042 which means the first three modes of
• seismic oscillation contribute  more than 65% of building weight as per ETABS analysis 
• The storey drift for seviceability base shear case (EQxor EQy) is tabulated from the following tool path
• Then go to display-->story response plot
• keeping load case to EQy and switching to max story drift the maximum drift  value is noted as 0.0016
• Keeping load case for EQx and switching to max story drift the maximum drift value noted is 0.001492

 

 

 

 

 

• so as per the clause  7.11.1, the maximum inter storey drift is limited to 0.004 for each story height.
• But our value is   is within the code limits