Modelling of 25 storey building with the specified properties using ETABS
Question– ETABS modelling of a 25 storey building
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.
ANS.
AIM :-
To model a 25 story building using ETABS with structural properties as given in the question and also to check out the results as per given requirements from the Indian Standard codes.
INTRODUCTION :-
ETABS is an engineering software product 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 are all the features that are provided in etabs software to do the analysis.
PROCEDURE :-
The first step involves is to open e tabs software and the interface will look like this then click on the new model option to start a new model.
After that a new tab will open and then from there go to use building settings with option and change the setting as per the required data given in the question.
Then select the custom grading spacing and go to the edit grid data
Now change the story as per your requirement and mention the height of the story. Here the after the base there is a plinth story and then we continue the story as story 1 ,2 etc.
Also make the master story as story one and other all stories as similar to Story 1.
Now a story dialogue box will open where mention the height and the number of story which to be added. Here we have added 22 stories to make it 25 overall
Hence our structure will look like this in 3D view
After that click ok
Name the property name as B300x400
Material as M30
Depth as 400mm
Width as 300mm
And then click ok
Type the property name as C800x800
Material as M30
Width and depth as 800mm
Click ok to proceed
Enter the slab property as per the property name as S 150 and slab material as M30 also the thickness will be 150 mm and then click ok
Now to assign the load patterns
Go to define then load patterns and dialogue box will open
Now to draw the columns and beams
Click on the quick draw columns option
And then change the property from the properties of object as the assigned column property
And then draw the columns on the grids
Now to draw the beams
Go to the quick draw option of colum beam
Select the property of the beam which we have assigned earlier and then draw the beams
And select the property of slab as we have assigned earlier S 150
And then draw the slabs on the required plan
Dialogue box will open from where enter the load pattern name as wall and type the uniform load as 10kn/m
And then click on apply
Now to assign the load for the slabs
Go to select then properties then slab sections
Then select the slab which we have assigned earlier as S150.
Now to assign the Diaphragm
Go to assign then shell then diaphrams
Then select the diaphragm as D1.
Hence the diaphragm has been created in our model
RESULT :-
1. For the fundamental translation natural period
In X direction we got - 4.41 Sec
In Y direction we got - 4.22 sec
Which is almost similar to 4.4 and 4.2 second
2.Torsional irregularities
As per IS 1893-2016(part1) table 5
We got ,
torsional mode time period = 3.311
3.311 is lesser than 4.416 , 4.22
so torsional mode time period is lesser than X and Y direction time periods
3. Vertical irregularity
As per IS 1893-2016(part1) table 6 , clause 7
In modal participation the first mode and the second mode participation percentage are 80.84% and 80.42% , so there is no need to add the second and third modes for X and Y direction because in the first mode only the condition is satisfied.
Also it is given that the fundamental lateral periods in two principle plane directions are away from each other by at least 10% But here in our model we got the difference as lesser than 10% so it is not possible in our model
4 interstory drift :-
As per IS 1893-2016(part1) clause - 7.11.1.
Story drift shall not exceed 0.004 times the story height for the base share with no load factors
We get the maximum story drift for EQ X as around 1.4 to 1.6
And the max.Story drift for EQ Y as around 1.5.to 1.75
Hence it is not near the given value as per IS code, so it is also satified.