Challenge

Modelling of 25 storey building with the specified properties using ETABS

TThanish Ahamed6 Dec 2023

Challenge 6 – 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.

Structural Element Sizes

Beams : 300 × 400 mm
Columns : 800 × 800 mm
Slab : 150 mm thick

Material Properties

Grade of Concrete : M30
Grade of Steel Reinforcement Bars : Fe 415

Dead Load on beams from infill wall : 10 kN/m (Let us assume the same for roof floor in view of parapet)
Live load on floor : 3 kN/m2 (Let us assume the same for roof floor)

a) Buildings are assumed to be pinned at the base

b) All columns in all storey are of the same size

c) All beams in all storeys are of the same size

d) Building is located on Soil type-II and in Zone-III. Assume other factors if required.

Carry out the following exercises:

Check if the translational fundamental natural period of vibration in both the x and y direction is approximately: Tx1��1= 4.4 second Ty1��1= 4.2 second

This check will help confirm if modelling is done correctly. Some deviations from the above values is possible (± 2%). But any major deviation will suggest an error in modelling.

Check if the following provision in Table 5 of IS 1893 (part 1) – 2016, on torsional irregularity satisfied:

The natural period corresponding to the torsional mode of oscillation must be less than the two fundamental translational modes of oscillation along each principal plan directions.

Check if the two provisions of clause 7 in Table 6 (shown below) of IS 1893 (part 1) – 2016, regarding vertical irregularity is satisfied

Check if provision on inter-storey drift limitations in clause 7.11.1.1 satisfied. Please note that this check is for Serviceability Limit State and hence is for situation when stucture is subjected to unfactored seismic base shear

AIM:-

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.

PROCEDURE:-

STEP 1:-

Open E-Tabs ->new file
A new tab will open

Use built-in settings ->change the units and codes as per Indian standard->Click Ok
A new tab will open

STEP 2:-

Click on custom grid spacing->Edit grid data->A new tab will open

Enter the grid ordinates in X direction And Y direction
Click on Add to make more grids as per requirement->Click on Ok
You will be brought back to the previous page(Quick templates page)
Click on custom storey data->A new tab will open

Right-click on and select "add new story"->Enter the number of stories you want-> Enter the distance between them
Select story 1 as the master story and all others as No(as shown in the above pic)
Select similar to "Story 1"->SO that all other stories will be similar to Story 1
Click Ok

STEP 3:-

Will be taken to template page->click Ok
The main page will open showing the building structure you designed(shown below)

STEP 4:-

Click on Define bar->material properties->a new tab opens

after selecting material properties->new tab will open

STEP 5:-

Click on add new material->New tab opens-.selct as per the standard(concrete/rebar etc.)

Next we need to check material property data

STEP 6:-

Next we need to add rebar as the material

we need to check the material property data of the HYSD bar

click on OK

STEP 7:-

Also do the same for 415 rebar similar to the above 500HYSD

STEP 8:-

After adding the material properties->we have to add the column and beam sections
Go to define->section properties->frame sections

a new tab will open->Click on Add new property

STEP 9:-

After clicking Add new property->A new tab opens -> From here select the rectangular concrete and click ok
To add new beam and column frames

Next a frame section property data will open->you have to enter the data for the beam and columns
Change the property name as per given data B300x400-> Change material into M30
enter the depth and width of the sections

Click on Modify/show rebar->to enter the rebar types and numbers
A new tab will open->click on M3 design only
Change longitudinal bars and Tie bar types to the ones you made before
Enter the covers distance ->click on OK

STEP 10:-

Again on frame sections->Add new property
Select the rectangular concrete section->click on OK
A new tab open->rename the property as C800x800
Enter the width and depth of the column

Click on modify/show rebar->To enter the bars type of columns
A new tab will open->click on P-M2-M3 design->Enter longitudnal and tie bars type
reinforcement to be designed->Enter the number of bars you want in 2&3 direction

STEP 11:-

Next we select the slab section for the slab of 150mm
Go to define->section properties->slab sections

A slab properties tab will open->Click on slab1 ->modify/Show property
Slab property data tab will open->rename the slab as Slab150
select the slab material as M30->Modeling type as "membrane"
enter the thickness of the slab->click OK

STEP 12:-

Now we will add columns to the structure.
Go to the bottom right corner and select ALL STORIES
Click on "Quickdraw columns" of left side toolbars->a new tab will open
select the C800x800 from the property

select all the columns ->all the columns will be applied to the grids

STEP 13:-

Now beam will be added->Select quick draw beams (keep the selection to ALL stories)
a tab will open->select the property to B300x400
select all the beams section->the beams will be applied

STEP 14:-

Now add slabs to the section quick draw floors/Slabs
a tab will open->change the property to slab 150
Change the selection To similar stories
select all the slabs of any one floor ->the floors will be applied

STEP 15:-

Now joints will be added to the base
Goto Assign bar->Joints->Restraints

A new Joint assignment tab will open->select the pin joint

Now the pin joint is assigned to the base of the columns

STEP 16:-

Now we need to define load patterns->Go to Define Bar "Load patterns"
Add dead load, live load, brick wall load and earthquake load as shown below

Now we have to modify the earthquake load as per the direction of the applications
To modify , click on earthquake loads "EQx-" ->CLick on Modify lateral load
A new tab will open-> select only the Load direction you want(X dir-eccentricity in this case)
Select Site III, as suggested in the question & period, user-defined 0.5 sec

//Do this for all the earthquake directions, just change the eccentricity and direction in the above

STEP 17:-

Now we have to assign the live load to the slabs and brick wall loads
Select all the slabs of any floor
Go to Assign->Shell loads->Uniform

A Shell load assignment will open->Input a live load of 3 KN/m^2 as per the question
Make sure the similar stories are selected

Now the live load is applied to all the floors

STEP 18:-

Now the live load will be applied to the roof
Go to the roof plan->Change the selection into One story
select all the slabs of the roof
Go to assign->shell loads->Uniform
Put a live load of 1.5KN/m^2 (the roof has a live load of 50% of the floor)

STEP 19:-

Now assign the brick wall load to the beams //Make sure u change the selection to all stories
GO to select menu->object types->select beams(all beams will be selected)

Now go to Assign menu->Frame load->distributed

load assessment tab will open->select the brickwall from the selection
enter the value of 10KN/m

brick wall is distributed all over beams

STEP 20:-

Now we define the mass source
Go to Assign Menu->MAss source
A new tab will open->Click on Modify/show mass source
modify tab will open->select specified load patterns
Input dead=1,brick wall-1,live=0.25

STEP 21:-

Now load combination will be defined
From the define menu->go to load combination
a new tab will open->click on Add default design combos
Select concrete frame design

Click oK

STEP 22:-

MAking the diaphragm of the structure
Go to select menu->object types->seelct the floors
Assign->Shell->Diaphragm

A new tab will open->in that select D1 and apply

STEP 23:-

Now we check the model for errors
Go to analyze menu->check model
A new tab opens->tick all the checks

A no-error message will be shown if there are no errors in the structure

STEP 24:-

Now Go to analyze menu->run analysis->analysis will take some minutes

Go to "Show deformed shape or F6"->Tab will open and select any case(live/dead,earthquake) you want view the deformed shape

//Check on all other cases and see the deformed shapes

STEP 25:-

click on Display menu->Show tables->TAbles display will open
select anaylysis results->structure output->modal information->Modal participation mass ratios

A Modal participation mass ratios table will appear with all the mass ratios action on the building

From the table Natural period of mode1 is noted and torsional DOF is noted
Tx1=4.6sec,Ty1=4.394sec and Txy=3.436sec
so it is clear from the table that the torsional period is less than the two translational periods as required by IS 1893 provision table 5

CONCLUSION:-

The analysis is done and the result is within the range

Modelling of 25 storey building with the specified properties using ETABS

Ship work like this
in your own course.

Talk to a career counsellor

Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.