Modelling of 25 storey building with the specified properties using ETABS

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

Loading

• 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= 4.4 second Ty1= 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

Procedure:

• Open the ETABS software
• Open the file menu and choose to create a new model
• After choosing a new model a dialogue box will appear as model intialization .

• After setting the use built in settings in model initialization
• then open the new model quick templates

• Select the Custom Grid spacing to give the specify data for grid lines
• then we open the grid system data
• Give the X Grid data and also y grid data And give the spacing of the grid lines of 4m
• After giving the data for the grid click ok

• After giving the Grid Lines data
• Then Click on the custom story Data then open the story data template
• And Give the 25 storeys has a storey height of 3 metres.
• And give the Give the plinth height of 1.5 and Give the Every story similar to the story 1 And Give okay for it .

How we can seee the Grids on the Plan view and 25Story plan in 3d view

Now add the material

Material Properties

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

Go ot the define and select the material and add the new material

Give the material type as concrete and give the Grade of M30

Add the steel material property of material type of reber and give the Grade of HYSD 415

Structural Element Sizes

• Beams : 300 × 400 mm
• Columns : 800 × 800 mm
• Slab : 150 mm thick
• Go to the Define and select the sectional properties

Then open the Frame properties tamplet then add the new properties

Give the property name as B 300x 400 and give the sectional dimension if we want to change the properties we can change in the property modifiers

Give the property name as C 800X800 and give the sectional dimension if we want to change the properties we can change in the property modifiers

Now go to the Slab property and add the new salb property of slab 150

And Give the property name S150 and slab material M30 and thickness of 150mm

Go to the define and select the Load patterns ,And add the load

And add the load cases to it

Go to the define and add the mass source

After add the mass combination then add the Load combination and design type for load combination as concrete frame design then we can see the load combination and click on ok

Now select the quick draw select property as column and select to all the all the story and give the column at intersection of the grid .

Now select the quick draw the select the propertie of beam and select all the grid lines we have give the beam .

Now select the quick draw the select the propertie of slab and we have give the slab.

Go to the Assign and select the frame section and distribution and frame load

Load pattern name ad wall and give the uniform load of 10N/mm^2 and cilick on apply

And Go to the assign and Asiggn the 3kn/m^2 live load for the floor

Go to the assign and select the shall and go to the diaphram give the d1

Save the file and Run the analysis

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

After completion of analaysis go to the tables and go to the model information and open the model period and frequencis

• Tx1=4.4 seconds and Ty1=4.3 seconds

go to the tables and go to the model information and open the model participation mas ratio

• 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