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.

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: Tx1Tx1= 4.4 second Ty1Ty1= 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

1. Open the ETAB software

2. Open a new Project

3. Select the Grids for X direction and Y direction

4. Set the Grid Dimension to 4m

5. Then go to floor and select the no. of storey

6. According to the Question there are 25 storey in this project

7. Select the No. of storey and name it accordingly

8. Go to the Define option and select the material

9. Select the Beam first 300 X 400 mm

10. Select the Column size to 800 X 800 mm

11. Select the slab size as 150 mm

12. Now select any of the given options and then Select the Column of particualr size of given Dimension

13. Same process is done for the Beams

14. For Replicating go to Edit opton and select the replicate option and select the size of the grid which will create the beams and columns according to the given number and size

15. Select it for All stories so the beam and column which are selected will be replicated for all floors

16. In following way the beam and column will be selected

17. Then go for ththe plan option and select the first storey

18. After selecting the first storey make it to similar to all storey

19. Then go to Select Option and then Select, Properties and then take frame section

20. Then go to Assign option, Frame load and then Distributed

21. The load will be applied as follows

22. Then go to Select Option and then Select, Properties and then take Shell section

23. Then go to Assign option, Frame load and then Distributed

24. Select the Live Load 3 kn

25. The load will be applied as follows

26. Do the same process for Diaphragm

27. Fundamental Transistional Period for Modal 1 is = 4.4

28. Fundamental Transistional Period for Modal 1 is = 4.2

29. Transistional irregularity = 3.2

30. Vertical Irregularity Modal 1 and 2 occupies 80% of the weight of Building

Conclusion : The Challenge 6 is Complete