Modelling of 25 storey building with the specified properties using ETABS

1. Q) Model a 25 storey building on ETABS 2018 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 Live load on floor : 3 kN/m2 Buildings are assumed to be pinned at base All columns in all storey are of the same size All beams in all storeys are of the same size Carry out the following excercises: Check if translational fundamental natural period of vibration in both the x and y direction is approximately the following: This check will help confirm if modelling is done correctly. Some deviations from above values is possible (± 2%). But any major deviation will suggests error in modelling. Check if the following provision in Table 5 of IS 1893 (part 1) – 2016, on torsional irrregularity 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 ans) open etabs and select new model and make the following settings. an interface appears as shown ,click the custom grid spacing and maintain the spacing as 4m in both x and y direction. click ok, a box appears,enter the stories upto 25 maintaing height of 3m except for base to plinth which is 1.5m and 1st storey is entered as master story. now go to define and select material properties, and enter the following. M30 grade concrete and steel 415. now go to section properties and enter the size of beam column and slab. now go to the load pattern,and enter the loads as shown. now select the quick draw column from the screen and place the columns at each grid. similarly place the beams and slabs. now assign the load to roof slab,select all the slabs and go to assign option. select the load as live and 1.5kn/m2.

from the table we can say that time period of mode of torsion is less than fundamental mode. first 3 modes contributre more than 65% in the mass participating ratios of each plan direction.