Seismic Torsion Behaviour and Rigidity Analysis of Multistory Plan Asymmetric RC Building

Due to the client demand on architectural drawings and land structure of Nepal, it is very difficult to make the structure with regular plan shapes, and thus, horizontal or vertical irregularity may be developed. These irregularities of the structure are more responsible for the collapse of building under the dynamic loads action during strong ground motions of earthquake and cause a significant torsional reaction in the structure. The main objectives of this paper are to study the torsional behaviour of reinforced concrete building with plan asymmetry which is located in zone V subjected to earthquake load and its parameters reflect the torsion effect and recommending the practical solution in order to reduce torsional effect. To carry out the study, both symmetric and asymmetric (L-SHAPE, + shape and T shape) plan buildings of eleven storey were modelled and ETABS software is used for analysis. The result proves that asymmetrical plan buildings are more vulnerable than symmetrical plan buildings. To reduce the torsional irregularity effect of asymmetrical plan structure curtailed shear wall system is recommended as practical solution with considering the stiffness. It was concluded that curtailed shear wall system improves the seismic performance of the structure reducing the cost criteria. After additional of shear wall, the torsional irregularity ratio of asymmetrical plan structure comes with in permissible limit as per IS 1893. Torsion creates damage or complete structures collapse, to control torsion, irregular structures should be carefully analysed.