Effect of Diaphragm on Seismic Response of Buildings

Abstract

In the current scenario, many buildings have irregular structural configurations. These irregularities may be present in both section and plan. In the event of earthquakes, such buildings may be subjected to poor performance due to such irregularities. Therefore, it’s crucial to evaluate the earthquake resistance of both new and existing buildings with such irregularities to ensure their safety and resilience. Openings in floors and discontinuities in diaphragms are very common now-a-days for the sake of lighting, aesthetics, staircase, lift shaft, etc. Such diaphragm discontinuities can affect the performance of the building. All recent software’s give facility to assume the diaphragm as rigid, flexible, and semirigid. In this report, an attempt has been made to found out the difference in seismic response of structure having the rigid and semi-rigid diaphragm. In present study, buildings having cutout at the centre and edge with different size of cutout are anaysied.Here, the areas for center cutout are 10%, 20%, 30%, 45%, and 60%, respectively, and the areas for edge cutout are 5%, 10%, 15%, and 20%. and various building heights were taken into consideration for the analysis; these included six, eight, ten, twelve, fourteen, and sixteen stories. then analysis results of base shear, time period, peak displacement, storey drift and overturning moments are compared with respect to rigid and semi rigid diaphragm, cutout area and height of building.from the results obtained from analysis it is found out that models with semi-rigid diaphragms gives higher values for displacement,drift and overturning moments then rigid diaphragm models. In the present study, Irregular structures with irregularities plan discontinuity like openings are studied through Single Degree of Freedom Systems (SDOF) building model through shake table. A SDOF model fabricated with four columns are made of aluminium. Also, SDOF building modes are subjected to free as well as forced vibrations to determine its behaviour in terms of Natural Frequency, Damping constant and Acceleration response of the mass.