Earthquake doesn't kill people, buildings do. We blame the earthquake for disasters, but we make soft and weak and odd-shaped structures that have no such abilities to counter seismic forces which act horizontally. and in all possible directions, collapse within minutes resulting in heavy loss of life and properties.
In most of the Indian urban areas, modern apartments are built mostly without consulting a knowledgeable Structural Engineer. They usually keep the ground floor left open for open-type car-parking use. No partition, no walls between columns. These buildings are quite vulnerable to earthquakes.
These buildings shake like a heavy mass on feeble sticks on earthquakes. Under repeated shaking, those columns, though they were made strong enough, break. Most of the designers calculate their structures with bare frames for the sake of simplicity and don't consider infill walls in the upper storyes. In real construction practice, stiff masonry walls are constructed above expect the ground floor. Hence, there is a sudden drop in stiffness at the ground storey. However, the code suggests designing ground floor columns to be designed 2.5 times the force obtained from analysis of bare frame structure.
In the case of a newly proposed multistoried building, it is necessary to build walls i.e., infill walls on the ground floor as much as equal to the upper floors to reduce the sudden drop in stiffness. In this simple way, structural designers can avoid disastrous effects due to flexible and weak ground storeys. Moreover, columns should be designed considering ductility recommendations. If the problem is laying with old or existing buildings, a proper retrofitting method should be adopted and infill walls to be provided under technical guidance maintaining the use as much as possible.
