During an earthquake, ground motions occur in a random fashion, both horizontally and vertically, in all directions, radiating from the epicentre. The ground accelerations cause structures to vibrate and induce inertial forces on them. Hence, structures to be constructed in earthquake-prone areas need to be suitably designed and detailed to ensure stability, strength and serviceability.
The magnitude of the forces induced in a structure due to a given ground acceleration will depend, amongst other things, on the mass of the structure, the material and type of construction, the damping, the ductility and energy dissipation. Ductility of a material is the ability of a structure or member to undergo inelastic deformations beyond the initial yield deformation with no decrease in the load resistance.
Thus by enhancing ductility and energy dissipation capacity in structure, the induced seismic forces can be reduced and also the probability of collapse reduced (Pillai and Menon, 2012). Further, it is desirable to avoid discontinuities in mass or stiffness in plan or elevation. Torsional effects should particularly be accounted for in buildings with asymmetry in plan or elevation.
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