Authors: M.Tech. Scholor Harish Mishra, Assistant Professor Dr. Hariram Sahu
Abstract: Reinforced concrete (RC) multi-storey buildings are highly susceptible to lateral forces induced by earthquakes, which can cause excessive storey displacement, inter-storey drift and structural damage. Steel bracing is a widely used and economical means of improving the lateral stiffness and seismic performance of RC frames, but its effectiveness depends strongly on configuration. This paper presents a comparative seismic evaluation of a three-dimensional twenty-storey (G+20) RC building modelled with and without peripheral X-type steel bracing, analysed under Seismic Zones II, III, IV and V using the Equivalent Static Method in STAAD.Pro CONNECT Edition, in accordance with IS 456:2000, IS 875 (Parts 1 and 2):1987 and IS 1893 (Part 1):2016. Eight structural cases were compared in terms of maximum bending moment, axial force, shear force, support reaction, overall roof displacement, storey displacement and inter-storey drift. The results show that peripheral X-type bracing reduced every response parameter examined in all four seismic zones. The largest and most consistent benefit was in lateral deformation control, with roof displacement reduced by 28.0-33.0% and maximum inter-storey drift reduced by 29.4-32.5%, both widening as seismic zone increased. Reductions in axial force (15.9-34.3%) and support reaction (15.4-34.3%) grew markedly with seismic zone, while the benefit on bending moment fell from 23.4% in Zone II to about 1.9% in Zones IV-V, and the shear-force benefit stayed nearly constant near 25%. The study concludes that peripheral X-type bracing is most reliably effective as a deformation-control measure across all seismic zones, and recommends its use as a supplementary lateral load-resisting system in multi-storey RC construction.
