Limiting Projection Area in Re-entrant Corners of RC Buildings under Earthquake Loading

Buildings with re-entrant corners evidenced greater vulnerability to past earthquakes due to the diverse movement of building components in different directions. Building codes do not give any requirement for the design of re-entrant corner in buildings rather than placing an upper limit of allowable projection ratio. It is either based on: (i) area of projection of 5 or 30% (e.g., Eurocode and Venezuela) or (ii) length of projection varying from 15 to 40% (e.g., India, Turkey, Iran, Venezuela, etc.). This study aims to delve into the impact of projection area on the performance of 5-storey H, T, and L-shaped buildings (having almost same plan area) by varying the projection area ratios (6.25%, 9.09%, and 12.50%). The design process adheres to the standards of IS 456, IS 1893(1), and IS 13920 for analysis, design, and detailing. Elastic behaviour is studied using modal and response spectrum analyses; inelastic behaviour is studied using nonlinear static and dynamic analyses considering maximum considered earthquake. Confining the projection ratio solely based on projection length may not be sufficient when dealing with buildings featuring re-entrant corners. Thus, all the building code provisions should also limit the projection in buildings with respect to the projection area like Eurocode.