Influence of Effective Stiffness on Seismic Response of RC Shear Wall Buildings

Effective stiffness of structural elements i.e., beams, columns, shear walls etc. plays a pivotal role in seismic evaluation of Reinforced Concrete (RC) shear wall buildings which are predominantly considered through use of stiffness modifiers in Indian design standard like various national design standards worldwide. The reduction in stiffness of the structural members is mainly due to crack formation in members due to shrinkage, creep, bond-slip of the reinforcement, etc. which further aggravates due to large inelastic deformation caused by seismic events. Stiffness modifiers for various structural members i.e., beams and columns have been recommended in revised Indian seismic standards (BIS in IS 1893 (Part 1)-2016 Indian standard criteria for earthquake resistant design of structures, Part 1: general provisions and buildings (fifth revision). New Delhi, Bureau of Indian Standards, 2016), however specific guidelines for the same is missing for RC shear walls. This paper presents a comprehensive review of the available effective stiffness recommendation by various national seismic design standards viz., ASCE (Seismic evaluation and retrofit of existing buildings (41-17), ASCE Standard, 2017), Eurocode (Design of structures for earthquake resistance-Part 1: general rules, seismic actions, and rules for buildings, 2005), New Zealand code [NZS in NZS 3101:2006 New Zealand standard concrete structures standard, 2006), Turkish standards (TS500 in TS 500-2000 Turkish standards requirements for design and construction of reinforced concrete structures, 2000) and assess the influence of effective stiffness on seismic evaluation of high-rise RC shear wall buildings. The results obtained showed a significant difference in peak strength with variation in stiffness modifiers of beam and column, whereas their peak strength is not significantly sensitive to effective stiffness of the shear wall due to higher stiffness of shear walls compared to other structural elements.