Axial cyclic earthquake loading protocol for idealized RC wall boundary zones

Abstract

Seismic performance of a flexurally-dominated reinforced concrete wall is dependent on the response of its end boundary zones. In order to evaluate the performance of structural walls, a common practice adopted in laboratories is to test reinforced concrete columns representing the corresponding wall boundaries under uniaxial cyclic loading. This paper presents a numerical investigation leading to the development of a quasi-static uniaxial cyclic loading protocol based on the inelastic strain demands at the wall boundaries, when the corresponding structural wall is subjected to earthquake ground motions of various characteristics. With an increasing emphasis on performance-based design, the proposed loading protocol is structured around inelastic strain demands generated at the performance-based drift limits of structural walls. Non-linear time history analyses are carried out on a numerical wall model to obtain the average strain histories at the wall boundaries. A statistical evaluation of the number of inelastic cycles and the corresponding strain ranges forms the main basis for deriving the loading protocol. As damage is predominantly caused due to repeated large inelastic strain excursions, the rain flow cycle counting method is utilized for counting and sorting of the inelastic cycles. The proposed uniaxial cyclic strain histories are more representative of the cumulative demands imposed by moderate-to-large magnitude earthquakes, and their application would facilitate a more rational assessment of the seismic performance of flexurally-dominated RC walls than the current approach of testing boundary zones under arbitrarily decided tension-compression cycles.