Effect of loading history on axial cyclic behaviour of RC prisms representing wall boundary zones

Abstract

Susceptibility of flexure-dominated reinforced concrete walls to premature compression failure modes (global lateral instability, local rebar buckling, etc.) was exposed during the recent past earthquake events in Chile and New Zealand. Numerous experimental studies have been conducted since then on isolated columns representing wall boundary zones to study critical parameters influencing these compression failure modes. However, a specific study including the effect of different loading histories, particularly in terms of cycle content (strain range and corresponding cycle count), is missing in the literature. In this study, uniaxial cyclic tests were performed on six doubly reinforced prisms idealised as the boundary elements of rectangular flexure-dominated walls to evaluate the effect of various loading histories on different compression failure modes. The uniaxial cyclic loading histories applied to these specimens included a conventional loading protocol (obtained directly from lateral cyclic loading test of a prototype wall) as well as two earthquake loading histories comprising cycle content representative of the cyclic demand expected from near-fault and far-fault earthquakes. In some of these tests, the level of compressive strains in the adopted loading protocol was reduced to study their impact on the compression failure modes. Although results re-affirmed the influence of imposed tensile strain on the global lateral instability and rebar buckling phenomena, the effect of variation in the number and amplitude of the strain cycles in the loading history was also displayed. Furthermore, results not only highlighted the impact of compressive strain variation on the global out-of-plane buckling response but also revealed the detrimental effects of rebar buckling on the low-cycle fatigue life of the specimens.