Evolution of out‐of‐plane deformation and subsequent instability in rectangular RC walls under in‐plane cyclic loading: Experimental observation

Abstract

Summary In this study, to understand the causes and consequences of out‐of‐plane instability in rectangular RC walls, the sequence of events observed during a rectangular wall experiment campaign where out‐of‐plane instability was the primary failure pattern is discussed in detail. Large tensile strains developed in the boundary zone longitudinal bars at large in‐plane curvature demands and caused subsequent yielding in compression during load reversal before crack closure could activate contribution of concrete to the load‐carrying capacity of the wall. The specimen deformed in the out‐of‐plane direction when this phenomenon progressed along a sufficient height and length of the wall and led to significant reduction of its stiffness in the out‐of‐plane direction. One of the major sources of inherent eccentricity that could potentially affect development of this failure pattern is identified to be the postyield response of the longitudinal bars across the wall thickness, generating different values of residual strains and consequently inducing their asynchronous yielding under compressive actions. Analytical models proposed in literature for prediction of out‐of‐plane instability failure as well as their relevant assumptions are compared with the test measurements. While the observations presented in past research on development of out‐of‐plane instability in concrete columns representing the boundary zones of rectangular walls are in line with the sequence of events observed in this study, the assumptions made in the analytical models regarding the height of the wall effectively involved in formation of out‐of‐plane deformations (effective buckling height) were found to be different.

Research Programme on Seismic Performance of Reinforced Concrete Walls: Key Recommendations

“…Stages iii and iv were found to be in correlation with the stability criterion and upper bound limits proposed by Paulay and Priestley [49], respectively. Figure 12 indicates development of these stages in one of the wall specimens tested by Dashti et al [41]. Stage iv would result in abrupt strength degradation of the wall and possibly collapse of the structure.…”

“…An experimental campaign was conducted to investigate the effect of slenderness (unsupported height-to-thickness) ratio, length, axial load and longitudinal reinforcement ratio of the boundary regions on the out-of-plane failure mechanism of rectangular walls [14,18,41]. The progression and recovery of out-of-plane deformation and evolution of the subsequent instability observed in the wall experiments was in agreement with the numerical model predictions and with the theoretical description of the out-of-plane section buckling mechanism by Paulay and Priestley [49] and Chai and Elayer [50].…”

“…Paulay and Priestley previously assumed a buckled length equal to the length of the plastic hinge, whereas testing by Dashti et al [41] and several others [51,52] has shown that the buckled length can exceed the plastic hinge length by more than a factor of two. The buckling length may be better quantified by a fraction of the unsupported wall height, with ratios of 0.7-0.75 observed in testing [41,51,52], though the type of restraint at the storeys will affect this value. [26].…”

“…The progression and recovery of out-of-plane deformation simulated by curved shell finite element model [39]. Evolution of out-of-plane deformation and subsequent global instability -experimental observation[41].…”

Deformation limits of L‐shaped reinforced concrete shear walls: Experiment and evaluation

“…Such walls consist of two perpendicular wall segments, leading to significant stiffness and strength in both directions, which are contributed to the resistance of action induced by earthquake ground motions. Unlike conventional rectangular shear walls, the seismic behaviors of which have been thoroughly investigated by a significant number of experiments and finite element models, the seismic performances of L‐shaped RC shear walls are rarely available in literature. Zhang et al developed a cumulative damage model verified by the experiments of six L‐shaped shear walls.…”