Behavior of reinforced concrete walls with diagonal web reinforcement subjected to axial and cyclic lateral loadings

Abstract

It is widely accepted that diagonal web reinforcement improves the shear behavior of structural walls. However, the real mechanism leading to such an improved behavior is yet to be investigated, which is the main objective of this study. Six reinforced concrete structural wall specimens were subjected to cyclic loading in order to study the influence of diagonal web reinforcement. The experimental parameters included the amount and configuration of reinforcing bars in the web and axial load level. The finite element procedure was used to predict the envelope curve of the cyclic hysteresis loops obtained from the experiments, taking into account the effects of buckling of longitudinal bars on the behavior of confined concrete and the difference in stress-strain characteristics of the cover and core concrete through the boundary columns. The conventionally reinforced wall failed due to web crushing with an abrupt drop in load capacity, whereas the walls reinforced with diagonal web reinforcement failed in a more ductile mode. Test results clearly indicated that the diagonal web reinforcement reduced the shear and sliding displacement components. The specimens with diagonal web reinforcement exhibited less pinching in the hysteresis loops than the conventional one. Consequently, the energy dissipation capacity of the former was superior to the latter by about 23% at drift ratio of 1.5%. An alternative web reinforcement configuration which combines the superior performance of the diagonal reinforcement and the simplicity of placement of the conventional type was also proposed. Finite element analyses confirm the effectiveness of diagonal web reinforcement in reducing the compressive strain in the critical concrete strut in comparison with the conventional one. The reduction is about 23% at the ultimate drift ratio of the latter, thereby deferring web crushing with enhanced performance. The web crushing strength provided by AC1318-05 code gives over-conservative estimates of the shear strength of walls with diagonal web reinforcement. To better account for web crushing, a sectional analysis procedure considering shear effect is proposed, with flexural and web crushing mechanisms considered in the procedure.