Strength and ductility of high-strength concrete shear walls under reversed cyclic loading

摘要

This study concerns the strength and behaviour of low-rise shear walls made from high-strength concrete under reversed cyclic loading. The response of such walls is often strongly governed by the shear effects leading to the shear induced or brittle failure. The brittle nature of high-strength concrete poses further difficulties in obtaining ductile response from shear walls.An experimental program consisting of six high-strength concrete shear walls was carriedout. Specimens were tested under inplane axial load and reversed cyclic displacements withthe test parameters investigated being longitudinal reinforcement ratio, transversereinforcement ratio and axial load. Lateral loads, lateral displacements and the strains ofreinforcement in edge elements and web wall were measured. The test results showed thepresence of axial load has a significant effect on the strength and ductility of the shearwalls. The axially loaded wall specimens exhibited a brittle behaviour regardless ofreinforcement ratio whereas the specimen with no axial load had a lower strength but higherductility. It was also found that an increase in the longitudinal reinforcement ratio gave anincrease in the failure load while an increase in the transverse reinforcement ratio had nosignificant effect on the strength but influenced the failure mode.A non-linear finite element program based on the crack membrane model and usingsmeared-fixed crack approach was developed with a new aggregate interlock modelincorporated into the finite element procedure. The finite element model was corroboratedby experimental results of shear panels and walls. The finite element analysis of shear wallspecimens indicated that while strengths can be predicted reasonably, the stiffness of edgeelements has a significant effect on the deformational results for two-dimensional analyses.Therefore, to capture the deformation of walls accurately, three-dimensional finite elementanalyses are required.The shear wall design provisions given in the current Australian Standard and the BuildingCode of American Concrete Institute were compared with the experimental results. Thecomparison showed that the calculated strengths based on the codes are considerablyconservative, specially when there exists the axial load.