Cyclic loading tests of slender concrete masonry shear walls

Abstract

The design, construction and testing of three slender concrete masonry shear walls is reported. The three walls, modelling 190 mm thick blockwork walls of four to five stories height to a scale of 1:0.737 were subjected
to cyclic reversals of in-plane displacements at gradually increasing ductility factors, simulating the effects of seismic loading. Variables between walls included axial load level, and whether or not confining plates were placed in the mortar beds in the compression zones of the potential plastic hinge region. All walls were constructed by conventional methods, and included lapped starter bars within the plastic hinge. Results indicated that the unconfined walls suffered strength degradation at levels of ductility lower than those required by current ductile design practice. This was particularly the case for the wall with heavy axial> loading, and confirmed theoretical predictions of available ductility based
on a limiting ultimate compression strain of 0.25%. Response of the
confined wall exhibited greatly improved behaviour compared with an
otherwise identical unconfined wall. In all walls behaviour was significantly, and adversely, affected by the lapping of flexural steel at the wall base.