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.
Highlights
Over recent years there has been considerable research activity into the seismic performance of masonry shear walls
Results indicated that the unconfined walls suffered strength degradation at levels of ductility lower than those required by current ductile design practice
Research on squat walls has indicated that ductile flexural failure modes can be obtained, with brittle shear failures inhibited, by use of a capacity design approach!"^
Summary
Over recent years there has been considerable research activity into the seismic performance of masonry shear walls. DESIGN OF TEST WALLS: Wall Dimensions - The size of the masonry shear walls was limited by the available clear height within the structural testing laboratory, and by the 500 kN capacity of the jack to be used for horizontal load application Within these confines, the walls were chosen to have a high effective aspect ratio, and detailed to violate the slenderness regulations of the draft concrete and masonry design codes. The increased lap length for Wall 3 was based on observed bond breakdown of lapped flexural reinforcement at the ends of the wall in Wall 1, and reflected an increased lap length requirement within plastic hinge zones agreed to by the drafting committee of the masonry design code between times of constructing Walls 1 and 3. Despite the less than ideal vibration provided, no significant settlement was noted, and condition of the grout core, when examined after completion of testing the walls, was good
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