EFFECT OF HORIZONTAL REINFORCEMENT ANCHORAGE END DETAIL ON SEISMIC PERFORMANCE OF REINFORCED MASONRY SHEAR WALLS

摘要

The most recent design codes for masonry structures necessitate the use of reinforced masonry (RM) shear walls in medium and high seismic areas. There are several factors that control the contribution of the horizontal reinforcement to the in-plane shear capacity of RM shear walls. One of these factors is its anchorage end detail. The current version of the Canadian Standards Association CSA S304-14 for design of masonry structures requires that the anchorage of the horizontal reinforcing bars in the plastic hinge region shall have a 90° or more standard hook at the ends of the wall. However, a 180° standard hook is required for ductile shear walls. On the other hand, some masonry design codes (e.g. New Zealand, NZS 4230:2004) permits a 90° anchorage hook for ductile walls. This paper discusses the results of three identical RM shear walls that were tested under in-plane axial compressive stress and cyclic lateral excitations. All the walls were dominated by shear failure before reaching their flexure capacity. Wall W-180° was constructed with a 180° hook while walls W-90° and W-Str had a 90° hook and straight bar. The test results show that a 180° hook is the most effective anchorage end detail in terms of lateral force capacity and ductility. However, wall W-Str reached a lateral resistance, Q_(ue), of 398 kN compared to 412 kN and 418 kN for walls W-90° and W-1800, respectively, with less than 5% difference. Moreover, wall W-180° achieved a high level of displacement ductility of 4.2 instead of 3.9 and 3.6 when using a 90° hook and straight bar at a drop in wall capacity to 80% of Q_(ue). More results are analyzed and presented in this paper according to force-based, displacement-based, and performance-based seismic design considerations.