Design recommendations for hollow concrete masonry walls subject to concentrated loads, based on a test program

Abstract

Concentrated loads are one of the most common types of load applied to masonry walls. Concentrated loads occur under beams, trusses, and joists resting on a bearing wall ; they could also occur from the prestressing anchorages of a post-tensioned masonry wall. The current typical design detail of grouting some of the blocks in hollow concrete masonry beneath the concentrated load increases the bearing capacity of the wall. However, the present configuration of grouting is empirical, not being supported by any analytic procedure or published experimental data, despite the fact that it actually does improve the bearing capacity of the wall. An experimental investigation into the effect of grouting on the bearing capacity of hollow concrete masonry walls is described. A grout configuration is proposed, supported by a previous numerical analysis, which improves the bearing capacity of the wall beyond that obtained with the current pattern. The effect of the concentrated load location with respect to the block geometry on the wall capacity was also studied. The strength enhancement factors for the zone directly under the concentrated load are given for the walls analyzed. Recommendations for both the best location of the load with respect to the block geometry and grout configuration beneath the load are provided.