DESIGN RECOMMENDATIONS FOR HOLLOW CONCRETE MASONRY WALLS SUBJECT TO CONCENTRATED LOADS, BASED ON A TEST PROGRAM

Concentrated loads are one of the most common types of load applied to masonry walls. Concentrated loads occur under beams, trusses, and joi sts resting on a bearing wall; they could also occur from the prestres sing anchorages of a post-tensioned masonry wail. The current typical design detail of grouting some of the blocks in hollow concrete masonr y 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 d ata, despite the fact that it actually does improve the bearing capaci ty of the wall. An experimental investigation into the effect of grout ing on the bearing capacity of hollow concrete masonry walls is descri bed. A grout configuration is proposed, supported by a previous numeri cal analysis, which improves the bearing capacity of the wall beyond t hat 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 direct ly under the concentrated load are given for the walls analyzed. Recom mendations for both the best location of the load with respect to the block geometry and grout configuration beneath the load are provided.