Tie system to upgrade out-of-plane performance of infill masonry walls

Abstract

The objectives of this study were to investigate the out-of-plane behavior of unreinforced masonry (URM) infill walls and to identify the effectiveness of tie systems that were proposed to enhance the infill stability under both in- and out-of-plane effects. This study examined three types of tie systems: a full-length tie system (prototype), a staggered tie system and a half-length tie system. For this purpose, four 1/4-scale, single-story, one-bay masonry infilled reinforced concrete (RC) frame specimens with and without the proposed tie systems were sequentially tested under in-plane static cyclic loading and out-of-plane dynamic excitation. In the experimental study, two series of shaking table tests were conducted to investigate the out-of-plane behavior of the infill walls. The first series compared the fundamental out-of-plane performance of three proposed tie systems, and the second series verified the effectiveness of the full-length tie system to prevent infill out-of-plane failure under an excitation simulating the severe floor response in medium-rise buildings. The test results indicated the following: (1) the presence of the tie systems caused minor differences in the in-plane capacity and ductility of each specimen, (2) the effectiveness of the full-length and staggered tie systems was superior to that of the half-length tie system, and (3) the full-length tie system not only prevented the infill out-of-plane failure but also significantly reduced the infill damage under realistic excitation conditions. The above research outcomes provide a useful contribution of the infill to upgrade the seismic resistance of buildings.