Alternative Strategies to Enhance the Seismic Performance of Reinforced Concrete-Block Shear Wall Systems

In this paper, seven reinforced concrete-block shear walls with aspect ratios of 1.5 and 2.2 (two- and three-storey high) were tested under displacement-controlled cyclic loading. The response of rectangular, flanged, and end-confined walls, designed to have the same lateral resistance when subjected to the same axial load, is discussed. In general, high levels of ductility accompanied by relatively small strength degradation were observed in all walls with a significant increase in ductility and displacement capabilities for the flanged and end-confined walls compared to the rectangular ones. For both aspect ratios evaluated, the drift levels at 20% strength degradation were 1.0, 1.5, and 2.2% corresponding to the rectangular, the flanged, and the end-confined walls, respectively. The ductility values of the proposed flanged and end-confined walls were, respectively, 1.5 and 2 times those of their rectangular wall counterparts (with the same overall length and aspect ratio). In addition to the enhanced ductility, a saving of more than 40% in the amount of vertical reinforcement was achieved using the proposed alternative strategies while maintaining the same lateral wall resistance. Existing design clauses were used to predict the wall capacities using the American and the Canadian masonry codes and showed excellent agreement. This will facilitate adoption of the new construction categories with minimal modifications to existing code clauses. The test results indicate that higher ductility than the currently endorsed values by North American codes should be used for rectangular walls. Moreover, higher values should be expected when the proposed strategies are adopted which would significantly reduce the seismic demand on reinforced concrete-block shear wall construction.