Behaviour and design of concrete masonry infill walls

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Masonry infill walls are commonly used as interior partitions as well as exterior wall infills in both steel and reinforced concrete frames in modern building construction. Due to the lack of scientific information in quantifying the extent of composite action between the infill and the frame, the common design practice applied in industry has been to treat masonry infill walls as non-structural elements and to design frames for both gravity and lateral loading. The contribution of masonry infill walls to the frame stiffness and strength is therefore ignored. It is, however, a misconception that ignoring the contribution of the infill wall is a conservative approach. Infill walls significantly stiffen the frame and thus reduce its ductility, which in turn attracts larger forces to the infill region in a structure. The poorly designed infill walls have been identified as a contributing factor to catastrophic structural failures in earthquakes. Although the current Canadian masonry design standard CSA S304 provides equations for the consideration of infill stiffness and strength, the values obtained using these equations are found to be in disparity with those obtained from experimental testing conducted by various researchers and also with values obtained from other recognized codes such as New Zealand masonry code NZS 4230 and Eurocode 8. In order to incorporate masonry infills in the design of lateral and gravity load resisting systems of a structure, the rational and accurate evaluation of their stiffness and strength is crucial. This proposal is therefore motivated to investigate, both experimentally and analytically, the behaviour and capacity of masonry infill walls with the focus on the concrete block masonry infills. The stiffness, strength and failure modes of infill walls will be studied for various material, geometric and loading characteristics. This research, upon its completition, is expected to contribute to the advancement of a rational design approach for masonry infill walls and associated infilled frames and to provide recommendations for practical implementation.