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Masonry infill ͑MI͒ walls are remarkable in increasing the initial stiffness of reinforced concrete ͑RC͒ frames, and being the stiffer component, attract most of the lateral seismic shear forces on buildings, thereby reducing the demand on the RC frame members. However, behavior of MI is difficult to predict because of significant variations in material properties and because of failure modes that are brittle in nature. As a result, MI walls have often been treated as nonstructural elements in buildings, and their effects are not included in the analysis and design procedure. However, experience shows that MI may have significant positive or negative effects on the global behavior of buildings and, therefore, should be addressed appropriately. Various national codes differ greatly in the manner effects of MI are to be considered in the design process from aseismic performance point of view. This paper reviews and compares analysis and design provisions related to MI-RC frames in seismic design codes of 16 countries and identifies important issues that should be addressed by a typical model code.

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Summary Eight half‐scale brick masonry walls were tested to study two important aspects of confined masonry (CM) walls related to its seismic behavior under in‐plane and out‐of‐plane loads. Four solid wall specimens tested to investigate the role of type of interface between the masonry and tie‐columns, such as toothing varying from none to every course. The other four specimens with openings were tested to study the effectiveness of various strengthening options around opening to mitigate their negative influence. In the set of four walls, one wall was infilled frame while the other three were CM walls of different configurations. The experimental results were further used to determine the accuracy of various existing models in predicting the in‐plane response quantities of CM walls. Confined masonry walls maintained structural integrity even when severely damaged and performed much better than infill frames. No significant effect of toothing details was noticed although toothing at every brick course was preferred for better post‐peak response. For perforated walls, provision of vertical elements along with continuous horizontal bands around openings was more effective in improving the overall response. Several empirical and semi‐empirical equations are available to estimate the lateral strength and stiffness of CM walls, but those including the contribution of longitudinal reinforcement in tie‐columns provided better predictions. The available equations along with reduction factors proposed for infills could not provide good estimates of strength and stiffness for perforated CM walls. However, recently proposed relations correlating strength/stiffness with the degree of confinement provided reasonable predictions for all wall specimens. Copyright © 2016 John Wiley & Sons, Ltd.

Some traditional designs of masonry structures have shown acceptable structural performance during past earthquakes. In these structures, a grid of horizontal, vertical, and/or diagonal elements divide a large wall into smaller wall areas and provide confinement to masonry panels. In addition, grid elements provide a definite shearing plane along which masonry blocks can slide adding to deformability and energy-dissipation capacity. Inclined elements significantly add to lateral stiffness and strength depending on whether they can develop a complete truss action for lateral loads. Cyclic tests were conducted on five half-scaled wall specimens with different sub-paneling schemes using RC precast grid elements. Experimental results and finite element studies were used to develop simplified predictive relations for strength and stiffness response based on a confinement factor representing the grid element density. These relations can be used to configure the grid elements for desired performance levels with additional inputs about the global behavior.