مهندسی عمران شریف (May 2018)
EFFECT OF OPENING ON THE LATERAL STIFFNESS OF MASONRY WALLS WITH AND WITHOUT CONCRETE TIES
Abstract
Necessity for making openings in masonry walls due to architectural considerations justifies a comprehensive study to have a thorough understanding of the behavior of masonry walls with openings. Based on size and place of an opening, different modes of failure may develop within the body of wall. Failure around the opening can govern the total lateral behavior of a masonry wall. If the pier besides an opening is too slender, in-plane or out-of-plane buckling might occur due to large compression in such components under overturning moment of wall. Since a large opening reduces the effective horizontal section area of a masonry wall, shear failure in the shape of long and wide diagonal cracks might govern the lateral behavior. On the other hand, if no sufficient depth remains for the lintel above a tall opening, the wall might fail because of shear or bending failure of the lintel as a local behavior. In this study, lateral response of masonry walls with openings is studied. The numerical modeling and analysis is followed and the developed models are validated using available experimental results. Samples selected for validation analysis include two masonry walls confined with reinforced concrete perimeter ties and one masonry wall with no ties. Validity of the numerical models has been established against the experimental samples within Abaqus software using nonlinear static analysis. Variations in the size, location and aspect ratio of the opening are taken into account and the lateral stiffness and strength of the walls are calculated. In addition, a series of equations have been developed based on the strength of materials for simple calculation of lateral stiffness, strength and ductility of masonry walls with opening. This has the important advantage of avoiding complex and time consuming 3D nonlinear finite-element analysis for the same purpose. To do this task, three different cases of failure are accounted for the walls including: when presence of the opening is not effective, when behavior of the two piers besides the opening is governing, and when the overhead lintel governs the lateral behavior of wall. Each of the mentioned cases is in turn divided into other sub-cases and several nonlinear finite-element analyses are undertaken. Results of the developed analytical equations are compared and calibrated with those of the finite-element analysis and the desirable accuracy of the relations developed in this study is confirmed.
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