Force Reduction Factor R for Shear Dominated Low-Rise Brick Masonry Structures

This paper presents investigation carried out, including experimental and numerical studies, on low-rise shear-dominated brick masonry structures for the calculation of force reduction factor R. Basic experimental tests were conducted on masonry constituent materials for mechancial characterization. In-plane quasi-static cyclic tests were conducted on twelve full scale brick masonry walls, to understand behavior of shear-dominated walls under in-plane lateral loads. The tests’ data were analyzed to obtain the lateral shear strength, elastic and inelastic displacement capacities and hysteretic response of walls to facilitate numerical modelling of masonry structures. The numerical study included incremental dynamic analyses of shear-dominated brick masonry structures for the derivation of structures’ response curves, correlating the ground motion severity with the inelastic displacement demand on structure. The ductility dependent R factor is computed by identifying the ground motion intensities: capable to initiate global yielding in the structure (PGAy) and that exceeding the limit state displacement capacity of structure (PGAu), respectively. The ratio of the two PGAu/PGAy provides estimate of structures’ R factor. The calculated R factor varies in the range of 1.20 to 2.74, with a mean of 1.64; 1.5 may be conservatively used in the design and assessment of considered structures.