Behavior and Strength of Masonry Prisms Loaded in Compression

Abstract

The compressive strength of masonry is the most important material property for the design of structural masonry. The behavior and strength of masonry prisms under compressive loading has been a fundamental research topic. In most practical applications, the compressive forces are applied normal to the masonry bed joint and thus the masonry compressive strength is obtained by subjecting the masonry prisms in compression normal to the bed joint in the experimentation. However, there are other masonry members that rely on the compressive strength of masonry either parallel or inclined with an angle to bed joints such as masonry beams or masonry infills. For the latter application, the current practice is to use a reduction factor ? in combination with compressive strength of masonry normal to the bed joint to account for the effect of loading direction on the compressive stress. Despite considerable research has been conducted on the masonry prism strength under compression normal to bed joints, the information on the effect of loading direction on the masonry prism strength is limited. Some conflicting findings have been reported by different researchers in terms of the value of the reduction factor. An experimental program involving the test of 47 prisms and 27 square panels was therefore conducted to investigate the effects of a few influential parameters on the behavior and strength of masonry in compression. Parameters that were considered in the experimental program included loading orientation, height-to-thickness ratio, grouting arrangement, mortar strength, and central web interruption. Results from this study were used to augment the existing database and to verify the reduction factor for loading direction effect currently specified in the design standard. The unit-mortar method currently used in the standard for masonry compressive strength determination was also evaluated. Key observations are reported and recommendations are made as appropriate.