Experimental investigation of size effect on unreinforced concrete brick masonry walls under in-plane shear loading

The size effect is one of the primary structural characteristics exhibited in reinforced concrete (RC) members in shear. Even though numerous studies have been conducted on masonry walls under shear, very few studies have been conducted that definitively answer whether a size effect exists for masonry walls. Diagonal compression tests on two groups of masonry walls with different dimensions were conducted to investigate the size effect on concrete brick masonry walls. A total of sixty masonry wall panels were tested. Five bed-joint mortar mix properties were used for each specimen. Test results showed that four failure modes were observed: diagonal tension failure, combined failure, sliding failure, and toe-crushing failure. In particular, the diagonal tension strength was significantly related to the specimen size. The larger specimen size led to a lower shear strength. Also, the shear modulus was highly dependent on the specimen size. Through experimentation, this study demonstrated that masonry walls exhibit a size effect. Moreover, the size effect is valid only in cases of diagonal tension failure. Based on the test results, this study revealed a correlation between diagonal tension strength and wall size. Lastly, the adequacy of the predictions was compared to the existing masonry codes.