Stress‐Strain Curves for Brick Masonry in Biaxial Compression

A generalized approach is proposed to determine the envelope, common‐point, and stability‐point curves for brick masonry in cyclic, biaxial compression. The approach uses a family of interaction curves to predict the peak stresses of the envelope, common‐point, and stability‐point curves at different principal stress ratios. The corresponding strains at the peak stresses are determined using an empirical relationship involving the principal stress ratio and the strain at the peak stress of the envelope curve. A general stress‐strain equation is then used to determine the envelope, common‐point, and stability‐point curves for each principal stress ratio. The method is developed using the test results of 45 and 18 half‐scale brick masonry models tested under biaxial and uniaxial cyclic compressive loading, respectively. The test specimens are $360\mathrm{mm}\times 360\mathrm{mm}\times 115\mathrm{mm}$ constructed with half‐scale clay bricks $115\mathrm{mm}\times 55\mathrm{mm}\times 35\mathrm{mm}$ and with 6 mm thick bed joint mortar. The proposed generalized approach is simple and accurate.