Investigating interface shear resistance through slant shear tests

This thesis presents the results of a study investigating interface shear resistance through slant shear tests. A total of 54 small-scale and 4 large-scale slant shear specimens were designed across six intrinsic variables: interface angle, interface roughness, concrete strength, casting age difference, aggregate size, and minimum amount of interface shear reinforcement. The slant shear specimens were tested to failure under a uniaxial load, monotonically increasing at a displacement-controlled rate. Based on the test results, interface roughness, aggregate size, and casting age difference were the most influential parameters affecting the interface shear resistance. Additionally, a comprehensive comparison of the interface shear resistance models in five design codes was performed, including AASHTO LRFD, ACI 318-19, CSA A23.3:19, fib MC2010, and Eurocode 2. A modified approach is proposed to calculate the cohesion and friction factors based on intermediary levels of roughness to improve interface shear resistance estimations in current design codes. Ultimately, the research presented in this thesis serves as the initial step in investigating the strength of struts crossing cold joints.