Shear Friction and Strut-and-Tie Modeling Verification for Pier Caps

Abstract

This study reports on experimental test results of reinforced concrete pier caps with different shear spans to effective depth ratios (a/d) of 0.5, 1, and 1.5. Each test specimen is then designed theoretically using both shear friction (SF) and strut-and-tie modeling (STM) approaches, according to Section 16.5 and Chapter 23 of ACI 318-14, respectively, and the results are compared with the pier caps experimental test results. The cracking load, failure load, deflection, crack pattern, crack width, steel reinforcement strains, concrete surface average strains, and failure modes are observed, recorded, and discussed. The experimental load capacities are compared with the theoretical load capacities of SF and STM. Experimental test results indicate that both STM and SF are conservative approaches and STM is more conservative than SF. The reason for this is because they do not take secondary reinforcement into direct consideration. That is why, a model is proposed, modifying STM, for estimating the ultimate capacity of pier caps based on calculating the strength of concrete and secondary reinforcement separately that gave more realistic results.