Experimental and Numerical Assessment of Corbels Designed Based on Strut-and-Tie Provisions

Abstract

Reinforced concrete (RC) corbels are short cantilever members that are used to transfer eccentric loads into columns or walls. Due to discontinuity in load and geometry, RC corbels cannot be adequately designed using methods that are based on beam theory. AASHTO LRFD Bridge Design Specifications permit the use of the strut-and-tie method (STM) for designing corbels. However, these specifications also require that the reinforcement details satisfy the requirements of an empirical design method, which prevents the efficient use of STM for such members. Moreover, the crack-control reinforcement requirements in the current STM provisions of AASHTO LRFD have been developed based on studies on deep beams, and the suitability of these provisions for corbels has not been investigated. This paper evaluates the behavior of reinforced concrete corbels designed according to the STM provisions of AASHTO LRFD. To do so, first, the performances of three full-scale corbel specimens designed according to STM were experimentally evaluated. Then, a numerical study using experimentally validated nonlinear finite-element models was conducted to investigate the crack-control reinforcement requirements for RC corbels. The results from the experimental study indicate that the STM provisions of the AASHTO LRFD provide conservative estimates of the load-carrying capacity of RC corbels; however, examination of the smeared node near the corbel-column interface, a check not currently required in AASHTO LRFD, is highly recommended. The results from the numerical study suggest that a reduction in the amount of secondary reinforcement currently required by AASHTO LRFD may be feasible, depending on the reinforcement layout used.