Shear Capacity of Reinforced Concrete Box Culverts Compared with AASHTO Shear Equation

This study focuses on the concrete shear strength (V_c) of the top slab of reinforced concrete (RC) box culverts deeply buried under uniformly distributed loads. Experimental data was used to calibrate the finite-element models of the RC box culverts and several parameters that impact the shear strength, such as span, rise, and the top slab’s thickness, were investigated using numerical models. The results of 210 case studies assessed AASHTO’s methodology for determining the shear strength of the top slab of a box culvert. A comparison of the results of the analysis with the equations in the specification indicated that AASHTO’s approach results in an underestimation of the prediction of the concrete shear strength (the β factor); however, the difference is reasonably acceptable in predicting the strain value of the longitudinal rebar. The comparison revealed, on average, an 89% difference in the prediction of the β factor and a 19% difference in the prediction of the strain in the longitudinal rebar in the shear critical section, which is at a distance d from the haunch. The regression analysis proposed multivariable formulations to predict the shear strength of the concrete in the shear critical section of the top slab of RC box culverts.