Finite-Element Modeling and Analysis of Reinforced Concrete Box Culverts

There have been several controversies with regard to the true behavior of reinforced concrete box culverts in recent years. To be able to conduct a parametric study to develop design equations, a complete three-dimensional verified finite-element model of culverts is essential. This study presents the development of an analytical program to investigate the shear capacity of precast reinforced concrete box culverts. To simulate the experimental results, complete and detailed three-dimensional finite-element models (FEMs) of the test specimens were developed and analyzed. Three-dimensional shell and solid elements were used to model the culvert systems. The welded wire fabrics were modeled by using the rebar elements placed on the surface elements provided by the ABAQUS software. The contact surface between the outside face of the bottom slab and reaction floor was modeled by using a nonlinear node-to-surface contact analysis procedure. The analysis procedure consisted of an incremental loading history to capture the problem of nonlinearity. The load was placed at a distance $d$ from the tip of the haunch of the box culvert, where $d$ is the effective depth of tension reinforcement at mid span, in the top slab of the box culvert. To simulate the wheel load a $25.4\mathrm{cm}$ $\left(10\mathrm{in.}\right)\times 51\mathrm{cm}$ $\left(20\mathrm{in.}\right)$ plate is used experimentally as well as in finite-element modeling, which is used by AASHTO to model the wheel load of a HS20 truck. The smeared crack model along with the Riks analysis procedure were incorporated to analyze the system for microcracks and to stabilize the solution, respectively. The converged solution was obtained by using $H$ convergence coupled with the difference between the external work done and the strain energy density of the system. The load-deflection plots obtained from the FEM analyses were compared with those obtained from the experimental results, which showed close correlation.