In this paper a numerical and an experimental study on reinforced concrete box culverts (BC) behavior is presented. A BC under a 9.5 m high embankment was instrumented and observed during the construction period. Numerical analyses were then performed using a finite-element code capable of considering the construction sequence, the nonlinear behavior of the reinforced concrete structure, and an elastic-plastic behavior for the soil and the interfaces. Once the computed results were in good agreement with the observed behavior, a parametric study was developed for the identification of the main parameters influencing the interaction mechanism and to evaluate the BC structural performance up to failure. The influence of the BC nonlinear behavior on the interaction mechanism, both in service and ultimate limit state conditions, was analyzed and discussed. It is concluded that the soil pressures and the BC nonlinear behavior are directly related and should be reflected in the design stage in order to achieve ...