Effect of wheel live load on shear behavior of precast reinforced concrete box culverts

This study reports on a part of a comprehensive study to evaluate the shear capacity of the precast reinforced concrete box culverts. Six full-scale 2.4 m (8 ft) span box culverts were tested to failure by subjecting each culvert to the AASHTO HS-20 wheel load. The location of the wheel load was varied from the tip of the haunch as a function of the top stab effective depth in order to identify the critical shear location. Each test specimen was loaded incrementally up to failure in which crack initiation and propagation were identified and recorded in each load step. In some specimens the top slab compression distribution steel was precluded during specimen fabrication the effect of which was shown to be insignificant in culvert's performance experimentally. Even though the test specimens were loaded to introduce shear behavior, it was shown that all the test specimens behaved in flexural mode up to and beyond standard factored live load. The test specimens only experienced shear cracks at loads equivalent to approximately twice of the aforementioned factored load. This study concludes that shear is not the governing behavioral mode for the concrete box culverts, and the live load distribution width equations along with the provisions for shear transfer devices for box culverts reported in the current standard need to be revisited.