Experimental Study on the Construction Stages of an RC Closure Pour in Bridge Widening

Bridge widening is commonly required in congested bridges. During construction, one or two lanes on the old bridge remain open; the vehicle traffic generates vibrations affecting the early age concrete of the closure pour, which may induce a negative effect on the durability of the bridge, i.e., initial crack in the closure pour. To quantitatively evaluate the mechanical performance of closure pours under vibration load, this paper examined three construction schemes for closure pours in bridge-widening projects. An equivalent full-scale segment model was designed to test the three schemes, including vibration tests and static tests. In the vibration tests, the setting time, the development of deflection, strain, and cracking of the closure pour during the construction period were obtained. Adding I-shaped steel beams to restrain the movement of the old and new bridges significantly improved the performance of the closure slab. In the static test, the final load-carrying capacity, damage, and failure modes were investigated. The slabs poured with the restraining steel beams showed superior crack resistance performance. The peak load-carrying capacity of the closure pour was about 50 times the maximum expected load, demonstrating the satisfactory load-carrying capacity of the closure pour.