Experimental Study on Failure Mode of Precast Assembled Segmental Beams under Impact Loading

Precast segmental girder bridges are threatened by impact loads during service, but there is currently little research on the impact behavior of such bridges. This study investigated the dynamic responses and failure modes of precast assembled segmental beams experimentally and numerically. 10 beam specimens were designed for static and impact tests, respectively. Numerical simulations were conducted in LS-DYNA and verified by comparing them with the test results. Failure mechanisms were analyzed by verified models. The results show that the local shear failure mechanism is prominent under impact loading. Two typical failure modes were obtained: oblique section failure and joint section direct shear failure, which are related to the relative positions of joint and impact point. Confining stress can effectively improve the static bearing capacity and impact resistance, but has little effect on the early response and final failure mode. The main failure cracks occur near the joint bottom in the initial stage of impact, when the impact force is resisted by the inertia force, resulting in a characteristic “N” shape in shear force distribution. Shear failure of the joints dominates the beam failure mode. A dynamic shear span ratio can evaluate the early force characteristics of the joint section.