Experimental Study On Failure Mechanism Of Prestressed Concrete Hollow Slab Beam Bridge

With the rapid development of Chinese social economy in recent years, the contradiction between transportation needs and load capacity of existing bridges becomes more and more prominent due to the quickly increasing traffic flow and vehicle axle load. Affected by some harmful factors such as frequent overloaded vehicles, design defect, construction quality problem, environmental erosion, et al, the number of damaged or dangerous bridges gradually increased and quite a few of them need to be strengthened. The key problem of utilizing those old bridges properly is to deeply carry out the scientific research on load-carrying capacity assessment of in-service bridges and evaluate their damage degree, bearing potential, and safety reserve, et al, and therefore carrying out relevant research is of great significance for transportation safety and sustainable development of highway transportation construction in China.So, in this paper a comprehensive field experiment is performed using an existing prestressed concrete hollow slab bridge. The experiment includes three steps: first destructive test before reinforcement, strengthening test, and second destructive test after reinforcement respectively. Combined with test results and three dimensional nonlinear FEM simulation, the safety reserve, bearing potential, failure mechanism, as well as structural response of the prestressed concrete hollow slab bridge under ultimate loads are studied systematically. In addition, the influences of reinforcement on mechanical behavior and bearing capacity of the bridge are deeply analyzed. The main content can be summarized as follows:(1) Using a prestressed concrete hollow slab bridge, East Meng Jiang Nu bridge, which belongs to An-Xin expressway, a destructive test is performed. The variation laws of deflections, cracks, and strains of the bridge during test are obtained. Moreover, its failure mechanism, failure mode, and actual load capacity are studied.(2) For the damaged prestressed concrete hollow slab bridge which experienced first destructive experiment, a strengthening test research is carried out by applying longitudinal and transverse external prestressing to it. The reinforcement technology and progress of external prestressing to the bridge are preliminarily summarized. The changes of bearing capacity and mechanical state of the bridge after reinforcement are also investigated.(3) Based on the test results and using the FEM software, ANSYS, a three-dimensional (3-D) finite element (FE) simulation study on the twice destructive test of East Meng Jiang Nu bridge is carried out considering material nonlinearity. The bridge's mechanical responses and failure mechanism during the test are deeply discussed. In addition, the influences of external prestressing reinforcement on the mechanical behaviors and damage mechanism of the bridge are explored.