Safety Assessment System For Hollow Slab Bridge Based On Routine Testing

With the development of C hinese economy, more and more bridges on the highway appear. Because of the effect of the factors such as overloading, the design capacity of some of the bridges do not conform to the current requirements of use though they are still in service. While the new bridges could be damaged due to the defects in design or construction, and these damages are threatening the safety of the bridges in different extent. Hollow slab Bridges are widely used in highway Bridges due to their simple structure, suitable for standardization construction, and the advantages of convenient construction, etc. And with such larger proportion,their security problems are relatively more than others. Under the above background, in this paper, hollow slab bridges as the research object, specific to the study of the safety assessment problems, main includes:①Firstly, we classified and analyzed the common damages of hollow slab bridges, and made detailed introduction of the damages with representativeness and universality.②In a span of 10 m of ordinary reinforced concrete slabs and the bridge of 13 m, 20 m prestressed concrete slabs bridge as the prototype, the Midas Fea models were set up(no damage hinge joints, a single hinge joints damage, adjacent two hinged joints damage) to simulate the hinge joints damages with degree in 20%, 40%, 60% and 80% respectively. By analyzing the deflection transverse distribution coefficient in different damage degree, we can confirm the impacts of the hinge joints damage on the safety performance of hollow slab bridges.③We established FEA models reflecting the true state of structure of 10 m ordinary reinforced concrete and 20 m prestressed concrete slabs bridge by Midas Fea. With the fracture height as the study parameter, we made the nonlinear finite element analysis for the monotonous loading and repeated loading to study the inner force and deformation conditions of hollow slab bridges under different crack states, and built slabs bridge safety assessment technology based on the degree of crack propagation eventually. Also we made analysis on the occurrence of the beam end longitudinal cracks of prestressed slabs bridge model.④With the premise that the concrete strain reached the ultimate strain in the main bean compressive zone, by means of mathematical analysis, through the analysis of various determining factors, we established permanent deformation limit value formula of hollow slab bridges which are easy to use. Then, through Midas C ivil, we set up prestressed concrete slabs bridge FE models in span of 13 m, 16 m, 20 m respectively to study the impacts of downwarping on slabs bridge caused by the loss of prestress. By comparing the limit value formula with the FE simulation results, we got the conclusion that the limit value formula in permanent deformation theory can be used for slabs bridge safety assessment.The research results of this paper has good prospects for application. It not only provides a good theoretical and practical basis to evaluate the safety of the hollow slab bridges objectively, but also has positive practical significance to ensure the safety of slabs bridges.