Research On Hinge Joint Damage Identification Method Of Hollow Slab Bridge Based On Influence Line Of Lateral Load Distribution

In China,hollow slab bridge is widely used among small and medium span bridges because of its simple form,convenient construction and low cost.As the main component of hollow slab bridge,hinge joint plays an important role in ensuring good lateral load distribution performance of the bridge.With the increasing traffic and load levels,hinge joint damage has become the main disease form of hollow slab bridge.If it cannot be found and treated in time,hinge joint damage may lead to the phenomenon of “Single Plate Load Effect” and seriously endanger the structural safety.Therefore,it is of great significance to carry out the research on hinge joint damage identification method to ensure the safety of hollow slab bridges.In this paper,the variability of influence line of lateral load distribution with hinge joint damage is analyzed,and three damage identification methods are proposed.The main research work is as follows:(1)Based on the commonly used hinge plate method and the existence of relative displacement between damaged hinge joints,the hollow slab bridge is reasonably simplified as a rigid plate analysis model connected by springs.The force method is used to solve the shear force between plates and the lateral load for each beam.And the calculation method of influence line of lateral load distribution of hollow slab bridge with hinge joint damage is proposed.Based on the grillage method,the finite element model of a hollow slab bridge is established and the hinge joint damage is simulated by changing the stiffness of the virtual beam.The results of the finite element model verify the rationality and accuracy of the lateral force analysis model and the influence line calculation method under hinge joint damage.(2)Based on the lateral force analysis model of hollow slab bridge with hinge joint damage,the variation of influence line of lateral load distribution under hinge joint damage is explored.Firstly,the influence of hinge joint stiffness degradation on the vertical scale value and slope of the influence line is deduced through the simplified mechanical model,and the reasons for the intersection phenomenon and slope change of the influence line at the damaged hinge joint before and after the damage are explained.Then,taking the typical hollow slab bridge as the analysis object,the variation of influence line under single damage,multiple damage,different slab beam number and section parameters is analyzed and verified.(3)Based on the variation characteristics of the influence line of lateral load distribution,a method is proposed to identify the damage location of the hinge joint by using the cross coordinates of the intersection point of the influence line before and after damage.In order to solve the problem that the whole damage locations under multiple-damage conditions and the damage degree cannot be identified by the intersection phenomenon,the average value of slope ratio between the measured influence line and the original influence line at each hinge joint is defined as the damage identification index,and the method of hinge joint damage location and quantitative identification based on the index is proposed.In order to solve the problem that the slope indices of influence line change under different beam-section conditions,based on the lateral load analysis model of hollow slab bridge,a method for damage location and quantification is proposed based on the relative flexibility index of hinge joint by the value of influence lines.In the process of solving,the non-negative linear least square method is introduced to ensure the correctness of the results.Finally,the applicability and effectiveness of the three damage identification methods are verified by finite element numerical simulation under various working conditions.