Failure Mechanism And State Evaluation Of Hinged Joint Of Hollow Slab

Small and medium-sized bridges account for a large proportion of the total number of bridges,damage of hinge joints is an important reason for the failure of such bridges.Based on a large number of existing researches on new-old concrete interface and interface of hinge joint,combined with indoor model experiment and data acquisition.The finite element analysis model is established.The failure mechanism of hollow slab beam are studied,the main research contents are as follows:(1)Customized formwork,casting 8 test models,the destructive test was carried out by loading in the mid span with supports.Considering concrete strength,and top shear reinforcement and bottom reinforcement,the test sample was designed,describing the failure state.During the whole process of the test,lateral and vertical displacement of bottom of hinge joints were collected.This paper described the failure model of hinge joint,and the results of destructive test show that the failure of hinge joint is destruction without obvious signs after bottom of the hinge joint is opened.It also shows that the inner of hinge joint is easyly to be damaged,which is closer to the loading position.The paper analysis theoretical of the failure phenomenon,and reveals the damage mechanism of the hinge joint.(2)Considering the shear reinforcement at the upper part of hinged joint and the door reinforcement at the bottom.The paper compares GB50010-2002,ACI 318-08,AASHTO,CSA A23.3-04 code with the formula in this paper.The results show that the calculated value is agree well with the experimental value.(3)It is established the refined numerical finite element model of the destructive test sample,considering bonded interface unit.By comparing the test results and finite element calculation results,the test verify the accuracy of the numerical model.Furthermore,it is compared the failure state of the test sample with the numerical model,shows that the distribution characteristics of the slip value and the shear stress value along the different height of the hinge joint.The results show that the shear stress at the top of the hinge joint is larger than that other positions.(4)Relying on two bridges of 8m slab girder,it was set vertical and horizontal displacement meters at the hinge joints of slab girders,with 500 Hz of sampling frequency.When vehicles passed,the test data were collected continuously for 72 hours.And the probability distribution function of the samples is obtained by non parametric hypothesis test method.It is judged that the service safety performance of hinge joint,based on the statistical eigenvalue of probability distribution.The test results show that the vertical deformation of hinge joint is not significant under the action of vehicle live load.The transverse opening value is obvious,so it is suggested to use the transverse opening value at the bottom of hinge joint to evaluate the safety state of hinge joint.(5)It is established the refined numerical model of spatial finite element.Based on the results of numerical simulation,it is established the relationship between the equivalent elastic modulus of hinge joint and the opening value of bottom of hinge joint,which provides theoretical support for the safety assessment of hinge joint.Furthermore,the paper is considered the mechanical performance analysis of hinge joint under the action of vehicle live load,and put forward the calculation method of limit value of hinge joint in normal use stage.