Dynamic Response And Hinge Joint Damage Evaluation Method Of Prestressed Hollow Slab Girder Bridge Under Vehicle Load

With the rapid development of highway transportation infrastructure,bridges account for an increasing proportion of highway mileage.Prestressed hollow slab girder bridge is widely utilized because it is characterized by simple bridge type,convenient construction and good stability.However,large number of hinged joints damage appeared in the hollow slab girder bridge with increased serving time.At present,the identification of the joint damage is mainly through visual inspection,it is difficult to judge the actual damage degree.Most of the evaluation methods of the degree of hinge damage are based on the static load test,but the traffic has to be interrupted,so the cost is very large.Also the damage degree of joint can only be qualitatively evaluated by these methods,and it is difficult to quatitatively measure the damage degress.With the development of vehicle-bridge coupling,dynamic response analysis of bridges under vehicle loads has been widely used to evaluate the state of bridge.Therefore,a three-dimensional vehicle-bridge finite element model with different degree of hinge damage is created and its effects on the dynamic response of the bridge system are studied through LS-DYNA based on an actual project.Damage index is proposed in this work to judge the hinge disease,location and degree of damageFirst,through the investigation of the regular maintenence data of the prestressed hollow slab girder bridges in service on the Jinghu Expressway,the damage of bridge with two types of span are compared and analyzed,The statistical analysis of the hinge disease was carried out from the perspective of the number of diseased bridges and the proportion of holes.From the Hinge damage frequently happens at the two ends or middle of beam leading by the damage of bearing and overload.Therefore,a 13-meter prestressed hollow slab girder bridge and a vehicle finite element solid model are established.The influence of vehicle speeds and tonnage on the dynamic response index are investigated based on dynamic analysis through LS-DYNA.The results show that the fluctuation of the time-history curve became smoother under higher vehicle speed.The difference of the deflection of the beam-slab is very small at different speeds.The deflection of beam increases with vehicle tonnage.Compared to the vehicle tonnage,vehicle speed has greater influnece on the acceleration of the beam.Because higher vehicle speed has large impact on bridge resuling in the higher acceleration amplitudeThrough the statistical anlaysis of regular bridge maintenance reports,the damage location of the hinge joint(at the end and middle of beam)is determined in the numerical simulation Three damage degrees(25%,50%,75%,etc.),and different damage locations of the joint are simulated in the finite element model.The dynamic response of the bridge under different degrees of damage is calcuated.The results indicate that compared with the relative displacement and relative opening and closing,the jointing damage has greater influence on the acceleration of the beam plates close to both sides of the joint,and the acceleration response is the most sensitivest.For a beam with small part of joint damage,its relative displacement and relative opening and closing are relatively small by comparing to that of a pristine structrue,but the acceleration amplitude ratio changes significantly.Finally,based on the above research,an evaluation method for judging the degree of hinge damage is proposed,which is based on the amplitude ratio of the beam plates on both sides of the joint.The joint state can be regarded as intact when the accelearation amplitude ratio is close to 1.0;the joint damage degree is less than 25%when the acceleration anplitude ratio is at[1,1.51;The degree of damage is within[25,50%]when the the acceleration amplitude ratio is at[1.5,21;the degree of joint damage is about[50%,75%]when the acceleration amplitude ratio is at[2,2.5];it can be considered that the degree of damage of the joint seam exceeds 75%when the acceleration amplitude ratio exceeds 2.5,and the beam is in the state of“single plate”.The proposed method is utilized to evaluate the joint state of a prestressed hollow slab girder bridge of Beijing-Shanghai Expressway by measuring the acceleration history curve under regular vechicle loads.The results indicate that the 6#hinge joint of the bridge is in slight damage state.The proposed evaluation method can provide reference for the health assessment of the actural engineering joint without the interruption of traffic.