Research On Damage Mechanism And Strengthening Technologies Of Slab Bridges

Slab Bridge is an important component of medium and small span Bridges in China,many slab bridges have been constructed for a long time.Due to low bridge design standards,poor construction quality,vehicle overload,insufficient maintenance and other reasons,a large number of slab bridges have occurred many diseases,the most typical diseases are the longitudinal cracking on beam bottom and the hinge joints damage,result in structural integrity decreasing.This paper takes simply-supported concrete slab bridge as the research object,the main research contents and conclusions are as follows:(1)The development history and present situation of slab bridge are reviewed,this paper also elaborates current calculated theory,furthermore,the researches clarifys current analysis of damage mechanism and reinforcement technologies.(2)Based on the thin plate bending theory,the Ritz method was used to derive the analytical solution of the simply supported plate beam under concentrated force.Taking a 10 meter span slab girder under concentrated load as an example,using the analytical solution to calculate the results,by comparing the results with the rigid plate method and the hinged plate method,the accuracy of the analytical solution was verified.(3)For the beam with a certain width,assumed that it was assembled by several component.The shear envelope diagram of hinge joints with different assembly numbers was drawn,and the optimal assembly numbers were obtained.(4)The solid element model of ABAQUS was established to study the hinge joint damage problem of the fabricated slab bridge.By changing the load,the regularity of stress in the hinge joints was analyzed,founded the most unfavorable loading location.By comparing the difference of load lateral distribution coefficient between the solid element model and the hinged slad method,the study discussed the influence of hinge joint damage degree and position to the integrality of the structure.The results show that: the calculation coefficient of the hinged slab method and the solid element method are similar.When the damage degree of hinge joints is above 60%,the integrality of the structure will be distinctly reduced.(5)Testing and analyzing an existing bridge.First,the study compared the new bridge design specification and the old specification,and then,calculated the ultimate state according to the new and old design specification.The results show that the structure resistance by the means of the new and old specification is similar,but the combined value of load effect by the new bridge design specification is bigger than the old specification value,it means that the early constructed bridge may not meet the requirements of contemporary bridge design specification.Then,according to the evaluation of the the static load experiment,the finite element model of damaged hinge joint was established.By comparing with results of bridge technical condition,the accuracy of the model is proved and the damage level and position of the hinge joints are demonstrated.(6)In the end,based on the model of damaged slab bridge,the paper discussed the improvement effect on the integrality of the transverse prestress reinforcement method and the steel beam reinforcement method.