Research On Causes Of Cracks In Main Girder Of Cable-stayed Slab Bridge And Reinforcement Technology

While the cable-stayed slab bridge has the characteristics of continuous steel structure bridge and cable-stayed bridge,it also has its own advantages,such as reducing the height of bridge tower,reducing the cross-section of main girder,greatly reducing the cost and so on.However,most of the cable-stayed slab bridges in China were built in the 1990 s,which have been in operation for more than 20 years.Inevitably,the phenomenon of cracking of bridges occurs,which seriously affects the beautiful appearance of bridges and reduces the cost.The bearing capacity of the bridge structure endangers the operation safety of the bridge.Therefore,it is of great significance to study and analyze the causes of cracks in existing cable-stayed slab bridges and to find appropriate and effective reinforcement methods to prevent further damage to bridge structures according to the research results.Based on an in-service cable-stayed slab bridge as an engineering example,this paper mainly does the following research:(1)Based on the finite element software MIDAS/Civil,the member element model of the structure is established,and the effects of prestress loss,shrinkage and creep at different temperature gradients,different years,different vehicle loads and different cable force losses on the maximum principal stress of the structure are analyzed.The influence rules of different factors on the maximum principal stress of the structure are obtained,which can provide data support for further crack formation.(2)By means of simulation calculation,the sensitivity analysis of various factors affecting the cracking is carried out,and the main causes of the cracks on the web and floor are screened through sensitivity analysis.(3)Based on the finite element software MIDAS/FEA,the solid element model of the structure is established,and the damage model is established on the basis of sensitivity analysis.The crack direction and the crack width of the web of typical diseased box girder are analyzed.(4)According to the existing reinforcement technology and principle,the damage model is strengthened by four methods: Pavement Reinforcement method,bonding steel plate method,external prestressing reinforcement and combined reinforcement.The results of reinforcement are compared and analyzed,and the optimal reinforcement scheme is summarized to provide reference for similar bridge reinforcement in the future.