| Simply supported hollow slab is a widely used form of girder element for small span girder bridges in China,mainly because of its advantages such as excellent flexural strength,light weight,low cost.However,due to the unfavorable factors such as small web cross-section,longitudinal gap between the plates,the lateral connection of the girders is weak and prone to hinge joint failure after long-term used,followed by cracks at the bottom of the slab,stresses on the single slab of the girders,as well as cracking and pot holes in the pavement,which endanger the structure and traffic safety and affect traffic comfort.Structural reinforcement of simply supported girder bridges is a necessary measure to restore bridges load-bearing capacity and performance,extend their service life,reduce financial burden,and ensure traffic safety.At present,large span concrete bridges are mainly strengthened with pasting steel plate reinforcement,pasting carbon fiber cloth reinforcement,polymer mortar reinforcement and increased section reinforcement,but not enough attention is paid to small span simply supported hollow slab girder bridges.In order to obtain an effective strengthening method for small span simply supported hollow girder bridges,this paper relied on the actual project,and carried out a three-dimensional nonlinear finite element numerical simulation analysis and selection of three representative strengthening solutions without interrupting traffic based on the analysis of the failure process and causes of hinge joint damage and field test evaluation.The influence factors of steel plate thickness,hollow slab length,inclination angle,and hinge joint location were analyzed for the selected paste steel plate reinforcement scheme,and the engineering application verification was carried out based on the analysis results.Main research contents are as follows.(1)Field research was carried out for the small span simple supported slab girder bridges with damaged hinge joints or hinge joint failure as the main disease in Shenshan section of Beijing-Harbin Highway.The different stages of hinge joint failure process were divided.The hazards after complete failure of hinge joints were theoretically analyzed.And the causes of hinge joint failure from design,construction and operation aspects were analyzed.Finally,a representative simple-span girder bridge was selected to carry out field static load test and compared with the theoretical calculation results to verify that the girder bridge was in an unfavorable state of single-plate stress after hinge failure.(2)For the actual characteristics of the small-span simply supported slab girder bridge,three reinforcement solutions were selected without interrupting the traffic.The three reinforcement solutions were paste steel plate reinforcement,paste fiber cloth reinforcement and polymer mortar-steel strand reinforcement program.After that,a three-dimensional nonlinear model was used to establish a computational analysis model for the strengthening of the simply supported slab girder bridge for comparison and analysis.The rebar unit of the simply supported hollow core slab was simulated by the Von Mises constitutive model,and the cement concrete unit was nonlinearly simulated by the rotating crack model;the stress and load displacement curves of the unreinforced beam and the above three reinforcement solutions were compared,and the paste steel plate reinforcement solution was determined to be the preferred solution.(3)For the selected reinforcement scheme,finite element modeling was carried out for a simply supported assembly pretensioning prestressed hollow slab bridge in an engineering project,and the influencing factors of reinforcement steel plate thickness,hollow slab length,hollow slab inclination angle and hinge joint position on the reinforcement effect were analyzed.The results show that the bridge deflection was significantly reduced after the reinforcement with steel plates,but the reduction rate did not change significantly due to the increase of the steel plate thickness,and the stress in the reinforced steel plate was much lower than its tensile strength.Under the premise that the length of steel plate remains unchanged,the increase of hollow plate length could weaken the reinforcement effect and increase the deflection significantly.As the inclination angle of the hollow slab girder bridge increases,both the tensile stress and deflection within the reinforced steel plates decreased.The location of the damaged hinge joint had no significant effect on the reinforcement effect.(4)Based on the results of finite element analysis,engineering application verification was carried out to determine the material technology requirements and corresponding reinforcement scheme to form the construction workflow.Material requirements were steel plate grade Q235 steel,4.6 grade steel bolt anchors,two-component modified epoxy resin structural adhesive(HM-120).The application results show that the reinforcement effect was good and the long-term performance was under continuous follow-up observation. |
