| Corrugated steel web combined box girder bridges have many advantages and are widely used at home and abroad.However,due to the presence of numerous corners in its web,it is easy to deposit harmful impurities.China has an extensive chloride salt corrosive environment,and chloride ion-induced corrosion of reinforcement and exposed steel and concrete strength degradation are important causes of bridge load carrying capacity deterioration.At present,the research on the residual load carrying capacity of waveform steel web combined box girder bridges is mainly focused on fatigue damage.To this end,this thesis uses ABAQUS to establish a refined model of a waveform steel web composite box girder bridge to investigate its remaining bearing capacity and reliability under chloride salt environment.The main research contents and conclusions are as follows:(1)The nonlinear analysis of the waveform steel web combined box girder bridge was carried out by ABAQUS,and the results showed that the concrete slab mainly resisted bending and the waveform steel web mainly suffered shear,and the obtained finite element values of mid-span deflection were basically consistent with the values calculated by theoretical equations.The above results verify the correctness of the finite element model.(2)The failure form of the corrugated steel web composite box girder bridge under the limit state and the stress of each component were analyzed by ABAQUS,and the obtained load-span mid-deflection curve was roughly divided into three stages: elasticity,plasticity and unstable state,and the unstable state was manifested as that even if the applied load no longer increased,the mid-span deformation gradually increased.The load-beam end slip curve indicates that the slip value of the composite box girder interface before failure occurs.(3)Based on "Code for Design of Concrete Structures",the parameters of the concrete plastic damage model were calculated by writing a program in Excel,and then the two parameters of the concrete strength grade and the thickness of the corrugated steel web of the composite box girder were analyzed by using ABAQUS.The results show that both the concrete strength and the thickness of the corrugated steel web have a great influence on the ultimate bearing capacity of the corrugated steel web composite box girder bridge.(4)Considering the unfavorable service environment of chlorine salt that the bridge may be in,the performance degradation of concrete materials,steel bars and steel materials that may be caused by chloride ion diffusion and corrosion of steel and steel is studied,the time-varying model of concrete and the constitutive relationship of steel bars and steel with different degrees of rust are established based on relevant prediction models and specifications,and they are introduced into numerical simulations to establish a timevarying deterioration model of bridges,and the ultimate bearing capacity and interface slip of the corrugated steel web composite box girder bridge under different years are studied.The results show that its ultimate bearing capacity increases slightly in the first10 years,after which the decline is larger in the early stage,and the decline in the later period becomes smaller,and the decline rate has exceeded 28.6% in 70 years.None of the interfaces exhibited large slip values before the failure,indicating that the use of TwinPBL shear bonds was reasonable.(5)The time-varying resistance model is established based on the limit state of the corrugated steel web composite box girder bridge by ABAQUS,and the constant load effect model and the time-varying load effect model considering automobile load are established through ABAQUS and Dload subprograms.On this basis,the JC method calculation program is written by MATLAB,and its time-varying reliability index is obtained,and its service life is predicted to be 68 years through the minimum reliability index of the bridge. |
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