Study On Load Limit Of Heavy Transport Considering Simplified Analysis Method Of Curved Girder Bridge

Curved girder bridges are not only able to adapt to the constraints of complex route structures,but also have the advantages of beautiful lines and small footprint,and are widely used in mountainous roads,urban interchanges and highway ramps.On the other hand,large transport vehicles are responsible for the protection of major national projects and key equipment manufactured in China,and their gross vehicle weight is generally significantly higher than that of conventional vehicles,posing a threat to the safety of curved girder bridges during the operational phase.Therefore,to address the above issues,a simplified analysis method for curved girder bridges and the load limits under the action of bulky vehicles are investigated.The main research elements and conclusions are as follows:(1)On the basis of the random vehicle-Bridge Dynamic Analysis System(BDANS)developed by the research group,the vehicle-curved girder bridge coupling vibration analysis system was further developed,and the bridge scale model test was carried out to verify the analysis system.The results show that the accuracy of the analysis system meets the engineering requirement.(2)The structural parameters of curved girder bridges commonly used in engineering are obtained through bridge survey and analysis,including bridge span,bridge width and curvature radius,and 80 groups of bridge parameters are obtained through cross combination.Then,the girder lattice model and single beam model of bridge under each group of structural parameters are established respectively.By analyzing and comparing the characteristic responses of the two models,such as fundamental frequency,dead load support reaction,shear force and bending moment under dead and live load respectively,the errors of fundamental frequency and dead load support reaction exceed 5% when the bridge width is 16 m.The shear force,relative error of bending moment under dead load and relative error of bending moment under moving load are all within 10%.Based on the control error requirements of each characteristic response,the range of structural parameters for simplified modeling analysis of three-span curved box girder bridges can be obtained by using single beam method,and further extended to the simplified modeling applicability analysis of four-span curved box girder bridges.(3)Based on the established three-span curved box girder bridges lattice model,the bending moment and torque effects under dead and live load were taken as the characteristic responses of straight bending analysis,and the correlation between the straight bending errors of each characteristic response and structural parameters such as span,width and radius of curvature was determined by fitting the calculation formula of the changes of the straight bending errors of different characteristic responses with multiple structural parameters was obtained.Based on the requirement of 5% control error,the limit of structural parameters for the analysis of bending moment and straight bending of three-span curved box girder bridges is determined to be 1.13,and the limit of structural parameters for the analysis of torque is 0.5.(4)According to the engineering reliability theory,the function function of curved girder bridges under the action of large vehicles is established based on the limit state of bearing capacity.The simplified analysis method obtained in the previous study is used to model four curved girder bridges.The JC method is used to iterate the positive bending moment effect threshold under different target reliability indexes.BDANS software was used to calculate the positive bending moment effect of curved girder bridge under different axle loads of large vehicles,and then the load limit of large vehicles under the most unfavorable driving condition was calculated.The load limit of large vehicles varied with the target reliability index in different bridge widths.