The Cable Force Adjustment And Internal Force Analysis Of Existing Cable-Stayed Bridge Without Backstays

There are more and more cable-stayed bridge without backstays construction projects,because of the appealing design as well as economy. However, due to reasons such as the design, construction and maintenance,some cable-stayed bridges are not in a reasonable internal force state,and it has some potential problems. In China, it’s the first example of established cable-stayed bridge without backstays for cable force adjustment and optimizes the internal force in the already built cable-stayed bridge without backstays,so it is necessary to solve and research those problem.In this paper, based on the Jinzhou main bridge in Dalian construction projects to study cable force adjustment,which spans103meters with the single pylon single cable plane,the main research content and result are as follows:Firstly,summarizing the history and main characteristics of Cable-stayed bridge without backstays,introducing the necessity and research status of established cable-stayed bridge force adjustment,stating the method of optimization of cables tensions,then according to the structure minimum excess principle to establish the optimal target function,introducing restraint condition of deformation,determining the target value of cable force adjustment,and introducing the process to achieve the goal of cable force adjustment.Secondly,analyzing the current measured alignment and the state of cable tension of Jinzhou Bridge,and compared with the design limits of the control specification,and the results show that the maximum deviation of cable force by40percent,the maximum deviation of main girder and main tower accounted for17cm and150cm,which is not meet the limit. According to the measured data to modify finite element model,analysis the current structure of the theoretical internal force state,as a result that stress does not meet the specification requirements,then make sensitivity analysis for change laws of cable force and feasible zone analysis for dead load stress,in order to determine the reasonable internal force state and final cable force after adjusting the tension force.Thirdly,putting forward two different types of cable force adjustment scheme,using the cable force、the stress and displacement of main girder、the stress and offset of main tower as analysis target,and comparing the scheme on their mechanical characteristics and the influence of linear structure,using mean-square deviation evaluate two kinds of cable adjustment, found that the dispersion degree of cable adjustment scheme from short to long cable is considerably larger than the scheme from long to short rope, and choose the latter as the actual cable adjustment,and calculate the cable force adjustment quantity and elongation of each cable in the process.Fourthly, appling the certain cable force adjustment order to Jinzhou bridge, according to the characteristics of the cable-stayed bridge without back cable, determine the construction technology, principle and monitoring content,after the construction monitor control of Jinzhou Bridge,the results show that the main girder displacement errors is less than0.3mm,the maximum deviation is7.4%,the main tower longitudinal offset errors within2.5mm,structural stress measured values agrees well with calculated value, Cable force errors within3%t with the maximum error is only1.58%,which indicates that construction monitoring gave good results, it has completed the cable force adjustment project of jinzhou bridge which is a Cable-stayed bridge without backstays successfully.