Suspender Force Detection Of Tied Arch Bridge And Deviation Influence Factors Analysis

Suspender is one of the most critical load-bearing components of tied-arch bridges,the force of the suspender has always been an important indicator for the construction control of the tied-arch bridge and the guarantee of operation stages.Summary in recent years,the collapse of the arch bridge found that most of the causes were caused by failure of the anchorage of the suspender or corrosion and fracture of the suspender.Therefore,it is of great research significance to identify and detect the tension of the suspender of the mid-through arch bridge.In this paper,the most widely used frequency method to measure the cable force is studied.This paper focuses on the most widely used frequency method to determine the cable force,taking the tension test of suspenders of the through tied arch bridge in Xucun of the new Heshun-Xingtai railway as the background.Calculation formula of cable force identification based on the frequency method,and the main influencing factors of the deviation when testing the cable force of the derrick boom with the frequency method are analyzed.The specific research content is as follows:The structure of rigid suspender and flexible suspender is introduced.For the most widely used flexible suspender of mid-through arch bridges,the advantages and disadvantages of the main methods of cable force testing are analyzed.the basic principle of testing cable force with suspender frequency method is described,and the vibration model of derrick axial force beam considering bending stiffness is established,the solutions of the basic vibration equations under three kinds of boundary conditions are given.In view of the fact that no explicit solution can be obtained under the boundary conditions of one end hinged at one end and two ends consolidated,a large number of relevant literatures are sorted out,the representative practical cable force calculation formulas are summarized and analyzed to summarize the cable force calculation formulas.It is a basic mathematical model.The concept of tension bending ratio?is introduced,and the calculation formula of cable force based on?with only one parameter a to be identified is established.By changing the form of vibration frequency characteristic equation of cable under the boundary condition of consolidation at both ends and by dimensional analysis of?~2 and k,the vibration frequency characteristic equation is only related to?~2 and k,and these two dimensionless parameters are only related to the bending rigidity,linear density,calculated length and cable force of suspender.It is verified that the linear relationship satisfied by?~2 and k is applicable to any suspender situation.Then use ANSYS finite element software to establish the finite element model of the suspender under the condition of consolidation at both ends,by changing the length of the boom and the tension of the boom,the fundamental frequency of the boom under different?is obtained,and then the value of k and the proportional coefficient A about?~2 and k are calculated.After numerically fitting the data,the cable force calculation formulas in different?intervals are obtained,and the accuracy of the calculation formula established in this paper is verified with other commonly used calculation formulas of cable force,the results show that the error of the established formula is basically controlled within 1%.Among the many influencing factors of the frequency method for measuring the suspender force,the influence of bending stiffness,boundary conditions,cable length,and cable force on the frequency of the short boom is particularly significant.The ANSYS finite element model of suspender under different boundary conditions is established,and the results of the first five frequencies are analyzed.The results show that with the decrease of?,the difference of frequency values under different boundary conditions is more and more significant;For the influence of bending rigidity,the frequency data of chord element suspender model and beam element suspender model are compared and analyzed.For the short suspender considering bending rigidity,the cable force calculation with low frequency should be used as far as possible to reduce the error.The comparison between the elaborate steel strand model and the round rod model shows that the actual bending stiffness of the boom is difficult to identify,and a method for identifying the bending stiffness using the cable force formula established in this paper is proposed.Based on the construction monitoring of Xucun tied arch bridge,this paper introduces the whole bunch of extruded derrick boom,Apply the linear calculation model of cable force and frequency square and cable force calculation formula established in this paper to the cable force tension test phase,then theoretical cable force,measured cable force and the existing simplified formula are compared and analyzed,and satisfactory results are obtained.