Research On Tension Testing Method For Suspender Of Arch Bridge

Half-through and through arch bridge is a new type bridge which is widely used.With its good spanning ability and beautiful shape design,it is favored by the majority of designers.However,in recent years,there have been many collapse accidents of arch bridges at home and abroad,resulting in many casualties and enormously economic losses.According to statistics,most accidents are mainly caused by anchorage failure and corrosion as well as fracture of suspenders of arch bridges.As the main bearing component of the through arch bridge,the suspender determines the safety and service life of the bridge to a certain extent.Therefore,it is of great significance to identify suspender tension of half-through and through arch bridge.Taking the Liujiang Yellow River Bridge in Zhengzhou as the research background,the tension identification of suspenders of half-through and through arch bridge is studied in this paper.The main contents and conclusions are as follows:（1）In practical,there are many methods for measuring suspender cable force.This paper compares and analyses the measuring methods from their working principle,application scope,accuracy requirements as well as advantages and disadvantages.It is found that vibration frequency method is widely used in practical at present.This method has mature theoretical basis,field testing is simple and also could adapt to various working conditions.However,the accuracy of this method is affected by various factors.（2）Based on the principle of structural dynamics,the influence of complex boundary conditions such as rotation constraint,bending stiffness and viscous sheath on the identification of suspender tension is considered.The analytical expression between suspender tension and vibration frequency is deduced by establishing the calculation model of suspender tension.In order to facilitate engineering application,the concept of boundary influence coefficient is proposed,and the practical expression of suspender tension under arbitrary rotational restraint stiffness is given by piecewise fitting method.Taking the Liujiang Yellow River Bridge as an example,the accuracy of the implicit expression is verified.By comparing the twice tension data of suspenders,the accuracy of the implicit expression is similar to that of the practical expression,but the practical expression overcomes the shortcomings of the cumbersome calculation of the implicit expression,highlights the advantages of simple calculation and strong practicability of the practical expression.（3）The suspender vibration model considering the influence of boundary conditions such as rotation constraint,bending stiffness and elastic support is established,and the implicit expression of suspender tension is derived.Due to the complexity of calculation,the explicit expression of suspender tension is deduced by using the dynamic response of suspender.By identifying the boundary conditions of the suspender,the embedding coefficients B₁、B₂reflecting the rotation constraints and the parameters k reflecting the elastic support are calculated.This method can skillfully avoid the numerical calculation of the rotation constraints and the elastic support of the suspender.Recognition of suspender tension according to the explicit expression and the parameter identification results verify that the advantages of high accuracy and practicability of the expression.（4）Comprehensive considering the influence of factors such as bending stiffness,length,cushion,additional mass,elastic support,viscous sheath,ambient temperature and so on,the calculation model of suspender tension under complex boundary conditions is established,and the relationship between suspender tension and vibration frequency is given.According to the boundary conditions,the influence coefficients are defined,and the boundary influence coefficients of suspenders of arch bridges are calculated according to different boundary conditions.In addition,the practical expressions of suspender tension considering viscous sheath,ambient temperature and boundary conditions of suspenders are given.The Liujiang Yellow River Bridge is taken as an example to verify that the influence of ambient temperature cannot be neglected when the suspender tension is tested during the operation period.At the same time,it shows that the practical expression deduced by the boundary influence coefficient method has the characteristics of high accuracy and wide application for suspender tension identification.