Study On Structural Characteristics And Carrying Capacity Of Cable-stayed Bridge Under Changes In Cable Force

Whether studying the structural response of of the bridge,or monitoring the health of the bridges for long-term,an accurate and effective "baseline" finite element model is essential. But,the deteriation of structural state for cable-stayed bridge is inevitably occoured due to material aging and overloading during the service life.Therefore,the updated model should be built with the measurement of the field test,which correlates the analysis model with the currently structural state.For cable-stayed bridge,the model updating involves in not only the the material parameters but also the cable forces since the values of the cable force actually deviate from the design values due to construction error,loading and creep.Moreover,the corrosion may cause the lapse of the cable,and the service life of the cable is only 20 years. As result,it is necessary to study the effects of the cable lapse on the global safety of the bridge and to simulate the structural behaviour in the case of replacing the cables without closing the traffic.The objective of this dissertation is to update the analysis model and to study the structructural characteristics for Shengli Yellow River Cable-stayed Bridge in service for many years.The main contents of the study are summarized as following:(1) The state of the art of the structural analysis,health monitoring and model updating for cable-stayed bridge is briefly analyzed in the Chaper 1.The research objective and contents are extracted from the real situation of Shengli Yellow River Cable-stayed Bridge.(2) An approach based on ANSYS is developed to adjust the cable force,which can be applied to the model updating for Shengli Yellow River Cable-stayed Bridge.An initially finite element model is built with the design parameters of the bridge.Then the different structural systems for cable-stayed bridge as well as the method for model simplification are studied respectively.It is found that the construction order has the important effect on the state of the accomplished bridge for structural modeling.By using of the technique of element killing and birth,an ANSYS-based program is proposed to simulate the structural state under the different construction sequence.(3) The objective fimction for model updating of large-scale cable-stayed bridge is presented to correlate the analysis responses of the 3-D finite element model with the measured data of the deflection and cable force.With the measuremets of the deflections and cable forces,the structural model is updated by chaging the cable forces,and a sensitivity analysis-based algorithm is proposed in the study.The numerical simulations are carried out in the ease of removing the stayed cables in the different positions,and then the carrying capacity of the bridge is studied.The static and dynamic characteristics of the bridges are analyzed before and after the cable lapse.The strategies of adjusting the cables are also proposed in the event of cable lapse.(4) The dynamic properties of the Shengli Yellow River Cable-stayed Bridge are studied, which provides the basic parameters for structural health monitoring.