Research On Damage Evaluation Method Of Tie Bars In Caiyuanba Bridge

It is especially important to carry out health monitoring and safety evaluation in service period of bridges due to the decrease of bridges'safety resulting from exterior factors such as vehicles, wind and interior factors such as fatigue effect.The main structure of Caiyuanba Yangtze Bridge in Chongqing, up to date the largest-span tie bar arch bridge, is formed by two side tie bars and one middle tie bar which unite the Y-shape rigid framework and arch rid . Therefore, tie bars are one of the key components. Based on Caiyuanba Yangtze Bridge project, the static and dynamic evaluating indexes and threshold values of tie bars are analyzed in this paper, which aims to provide an important reference data for the safety evaluation scheme of the bridge.In this paper, the stubble, rust of tie bars and destruction forms of anchorage device are considered equivalent to the loss of tie bars'sections which is the analysis parameter of this paper. And then the variation laws of static response and dynamic characteristics under different work conditions are analyzed in this paper. The content of this research mainly include:1) with the increasing loss of tie bars'sections, variation laws of cable force, internal force and displacements in each monitoring spots are analyzed on work conditions of constant load, light rail, automobiles and temperature. On this basis, the evaluating indexes of safety state of tie bars are determined.2) On the basis of calculation, evaluation indexes are quantified according to the following four conditions: normal state, regular observation, regular warning and urgent warning. Then, the static evaluation threshold value of tie bar is preliminarily determined.3) Based upon analyzing the variation laws of bridge's dynamic features, it is proposed in this paper that structure frequency and mode of vibration should not be used as the"dynamic index"of cable force dynamic evaluation, because the variation of structure frequency and mode of vibration resulting from tie bars'loss is very small.