Finite Element Model Updating Of Suspension Bridge And Sling Safety Performance Assessment During The Whole Life Cycle

The safety of hangers of suspension bridge during operation is one of the most important factors, Due to the complexity of cable system and the lagging study on damaged cable, there is not a systematic research for cable about mechanism analysis, damage identification, mechanic calculation and safety evaluation of damaged cable. This paper mainly study the damage of sling and the safety of sling after injury, discussing around sling damage identification and degradation model and safety of sling. By using the research method of combination the experimental model and simulation analysis, the change of the static and dynamic characteristics of suspension were studied caused by the injured sling, using finite element software to do simulation analysis the damage identification of sling, creating degradation model of sling and after safety performance evaluation of the injured sling. In order to accomplish the above tasks, the main contents are as followings:1. Based on the engineering background of he left Ma’anshan bridge Branch bridge, a small scale suspension bridge model with the scale ratio 1:80 was built according to the similarity theory and the model tests were carried out to obtain both of the static and dynamic experimental data.the study on the effects of bridge displacement and cable force change caused by the damage of the cable is carried out, and the influence of the cable force change on the bridge health status is discussed. This physical model was used as a baseline model for the study of cable-stayed bridge of structural health monitoring and damage identification.2. To provide an accurate basis for structural damage identification and safety monitoring of suspension bridges,Using step correction model strategy to update finite element model of suspension bridges, and multi-response target functions were constructed, including frequency response residuals, modal response residuals and displacement response residuals. The results show that, to establish a finite element model which reflecting the static and dynamic response of suspension comprehensively, the residual term of static and dynamic response should be included in the objective function. Such modified model has a high accuracy, whether in the dynamic response containing the original bridge frequencies, mode shapes, etc, or in the aspect of static response including displacement, cable tension and so on. The results obtained provide reference values for FE model updating of long-span cable-supported bridges.3. For the thorough research of the damage identification and location of suspension bridge’s hangers, i make the finite element model of the whole bridge by the finite element software-Midas. This paper discusses the change situation of structural multiple order modal in the different degree of damage. By the index of susceptibility and the numeric analysis,we can achieve the identification of the degree of damage, and accurately、reliably、effectively identifies and locate the damage of hangers by this way.4. The paper studies the four stages of degradation mechanisms of sling and calculation formula of degradation time, and established theoretical relationship between the degree of degradation and resistance reduction coefficient, and then discussed the safety analysis method of sling which broken wire considers the effect of Daniel, Finally, Taking an example of the 3rd sling of left Branch Bridge of Ma’anshan bridge, conducted theoretical calculations of degradation time of sling and security calculations of sling after degradation. The method is purely a theoretical calculation, and there was an error between the real data and it, if combined the real monitoring data and used it after parameter modification, can improve the scientific of the strategy of preventive maintenance greatly.