The Condition Assessment Research On A Long-span Suspension Bridge Based On The Dynamic Characteristics

At present, the long-span suspension bridge has become the first bridge of long-spanbridge. Its traffic position is important, and has very high sensitivity about the externalenvironment and dynamic loads such as the wind, the earthquake and the vehicle. And itsformation of corrosion and fatigue are easily damaged. People concerned about the safety，thedurability and the applicability and their attention degree enhances unceasingly. Thus it isnecessary to research on a long-span suspension bridge condition assessment based on thedynamic characteristics. In recent years, the development of technology of the vibrationtesting, modal analysis and damage location provide the necessary guarantee for the bridgecondition assessment. This paper take the based on the Bapan Gorge Suspension Bridge as theresearch background, exploring and researching on the problems meet in the process of thecondition assessment.This paper summarize in detail about the commonly used method of bridge structurecondition assessment in recent years, setting up condition assessment model as the pointcut,highlight the member damage impact on the dynamic characteristics of long-span suspensionbridges, and using grey correlation analysis theory to comparative analysis the safetycondition before or after reinforcement on the Bapan Gorge Suspension Bridge. The mainwork of this paper is as follows:Firstly, summarize the method of structure of the bridge condition assessment,establishing the evaluation model based on dynamic characteristics, and making a relationshipbetween the condition assessment index and the suspension bridge safety state evaluation.Secondly, expounding in detail the theory of grey relation analysis, summarizing thecalculation method of grey correlation degree, and making the grey correlation analysis theoryapplied to the real bridge condition assessment.Thirdly, according to the actual structure of suspension bridge and the differencesbetween the theory of finite element calculation model, to make a sensitivity analysis ofparameters on the cable tower，stiffening girder, main cable and hanger of Bapan GorgeSuspension Bridge, choose the main cable stiffness and stiffening girder stiffness to becorrection parameters，and combining with the static and dynamic measured data forcorrection finite element model of the bridge.Fourthly, research on the structural dynamic characteristics of suspension bridge, andmaking an analysis of suspension bridge based on main cable damage, stiffening girderdamage, cable tower damage and hanger damage on the Bapan Gorge of Suspension Bridgenatural frequency of vibration influence. Through research that main cable damage, cable tower damage，hanger damage and fracture impact on the natural frequency of vibration isvery small, but stiffening girder damage impact on the natural frequency of vibration is verybig.Fifthly, with the top15order natural frequency of vibration of the Bapan GorgeSuspension Bridge for condition assessment index, and take the condition assessment methodfor grey correlation analysis theory, calculating the grey correlation degree by the greyweighting correlation degree method and the gray comprehensive correlation degree method.Then proceed to assess the safety before or after reinforcement on the bridge. Throughresearch that the entire safety of this bridge after reinforcement is close to the finished bridgestate.