The Research Of Safety Assessment For Long-term Monitoring Bridge Based On Nonlinear Dynamics

Routine periodic visual inspection of the bridge is simple, but the believable degree of the conclusion depends on the work experience and ability for the assessors, therefore it subjects to the greater impact of factitious subjective factors. Bridge load test has positive significance for the bridge safety assessment before the new bridge putting into use or during the accidental injury, however, the load test needs to interrupt traffic and double spends a lot of manpower, material and financial resources etc., so its costs are relatively high, what's more, it exists the problem of poor timeliness and it is only appropriate at some time. On another hand, remote monitoring of the bridge is safe, real-time, continuous, and timely early warning and forecast, so it becomes the direction and focus of international bridge research. At present, the research mainly starts from the static and dynamic assessment methods to the safety assessment of the long-term health monitoring existing bridges, but the assessment method, whether it is static or dynamic, has certain shortcomings. This paper aims to get the system characteristics from the nonlinear dynamic behavior of the bridge structure essences, which is based on the monitoring information, and then makes a safety assessment of in-service bridges.First of all, based on the knowledge and understanding of the nonlinear chaotic dynamic behavior, and the analysis of the three nonlinear factors of the dynamic behavior, by the use of mathematical method, this paper obtains the chaotic conditions for the Smale Horseshoe of complex structure, while considering simple zero for the system's Melnikov function, thus the paper reveals the essences of the evolution of nonlinear dynamic system behavior for complex structure. Second, considering the conventional function, Z=R-S, to determine the security state of structure beening limited, because of the resistance of bridge beening effected by the facter that itself to change, but also many uncertain factors, this paper seeks another way, useing the bridge health monitoring system to understand the system state from a variable time series of system's own response to the changes in the existing bridge structure, that putting forward the theory and method assess the security status of existing bridges, based on the characteristics of chaotic systems. Finally, by using of numerical simulation and real bridge application, the technique of safety assessment of the long-term monitoring existing bridge based on characteristics of chaotic systems is feasible and effective.The research results of this paper has certain reference for promoting theorization and systematization of assessment technology of the bridge safety monitoring.