Study Of Fast Safety Assessment Of Concrete Girder Bridge Based On Real Time Monitoring

With the rapid development of transportation and logistics in our country, concrete beam bridges which is the most widely used appear more and more diseases. Finding the bridge diseases in time to prevent further bridge safety performance degradation and timely maintenance and reinforcement, and fast assessment of sate performance for the existing bridges is particularly important. This paper takes Lieshihe Bridge in the Jiangsu section of Shen Hai high-speed (G15) as the engineering background. The main work is as follows:(1) The health monitoring system of Lieshihe Bridge is established, and the data collected by the system is systematically analyzed.(2) Based on the result of the environmental vibration test, the initial finite element model of Lieshihe Bridge is updated, the baseline finite element model which can reflect the actual operation state is established, and further more, the threshold of safety evaluation for Lieshihe Bridge is established.(3) Based on uncertain analytic hierarchy process (AHP), group-decision, the principle of set-valued statistics, variable weight comprehensive theory, entropy value method and so on, the Lieshihe Bridge safety assessment model is established. A bridge safety comprehensive performance assessment software is self-developed, and the software is applied on Lieshihe Bridge for safety assessment.(4) The deflection influence line expression and its first and sencond order derivative expression of two-span continuous girder bridge is deduced, based on the deflection influence line, the preliminary evaluation method of bridge bearing capacity is built, and numerical example verification for the method is done.(5) Based on ChangDing △r—η regression model and the monitoring data from the online health monitoring system, the fast assessment method of bridge bearing capacity combined with dynamic deflection influence and real-time vehicle load is studied, and the assessment method is applied to Lieshihe Bridge to evaluate its bearing capacity.The main conclusions are as follows:(1) The structural health monitoring system of Lieshihe Bridge has the characteristics of function integrity, maintenance convenience, advanced practicability, etc. The monitoring result accords with the basic mechanical behavior of partially prestressed concrete continuous girder bridge. The structural health monitoring system achieves the basic requirements of the health monitoring system design and can provide powerful support for the study of Lieshihe Bridge safety evaluation.(2) Based on the environmental vibration test and the third order Response Surface Method, Lieshihe Bridge finite element model is updated, and the mode computed has good agreement with the mode measured. The updated finite element model of Lieshihe Bridge can be used as a baseline finite element model of safety assessment of Lieshihe Bridge.(3) Lieshihe Bridge safety comprehensive assessment model is established, and the comprehensive safety assessment software is developed based on Matlab. Lieshihe Bridge safety assessment for 7 months scored an average of 89.3 points, suggests that the safety performance of Lieshihe Bridge is in good condition.(4) Based on deflection influence line, the preliminary evaluation method of bridge bearing capacity is established, which can be used for bridge damage identification and bearing capacity evaluation.(5) Based on the real-time monitoring and the Online Model Updating method, the fast assessment method of the ultimate bearing capacity of Lieshihe Bridge is established; the assessment results show that Lieshihe Bridge is in a state of safe working performance and and its safety coefficient of ultimate bearing capacity is over 3.5.