| Damage alarming and state assessment are the most important aspects in health monitoring system,how to effectively and accurately process and analyze the monitoring data for realizing damage alarming and state assessment is the current research hotspots at home and aboard.In this paper,taking an ordinary-speed and a high-speed typically large bridge as the engineering background,around two research direction of damage alarming and state assessment,systematically carried out the application research on damage alarming and reliability evaluation of fatigue and capacity based on health monitoring data.The main results of this paper are as follows:(1)Using sensitivity analysis studied the influence of bridge damage on vehiclebridge coupling system,and the results show that the influence of bridge damage on bridge vibration is much greater than vehicle vibration,and the acceleration of mid span is most sensitive to damage,followed by speed,and the displacement is minimal.And proposing a sensitivity damage identification method based on the correlation function of single point acceleration,this method has better recognition performance for small damage less than 4%,and has a certain noise immunity.(2)Established time ARMA model of bridge acceleration data,analysis the stability and sensitivity of model to damage,the results show that the environment factors have little influence on this model,and the AR coefficients fluctuate with damage occurred.And proposing the damage alarming indictor and method based on AR coefficients,using the multiple hypothesis testing to recognize the slight change of alarming indictor,which means that the alarming indictor and method can effectively judge the damage of bridge.(3)Analyzing the influence of environment temperature and vehicle load on bridge measured modal frequencies,and established the relational model by BP neural network.And proposing the damage alarming method based on modal frequencies,which can recognize slight change of frequencies by using BP neural network and multiple hypothesis testing.It means that the method has good applicability and can judge the damage of whole bridge more accurately.(4)The reliability evaluation method of bridge bearing capacity is established based on health monitoring,and the reliability index of the bearing capacity of one top through steel truss girder bridge and through steel truss girder bridge is systematically studied.The probability distribution of the parameters in the limit equation is analyzed.The distribution of live load on any member is realized based on load spectrum which established through probability theory according to the measured data.And the influence of temperature load on the reliability index is studied.The results show that: the bridge bearing capacity meet the requirements,the effect of temperature load has great influence on bearing capacity reliability index of the end part of the lower chord,and little effect of the lower chord in cross.Finally,the renewal theory of Bayes probability model is introduced to ensure that the live load distribution of the vehicle can reflect the actual situation.(5)A deterministic and a reliability fatigue evaluation method for Steel Bridges based on health monitoring are established.Based on the Palmgren-Miner linear cumulative damage theory and the S-N curve in the AASHTO code,the deterministic fatigue life and reliability fatigue life of an upper and lower through riveted steel truss bridge are analyzed.The influence of vehicle load growth and load effect on fatigue reliability is studied,and system fatigue reliability of steel bridge is calculated according to the bound method.The results show that: The reliability fatigue life is far less than the deterministic fatigue life,the system fatigue reliability is less than the component's,but more in line with actual situation,the increase of vehicle load and t the equivalent stress variation will lead to the decrease of fatigue reliability.Generally,the method based on reliability can make use of monitoring data reasonably to evaluate bridge fatigue,and it can provide scientific basis for the maintenance and repair of steel bridges.(6)The reliability analysis method of vehicle bridge coupling system is discussed.The coupling system is regarded as a series system consists of the vehicle subsystem based on derailment coefficient and reduction rate of whole load as the safety indexes and the bridge subsystem based on lateral acceleration of mid span as the safety index.The results show that: the average axle load has great influence on the bridge safety reliability,the train speed has great influence on the vehicle safety reliability,and the vehicle safety is the main factor to restrict the safety reliability of vehicle bridge system. |
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