Temperature Effect On Bridge Health Monitoring

In order to achieve the purpose of bridge health monitoring,the responses of bridge were collected in a protracted period by sensors,then the characteristics about damage could be extracted from response signals,finally,judged the bridge was normal or not.Recently,not only the monitoring systems of long-span bridges are valued,but also medium and small-span bridges receive attention.In application,the damage detection method based on the structural dynamic parameters would be affected by environmental change.The damage indices caused by environmental change sometimes may cover the change caused by the structure damage.So the effect of environmental factors on bridge health monitoring can't be ignored.The temperture effect on dynamic strain and bridge health monitoring are analyzed based on two of the bridges in Hai Yan.(1)The article introduces the structural health monitoring equipment and method for medium and small-span simple beam bridges.The structural health monitoring system was built on two bridges in HaiYan,and was experienced the field driving test.After collecting the dynamic strain signals and making a preliminary analysis on those signals,this system was proved that it can run successfully.(2)Based on the regressive analysis,the experiential regressive equation of temperature effect and dynamic strain could be decided,then temperature effect could be separated,finally the feasibility of the method was verified.When the bridges without vehicles,the separated strain fluctuates around zero,the result conforms the theoretical.The relative peak and recognized speed were analyzed based on original and separated strain,it was the analyzable results show temperature effect on dynamic strain,and the feasibility of the health monitoring of the separated dynamic strain was verified.(3)The method for coefficient of bridge weigh-in-motion‘k'was proposed,proved the coefficient was only related to the system parameters of bridge.The conclution was proved by analysis based on the data of two bridges.Compared the coefficient of bridge weigh-in-motion on total strain with separated strain,the result of separated coefficient was more stable showed that the separated result was more apply to bridge health monitoring.(4)Correlation function amplitude vector of dynamic strain was defined.It was verified after normalization of amplitude vector showed a fixed proportion of morphology.Based on the results of comparative analysis,in different time period,the shapes of correlation function amplitude vector based on original data were distinct,while the shapes performed consistent based on separated strain.It was showed that ignoring the temperature effect on correlation function amplitude vector,the health condition of bridge may deviate.