| With the development of the city,people’s demands for daily travel have significantly increased,and infrastructure constructions such as rail transit can effectively alleviate the pressure of ground traffic during peak hours.As one of the rail transit facility,the light rail is laid on a full-line elevated bridge.During the operation period,the light rail bridges are deformed owing to long service transportation by trains.While the traditional contact measurement methods are used for the monitoring of the bridge structure,these methods has certain limitations.Therefore,it is necessary to use new methods to conduct corresponding research.Based on the knowledge of digital image correlation,the measured image data is divided into following types according to the difference of measuring points or load forms during the service times at some cities.i.e.,basic working conditions(I)and different loads at the same measuring point forms of working conditions(II),different load points(III),different structural positions(changing spans),the same load conditions(IX)and the intersection conditions(V).The image correlation calculation is performed on the measured data to obtain the time series curves of different working conditions,and the working condition curves are compared with the basic working conditions to study the deformation law of the floor measuring points under different load conditions.The main results are obtained in below:(1)The measured and integrated horizontal and vertical deformation and strain versus time curves of the relevant data measured by the basic working condition show that the train recorded significant fluctuations in the time period from the arrival of the bridge to the front of the measuring section to the rear of the pier.That is,during the duration of the load,the curve fluctuates and the bottom plate deforms accordingly.(2)The comparison between working condition III and basic working conditions shows that the deformation trend of the position of the measuring point in working condition III is consistent with the basic working condition under the same load condition,while the correlation curve of the measuring point falls clearly under this working condition,and the peak value of the vertical deformation is slightly increased in comparison with the basic condition.(3)Comparing the working condition IX curve with the basic working condition curve,it is shown that the horizontal strain curve of the basic working condition changes less than the working condition IX;the horizontal deformation curve show trend of distribution,while the maximum deformation extremum of the working condition IX is higher than that of the basic working condition,and the difference of the minimum deformation value is almost same;the strain curve in the vertical direction shows that the initial growth rate of the basic working condition curve is more than the working condition IX,and the later falling speed is slower.The overall change requires a longer duration and the maximum strain curve amplitude of the basic working condition is less than that of the operating condition IX,but both of the minimum strain amplitudes are relatively close.(4)The working condition II shows the same measuring point compared with the basic working condition,and the position of the measuring point is directly above the load on the bottom plate,the deformation value of the test area is greater than that of the inclined side.At the same time,the comparison of the deformation curves measured in the vertical direction of the two working conditions suggests that the deformation curves of the basic working condition and the working condition II are symmetrically distributed.(5)Different from the basic working condition,the maximum deformation value curve is gentle,and the minimum deformation curve has a significant change.The maximum deformation value curve of the intersection condition has same trend as the minimum deformation value curve.The time period of change is 11 seconds from the 9th to the 22 nd second and 11 seconds longer than the basic working condition,this result indicates that the influence of the intersection condition on the deformation of the bottom plate is longer. |
