| Bridge plays an important role in the transportation system.With the remarkable achievements in bridge construction in China,more and more diseases of bridges are also found.It is becoming more and more important to its management and operation.Its safety,durability and performance are gradually paid attention by people.In order to make the bridge run healthily for a long time,it is necessary to monitor the structure health.In this process,it is a challenge for engineers to use monitoring data well.For the displacement influence line which can reflect the overall state information of the structure,it becomes an index for the rapid evaluation of the bridge state and develops corresponding research.It is the premise of using displacement influence line to detect the bridge state and identify damage.The main contents of this paper are as follows(1)In order to extract the accurate influence line data from the real-time response information of the bridge excited by the mobile vehicle load,a new method of bridge influence line identification based on the combination of variable mode decomposition and Tikhonov regularization is proposed.This method decomposes the displacement time history response of the bridge under the driving vehicle load,eliminates the dynamic fluctuation part of the dynamic response of the bridge,and carries on the mathematical theory derivation on the basis of the quasi-static influence line.The Tikhonov regularization and the cubic B-spline function are introduced to deal with the inverse problems to reduce the recognition error.By establishing a coupling model of 1 / 2 vehicle simply supported beam bridge,four different high-speed vehicle load excitation are made,and the effectiveness of the method is verified by the response data.(2)The damage index based on displacement influence line is theoretically deduced and verified by the results.The advantages and disadvantages of four indexes on damage location effect are summarized.Based on the displacement influence line,a quantitative method of damage degree is proposed.Inspired by the physical significance of flexibility matrix,the damage state can be regarded as the starting point through the relationship between stiffness and flexibility and damage state as the starting point The correlation equation between the damage degree and the displacement influence line.The unit stiffness matrix is extracted and the feature is decomposed.The difference of displacement influence line is taken as the input data of matrix,and the damage degree is calculated by inverse problem method.The damage simulation of simple supported beam under different working conditions is carried out,and the result is better.(3)The feasibility and effect of the method proposed in this paper are verified by making the simple supported beam and trolley model of aluminum box section.The experimental results show that the dynamic wave part of bridge dynamic response is eliminated based on VMD,and the influence line is basically consistent with quasistatic response.The overall trend and peak value of the influence line of unit force deflection identified on this basis are in good agreement with the reference solution,which provides a reliable new method for identifying the influence line from the actual monitoring data.The damage identification based on displacement influence line mainly verifies the effect of quantitative damage.In natural environment,it is insensitive to noise and has good effect on damage degree quantification. |
