| The evaluation of structural health monitoring technology in civil engineering plays an extremely important role in structural safety assessment and reliability evaluation.As the main content of structural health monitoring,structural damage identification has always been a hot topic and frontier of research.There are some limitations of traditional damage identification methods in the process of damage identification of ultra-long linear structures,such as excessive sensor demand,inputted information can not be obtained accurately,output data can not be collected completely,and the influence of noise.Therefore,it is very necessary to study the damage identification of ultra-long linear structures under moving load,and it is urgent to provide a new technical support and approach for damage identification of ultra-long linear structures.This paper is based on the National Key Basic Research and Development Program 973 project,"Health Diagnosis and Service Performance Prediction Theory of Underground Structures under Dynamic spatio-temporal Environment Effect"(2011CB013800)and the National Natural Science Foundation project "Research on Output-Only Damage Location Method of Ultra Long Linear Shield Tunnel Based on Distributed Identification Strategy"(No.51578261).On the basis of existing research work,based on information theory and wavelet theory,through theoretical analysis and derivation,numerical simulation,experimental verification and engineering practice,the damage identification and optimal sensor placement of ultra-long linear structure are analyzed and studied systematically and thoroughly.The main contents of this paper are as follows:(1)A modified method for ultra-long linear structure based on acceleration frequency response function is studied.Dynamic analysis of the structure is carried out by using the acceleration response under moving loads,and the structural model is modified by the measured acceleration frequency response function,so that the acceleration frequency response function of the modified finite element model are consistent with the actual structure as much as possible.The finite element model of the combination of soil and ultra-long linear structure is modified by the measured acceleration frequency response function of the reduced-scale soil box-aluminum tube model structure under moving load.After the modification,the standard deviation of first order frequency,second order frequency,vertical deformation and acceleration response between the original model and the modified model are compared.It is verified the advanced nature and accuracy of the proposed method,and provides a reliable guarantee for the damage identification analysis of structures in this paper.(2)The damage identification and location method of ultra-long linear structure under moving load is studied.Based on the wavelet theory and the wavelet residual force,the reconstructed modified wavelet residual force index is used to identify and locate the damage of ultra-long linear structure under moving loads.Through the numerical examples of soil-shield tunnel structure under moving load,the results of structural damage identification are analyzed,and the damage identification results of ultra-long linear structure under different measuring points and different measuring noises are compared.At the same time,the model test of the shrinkage aluminum tube in soil box under moving load is carried out,and the results of the two tests are basically in agreement,which verifies the correctness of the algorithm.(3)The influence of different moving loads on structural damage identification of ultra-long linear structure is analyzed comprehensively.The results show that the magnitude of the moving load has little effect on the damage identification of the structure.When the moving load changed 200%,it is also feasible for the damage localization.At the same time,no matter under uniform load or variable velocity load,the damage index of pre-set damage by mutation can be identified effectively.(4)A quantitative method for structural damage identification of ultra-long linear structure under moving loads are studied.Based on the damage identification and location method of ultra-long linear structure under moving loads,the damage degree and damage index are quantitatively analyzed by using Lipschitz index,and the relationship between damage index and damage degree is determined.Through the numerical example of soil-shield tunnel structure under moving load and he model test of shrinkage aluminum tube in soil box under moving load,the relationship between different damage magnitude and form and damage index of structure is analyzed.The results show that the method based on combining modified wavelet residual force with Lipschitz exponent ? is very close to the actual damage setting,and the error rate of damage degree is controlled in the range of 5%.It provides a new idea for the quantitative study of damage identification of ultra-long linear structure.(5)An improved method based on mutual information for optimal sensor placement is studied.This paper is based on the mutual information theory in information theory,the ultra-long linear structure is divided into linear connected sub-intervals,and the partition of the sub-interval can be reduced to the optimal placement of the sensor.At the same time,the idea of monkey swarm algorithm is introduced to add the process of "climbing","looking" and "jumping" in the optimization process,thus reducing the trial calculation process and increasing the calculation efficiency,it provides a new idea for the research of optimal placement of sensors before ultra-long linear structure damage identification.Based on the numerical example of soil-shield tunnel structure under moving load,the influence of different sensor arrangement on the result of damage identification of ultra-long linear structure is analyzed,and the optimal sensor placement scheme is selected by synthetically discriminating efficiency and economic factors. |
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