Health Monitoring And Damage Identification Of Single-Column Single-Tower Self-Anchored Suspension Bridge

With the construction of transportation infrastructure,the rapid development of long-span bridges has brought good economic and social benefits,and at the same time,the safety problem of bridge structure has become increasingly prominent.As the service life of the bridge increases,the coupling effect of many factors leads to the decline of its bearing capacity,and it is easy to cause safety accidents in extreme cases.Therefore,the long-term health monitoring technology of bridge structure during operation has been paid more and more attention.On the other hand,due to practical engineering needs,new structural forms are constantly applied in bridges,and new requirements for health monitoring and structural evaluation are constantly put forward.At present,there is a problem that the combination of system construction strategy and concrete bridge structure characteristics is not deep enough in bridge health monitoring.In the selection of monitoring content and arrangement of measuring points in design scheme is often based on the traditional structural analysis,the design theory and experience,and not from the specific structure of state evaluation and damage identification method for monitoring system.The sensitivity of monitoring parameters to damage condition and structure state is not fully considered.This will lead to insufficient data information and low utilization rate,greatly reducing the efficiency of the monitoring system.Based on the above problems,this thesis takes the single-column single-tower self-anchored suspension bridge structure as the object to carry out the monitoring system design scheme and damage identification research.The main contents are as follows:(1)The basic finite element model of single-column single-tower self-anchored suspension bridge(Dagu River Channel Bridge)is established by using finite element software,and the accuracy of the model is verified by comparing with the measured results of bridge load test.A multi-scale model is established for the triangular braces of the tower side support structure,and the model is modified,which can be used for subsequent analysis.(2)The static and dynamic analysis of the model is carried out,in which the vehiclebridge coupling and seismic action are considered in the dynamic analysis.According to the static and dynamic response of the bridge,the vulnerable position is judged and the damage condition to be considered is determined.Based on the comprehensive analysis of structural response under various load conditions,the following components or parts are relatively more vulnerable to damage: short suspender,middle section of main and side span of stiffening beam,straight triangular brace,inclined bar and support,section near the bottom of bridge tower.(3)According to the damage condition,the damage sensitivity of the structural response was analyzed,and the following monitoring parameters were initially selected: the tension of part of the suspender,the deflection and strain of the main beam of the relevant section,the strain of the triangular brace,and some low order frequencies of the bridge.(4)The method of BP neural network is used to study the damage identification based on the selected sensitive parameters,and the influence of noise on the network is considered.The results show that BP neural network has a good identification effect on the location and degree of damage,and the identification effect is still good under the noise interference,and the network has a strong anti-noise ability.(5)Based on the above analysis,considering the sensitivity requirements of monitoring parameters to damage condition and structure state,as well as the simulation effect of damage identification,the monitoring items and the arrangement of measuring points were determined,and a structural monitoring system scheme of single-column single-tower self-anchored suspension bridge oriented to damage identification method was proposed.