Research On Monitoring And Typical Damage Identification Of Railway Simply Supported Steel Truss Beam

Existing railway bridges are inevitably damaged or degraded due to the long-term load of trains and environmental factors.In this paper,simply supported steel truss bridge is taken as the research object,and the monitoring data are processed and analyzed in combination with the long-term monitoring system.Then the static and dynamic responses of simply supported steel truss Bridges under different vehicle types and speeds are studied.Then the sensitivity coefficient is combined with the modified finite element model for damage identification.Finally,the damage index related to the modal strain energy of the element is studied and its feasibility is studied.The main contents and conclusions of this paper are as follows:(1)Based on the long-term monitoring system of railway simply supported steel truss bridge,combined with the principle of data processing,the time-domain and frequency-domain analysis is carried out.The data analysis results show that all the indicators meet the requirements of the railway bridge verification specification,and the overall operation of the bridge is in good condition.(2)The finite element model of simply supported steel truss bridge is established by ANSYS software.The internal forces and deflections of simply supported steel truss railway Bridges under the static and live load of trains are calculated and the static performance of the Bridges is analyzed.Considering different train loading methods,modal analysis and dynamic time-history analysis are carried out to analyze the dynamic performance of the bridge under different weights and speeds.The above analysis results show that under the influence of increasing axle load and increasing train speed,all indexes of the bridge do not exceed the safety limit,and the static and dynamic performance of the bridge is good.(3)Based on the finite element model of simply supported steel truss bridge,the finite element model is modified by response surface method(RSM).The finite element model which is consistent with the reality is obtained.Then,the sensitivity coefficient and the modified finite element model were used to identify the damage location and damage degree successfully.The sensitivity coefficient is used to analyze the dynamic response under the condition of partial damage of the structure,and the sensitivity degree and sensitive position of the response are obtained.The sensitivity related equations are constructed for damage identification.The sensitivity of the vertical acceleration is slightly higher than that of the velocity and displacement when the longitudinal beam,joint plate and inclined bar are damaged.When a damage occurs to the structure and the damage degree is small,the sensitivity coefficient has a better effect on the damage localization.In conclusion,the identification results of the three kinds of damage are relatively accurate.The degree of damage can be determined by measuring the acceleration response of the sensitive position.It is of great significance to realize damage identification of bridge long-term monitoring system.(4)When sensitivity method is used for damage identification of steel truss Bridges,the problems of calculation times and low efficiency appear.Therefore,the damage identification method based on element modal strain energy correlation is used to identify the joint plate and longitudinal beam damage of simply supported steel truss bridge.The identification results show that the accuracy of the damage location and damage degree is high.