Analysis On The Bearing Capacity And Residual Fatigue Life Of The Medium And Small Span T-rigid Frame Bridge

This paper takes the medium and small span T-type bridge as the research object.Based on the health monitoring system for the medium and small span bridge which is in service,the characteristics of the health monitoring system for the medium and small span bridges are analyzed.And the early warning threshold of the key components of the structure is set up to obtain long-term effective data.Then the dynamic response of the structure is obtained by eliminating the influence of temperature stress by the principal stress separation method.At last,the reliability and applicability of the calculation method of the bearing capacity utilization and the residual fatigue life of the key components of the long span bridges are verified,providing a feasible method for the effective evaluation of the health monitoring system of the medium and small span of the T-type rigid frame bridge.The main work of this paper is as followed:(1)The conceptual design for the bridge health monitoring system is analyzed,including the design principles,monitoring methods,the information acquisition equipment of the structural dynamic response and the layout principle of the Sensor position.At the same time,the health monitoring system for the Qixing bridge is introduced and analyzed in detail.It provides important practical samples for the structural health monitoring of the medium and small span bridges in service.Finally,the overall design of the early warning system for the bridge structure is briefly introduced.(2)According to the research situation of the analysis to the structural early warning threshold,the method of setting the early warning threshold is identified as the method of the grey correlation degree.Based on the data of two years,the early warning threshold of each key component is analyzed and set up.At the same time,the abnormal reporting mechanism is set up to deal with the abnormality of bridge monitoring data timely.(3)The calculation method of the bearing capacity of the key components is introduced emphatically.According to the characteristics of the design load SUF(bearing capacity utilization)and the measured static stress SUF,the SUF calculation formula based on the measured stress is proposed.And the separation of the measured dead load and live load effect is realized by the stress separation technique.Furthermore,the measured values of the SUF of the key components of the Qixing Bridge have been calculated.And the calculation of the early warning index of the utilization ratio of the bearing capacity based on the measured static stress is completed.(4)The calculation method of the residual fatigue life of key components is introduced emphatically.According to the real time dynamic stress process which is collected by each sensor,the stress process is converted to the stress spectrum for the fatigue analysis by using the rain flow method.And the residual fatigue lives of the key components have been calculated based on the S-N curve and the palmgren-Miner rule.And then the calculation of the early warning index of the residual fatigue life based on the measured method of the key components is completed.