Study On The Sensitivity Analysis And Detection Method Of Out-of-plane Deformation Fatigue Stress In Steel Bridge Web

The out-of-plane deformation at the gap of the steel bridge web is a common fatigue problem in steel bridges.However,the early steel bridge design lacks the fatigue classification grade in China.The specification does not expect the fatigue resistance to be so low,especially for some steel bridge partial components.The design did not fully consider its fatigue-prone characteristics,resulting in many disasters in which the in-service steel bridges experienced fatigue cracking and overall structural damage.In view of this,this paper explores the factors affecting the out-of-plane deformation fatigue stress at the gap of the steel bridge web,and introduces a method for detecting fatigue stress.The finite element software is used to analyze the equivalent stress distribution at the gap of the steel bridge web and the law of the out-of-plane deformation.The sensitivity analysis method is used to influence the gap size,web thickness and rib stiffness.The parameters were analyzed for the sensitivity of the equivalent stress and the deformation of the plane at the gap of the web.The results show that for the simulation model of this paper,there is an optimal web gap size G=30 mm,which makes the Von Mises Stress of the root of the web gap is the smallest.When the economic and technical conditions permit,the thickness of the web can be appropriately increased,and the Von Mises Stress and the out-of-plane deformation at the web gap can be reduced at the same time.The flexible rib material can effectively reduce the amount of out-of-plane deformation.Theoretically,the relationship between thermoelastic stress and surface temperature change of the member is established.The thermoelastic stress effect test and the effectiveness of the IR-TSA system are verified by the thermoelastic stress effect test of the perforated plate.The IR-TSA system is used to test the positionof the stress concentration at the gap of the web of the in-service steel bridge qualitatively.The research shows that in the thermoelastic stress effect test of the perforated plate,the maximum error between the measured temperature change of the measuring points A and B and the theoretical analysis result is 4% and 2.67% respectively;Under the action of the actual traffic load,the abrupt stress at the root of the steel bridge web rib can be detected by IR-TSA system effectively.