Natural/Vibration Stress Relief Analysis Of Welding Residual Stress Of Orthotropic Steel Bridge Deck

Orthotropic steel deck is widely used in long-span bridges because of its light weight,high strength and high bearing capacity.However,after decades of development,the fatigue damage is still a very prominent problem.At present,different degrees of fatigue cracks are appeared in many steel bridges,which seriously affects their safety and service life.Therefore,in this thesis,for the fully penetrated U rib–to-deck,the effect of natural stress relief(NSR)and vibratory stress relief(VSR)on the welding residual stress are studied based on the experiment and numerical simulation,respectively.The main research works are as follows:(1)The application of orthotropic steel bridge deck in bridge construction is introduced.The generation of welding residual stress and its influence on steel bridge are explained.The research progress and application of NSR and VSR are introduced.(2)Based on the existing orthotropic steel bridge deck specimen,the blind hole method was used to studied the effect of NSR on welding residual stress,and the distribution of residual stress before and after NSR.The research results show that the residual stress on the specimen surface is changed by NSR,but the effect degree on different parts is different.For the deck,NSR decreases the peak value of residual stress in the tension zone and homogenizes the residual stress of component;however,for the U rib,NSR results in a overall increase of residual stress.(3)The evolution of welding residual stress of orthotropic steel bridge deck under VSR is studied by numerical simulation.The results show that VSR can effectively reduce the residual peak stress of components and make the distribution of residual stress more uniform.(4)Based on the numerical simulation method,the parameters of VSR are systematically analyzed.The results show that,ensuring the condition of eliminating residual stress by VSR and avoiding fatigue damage of components,the residual stress reduction is more obvious as the amplitude of the excitation load increases;the closer frequency of the cyclic load is to the natural frequency,the better effect of VSR to eliminate residual stress;with the increase of loading times,the residual stress gradually decreases and finally tends to be stable,and the reduction of residual stress mainly occurs in the first few cycles of load.This thesis mainly studies the relaxation of welding residual stress of orthotropic steel bridge deck under NSR and VSR.The relevant research results can provide necessary data support for fatigue performance research of orthotropic steel bridge deck,which has important practical significance.