Research On Welding Residual Stresses In Steel Bridge Decks Stiffended With Upsetting Edge U-Shaped Ribs

Nowadays,orthotropic steel bridge deck has been widely used in modern steel bridges,while the welding residual stresses introduced by the welding processes of U-shaped ribs not only reduce the structural manufacturing precision,but also degrade the service performance.In order to mitigate the stress concentration of weld joints between U-shaped rib and deck,a new type of U-shaped rib has been put forward to enhance the local rigidity through extending the thickness of segmental rib near deck.The new rib which called upsetting edge U-shaped rib usually costs more weld joints than the traditional rib when welded to deck.Therefore,the distribution of welding residual stresses in the new rib is also different from the usual way,and it is well worth an in-depth study.In this paper,the weld joints between deck and upsetting edge U-shaped rib was selected to analyze its welding residual stresses,the main content could be summarized as follows:First of all,the basic knowledges and analytical methods about numerical simulation of welding were introduced.As to the weld joints between upsetting edge U-shaped rib and deck,two three-dimensional finite element models were separately built to simulate the welding temperature field and the welding stress field.The technique of dead-or-live-units was used to simulate the welding process.Secondly,the welding temperature field was analyzed,and it was found that once the heart source approaching,the temperature would increase rapidly and then reach the peak in a very short time.As the heart source passed away,the temperature reduced rapidly but not as fast as its increaring speed.The change rules about temperature above fit all points in the model.Besides,the farther distance from the centre of the weld joints,the lower temperature peak.Thirdly,the stress field was analyzed.Along the welding direction,the welding residual stresses are relatively stable in the middle of model,and the peak of its longitudinal components tends to be over the yield strength while the lateral compoents are very small.As for the longitudinal residual stresses on the cross section,tensile stresses exist near the weld joints and its maximum is 1.16 times the yield strength of Q345.In the sections far away from the weld joints,pressure stresses show up.The maximum of pressure stresses is 0.23 times the the yield strength in deck and 0.09 times in upsetting edge U-shaped rib.The distribution of welding residual stresses in the new rib is similar to the usual one except some differences in numerical values.The longitudinal residual stress changes barely.Except the decrease in the weld toe of rib,residual stresses in the new rib model are almost all higher when compared with the tradional rib model.The new rib costs more weld joints than the traditional rib,it follows that more welding heat is put into the model and the welding heart affected zone extends as well.In the last section of this paper,several geometrical parameters related to the new rib model were selected to analyze their influences on the welding residual stresses.It turns out that four parameters present obvious differences,they are the angle of welding groove,the thickness of deck,the thickness of rib and the increased thinkness of upsetting edge U-shaped rib.