Study On Fatigue Performance Of U Rib-to-deck Connection With Double Sides Welding In Orthotropic Steel Bridge Deck

The orthotropic steel bridge deck has the advantages of light weight and high bearing capacity,which is widely used in long-span bridge around the world.Because of the complex welding of the orthotropic steel deck and the stress concentration of the connection area,the structure is prone to fatigue failure during its service period.In this paper,to seek ways to improve the fatigue performance of U rib-to-deck connection weld,the static and fatigue performance of U rib-to-deck connection with single and double welded joints are studied,and the effect of adding an inner weld on the fatigue performance of U rib-to-deck connection is analyzed.Meanwhile,combined with different fatigue evaluation theory,comparative analysis of between the test data and the fatigue strength of other National norms is conducted to explore the evaluation criteria of the fatigue performance.The main conclusions are as follows:1.Through the finite element calculation,it is found that the longitudinal and transverse influence range of U rib-to-deck connection are small,the longitudinal influence range are not more than 0.4 m and 0.45 m.When the load is placed on the roof of the diaphragm,the stress of the U rib,deck and diaphragm connection is small.When the load is applied outside the diaphragm,the stress of the U rib-to-deck connection is larger.2.The fatigue test results show that when the load is applied in the midspan,the fatigue performance of the double side welded specimens is better than that of the single side welded specimens under the same stress amplitude.The fatigue life of the specimen with double side welding whose the weld penetration rate of the outer groove weld is 50% shows large discreteness.This may be related to the actual control of penetration rate.3.Based on the two methods of nominal stress and hot spot stress,there is little difference in the fatigue life assessment.When the hot spot stress method is used,the difference of hot spot stress at the weld toe of the joint between U rib and deck which is calculate by different extrapolation formula is not significant.4.Eurocode C90 has the highest requirements to this fatigue details among the current norms,but compared to the fatigue level of test,the C90 curve is still conservative,and the fatigue properties of the specimens were not well evaluated.According to the regression equation of S-N fatigue strength curve obtained by the same type test designed by Railway Scientific Research Institute,the fatigue level is very close to that of the test,and it can be used to evaluate the fatigue performance of the specimens.