| Due to the influence of fatigue disease,the development of orthotropic steel decks(OSDs)has been greatly limited.Among them,the fatigue crack of rib-to-deck welded joints seriously affect the OSDs’ s normal use.In order to improve the fatigue performance of the rib-to-deck welded joints,a variety of new type details have been proposed.However,the fatigue performance of the rib-to-deck welded joints has not been effectively improved,and fatigue failure are still emerging.Considering the above situation,taking the the new type of double-side rib-to-deck welded joint in orthotropic steel bridge deck as the research object,the following research work is carried out:(1)This thesis briefly introduces the development of orthotropic steel bridge panel,the causes of fatigue problems and the basic theory and basic concepts of fatigue analysis.Introduce the research status of the new structure,and on this basis,a new type of double-side rib-to-deck welded joint in orthotropic steel bridge deck is introduced,and its design concept is expounded.(2)The thesis presents a comprehensive introduction to the equivalent structural stress method,elaborates the theoretical basis of the equivalent structural stress method,summarizes the characteristics of the equivalent structural stress method and the similarities and differences with the nominal stress approach and the hot stress approach.Some key factors influencing the use of equivalent structural stress method are discussed.(3)The influence of the structural parameters of the orthotropic steel bridge deck on the structural stress and the equivalent structural stress is analyzed.The results show that increasing the thickness of the deck can effectively decrease the the structural stress and the equivalent structural stress of weld toe at the deck and weld toe at the U-ribs.The increasing the thickness of the U-ribs can effectively decrease the the structural stress and the equivalent structural stress of the rib-to-deck welded joints.While the increase in weld penetration can only effectively decrease the structural stress and the equivalent structural stress of DT-I.(4)The fatigue data of the rib-to-deck welded joints extracted from the existing fatigue test are systematic re-analysis and converted to the equivalent structural stress.The results show that the equivalent structural stress fatigue data are distributed within the main S-N curve recommended by ASME,so the equivalent structural stress method can be well applied in the fatigue evaluation of OSDs.(5)The fatigue life of the new type of double-side rib-to-deck welded joint in orthotropic steel bridge deck is evaluated by the equivalent structural stress method,and the key problems are studied.The results show that the equivalent structural stress can be used as an effective evaluation index to determine the difference of the weld root or weld toe in fatigue performance. |
