Fatigue Behavior Of CHS T-Joints With High Strength Steel Q460C Under Cyclic In-Plane Bending

Currently,more and more buildings,bridges and offshore platform structures begin to use high strength steel.The fatigue problem is one of the main reasons for the failure of steel structure,The material strength and weld ability of ordinary steel and high strength steel are very different,this difference is bound to impact fatigue properties of tubular joints.Therefore,it is necessary to study the fatigue performance of high strength steel pipe joints.In this paper,8 T-joint specimens made of circular hollow section(CHS)with high strength steel Q460 C under in-plane bending on the brace were tested to determin the stress concentration factors at hot-spot locations and investigate the fatigue behavior.On the basis of experiment,finite element analysis of CHS joints with high strength steel was been developed to obtain the influence of different parameters on the stress concentration factor(SCF)and fatigue behavior.And by Comparison of results between tests and current design methods,new design S-N curve was proposed.Through the study of fatigue properties by hot spot stress method mentioned above,the following important conclusions are obtained(1)Maximum SCF position and the the position of regional fracture is very near,SCF of test data is 35% lower than SCF calculated by IIW/CEDECT,which indicating the existing specifications for high-strength steel tubular joint prediction is conservative.(2)By Comparison of results between tests and current design methods,it was found that the predicted results based on the methods of AWS/API and DNV are obviously conservative for CHS joints with high strength steel.On the contrary,predicted results by IIW\CIDECT are not conservative.(3)The proposed S-N curve and design methods of CHS joints with high strength steel,which based on the test results and the forced slope of current design methods,have the advantages of universal applicability.