Design S-N curves for T-, K-, and X-concrete-filled steel tubular joints

High stress concentration at the weld vicinity in welded steel tubular joints results in fatigue failure. Researchers have tried finding an effective method to reduce these stresses. Although concrete filling of the steel tubes has been used to reduce stresses at the joints in the recent two decades, the fatigue performance of concrete filled tubular joints is not yet fully understood. This paper summarizes research on the fatigue strength of concrete-filled steel tubular T- , K-, and X-joints. Based on available experimental results, the nominal stress and hot spot stress design S-N curves for concrete-filled steel tubular joints have been derived. The least squares method is used in the derivation of the design S-N curves according to the American Society for Testing and Materials (ASTM) specifications.