Fatigue performance and design of concrete-filled steel tubular joints: A critical review

Over recent years, concrete-filled steel tubular (CFST) sections have been considered as a popular approach for the construction of new infrastructures as well as strengthening and repairing critical structural components such as joints. In contrast to the ultimate capacity of CFST sections, however, the fatigue performance of these members, especially CFST joints, has not been studied adequately. Therefore, this paper aims to provide a comprehensive review and statistical analysis on the available experimental fatigue data of CFTS joints and as well as to explore research gaps in this field. To this aim, firstly, fatigue design approaches that can be used for welded connections are briefly presented. Secondly, a fatigue database for these joints is developed through reviewing experimental fatigue studies of CFST joints and the outcomes are summarized based on crack propagation, failure modes, proper fatigue criteria, and the effect of concrete core. Finally, the fatigue database is used to generate basic S–N curves through the deterministic and least-squares method with and without considering the effect of tube wall thickness and the resultant curves are also discussed with respect to available design guidelines for empty tubular joints. Further experimental fatigue tests and finite element analyses are required to more accurately estimate the fatigue performance of CFST joints via hot-spot approach and improve the proposed basic hot-spot S–N curves.