Stress concentration factors of N-joints of concrete-filled tubes subjected to axial loads

Abstract

The use of concrete filled circular hollow steel section (CFCHS) members in bridge design is a relatively new concept. In the design of recently constructed steel-concrete composite bridges using CFCHS truss girders for the main load carrying structure, the fatigue verification of the tubular spatial truss joints is a main issue. This paper presents a comprehensive study on stress concentration in welded tubular steel N-joints. Finite element analyses are performed in order to derive stress concentration factors (SCFs) from hot-spot stresses for typical three load conditions. The SCF values are presented in the form of equations in terms of the non-dimensional joint parameters. The proposed SCF equation for CFCHS N-joints shows good agreement with the test results on a tubular girder model. The presence of infilled grout in the chord is found to reduce the SCF.