Fatigue behaviour of non-integral Y-joint of concrete-filled rectangular hollow section continuous chord stiffened with perfobond ribs

Abstract

This paper examines the fatigue behaviour of non-integral welded joint of rectangular hollow section (RHS) brace and a continuous concrete-filled RHS (CFRHS) chord stiffened by internal perfobond ribs. A total of eleven Y-joints, including two control specimens with hollow section chords, were tested under axial force in the brace. The effects of concrete infill and perfobond ribs on the stress concentration factors (SCFs) are examined. The crack-initiation fatigue life and loss-of-strength fatigue life were established. Comparisons of the measured fatigue life with existing experimental data of square hollow section (SHS) joints without concrete infill or perfobond ribs and with predictions made using design guides are also presented. The test results show that the same Sh-N curve based on the hot spot stress method can be adopted for RHS joints with and without concrete infill and perfobond ribs. However, a significant decrease of SCFs in CFRHS joints with perfobond ribs is observed compared to the RHS joints. In addition, for the full-width joints (β = 1), CIDECT and DNV design guides Sh-N curves overestimate the fatigue strength of CFRHS joint with perfobond ribs, while the API design guide underestimates its fatigue strength.