Fatigue Strength of Thin-Walled Welded Hybrid Girders in Bending

Abstract

An experimental study on thin-walled hybrid plate girders subjected to repeated loading is described.
Six large-sized hybrid plate girders which were fabricated of HT-80 (quenched and tempered high strength steel) at a tension flange, SM-58 at a compression flange and SS-41 at a web were tested under repeated bending.
Parameters investigated in this study were maximum stress, stress range, web slenderness ratio and rigidity ratio of longitudinal stiffener.
Test results were discussed on the observed fatigue crack patterns according to the classification proposed by Toprac, and S-N curves for hybrid girders were plotted and compared with several past research data. Consequently, it has been proved that the stress range is one of the most significant parameters that affect the fatigue strength of hybrid girders, and the fatigue failure can be evaluated well from the crack at the transverse stiffener-to-web fillet weld below the neutral axis (Type 2 crack). A good correlation was observed in the fatigue test results between model specimens with transverse fillet welded attachments and largesized girder specimens, and comparisons with several fatigue data on steel plates with transverse fillet welded attachments showed that SS-41 web is the most economical.