Extremely low cycle (ELC) fatigue cracking behaviour in steel bridge rigid frame piers

This paper describes extremely low cycle (ELC) fatigue experiments and three-dimensional elasto-plastic finite-element analyses to investigate the ELC fatigue cracking behaviour of both steel pier beam–column joints and column–base joints. The cyclic loading test was carried out by using box-sectioned beam–column joint specimens with or without a web-corner fillet, and column–base joint specimens with or without triangular ribs. Fatigue life of both the beam–column joint specimen without a web-corner fillet and the column–base joint specimen with triangular ribs was reduced to about 12 of that of the beam–column joint specimen with a web-corner fillet and the column–base joint specimen without triangular ribs, respectively. Finally, it was demonstrated that the ELC fatigue crack initiation life of both steel pier beam–column joints and column–base joints could be estimated by Manson–Coffin’s law and the plastic-strain range at the crack initiation point which was obtained by the finite-element analysis.