Fatigue in jointless bridge H-piles under axial load and thermal movements

Abstract

The seasonal and short-term temperature variations produce cyclic horizontal displacements in the continuous superstructure of jointless bridges and hence in the abutment piles. Thorough study of the available field measurement data for jointless bridges showed that the thermal-induced cyclic flexural strains in steel H-piles (SHPs) at the abutments are composed of large, primary small and secondary small flexural strain cycles. While the SHPs at the abutments of jointless bridges laterally deform and experience these cyclic flexural strains due to thermal effects, they also carry axial loads transferred from the superstructure through the abutments. Review of the literature revealed that there is no specific study on the combined effects of axial load and thermal-induced/flexural strain cycles with various amplitudes on the low cycle fatigue (LCF) performance of jointless bridge SHPs. For this purpose, parametric experimental studies on full scale SHP specimens are conducted to simulate the cyclic behavior of SHPs under thermal effects in jointless bridges by considering the effect of axial load combined with large and small flexural strain cycles with various amplitudes. It is observed that at large flexural strain amplitudes, local buckling of the pile due to the effect of axial load adversely affects the LCF life of SHPs at the abutments of jointless bridges. Furthermore, it is observed that the effect of small flexural strain cycles on the LCF life of uncompact SHPs depends on the amplitude of large flexural strains and the amplitude ratio of the small and large flexural strains.