Fatigue failure of welded details in steel bridge pylons

Multi-span suspension bridges show special structural characteristics compared with conventional suspension bridges. The mid-pylon is vulnerable to fatigue failure due to the effects of wind loads and traffic loads. In this study, based on the engineering context of the Taizhou Yangtze River Bridge, some investigations were conducted on the structural behaviour of this multi-span suspension bridge. Fatigue strength tests of two critical details on the steel mid-pylon were carried out. The two details were the butt weld of two segments near the longitudinal full penetration weld and the longitudinal full penetration weld near the diaphragm. Crack propagation was observed in the tests, and it was found that the initial crack propagation directions of the two details were different. S-N curves for these two details are not included in relevant bridge design codes, and in this study, fatigue strength values of the two details are proposed based on their fatigue tests. It is suggested that the fatigue strength value corresponding to two million-cycles for the detail of the butt weld of two segments near the longitudinal full penetration weld is 85.6 MPa, and the fatigue strength value corresponding to two million-cycle for the detail of the longitudinal full penetration weld near the diaphragm is 101.5 MPa.

Automated summary

This study investigated the structural behavior of the Taizhou Yangtze River Bridge, focusing on the vulnerability of the mid-pylon to fatigue failure. Fatigue strength tests on critical details of the steel mid-pylon revealed the need for strengthening measures to prevent crack propagation.