21.13: Experimental study on retrofitting method against fatigue cracking at the upper end of vertical stiffeners

Abstract

ABSTRACTLots of fatigue crackings were reported at the upper end of vertical stiffeners connected to sway bracings in steel highway girder bridges. In this study, we propose two types of retrofitting methods against fatigue cracking at the upper end of vertical stiffeners under RC slab. They are steel plate reinforcement using a jack‐up jig, and angle steel reinforcement using thread rolling screw (TRS). The effectiveness of those two types of retrofitting methods are experimentally investigated through fatigue tests using a large specimen with three main girders under alternative loading using two actuators. As a result, both retrofitting methods can reduce the local stress concentration at the crack initiation point to about half of that before reinforcement, and can prevent fatigue cracking. Post cracking measure, i.e. angle steel reinforcement using TRS after grinding away crack tips can extend fatigue crack propagation life more than 10 times of that without the reinforcement.