ABSTRACT

Center stay is installed to control a relative displacement between a girder and a cable, to restrict the inclination of short suspenders around the center of a span, and to prevent bending fatigue of the suspender. A center stay was designed so that the rod section breaks with 60% (equivalent of an earthquake whose return period is 25 years) of tension force during an earthquake. However, two rods under force lower than the designed tension broke at a mounting screw section, not at the section with the minimum cross sectional area of the rod, which is the assumed failure point. This paper discusses the detailed survey of a fracture surface observation to confirm damage factors, estimation of the level of fatigue damage by measuring a stress frequency on a real bridge, a method to improve fatigue durability, and the result of a fatigue test of improved rod with which improved fatigue durability is expected.