Examination of repair effect of fatigue crack occurs in the base of overhead sign structures

Abstract

Fatigue cracks were observed recently in lighting poles or overhead sign structures installed on elevated highway bridges. The fatigue cracks normally occurred at weld toes of ribs, which stiffen joints between base plate and tubular section. The fatigue cracks that occurred in actual structures were once repaired by two methods. One was to glue carbon fiber reinforced polymer (CFRP) sheets on and the other was to weld additional ribs for reinforcement. The structures were removed after two years, and the fatigue cracks were inspected to evaluate the effectiveness of the two retrofit measures. Then, static and fatigue tests were carried out on these structures to observe fatigue crack propagation life and to compare those without retrofit measure. Reduction of stress due to the retrofit measures was further confirmed by FEM stress analysis.