Cracks
develop in the welds between branch and chord members of aluminum overhead sign
structures due to fatigue
stresses by wind-induced vibration. The cracks
propagate to complete fracture of the welds which causes signs to fall. The
original design of aluminum overhead sign structures did not consider fatigue
as a limit state. A rehabilitation method for cracked aluminum welded
connections using Glass Fiber Reinforced Polymer (GFRP) composites is
investigated. The paper presents results from constant amplitude fatigue tests
of aluminum welded connections with no known cracks, cracked aluminum
connections from actual sign structures
rehabilitated with GFRP composites, and
aluminum connections with 90% of the weld removed that were rehabilitated with
GFRP composites. The fatigue limits of the welded connections and rehabilitated
connections are established for various stress ranges including the constant
amplitude fatigue limit threshold. The fatigue tests show that the
rehabilitated connection from actual sign structures exceeded the fatigue
limits of the welded connection with no known cracks. The repaired connection
with 90% of the weld removed satisfied the constant amplitude fatigue limit. A
cumulative damage index is established which can be used to develop a fatigue
reduction factor for the rehabilitation design using GFRP composites.