Repair of damaged welded connections in cantilevered steel sign structures

Cantilevered steel sign structures are widely used by commercial and retail businesses. This type of structure is flexible, has a low damping, and can be vulnerable to fatigue cracking due to wind-induced vibration. Damage and collapses of some sign structures due to fatigue and fracture at the sleeve connections have been reported. A common practice of strengthening or repairing the joint by welded gussets was not effective in mitigating fatigue cracking. To develop effective and economical repair procedures for damaged sign structures, various schemes were experimentally evaluated. Fatigue tests of three conventional connection specimens were first conducted to evaluate the fatigue resistance and the associated failure mode for comparison with field observations. Each of the three conventional specimens was then repaired by various combinations of welded gusset plates, grout, and steel cones or jackets. Testing demonstrated that conventional welded sleeve connections had a low fatigue resistance. A gusset-repaired specimen also showed a similar fatigue resistance to that of the conventional specimens. Steel-jacketing with cement grouting, or the use of a welded steel cone significantly improved the fatigue resistance of the most vulnerable fillet welded joint in the connection. This study also revealed the potential of cracking initiating from slot welds.