Examination of Broken Guardrails

After several decades of service, degradation was observed in the aluminum welds of the guardrails on a staircase leading to an industrial building. The staircase was used for regular inspections of the industrial structure; however, the guardrails themselves were not inspected until recently, when cracks were observed in several welds. Two welds had completely separated. Examination revealed that the welds were irregularly shaped, partially penetrated, and contained both shrinkage and gas porosity. Cracks initiated at the weld roots and propagated toward the weld face. Fatigue cracks initiated and propagated until the remaining cross-sectional area could no longer sustain the applied loads, resulting in complete separation.