Estimation of stress concentration factor at stop-hole repair strengthened by bonded patches

Abstract

Fatigue cracks detected in existing steel structures during periodic inspections are often tentatively repaired by drilling holes, called stop-holes, at crack tips. However, in some cases, fatigue cracks may reoccur at the edge of stop-holes, depending on the crack length and applied stress range. Although numerous studies have demonstrated the efficacy of patch plates in strengthening cracked steel plates and extending fatigue life of steel structures, there is a limited literature on the effectiveness of stop-hole repair strengthened by bonded patches. Particularly, the impact of the bonded patch configuration and position on the fatigue strength improvement remains unexplored. This study investigated the influence of the bonded patch configuration and position on the stress concentration factor of a stop-hole by finite element analysis. In this study, the material of bonded patch plates is assumed to be steel. Furthermore, this study presents a fatigue design equation for stop-hole repair strengthened by bonded patches, considering bonded patch configuration and position based on the fracture mechanics. The proposed design equation enables the design of patch configuration and the evaluation of remaining fatigue life to repair fatigue cracks in existing structures.