Blind prediction of FRP repairs for multiaxial fatigue cracks on Hydraulic Steel Structures

Abstract

Currently, over 80% of the navigation steel structures (NSS) within the United States’ inland waterway system have reached or exceeded their useful design life. Age has caused deterioration of the design boundary conditions (e.g. diagonal relaxation and quoin block deterioration) leading to overloads and causing multi-axial fatigue cracking. Furthermore, corrosion and deterioration of the protective system accelerate the fatigue crack growth rate. This paper presents numerical experiments to evaluate the viability of fiber reinforce polymer (FRP) retrofit methods as an alternative to repair mix-mode fatigue cracking. The numerical experiments use a combination of tension, shear, and bending forces to develop different cracking patterns. Afterward, an analysis is conducted to demonstrate the effectiveness of the repair techniques on the defined problem. The need for a retrofit method is first motivated by the lack of effective and easily implemented retrofit techniques for underwater structures when mix-mode fatigue cracks are present. Extended finite element (XFEM), with Paris’ Law and non-linear bond-slip behaviour of the adhesive, calibrates the crack propagation and strains surrounding the crack tip. The research then focuses on the discussion of the parametric analyses of large steel plate subjected to a combination of tension, shear and bending loads with and without CFRP repairs.