A state-of-the-art review of current code provisions for girders with flange holes

Steel structures construction often necessitates fabrication of holes in the flanges of steel beams and girders often for bolted connections. These holes facilitate connections between beams and other structural components in buildings, as well as between girders for continuity in bridge systems. While bolt holes in compression flanges have minimal impact on load-carrying capacity, they can significantly affect the strength and ductility of girders under tension or flexure. In such cases, the load-carrying capacity at the strength limit state may be governed by the fracture strength of the net flange section, rather than the yielding of the gross section. In the past, various design codes, including the AASHTO LRFD Bridge Design Specifications, accounted for bolt holes in tension flanges through the 15 % rule. This guideline was established by the American Institute of Steel Construction (AISC) in 1963 following the landmark study of Lilly and Carpenter (1940). Over time, international design codes have evolved from allowable stress design to load resistance factor design, reflecting advancements in steel production and improved understanding of structural behavior. This paper presents a detailed examination of the evolution of international design codes for flanges with bolt or fastener holes, focusing on determining flexural strength. It also introduces a proposed method, established based on full-scale experimental results, and provides a comprehensive comparison of this method with existing international standards.