Tensile and Fatigue Behavior of Punched Structural Steel Plates

The research work described in this report, “Tensile and Fatigue Behavior of Punched Structural Plates,” is part of a project entitled "Performance and Effects of Punched Holes and Cold Bending on Steel Bridge Fabrication,” sponsored by the Texas Department of Transportation. This research includes testing and analysis completed primarily at the Ferguson Structural Engineering Laboratory at The University of Texas at Austin.

This report discusses the method and ramifications of hole fabrication by punching in structural plate. Typically, punching is employed in the fabrication of structural elements related to connections, such as members, cross-frames, and gusset plates on bridges. AASHTO steel bridge specifications do not allow full size punched holes in primary load carrying members. Instead, holes are required to be formed by full-size drilling or reaming following punching.

In addition to literature review and analysis of previous research on the behavior and strength of connections with variables such as hole preparation, 120 plate specimens with punched, reamed, or drilled holes were tensile and fatigue tested during this study. Specimen variations included steel type, temperature, hole size, plate thickness, edge distance, edge preparation, punching clearance, punching operation, galvanizing, and amount of reaming. From this testing, net section stress, strength ratio, and usable elongation values at failure were determined for each specimen variation. While grade of steel, hole size, and plate thickness displayed some influence on strength ratio and usable elongation, edge distance, edge preparation, punching clearance, punching operation, galvanizing, and amount of reaming displayed little to no influence on strength ratio and usable elongation.

Overall, in strength performance, reamed specimens had the highest average strength ratio, followed by drilled and then punched specimens. In usable elongation performance, drilled and reamed specimens had the highest average elongation values, followed by punched specimens. Additionally, 41 replicate punched and drilled hole specimens were tensile tested to failure during this study in order to directly compare the performance of punched and drilled plate. Based on the strength performance of punched hole specimens, and particularly relative to drilled hole specimens, a capacity reduction factor is recommended for punched plate used in steel bridge connections.