Double-shear tests of high-strength structural bolts at elevated temperatures

The behavior of high-strength structural steel at elevated temperatures, especially under shear loading, is not well established in the literature. This paper presents results from recently conducted tests on high-strength structural bolts subject to double shear loading at elevated temperatures. The parameters varied between tests included the bolt grade, bolt diameter, and temperature. Bolt grades A325 and A490 were tested. For each bolt grade, three different diameters were tested (19 mm (3/4 in), 22 mm (7/8 in), and 25.4 mm (1 in)) at five different temperatures (20 °C, 200 °C, 400 °C, 500 °C, and 600 °C). At least three tests were conducted for each combination of parameters. Degradations in the mechanical and material properties including stiffness, strength, and deformation at fracture, are characterized and presented herein. The results from these experiments fill a critical knowledge gap currently present in the literature regarding the behavior of high-strength structural bolts under shear loading at elevated temperatures. These data will ultimately provide a thorough understanding of the overall behavior of structural steel systems under realistic fire loading by clarifying the (i) shear behavior of high-strength structural steel bolts at elevated temperatures, and (ii) degradation in the mechanical and material properties of high-strength steel bolts with increasing temperatures.