Abstract This paper investigates the net section tension strength of bolted connections in ultra-high strength sheet steel (yield stress greater than 1000 MPa) under various fire scenarios through laboratory testing. The specimens are tested at room (ambient) temperature and elevated temperatures up to 700 °C, and are subjected to air or water cooling from temperatures as high as 1000 °C. The degradations of the tensile strength at elevated temperatures are much more severe than design code predictions. Substantial recovery of the tensile strength is feasible using water cooling if the steel has been exposed to 1000 °C, by almost 90%. Based on finite element analyses incorporating tensile fracture simulation, the paper determines that elongation at fracture is the most relevant parameter of material ductility for a structural steel connection. Tension fractures in very low ductility materials tend to be inclined to the loading direction of the bolted connection. This paper also examines the alternative formulae for determining the net section tension strength of a stagger bolted connection. Their accuracy is verified through the use of a certain geometry, which eliminates any potential errors due to the use of incorrect material tensile strength in the calculations. Cochrane's original formula is confirmed to be significantly more accurate than the simplified version used in the literature and some design codes, for the tested specimens.

中文翻译：

---

火灾中和火灾后超高强度钢板螺栓连接的净截面抗拉强度

摘要 本文通过室内试验研究了各种火灾情况下超高强度钢板（屈服应力大于1000 MPa）螺栓连接的净截面抗拉强度。样品在室温（环境）温度和高达 700 °C 的高温下进行测试，并在高达 1000 °C 的温度下进行空气或水冷却。高温下拉伸强度的下降比设计规范预测的要严重得多。如果钢已暴露于 1000 °C，则使用水冷可以使抗拉强度显着恢复近 90%。基于结合拉伸断裂模拟的有限元分析，本文确定断裂伸长率是结构钢连接材料延展性最相关的参数。延展性非常低的材料中的拉伸断裂往往倾向于螺栓连接的加载方向。本文还研究了确定交错螺栓连接净截面抗拉强度的替代公式。它们的准确性通过使用某种几何形状来验证，这消除了由于在计算中使用不正确的材料拉伸强度而导致的任何潜在错误。对于测试样本，Cochrane 的原始公式被证实比文献和一些设计规范中使用的简化版本要准确得多。它们的准确性通过使用某种几何形状来验证，这消除了由于在计算中使用不正确的材料拉伸强度而导致的任何潜在错误。对于测试样本，Cochrane 的原始公式被证实比文献和一些设计规范中使用的简化版本要准确得多。它们的准确性通过使用某种几何形状来验证，这消除了由于在计算中使用不正确的材料拉伸强度而导致的任何潜在错误。对于测试样本，Cochrane 的原始公式被证实比文献和一些设计规范中使用的简化版本要准确得多。