MECHANICAL PROPERTIES OF STRUCTURAL STEEL AND HIGH-TENSION BOLT AT ELEVATED TEMPERATURE

This paper presents the test results of the mechanical properties of three types of structural steel at high temperature, which are generally used for the Pre-Engineered Building (PEB) system. The PEB system is generally used for non-residential buildings, such as factories and warehouses. The structural steel members are installed without fire resistance protection, which means they are very weak in the case of fire. The end-plate connection could be critical in the case of fire because most of the moment is resisted by the tensile force of the bolts. Therefore, the mechanical properties of bolts at elevated temperatures are tested. Coupon test specimens for SS400(SS275), (SM490(SS355), and F10T bolts were tested according to ASTM E8M. The high-temperature coupon tests were performed at 20ฐC, 400ฐC, 500ฐC, 600ฐC, 700ฐC, and 800ฐC. The test results were compared with the design reduction factors obtained from the American and European standards. The yield strength and tensile strength satisfied the minimum strength of the specified standards at 20ฐC. However, the reduction factor for yield strength obtained at a high temperature was lower than that of the standard value suggested by the code. In particular, the reduction factors for the high-strength bolt (F10T) were lower than those of the structural steel members (SS400(SS275), SM490(SM355)).本文提供了三类常用于预制装配式建筑（Pre-Engineered Building）体系的结构钢的高温力学性能试验结果。该PEB体系通常应用于非民用建筑场景，例如厂房与仓库。此类结构钢构件在安装时未设置防火防护措施，因此在火灾工况下力学性能极易劣化。火灾工况下端板连接节点（end-plate connection）可能成为结构薄弱环节，因为此时绝大部分弯矩由螺栓的受拉力承担。据此，本文对高温环境下螺栓的力学性能开展了试验研究。本次试验依据ASTM E8M标准，对SS400(SS275)、SM490(SS355)及F10T三类螺栓的拉伸试样开展了测试。高温拉伸试验的测试温度分别设置为20℃、400℃、500℃、600℃、700℃及800℃。将试验所得结果与美欧相关标准中给出的设计折减系数进行了对比分析。在20℃常温工况下，试样的屈服强度与抗拉强度均符合对应标准规定的最低强度限值。但在高温工况下，测得的屈服强度折减系数低于标准规范给出的标准值。尤为值得注意的是，高强度螺栓（F10T）的强度折减系数低于前述结构钢构件（SS400(SS275)、SM490(SS355)）的折减系数。