钢结构侧面角焊缝高温后力学性能

Mechanical Behavior of Longitudinal Fillet Welds in Steel Structures after Exposure to Elevated Temperature

开展了43个侧面角焊缝连接试件高温冷却后的拉伸试验,过火温度介于200~900℃,冷却方式包括自然冷却和泼水冷却.采用三直线模型计算高温后侧面角焊缝极限抗剪强度变化系数.结果表明：高温后侧面角焊缝破坏截面与钢板平面的夹角基本呈45°,表明焊缝是在剪切应力作用下发生破坏;过火温度超过400℃后,侧面角焊缝极限抗剪强度开始显著下降,过火温度为700℃时焊缝极限抗剪强度降幅约为25%;过火温度超过700℃后侧面角焊缝极限抗剪强度有所回升,冷却方式对焊缝极限抗剪强度的回升程度有显著影响;以三直线模型计算的高温后侧面角焊缝极限抗剪强度变化系数结果与试验值吻合良好.

43 longitudinal fillet welded connection specimens were first heated to specified temperature levels, and then cooled to ambient temperature and stretched to failure. Seven post-fire temperatures ranging from 200℃ to 900 ℃ were considered, and two cooling methods including natural cooling and water cooling were adopted in the test. The tri-linear model was proposed to calculate the variation factor of ultimate shear strength of longitudinal fillet weld after exposure to elevated temperature. Results show that the fracture angles of longitudinal fillet welds after exposure to elevated temperature are about 45°, indicating that fracture of these welds is caused by shear stress. When the post-fire temperature is above 400 ℃, the ultimate shear strength of longitudinal fillet weld starts to decrease significantly, and the decrease range reaches about 25 % at 700 ℃. The ultimate shear strength of longitudinal fillet weld starts to increase when the post-fire temperature is above 700 ℃, and the cooling methods have a significant effect on the strength variation degree at this stage. The predicted values of variation factors of ultimate shear strengths of longitudinal fillet welds after exposure to elevated temperature calculated by tri-linear model agree well with the test values.