Correlation Between Loading Rate, Temperature Rise, and Material Properties Changes in Plastic Rotation Capacity of Steel Welded Beam-to-Column Connections

本研究的重点是量化加载速率、温升和材料性能变化之间的复杂相互作用，以考虑钢焊接梁柱连接的塑性转动能力。本研究的背景是可能的联系，从动态加载开始，塑性耗散的能量，耗散的能量转化为热能，由于热能引起的温升，由温度升高引起的材料韧性的变化、材料延展性的变化以及连接件塑性旋转能力的最终变化。为此，进行了应用于实际比例的梁-柱组合件的动态加载试验、详细的非线性有限元分析和数值热传导分析，并获得了以下结果。(1)累积塑性应变和温升有很强的相关性;经典的假设，即平截面保持平面是不适用于附近 ...更多信息 以及为避免局部屈曲而设置的竖向加劲肋也改变了局部应变分布。(2)详细的非线性有限元分析支持的实验结果，它被发现，应变分布的复杂性的主要原因是灵活的柱翼缘（在其平面外弯曲）和存在的焊接通道孔。(3)热传导分析表明，在地震期间预期的加载速率中，与空气的热对流可以忽略不计，但钢材料内的热传递是显著的。分析还证实了梁端附近的温升小于稍远离梁端的区域的温升，这是由于梁端存在非塑化柱的缘故。(4)还提出了一种估计热能分布的程序（即，累积的塑性应变分布）。本程序旨在为结构健康监测提供一种新的、可靠的测量指标。少

This study focuses on the quantification of complex interaction between loading rate, temperature rise, and material's property changes regarding the plastic rotation capacity of steel welded beam-to-column connections.The background of this study is the possible linkage, starting from dynamic loading, energy dissipated by plastificatiori, conversion of the dissipated energy to thermal energy, temperature rise due to thermal energy, change in material's toughness caused by the temperature rise, change in material's ductility, and eventual change in plastic rotation capacity of connections. To this end, dynamic loading tests applied to real-scale beam-to-column subassemblages, detailed nonlinear finite element analysis, and numerical heat conduction analysis were conducted, and the following findings were obtained.(1) Cumulative plastic strains and temperature-rise are correlated strongly ; the classical hypothesis that the plane section remains plane is not applicable in the proximity … More of beam end ; and vertical stiffeners arranged to avoid local buckling also altered the local strain distributions.(2) Detailed nonlinear finite element analysis supported the experimental findings, and it was found that the primary reasons for complexity of strain distributions are the flexibility of column flange (in its out-of-plane bending) and the existence of weld access holes.(3) The heat conduction analysis indicated that heat convection to air is negligible in the loading rate expected during earthquakes but that heat transfer within the steel material is conspicuous. The analysis also verified that the temperature rise in the very proximity of beam end is smaller than the temperature rise in regions slightly away from the end, and it is due to the existence of the non-plastified column attached to the beam end.(4) Proposed also was a procedure to estimate the thermal energy distributions (i.e., the cumulative plastic strain distribution) from the measurement of temperatures at discrete locations. This procedure is to provide a new, reliable measuring index for the purpose of structural health monitoring. Less