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

本研究以钢焊接梁柱节点的塑性转动能力为研究对象，从动态加载、塑化耗能、耗散能量到热能的转换、热能温升、温升引起的材料韧性变化、材料延性变化以及最终节点塑性转动能力的变化等方面，将加载速率、温升与材料性能变化之间的复杂相互作用定量化。为此，对实际规模的梁柱组合体进行了动力加载试验、详细的非线性有限元分析和数值热传导分析，得到了以下结论：(1)累积塑性应变与温升具有很强的相关性；经典的平面截面保持平面的假设不适用于邻近…。详细的非线性有限元分析支持了试验结果，发现柱翼缘的柔性(平面外弯曲)和焊接通道孔洞的存在是造成应变分布复杂性的主要原因。(3)热传导分析表明，在地震期间，对空气的对流换热可以忽略不计，但钢材内部的换热是显著的。分析还验证了梁端附近的温升小于略远离梁端的温升，这是由于梁端上附着了非塑化柱的存在。(4)还提出了一种通过测量离散位置的温度来估算热能分布(即累积塑性应变分布)的方法。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。较少

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