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对钢焊接梁柱连接塑性旋转能力的复杂相互作用。本研究的背景是可能的联动，从动加载开始，塑化耗散的能量，将耗散的能量转化为热能，热能引起的温升，温升引起的材料韧性的变化，材料延性的变化，最终导致连接件塑性转动能力的变化。为此，进行了实尺梁柱组合的动加载试验、详细的非线性有限元分析和数值热传导分析，得到以下结果：(1)累积塑性应变与温升相关性强；平面截面保持平面的经典假设在梁端接近时不适用；为避免局部屈曲而设置的竖向加强筋也改变了局部应变分布。(2)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（面外弯曲）和焊接孔的存在是导致应变分布复杂的主要原因。(3)热传导分析表明，对空气的热对流在地震时的预期载荷率中可以忽略不计，但钢材料内部的热传递很明显。分析还验证了离梁端很近的区域的温升小于离梁端稍远的区域的温升，这是由于附在梁端上的非塑化柱的存在。(4)还提出了一种从离散位置的温度测量中估计热能分布（即累积塑性应变分布）的方法。该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