中文摘要：

介绍了8个足尺节点试验的结果与连接焊缝断裂破坏的现象。采用二维有限元断裂模型,研究了抗弯钢框架梁柱节点的断裂行为。以I型裂纹尖端应力强度因子KI和J积分为定量评价指标,分析了焊接孔形式、初始缺陷尺寸及位置、焊接垫板、角焊缝补强等设计细节对节点材料断裂韧性需求的影响。弹性分析表明,切除垫板并以角焊缝补强的措施,能最有效地降低对材料韧性的要求。弹塑性分析表明,焊接高匹配时热影响区裂纹比界面裂纹对材料韧性的要求更高,且局部塑性应变累积使材料的断裂韧性降低;解释了节点试验中断裂易发生在梁下翼缘焊缝热影响区的现象。基于断裂分析得到的节点抗弯承载力与试验中节点的极限弯矩吻合较好,该文的研究为钢框架梁柱节点的防断设计提供了参考。

英文摘要：

Experimental results of eight full-scale beam-to-column connections are presented.Two dimensional finite element fracture models are used to simulate the fracture behaviors of the connections which are commonly applied in steel moment resisting frames.Mode I elastic stress intensity factor（KI） and inelastic J-integral（JI） at the crack tip are calculated to provide quantitative estimates of fracture toughness demands of the connections with different design details,such as weld access hole types,initial flaw size locations,weld backing bars,fillet reinforcement and other configurations.The elastic analyses indicate that the measure of removing the backing bar and reinforcing a fillet weld,is effective to reduce the toughness demand.The inelastic analyses show that the initial crack at weld heat affected zone（HAZ） causes larger toughness demands than the crack at column flange and weld interface when the weld is over matched.The analyses have confirmed the observation in former connection tests that the fractures are more likely to occur at the beam bottom flange weld HAZ area where extensive plastic strains accumulate resulting in low material toughness.The evaluated moments by fracture model analyses agree well with the ultimate moments obtained by the connection tests.This study provides valuable references for the fracture resistant design of beam-to-column connections in steel moment resisting frames.