设置低屈服点钢材“结构保险丝”的延性钢框架连接节点受力性能研究

Study on mechanical behavior of ductile steel frame connection with low yield point steel ’structural fuse’

为改善钢框架梁柱连接节点的受力性能,保护主体结构在地震作用下不损坏,实现震后建筑功能可快速恢复,提出一种设置低屈服点钢材"结构保险丝"的可更换连接组件的全螺栓连接延性节点。采用通用有限元软件ABAQUS建立非线性计算模型,结合已有钢框架螺栓连接节点拟静力试验,验证数值模型的准确性和适用性。在此基础上,建立不同连接形式、不同连接组件材料的节点模型,分析设置低屈服点钢材"结构保险丝"的螺栓连接节点的受力行为和作用机理。分析结果表明:采用低屈服点钢材的连接组件,能够耗散80%~95%节点能量,较好保护主体钢框架保持在弹性范围,充分发挥"结构保险丝"作用,实现震后功能可快速恢复的目标;实际承载力系数决定"结构保险丝"是否发挥作用,随着实际承载力系数的提高,节点的破坏由连接组件逐步转移到主体钢框架。并且由于钢材的循环强化行为,在加载过程中,连接节点的承载力均有明显的强化现象,在设计时应予以考虑,保证实际承载力系数在延性节点转角变形范围内小于1.0,避免"保险丝"设计过早失效;在达到同样转角的情况下,扩孔型节点进入塑性程度较小,总体耗能较小,这主要是由于扩孔型节点主要靠扩孔螺栓滑移增加节点变形能力,保护主体结构,"结构保险丝"机理与其他两种形式的节点有所不同。

In order to improve the mechanical performance of steel frame structure,protect the main structure from being damaged under earthquakes,and achieve quick recovery of building functions after earthquakes,a kind of replaceable bolted ductile steel frame connection with low yield point steel‘structural fuse’was proposed.Non-linear finite element models were established by software ABAQUS,which were proved accurate and applicable according to the published quasi-static tests of steel frame bolted connections.Based on the verified numerical method,connections with different forms and different component materials were established.The behavior and mechanism of these connections were compared and discussed in depth.The analysis results show that the connecting components with low yield point steel could dissipate 80%-95%energy of the whole connection,protect the main structure in elastic range,and play a role of‘structural fuse’to realize quick recovery of building functions after earthquakes.The actual coefficient of bearing capacity determined the effectiveness of‘structural fuse’.With the increasing of this coefficient,the failure point transferred from the connecting component to the main frame.Due to the cyclic hardening behavior of low yield point steel,the hardening phenomena of the bearing capacity were observed during the loading process.This phenomenon should be considered in design to ensure the coefficient of the bearing capacity less than 1.0 within the required range of rotation deformation,and avoid the‘fuse’failure.The connection with enlarged holes mainly depended on the bolt slipping within the slotted hole to increase the deformability of the connection and to protect the main structure;therefore,under the same rotation,the connection with enlarged holes had less plastic deformation and less overall energy dissipation.