通过改进节点性能确保火灾下钢框架结构的鲁棒性

介绍了钢框架结构火灾下鲁棒性的背景知识,建议对于非常重要的建筑结构,抗火安全设计必须包括通常设计中尚未考虑到的意外破坏模式。文章辨识了结构意外破坏的不同模式,并提出了保证结构安全性的可行方法。本文主要介绍了如何利用梁的悬链线效应,使荷栽从受损结构重新分配到相邻结构,该效应是梁受弯承载力状态的一种转变。为确保钢梁中悬链线效应的充分发展,最重要的是要保证节点具有足够的抗拉承栽力与转动能力。本文提出了一种节点转动能力需求的量纲分析方法,并根据一些试验结果,介绍了英国常用的梁柱节点可到达的转动能力。虽然一些延性较好的节点在升温时能够达到10°的转动能力,但当钢的温度非常高时,其仍不能满足使悬链线效应充分形成时所需要的转动能力（〉15°）。随后,讨论了如何提高节点的转动能力,包括：采用具有较好延性的节点（例如开反向槽口的节点）,改进节点的细部构造（如将节点的受拉区移近至受压区,并为螺栓开槽型孔）和采用更强的、延性更好的由耐火钢制成的螺栓。这些提出的节点技术需要与节点在其他设计要求下的性能要求相协调（如刚度）,为满足不同的结构性能要求,找到最优的节点设计方法,仍需要更深入的研究。

Ensuring Robustness of Steel Framed Structures in Fire through Improved Joint Performance

This paper explains the context of robustness of steel framed structures in fire and recommends that for very important building structures,design for fire safety should include provision for accidental damages which are not considered in normal Fire Limit State design.It identifies different modes of accidental damage and possible means of ensuring structural safety.The main part of this paper is about how to utilise catenary action in beams, which is an alternative load-carrying mechanism to bending,to redistribute loads from damaged structural members to the rest of the structure.To enable substantial catenary action to develop in steel beams,it is most important to ensure the joints to possess sufficient tension resistance and rotation capacity.This paper presents an order-of-magnitude analysis of the required joint rotation capacity and some experimental evidence of the available rotation capacity of common steel beam-column joints used in the UK.Some of the more ductile joints possess significant rotation capacity at elevated temperatures（about 10°）,but even this is not sufficient for the required rotation capacity（15°） to allow full development of catenary action when the steel temperature is very high.This paper then discusses how joint rotation capacity may be increased,including using inherently ductile joint components （for example introducing a reverse channel）,improving joint detailing such as moving the joint tension components closer to the compression components and using slotted holes for bolts）,and selecting stronger and ductile bolts made of Fire Resistant steel.Many of these proposed joint technologies may compromise joint performance for other design requirements（for example stiffness）,and more extensive research is necessary to find optimised joint solutions that are able to meet the different requirements of structural performance.