Response of Steel Beam-to-Column Connections to Dynamic Loading

2001年9月11日事件的后遗症仍在世界各地回荡。世界贸易中心(WTC)大楼倒塌事件将结构工程领域推到了聚光灯下，专业人士和公众对建筑物倒塌带来的危险都有了更高的认识。世贸中心结束后的讨论突出并突出了一场以前有限的辩论，辩论的焦点是我们对框架建筑对意外或恶意破坏的反应的认识上的不足。早在9·11袭击之前，美国政府的一个工作小组就表示，渐进式结构倒塌是建筑物倒塌的主要(如果不是主要的)原因，无论加载来源如何……因此，预测和设计在特定袭击情景下防止建筑物逐渐倒塌是(也应该是)主要目标……同一份报告指出，……关于建筑物倒塌和建筑法规要求的指导意见将是有价值的。尽管人们普遍认识到，大多数建筑物的倒塌都包括建筑物倒塌，但人们对渐进式倒塌的现象还没有很好的理解。尽管建筑规范告诫设计者确保不会发生倒塌，但它们并没有就如何实现或应该实现这一点提供指导。在他们的建议中，渐进性崩塌的性质和机制是一个值得学术界进一步研究的课题。近四分之一个世纪以来，这一主题一直没有在有意义的层面上得到解决，但它可能会在减轻许多危险的风险方面带来好处。英国的情况也类似。9月11日之前的一份报告承认，虽然对结构抗意外损坏的要求没有争议，但目前还没有确定需要多少冗余才能在发生损坏时提供可接受的安全水平，或估计损坏结构中的力如何重新分配的既定基础。同一份报告指出，建筑物固有的坚固性可能受到结构分析和设计方面的进步的影响，这使设计者能够更准确地对结构进行建模。它认为，这减少了通常为追求建筑经济性而过度设计结构框架的情况，并可能导致建筑物的坚固性降低。虽然英国目前的设计准则强调了悬链线作用在框架结构建筑中提供耐久性的重要性，以及由此对构件和连接的抗拉能力的要求，但在实践中，连接的弯矩抗力(Virendeel Bridge作用)和抗剪(抗碎屑荷载)很可能是同等重要的。最近英国和美国的权威出版物都强调了目前对螺栓钢连接的动力响应缺乏了解，迫切需要不同类型的框架结构对损伤的反应(这是提出者已经在调查的课题，也是先前研究方案的主题)和钢连接的动力性能的权威数据。本项目的总体目标是对钢连接对动态载荷的响应进行实验研究，并将结果与现有的设计建议进行比较。我们将研究一系列典型的英国建筑中使用的连接方式，包括腹板、鳍板、部分深度端板、平底端板和加长端板。

The after-effects of the events of 11 September 2001 are still reverberating around the world. The collapse of buildings at the World Trade Centre (WTC) has thrown the field of structural engineering into the spotlight and professionals and the public alike have a heightened awareness of the dangers posed by the collapse of buildings. The post-WTC deliberations have highlighted and brought into sharp focus a previously limited debate on the shortcomings in our knowledge of the response of framed buildings to accidental or malicious damage. Even before the September 11 attacks, an American government working party stated that Progressive structural collapse is a primary, if not the leading, cause of injury and death in building failures, regardless of the source of loading...For this reason, predicting and designing to prevent progressive collapse of a building under a specified attack scenario is (and should be) a primary objective... The same report noted that ...guidance on building collapse and building code requirements would be valuable. The phenomenon of progressive collapse is not well understood, despite the widespread recognition that most building failures include building collapse. Although building codes admonish designers to ensure that collapse does not occur, they do not provide guidance on how this can or should be accomplished. Among their recommendations is The nature and mechanism of progressive collapse is a subject that merits further study by the academic community. This topic, which has not been addressed at a meaningful level for almost a quarter of a century, could have benefits in mitigating risks from many hazards. The situation in the United Kingdom is similar. A pre-September 11 report acknowledged that, whilst the requirement for structures to be robust against accidental damage is not disputed, there is presently no established basis for determining how much redundancy is required in order to provide an acceptable level of safety in the event of damage, or to estimate how the forces in a damaged structure are redistributed. The same report pointed out that, inherent robustness of buildings may have been compromised by advances in structural analysis and design, which have enabled the designer to model a structure more accurately. This, it argued, has reduced the usual over-design of structural frames in the pursuit of economy of construction, and may have resulted in buildings with reduced robustness. Although current UK design guidelines emphasise the importance of catenary action in providing robustness against damage in framed buildings, and the consequent requirement for tensile capacity of members and connections, in practice, it is likely that both moment resistance (in Virendeel bridging action) and shear resistance (to debris loading) of connections will be equally important. Recent authoritative publications in both the UK and USA have highlighted the current lack of knowledge of the dynamic response of bolted steel connections and there is a pressing need for authoritative data on both the response of different types of framed structures to damage (a topic already under investigation by the proposers and the subject of an earlier research proposal), and the dynamic behaviour of steel connections.The overall aim of this project is to conduct an experimental study of the response of steel connections to dynamic loading and compare the results with existing design recommendations. A range of connections typical of those used in UK construction will be examined, including web cleats, fin plates, partial depth- , flush- and extended endplates.