Characterisation and advanced modeling of multidimensional strain-rate effects on structural steels for enhanced seismic design of building structures in Canada

用于轻工业、商业和娱乐目的的低层钢结构建筑在加拿大的建筑存量中占很大比例。这些建筑物大多位于太平洋沿岸、圣劳伦斯河和渥太华河沿岸的地震活动性和中度活动性地区。对于这种类型的建筑，加拿大国家建筑规范规定了设计各种抗震系统（SFRS）的能力设计理念，预计在地震等强烈动力激励下的非弹性反应。在这种类型的事件中，延性SFRS中的应变率往往非常高，这导致材料的行为与缓慢加载时不同。因此，在设计和/或在这种情况下对结构的响应进行数值模拟时，不考虑应变率可能会导致对结构的预期行为和预期破坏模式的错误结论。研究计划的主要目标是：1)表征应变率对结构钢屈服和极限应力轨迹的影响；2)开发数值工具，准确预测结构单元在复杂动力非弹性需求下的响应；3)从偏心支撑框架连杆（EBF）的动态试验结果中验证这些工具；4)研究应变率对当前设计实践的影响，即识别可能导致整体倒塌的结构破裂模式的潜在变化。最终，目前的研究计划旨在：1)更好地了解应变率对韧性钢元件的影响；2)提出考虑应变率影响的更好的抗震设计准则。更好的设计通常有利于金融经济，但更重要的是，在发生大地震时，更安全的结构。

Low-rise steel buildings used for light industrial, commercial, and recreational purposes, represent a vast proportion of the building stock in Canada. Most of these buildings are located in regions of active and moderate seismicity levels on the Pacific coast and along the St-Lawrence and Ottawa rivers. For this type of building, the National Building Code of Canada imposes a capacity design philosophy for the design of various seismic force resisting systems (SFRS), for which inelastic response is anticipated under severe dynamic excitation such as earthquakes. During this type of event, the strain-rates in ductile SFRS tend to be very high which causes the material to behave differently than when loaded slowly. For this reason, not taking into account strain-rates when designing and/or numerically simulating the response of a structure in such context might lead to erroneous conclusions on the structure's expected behaviour and expected modes of failure. The main objectives of the research program are: 1) to characterise the effects of strain-rates on the yield and ultimate stresses loci of structural steel; 2) to develop numerical tools to accurately predict the response of structural elements submitted to complex dynamic inelastic demands; 3) to validate those tools from dynamic test results on eccentrically braced frame links (EBF); and 4), to investigate the effects of strain-rates on current design practices, i.e. to identify the potential changes of rupture modes in structures that could lead to a global collapse. Ultimately, the current research program aims at: 1) better understand the effects of strain-rates on ductile steel elements; and 2) proposing better seismic design guidelines taking into account the effects of strain-rates. Better designs generally yield to financial economies, but more importantly in safer structures in the event of major earthquakes.