Reducing seismic residual deformations of existing reinforced concrete frames using shape memory alloys

以往的地震研究表明，钢筋混凝土框架结构的震害主要集中在梁柱节点附近。它以不同的形式发生，包括：节点剪切破坏，梁和/或柱的弯曲破坏，梁和/或柱的剪切破坏，以及粘结滑移破坏。虽然根据旧规范规定设计的框架容易受到所有上述形式的损坏，但根据当前标准设计的框架预计会因其梁的弯曲失效而倒塌。由于设计和/或施工过程中的缺陷或居住者的误用（改变预期用途并因此改变施加的载荷、施加临时重载荷等），新设计的框架中可能同时存在其他形式的损坏。在过去的几十年里，现有钢筋混凝土框架的改造受到了研究界的极大关注。已经提出了几种改造方法。虽然这些方法提供了一个解决方案的弯曲和剪切的缺陷，他们保持一个主要的缺陷：地震残余变形。这些变形是由于钢筋屈服而产生的，这是消散地震能量所必需的。然而，它们使地震后的改造工作复杂化。形状记忆合金（SMA）的独特之处在于它们能够经受大的变形并恢复到其未变形的形状。拟议的研究提供了一个全面的实验和分析研究，不仅将提供解决方案，现有的钢筋混凝土框架可能存在的缺陷，但也将显着减少其预期的地震残余变形。将开发利用SMA的新型改造技术。将开发能够预测改造后的结构元件的行为的分析模型，并使用实验测试进行验证。这些模型将用于分析全尺寸框架，以确定最佳的改造策略。拟议的研究将涉及对一名博士和三名MESc候选人进行最先进的实验和分析研究的培训。这些HQP将成为塑造智能结构未来和提高加拿大建筑业竞争力的关键人员。

Previous earthquakes have shown that seismic damage to Reinforced Concrete (RC) frames mainly concentrates in the vicinity of the beam-column joint area. It occurs in different forms including: joint shear failure, flexural failure of beams and/or columns, shear failure of beams and/or columns, and bond slip failure. While frames designed based on older code provisions are susceptible to all mentioned forms of damage, frames designed to current standards are expected to collapse due to flexural failure of their beams. Other forms of damage can co-exist in newly designed frames due to faults in the design and/or construction processes or misuse by occupants (changing the intended use and consequently the applied loads, applying temporary heavy loads, etc.). Retrofitting of existing RC frames has received significant attention from the research community during the past decades. Several retrofitting methods have been proposed. While these methods provide a solution to the flexural and shear deficiencies, they maintain a major deficiency: seismic residual deformations. These deformations result from yielding of the reinforcing bars that is necessary to dissipate the seismic energy. However they complicate post-earthquake retrofitting efforts. The uniqueness of Shape Memory Alloys (SMAs) lies in their ability to undergo large deformations and return to their undeformed shape. The proposed research provides a comprehensive experimental and analytical study that will not only provide solutions to possible deficiencies in existing RC frames, but will also significantly reduce their expected seismic residual deformations. Novel retrofitting techniques that utilize SMAs will be developed. Analytical models capable of predicting the behaviour of the retrofitted structural elements will be developed and validated using experimental tests. These models will be used to analyze full-scale frames to define optimal retrofitting strategies. The proposed research will involve the training of one PhD and three MESc candidates on state-of-the-art experimental and analytical studies. These HQP will be key personnel in shaping the future of smart structures and enhancing the competitiveness of the Canadian construction industry.