Development of Damage-Resislient Structures Using Smart Materials

基于力和基于性能的抗震设计方法将目标最大漂移指定为性能水平和破坏程度的指标。震后勘察观测进一步确认了残差漂移作为量化结构性能和结构运行状态的一种措施的额外重要性。因此，残余漂移决定了结构是否可以使用、是否需要维修或是否必须拆除。这项研究的总体目标是开发用智能材料加固或改造的弹性混凝土结构系统，以控制在地震激励响应过程中产生的永久性损害，这些地震激励导致结构立即可用。形状记忆合金(SMA)是一类能够控制永久变形的智能材料。这种材料具有承受大应变的能力，这种应变水平将在钢筋中引起显著的永久应变，但在去除应力(超弹性(SE)SMA)或施加热(形状记忆效应(SME))后具有恢复其原始形状的卓越能力。这是使该材料在地震应用中具有吸引力的主要行为特征。其他显著特征包括强度和位移能力与钢筋相当，以及稳定的滞回反应。*这里的重点是利用SE-SMA的力学性能来开发弹性结构，包括新旧结构。具体地说，将开发改进的建模能力，为SE-SMA钢筋混凝土结构的性能评估提供工具。这将通过一种新的SE-SMA的非线性滞回本构模型和有限元模拟程序来实现。对于现有的抗震不足的钢筋混凝土框架结构，将开发一种新型的屈曲约束支撑，其中包括充当保险丝的SE-SMA内芯。将设计和测试替代SE-SMA桥柱，以评估与加拿大公路桥设计规范(CHBDC)的兼容性，并建立基于性能的设计所需的损坏指标。最后，SE-SMA钢筋混凝土结构的长期性能将通过在桥梁柱中引起腐蚀来评估，然后进行实验测试，以确定横向强度和位移能力，以及柱在腐蚀损伤后重新定位的能力。

Force-based and performance-based seismic design approaches specify target maximum drifts as indicators of performance level and damage. Post-earthquake reconnaissance observations have further identified the additional importance of residual drift as a measure to quantify structural performance and the operational state of a structure. The residual drift, therefore, determines whether a structure can be serviceable, requires repair, or must be demolished. The overarching goal of this research is to develop resilient concrete structural systems, reinforced or retrofitted with smart materials, to control permanent damage that arises during response to seismic excitations leading to structures that are immediately serviceable. Shape Memory Alloys (SMAs) are one class of smart materials that have the ability to control permanent deformations. The material has the capacity to sustain large strains, levels that would induce significant permanent straining in steel reinforcement, but with the superior capability to return to its original shape after removal of stress (Superelastic (SE) SMA) or with the application of heat (Shape Memory Effect (SME)). This is the main behavioural feature that makes the material attractive in seismic applications. Other salient characteristics include strength and displacement capacities comparable to steel reinforcement, in addition to stable hysteretic response.****The focus herein is to exploit the mechanical properties of SE-SMA towards the development of resilient structures including new and old construction. Specifically, improved modelling capabilities will be developed to provide tools for performance assessment of SE-SMA reinforced concrete structures. This will be achieved through a new nonlinear hysteretic constitutive model for SE-SMA and finite element modelling procedures. Retrofitting with a novel buckling restrained brace that encompasses an SE-SMA inner core acting as a fuse will be developed for existing seismically deficient reinforced concrete frame structures. An alternative SE-SMA bridge column will be designed and tested to assess compatibility with the Canadian Highway Bridge Design Code (CHBDC) and to establish damage indicators required in performance-based design. Finally, the long-term performance of SE-SMA-reinforced concrete structures will be assessed by inducing corrosion in bridge columns followed by experimental testing to determine the lateral strength and displacement capacities, and the ability of the columns to re-center following corrosion damage.******