Collaborative Research: Multi-Hazard Response Mitigation Systems Using High Strength and Damping Capacity Shape Memory Alloys

设计结构以抵御地震、强风和飓风等动态自然灾害是土木工程师主要关注的问题。最近在建筑形式、结构系统和高性能材料方面的进步使得设计非常细长和轻便的结构成为可能。这些柔性结构在强风和地震下容易受到高水平振动的影响，这可能导致结构损坏和潜在的失败。该研究项目将探索多灾害响应缓解系统中高性能智能合金的设计和特性。在一种新型被动控制装置中使用智能合金将提高建筑物在各种不同大小的危险下的动态性能。这将减少灾害损失以及与未来自然灾害事件有关的社会和经济中断。由于其跨学科的性质，这项研究将与教育计划紧密结合，以促进自然的学习和发现过程。本课题的研究目标是设计、制造和表征具有高强度和阻尼能力的超弹性形状记忆合金，通过实施一种新型被动结构控制装置，减轻多重灾害下中高层钢结构建筑的损伤，增强其事后功能。利用具有高强度、高耗散/阻尼能力、良好循环稳定性和宽工作温度范围的镍钛铪钯（NiTiHfPd）合金，研究基于形状记忆合金的重新定心阻尼器（SMARD），为受风和地震激励的建筑物提供阻尼和重新定心能力。SMARD装置的优势特点包括大而可扩展的受力能力、优异的重新定心能力、高阻尼能力、被动性质、能够承受多级危险，并且在整个生命周期内不需要特殊的维护或更换。研究活动包括以下内容：(1)表征热处理后的NiTiHfPd合金的形状记忆行为，以建立显微组织-性能关系；(2)定制显微组织，以获得高强度（大于1.5吉帕）和阻尼能力（大于30焦耳/立方厘米）的NiTiHfPd合金，可以在零下20摄氏度到正50摄氏度之间工作，并具有稳定的循环行为；(3)检查选定合金的循环响应。(4)设计并制造了一个力容量为500千牛顿、行程为300毫米的SMARD原型，(5)对该设备的动态行为进行了表征和建模。

Designing structures to withstand dynamic natural hazards such as earthquakes, strong winds, and hurricanes is of primary concern for civil engineers. Recent advances in architectural forms, structural systems, and high performance materials have enabled the design of very slender and lightweight structures. These flexible structures are susceptible to high levels of vibrations under strong winds and earthquakes, which may lead to structural damage and potential failure. This research project will explore the design and characterization of high performance smart alloys in multi-hazard response mitigation systems. The use of smart alloys in a novel passive control device will provide enhanced dynamic performance of buildings under various hazards of varying magnitudes. This will lead to reductions in disaster losses and in social and economic disruptions associated with future natural hazard events. With its interdisciplinary nature, this research will be closely integrated with educational plans to foster a natural process of learning and discovery. The research objective of this project is to design, fabricate and characterize superelastic shape memory alloys with high strength and damping capacity to mitigate damage and enhance post-event functionality of mid-rise to tall steel buildings subjected to multiple hazards by implementing a novel passive structural control device. Using the Nickel-Titanium-Hafnium-Palladium (NiTiHfPd) alloys that have very high strength, high dissipation/damping capacity, good cyclic stability, and a wide operating temperature range, a shape memory alloy-based re-centering damper (SMARD) will be investigated to provide damping and re-centering capabilities to buildings subjected to wind and earthquake excitations. The advantageous characteristics of the SMARD device include large and scalable force capacity, excellent re-centering ability, high damping capacity, passive nature, ability to withstand multiple levels of hazards, and need for no special maintenance or replacement through the life-cycle. The research activities include the following: (1) characterize the shape memory behavior of heat treated NiTiHfPd alloys to establish the microstructure-property relationship, (2) tailor the microstructure to obtain high strength (greater than 1.5 gigapascal) and damping capacity (greater than 30 Joules per cubic centimeter) NiTiHfPd alloys that can operate between minus 20 degrees Celsius to plus 50 degrees Celsius with stable cyclic behavior, (3) examine cyclic response of selected alloys, (4) design and fabricate a prototype of a SMARD with a force capacity of 500 kilonewtons and stroke of 300 millimeters, and (5) characterize and model the dynamic behavior of the device.