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

土木工程师最关心的是设计结构以承受动态自然灾害，如地震、强风和飓风。建筑形式、结构系统和高性能材料的最新进展使得能够设计非常细长和轻质的结构。这些柔性结构在强风和地震下容易受到高水平的振动，这可能导致结构损坏和潜在故障。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表征。智能合金在新型被动控制装置中的使用将在不同程度的各种危险下提供增强的建筑物动态性能。这将导致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混乱。凭借其跨学科的性质，这项研究将与教育计划紧密结合，以促进学习和发现的自然过程。本项目的研究目标是设计、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，通过实施一种新型的被动结构控制装置来减轻遭受多种危害的中高层钢结构建筑的损伤并增强其事后功能。利用镍钛铪钯（NiTiHfPd）合金具有非常高的强度、高的耗散/阻尼能力、良好的循环稳定性和宽的工作温度范围，将研究基于形状记忆合金的再定心阻尼器（SMARD），以向受到风和地震激励的建筑物提供阻尼和再定心能力。SMARD装置的有利特征包括大且可扩展的力容量、优异的重新定心能力、高阻尼能力、被动性质、承受多个级别的危害的能力，并且在整个生命周期中不需要特殊维护或更换。研究活动包括：（1）表征热处理NiTiHfPd合金的形状记忆行为以建立显微组织-性能关系，（2）调整微观结构以获得高强度（大于1.5吉帕斯卡）和阻尼能力（大于30焦耳/立方厘米）NiTiHfPd合金可以在-20摄氏度至+50摄氏度之间操作，具有稳定的循环行为，（3）检查所选合金的循环响应，（4）设计和制造具有500千牛顿的力容量和300毫米的冲程的SMARD的原型，以及（5）表征和建模装置的动态行为。

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.