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

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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.