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Smart Materials for Protection from Extreme Events

Damage from past extreme events coupled with risk assessment of existing infrastructure has continued to highlight the need for improved methods to protect key components of our built infrastructure, such as buildings or bridges.  Padgett's research group along with academic and industry partners are evaluating the use of non-traditional building materials, known as shape memory alloys, to retrofit or enhance the design of structures particularly in seismic regions.  Shape memory alloys (SMAs) are a class of smart materials that have unique characteristics such as the ability to recover their original shape upon the removal of load or application of heat, as well as to dissipate energy and resist corrosion.  This research has demonstrated the viability of nitinol SMAs as restrainer cables in bridges through large scale testing, and their advantages over traditional retrofit devices to prevent bridge collapse.  Ongoing studies integrate the materials into bridge expansion joints to enhance typical non-seismic joints so that they can sustain earthquake excitation, requiring minimal to no repair and enabling traffic to pass after an event.  A new class of SMART expansion joints was recently developed and tested including full scale prototype testing, revealing that at minimal cost over base joints, the new systems were able to preserve desirable service load behavior while accommodating significant increases in longitudinal displacement under dynamic loads. As a part of this work, experimental testing and finite element modeling of compact, geometrically complex shape memory alloy components provides a new library for application to a broad range of structural systems. As an example, analytical studies explore the cost-benefit of SMA bracing systems in low ductility reinforced concrete buildings to show the mitigated risk of damage and expected seismic losses.

Smart Materials for Protection of Bridges from Extreme Events Smart_Joint SMA_Ring