SGER: NEESR Payload - Large-Scale Validation of Innovative SMA Recentering Devices for Multi-Span Bridges

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

0526889 Abstract This Small Grant for Exploratory Research (SGER) project is a NEESR payload project submitted in accordance with program solicitation NSF 05-527, NEES Research (NEESR). This project will use the experimental test set-up of NSF NEESR award CMS-0420347 entitled "NEESR-SG: Seismic Performance of Bridge Systems with Conventional and Innovative Materials." Results from this payload project will be archived in the NEES data repository maintained by NEES Consortium, Inc. (www.nees.org). Intellectual merit: Shape memory alloys are a class of unique alloys that have the ability to undergo large displacements and revert back to their original undeformed configuration via a martensitic transformation. Previous work by the Principal Investigator has focused on the optimization of the properties of the alloys such that they can be used in seismic applications. This has led to the development of ideal properties for both wire and large bars and the development and testing of component dampers and recentering devices. These studies were the first to show idealized flag-shaped superelastic properties in both large bars and wire. This NEESR payload project will use the multi-span bridge test set-up at the University of Nevada, Reno (UNR), NEES equipment site under NSF NEESR award CMS-0420347 to design, develop, and test innovative SMA devices on the bridge structure to validate the results of previous component testing and analytical studies. Three sets of devices will be tested: bundled SMA wire, optimized SMA bars, and SMA-based composites. The experimental tests will be coupled with analytical studies using OpenSees to determine the optimal properties of the devices to limit superstructure displacement and demands on columns and relative displacement at the abutment. Additional analytical studies will include the development of detailed models for SMAs. Several types of SMA elements will be developed and provided in the OpenSees element library. The results of the analytical models of the bridge will be used to develop bridge fragility curves to illustrate the viability of these innovative retrofit measures in a probabilistic framework and allow for comparison of the reduction in vulnerability of the bridge system with SMA recentering devices with other traditional retrofit measures. Using an instructional shake table located at Georgia Tech, a small-scale model of the test set-up will first be developed to evaluate concepts that will then be applied on the UNR bridge structure. Small SMA wires (0.08" diameter) will be used for the small-scale experiment. Broader Impacts: The project will leverage resources from an existing AGEP program at Georgia Tech to target and fund underrepresented undergraduate students to participate in all aspects of the research program, including the small-scale study, large-scale study, and analysis. The broader impact of the research is that the use of the promising, new SMA technology will be validated, which would significantly improve the performance of bridges during earthquakes, resulting in the potential reduction in casualties and economic losses from earthquakes. Furthermore, the knowledge gained by this project will provide the foundation for the use of smart materials in other structural systems.