This project developed and evaluated a new class of bridge expansion joints based on shape memory alloys (SMAs), which enhanced performance under service loads and extreme events, such as earthquakes. The project work comprised of three stages. Stage 1: design, develop, and test SMA joint-enhancement-components; Stage 2: dynamically test a full-scale as-built and SMA enhanced bridge joint; Stage 3: calibrate a nonlinear analytical joint model in OPENSEES and perform a cost-benefit analysis of the proposed joint configuration. The selected joint enhancement component is a 2.5 coil SMA spring, which can be placed in series with a standard polymer equidistant device. When placed in a real modular bridge expansion joint (MBEJ) and experimentally tested through a range of displacements at various frequencies, the enhanced bridge joint was observed to prevent the failure of internal components, which for real world applications translates into improved post-event bridge functionality and avoidance of intrusive repairs to the bridge joint. A fragility analysis, which results in probability curves stating the likelihood of failure given an earthquake intensity measure, performed on a representative bridge showed that for the moderate and extensive damage states the SMA enhancement had noticeable positive influences on the MBEJ component vulnerability. At the bridge system level, the use of the SMA enhancement reduced the probability of achieving the slight damage state, where functionality of the overall bridge may be inhibited. A probabilistic cost-benefit analysis was conducted to compare the SMA enhancement to the standard MBEJ for different seismic regions considering a remaining service life of 50 years. The results show that the cost-benefit ratio of using the SMA enhanced joint is 10.9 for the site in Missouri, 4.5 in South Carolina, and 218 in California. These results suggest a significant return on investment for the approximate 17% cost increase for the enhanced bridge expansion joint.
The contractor's final report is available.