The National Academies

NCHRP IDEA 20-30/IDEA 135 [Completed (IDEA)]

Active Confinement of Bridge Piers Using Shape Memory Alloys
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Dr. Inam Jawed

This project developed a system for the active confinement of reinforced concrete bridge piers using shape memory alloys (SMAs). Work in Stage 1 focused on evaluating SMA-based materials for the proposed confinement of bridge piers. A material testing program was completed to determine the stress-strain behavior of concrete cylinders actively confined with SMAs. SMA spirals were evaluated for their thermo-mechanical characteristics and effectiveness in enhancing the concrete compressive strength and ductility. A comprehensive study was conducted to examine the recovery stress of the SMA wires and its stability at various ambient temperatures. The tests revealed a reliable behavior for the SMA wires, which were able to develop a recovery stress of 75 ksi that was stable at room temperature.  A series of concrete compression tests were conducted to compare the effectiveness of the SMA spirals with glass fiber-reinforced plastic (GFRP) wraps. Hybrid type of wraps consisting of SMA wires and GFRP sheets were also included in the study. Results showed that the SMA spirals increased the concrete ultimate strain (ductility) by 24 times as compared to unconfined concrete. The behavior of the SMA-confined concrete was much superior to GFRP- confined concrete. Work in Stage 2 focused on a series of quasi-static lateral cyclic tests on four reduced-scale reinforced concrete circular bridge columns. The SMA products evaluated and selected in the first phase were used to retrofit the test columns using active confinement technique. Tests also included column specimens retrofitted using conventional GFRP wraps as well as as-built specimen. The results showed that the columns wrapped with SMA spirals were able to sustain 12% drift ratio with no significant signs of damage, while the GFRP wrapped column started experiencing major damage starting at 4% drift ratio. Furthermore, inspection of the damage sustained by tested specimens revealed that the actively confined columns sustained minor damages compared to the as-built and passively confined columns.  This contractor's report is available.

To create a link to this page, use this URL: http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2591