Shape Memory Alloy Tension/Compression Device for Seismic Retrofit of Buildings

A Tension/Compression damper and recentering device is developed for applications as bracing elements in buildings.  The device is designed to allow Nitinol forms such as helical springs or Bellville washers to be used in compression or for rods and wires to be deformed in tension. The device allows both overall extension and compression while subjecting the Nitinol to the optimum deformation mode. It is possible due to the versatility of the design to adjust the force and stroke of the device without changing the overall configuration.

 

 The new device is tested using a full-scale loading frame, where it is subjected to increasing cyclical strains up to 10% strain.  The effect of loading rate, and loading history is also evaluated in the study.  An analytical study is performed, where the device is placed in bracing elements in 3 story, 2 bay steel framed building.  The results of the analysis show that the recentering and damping properties result in significant reductions in building displacements, and forces transmitted to columns.