SMA-based tension control block for metallic tendons

Metallic tendons are frequently used in arches and vaults to absorb the lateral thrusting forces due to gravity loads or inertial forces caused by an earthquake. Traditional tendons, however, have some limitations (e.g. sensitivity to temperature variations, buckling under compression, etc.). Shape memory alloys (SMAs) can be used to enhance the performances of metallic tendons both in service and seismic conditions. This is achieved with the tensioning control block (TCB) system. The basic components of TCB are pre-strained superelastic SMA wires, in series with the metallic tendon. The number and diameter of the SMA wires is selected based on the force levels to reach. The length is optimised with respect to the thermal behavior of the system. A number of theoretical and experimental studies have been conducted to fully understand the thermal and mechanical behavior of TCB. In the paper, the main outcomes of these studies are described.