Structural control of smart prestressing with shape-memory alloy

Thermo-induced Shape-memory alloy (SMA) is a composite functional material with shape-memory effect (SME) and super-elasticity (SE) in large deformation situation. Applying this property, SMA wires were elongated beyond their plastic limit under room temperature and subsequently were embedded in concrete beams under low temperature, thus a smart prestressing is obtained. In this paper, basic principles and mechanical properties of smart prestressing are discussed, based on the relevant research and tests, the feasibility of inducing additional prestressing stress by SMA wires is also analyzed. And the stress losses caused by time history and other reasons can be controlled and adjusted by using this additional prestressing stress. In another words, the SMA wires can be heated to induce phase changes, and great stress is got when the SMA wires is not free to deform, when the current or voltage are adjusted, the stress is changing accordingly on an as-needed basis, in this way smart prestressing can be obtained.