Design, testing and implementation of a Cu-SMA-based device for improving the thermal behavior of steel tie-rods

Steel cables, tendons and tie-rods are the key components of many structures including masonry arches and vaults, timber roof trusses and several post-tensioned structures. In this paper, a device prototype based on the superelastic properties of Cu-based Shape Memory Alloys (SMAs), is proposed to enhance the thermal behavior of such structural elements. The thermal behavior of steel tie-rods with and without SMA is evaluated through comprehensive experimental tests in thermal room. During the tests, different temperature-time histories are considered, with air temperature varied between -10°C and 40°C. The results of the experimental tests confirm the great effectiveness of the proposed SMA device, with reductions of force changes due to air temperature variations of the order of 80-90%, compared to steel tie-rods without SMAs. In the paper, the main structural components and basic functioning principles of a SMA-based device prototype for masonry arches and vaults are presented and aspects related to its implementation in practice are discussed in detail.