SHAPE MEMORY ALLOY CABLES FOR CIVIL INFRASTRUCTURE SYSTEMS

Shape memory alloys (SMAs) have attracted a great deal of attention as a smart material that can be used in various civil engineering applications due to their favorable mechanical properties such as ability to undergo large defounations, high corrosion and fatigue resistance, good energy dissipating capacity, and excellent re-centering ability. In contrast to the use of SMAs in the biomedical, mechanical and aerospace applications, which requires mostly small diameter of material, the larger size bars are usually needed in a civil engineering application. It is well known that properties of large-section SMA bars are generally poorer than those of wires due to difficulties in material processing. Furthermore, large diameter SMA bars are more expensive than thin SMA wires. Shape memory alloy cables have been recently developed as an alternative and new structural element. They leverage the superior mechanical characteristics of small diameter SMAs into large-size structural tension elements and possess several advantages over SMA bars. This study explores the performance of NiTi SMA cables and their potential use in civil engineering. The SMA cable, which has a diameter of 8 mm, is composed of 7 strands and each strand has 7 wires with a diameter of 0.885 mm. The uniaxial tensile tests are conducted at various loading rates and strain amplitudes to characterize the superelastic properties of the SMA cable and study the rate-dependent mechanical response of the SMA cable under dynamic loads. An optical digital image correlation measurement system and an infrared thermal imaging camera are employed to obtain the full-field strain and temperature fields. Potential applications of SMA cables in civil infrastructure applications are discussed and illustrated.