Abstract
Concrete is the most widely used material for the design of civil structures. However, traditional cementitious materials are brittle and susceptible to cracking and have no functional properties. One approach to enhance longevity and structural performance of concrete structures is the use of high performance materials and structural systems that are durable and safe. Smart materials have received significant interest for civil engineering applications in recent years and are being increasingly explored for achieving high performance, adaptive, and resilient structural systems. A particularly appealing and interesting class of smart materials is shape memory alloys (SMAs). SMAs are a class of metallic alloys that possess several unique characteristics. As a result of their unique solid-to-solid phase transformations, SMAs can produce very high actuation strain, stress, and work output. In addition, SMAs have excellent self-centering ability, good energy dissipation capacity, high corrosion resistance, and long service life. The use of SMAs in concrete structures can enable more resilient designs.
This research explores the design and characterization of SMA-based innovative materials and structural systems to enhance the resiliency of concrete structures. First, the tensile and functional fatigue response of large-diameter SMA cables that offer large force capacities, superior mechanical properties, and lower cost were evaluated. An optical digital image correlation measurement system and an infrared thermal imaging camera were employed to obtain the full-field strain and temperature fields. A vibration control device that employs the studied SMA cables as re-centering elements was fabricated and tested. Second, the development of advanced cementitious composites by exploiting intrinsic smart properties of SMA fibers in a cementitious composite matrix was explored. SMA-fiber reinforced composite specimens with varying fiber volume fractions were prepared and tested under cyclic flexural loading. Test results were analyzed in terms of flexural strength capacity, mid-span deflection, crack width, and re-centering and crack recovery ratios. Finally, the feasibility of activating SMA tendons using heat of hydration of grout in order to develop self-post-tensioned concrete elements was explored. Results obtained from experimental test indicate that the materials and structural systems investigated in this research can provide good self-recovery and energy dissipation abilities and can potentially improve resilience of concrete structures.
