Innovative Near-Surface Mounted Iron-Based Shape Memory Alloy for Strengthening Structures
Abstract
A recent development of smart materials called Iron-based Shape Memory Alloys (Fe-SMA) envisages a new perspective in the rehabilitation of structures. SMAs are metallic alloys that recover their original shape through heating. Utilizing this interesting feature of SMAs to retrofit reinforced concrete (RC) beams is the main objective of the current research project. An innovative active self-prestressing technique using Near Surface Mounted (NSM) Fe-SMA bars/strips for flexural strengthening of RC beams is proposed. The pre-strained (elongated) Fe-SMA bar/strip is anchored in a pre-cut groove in the tension side of the RC beam; heating the bar/strip will then trigger the recovery of the induced strain (i.e. the bar/strip tendency to shorten). However, due to the restrained ends of the bar/strip, a tensile force develops instead (i.e. prestressing force). In this case, no jacking tools or special anchorage systems are required.
The main objective of this study is to examine the potential capability of the newly developed Fe-SMA as an active retrofitting material for RC beams. Consequently, its contribution to the flexural performance enhancement of the RC beam at service and ultimate load conditions was investigated. In addition, the long-term performance of the strengthened beams subjected to freeze-thaw cycles and fatigue loading was studied. In total, 11 RC beams were tested; 7 beams with a length of 2 meters and 4 large-scale beams with a length of 5 meters.
The experimental test results revealed the effectiveness of the proposed technique in enhancing the flexural capacity of the RC beams at the service and ultimate load conditions, while maintaining a ductile failure mode similar to the under-reinforced beams. The strengthened beams tested under severe freeze-thaw cycles and fatigue loading showed a good performance except for the bonding between the Fe-SMA bars and the grout which experienced a rapid deterioration and resulted in a rupture of the Fe-SMA bar at the anchorage location under fatigue loading.
Description
Keywords
Engineering--Civil
Citation
Rojob, H. (2017). Innovative Near-Surface Mounted Iron-Based Shape Memory Alloy for Strengthening Structures (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26542