Strengthening of columns is of great importance in repair and retrofit of concrete structures since the failure of a column has serious consequences for structural stability. Strengthening of concrete cylinders with shape memory alloys to improve their ductility and compressive…
Strengthening of columns is of great importance in repair and retrofit of concrete structures since the failure of a column has serious consequences for structural stability. Strengthening of concrete cylinders with shape memory alloys to improve their ductility and compressive behavior is nearly a new idea. According to this approach, upon external heating, a martensite-to-austenite phase transformation takes place and the material un- dergoes large shrinkage strains. This strain energy can be used to generate a significant prestreessing force in con- crete. In this research axial loading tests were conducted on RC concrete cylinders strengthened by prestressing SMA wires, after transforming from martensite to austenite phase by actuating them and significant results were obtained concerning the stress-strain curve, maximum stress, peak strain and initial young modulus (elastic modulus). The experimental results and test data would be an initial step toward the investigation of shape mem- ory wires for the purpose of their application in strengthening concrete columns. 1 INTRODOCTION improved by confinement using some kind of mate- rials. The first investigations on active confinement Designing more powerful structures and strengthen- performance were done by applying the lateral con- ing the existing buildings in different conditions, finement using a constant hydraulic pressure as an lead engineers to use flexible, adaptable and of active confinement kept constant during the loading course smart systems. Shape memory alloy (SMA) history [1]. Active confining the concrete cylinders as a kind of these smart materials, have been known or reinforced concrete columns using martensitic, in recent decades and have not been used much in Ti-49.7Ni (at %), or austenitic, Ti-50.3Ni (at %), the building industry until rather recently.