Zanyar Mirzaee - M.Sc Student, Technical faculty, University of Tehran, Tehran, Iran
Mohammad Shekarchi - Assosiate Professor, Technical Faculty, University of Tehran, Iran
Masoud Motavalli - Professor, Head of engineering structures laboratory of EMPA, Swiss
Mahmoud Nili - Professor, Technical Faculty, University of Tehran, Iran

Designing more powerful structures and strengthening the existing buildings in different conditions, lead engineers to use flexible, adaptable and of course smart systems. Shape memory alloy (SMA) as kind of these smart materials, have been known in recent decades and have not been used much in the building industry until rather recently.Strengthening of columns is of great importance in repair and retrofit of concrete structures since the failure of column has serious consequences for structural stability. Strengthening of concrete cylinders with shape memory alloys to improve their ductility and compressive behavior is nearly new idea. According to this approach, Upon external heating, martensite-to-austenite phase transformation takes place and the material undergoes large shrinkage strains. This strain energy can be used to generate significant prestreessing force in concrete. 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 memory wires for the purpose of their application in strengthening concrete columns

Shape Memory, Concrete, Spiral, Post-Tensioned