BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Tomul LV (LIX), Fasc. 3, 2009 Secţia CONSTRUCŢII. ĂRHITECTURĂ STRENGTHENING TECHNIQUES OF RC COLUMNS USING FIBRE REINFORCED POLYMERIC MATERIALS BY CIPRIAN COZMANCIUC, RUXANDRA OLTEAN and VLAD MUNTEANU Abstract. Fibre reinforced composite materials are becoming more frequently used in civil engineering structures. One of the most practical applications of these new materials concerns the strengthening of reinforced concrete columns by means of confinement with fibre composite sheets. In the literature, various theoretical models have been proposed to describe the behaviour of confined concrete columns. The principal advantages of this technique are the high strength-to-weight ratio, good fatigue properties, non-corroding characteristics of the fibre reinforced polymers (FRP), and the facility of its application. The maximum efficiency of confining systems using FRP materials is reached in case of columns with circular cross-section and is explained by the fact that the entire section of the column is involved into the confinement effect. Rectangular confining reinforcement is less efficient as the confinement action is mostly located at the corners This paper reveals the most utilized techniques of performing composite confining systems for reinforced concrete columns, with their advantages and also disadvantages. Key words: RC columns; fibre reinforced polymeric composites (FRP); strengthe- ning systems. 1. Introduction Over the years, engineers have used different methods and techniques to retrofit existing structures by providing external confining stresses. For the past few years, the concept of jacketing has been investigated to provide such forces. Externally applied jackets have been used as a reinforcement to contain concrete for different reasons. Engineers have used traditional materials such as wood, steel, and concrete to confine and improve the structural behavior of concrete members [7]. Section enlargement is one of the methods used in retrofitting concrete members. Enlargement is the placement of reinforced concrete jacket around the existing structural member to achieve the desired section properties and performance. The main disadvantages of such system are the increase in the