Fourth International Conference on FRP Composites in Civil Engineering (CICE2008) 22-24July 2008, Zurich, Switzerland - 1 - 1 INTRODUCTION The FRP composite materials are widely used to retrofit structural elements such as beams, col- umns or slabs. In the fib or ACI codes, each retrofitting procedure is presented individually, not taking into consideration the superposition of two or more retrofitting procedures. The main interest was to develop a retrofitting method for reinforced concrete columns that will allow the use of additional steel reinforcement and confinement with FRP wrapping. Consequently, a testing program was proposed in which all the different parts of the retrofitting system were applied on the reinforced concrete columns in a certain order. This meant that there were tested two reference specimens, one monotonically and one cyclically. The next phase of the program referred to two columns retrofitted in bending only, using additional steel rein- forcement. This was followed by another set of two columns strengthened by base confinement of the columns with CFRP wrap. The final part, at least up to this date, consisted of two col- umns strengthened both in bending and by confinement, thus realizing the final retrofitting sys- tem. 2 FINITE ELEMENT MODELLING The finite element modelling was done using the ABAQUS and the AxisVM programs. The Abaqus model simulates the theoretical behaviour of the specimens. A T-shaped model was subjected to both vertical and lateral loading. Figure 1 presents the distribution of isostresses in the initial unstrengthened model. Further refinement of this model was also done to include the retrofitting system. 3 EXPERIMENTAL TESTS Six experimental tests were performed in various configurations. The goal was to obtain an effi- cient retrofitting method for the concrete columns and to make a comparison between different test procedures and their influence in increasing the columns’ ductility and load bearing capac- ity. Carbon fabrics or glass fabrics were used for confinement and additional NSM steel rebars for lateral retrofitting in bending. Ductility Increasing for Concrete Columns. Experimental Results C. Al. Dăescu, V. Stoian, T. Nagy-György, D. Dan & I. Demeter Politehnica University of Timisoara, Romania ABSTRACT: The research program presented here contains a short theoretical and experimen- tal study upon the reinforced concrete columns retrofitted using composite materials. The aim is to clarify some of the aspects regarding the ductility of these types of elements. One part of the study is that it aims to establish the type of interaction between two methods of retrofitting, namely in bending and by confinement. The actual codes present only the computational meth- ods for each individual situation, but not for the superposition of the two retrofitting methods.