Strengthening of Reinforced Concrete Framed Structures in Seismic Zones by Using CFRP SORIN DAN, CORNELIU BOB, AURELIAN GRUIN, CATALIN BADEA, LIANA IURES Civil Engineering Department "Politehnica" University of Timisoara Str. T. Lalescu, No. 2, Timisoara ROMANIA Abstract: The paper deals with some aspects on efficient solutions for rehabilitation of reinforced concrete framed structures by using composite fibre reinforced polymers systems. The first part of the paper is devoted to general aspects of RC structures strengthening. The second part presents experimental studies on RC frames, which were tested as un-strengthened and as CFRP strengthened structures. Two parameters of the tested structures are reported: bearing capacity and top-displacement. The last part of the paper is focussed on the rehabilitation of existing RC framed structures having weak reinforcement at seismic action. Aspects of CFRP rehabilitation of columns and beams are presented. Key-Words: Rehabilitation; Existing structures; Seismic zones; RC structures; Strengthening; CFRP. 1 Introduction Reinforced concrete structures are to be repaired and/or strengthened in cases when the general damage is limited, and demolished when the structural safety is greatly affected and the rehabilitation cost is very high. Repairs are used for surface deterioration, cracks, casting defects and reinforcement corrosion. The methods used for repairs are: covering of damaged surfaces; infilling of cracks with cement mortar, epoxy resin or other polymers; replacement or strengthening of damaged reinforcement. Strengthening of RC structures takes into account the increase of strength, stiffness and ductility. In case of RC framed structures, the increase in stiffness and ductility is to be achieved by coating beams, columns and joints [1]. The coating is performed by reinforced concrete, steel profiles, carbon fibres, etc. Sometimes it is necessary to transform the existing structure completely, especially for framed structures. In this case, special techniques are to be used: steel bracing; infilling of frame holes with reinforced masonry or reinforced concrete. 2 Strengthening of RC Structures by Using of CFRP FRP systems are suitable for strengthening of RC structures due to their technical and economical advantages. Classic strengthening solutions may lead to some inconveniences; as such methods are costly and disruptive to operation. A typical approach is the increasing of elements’ dimensions with consequent mass increasing and leading to seismic problems. Furthermore, if reinforcement corrosion is present and its causes are not carefully removed the corrosion will continue. CFRP systems provide solutions to retrofit structures, to make its more seismic resistant: its increase load-carrying capacity; section designed only for gravity loads are able to withstand seismic loads; elements’ mass remains, practically, the same; the technology is simple and rapid. For strengthening of existing RC framed structures in seismic zones a very important target is to avoid the development of plastic hinges in columns. For this purpose there is necessary to increase bending and shear capacity. A retrofit using CFRP vertical strips and horizontal wrap for columns means increasing of local ductility and deformation capacity as well as of entire bending capacity. The strengthening of columns using CFRP vertical strips will increase the bending capacity as well as the stiffness of the element. The increased flexural strength of column will force the plastic hinge to form at beam ends. On the other hand the increase of vertical elements stiffness will reduce the structural story drift under seismic motion. The two effects of columns strengthening are responsible for increasing the horizontal load capacity and, finally, the structural dissipation WSEAS International Conference on ENGINEERING MECHANICS, STRUCTURES, ENGINEERING GEOLOGY (EMESEG '08), Heraklion, Crete Island, Greece, July 22-24, 2008 ISBN: 978-960-6766-88-6 67 ISSN 1790-2769