FLEXURAL STRENGTHENING OF REINFORCED CONCRETE BEAMS USING CARBON FIBER REINFORCED POLYMER (CFRP) SHEETS WITH GROOVES

Abstract

THE MOST COMMON METHOD USED TO STRENGTHENING, REHABILITATION OR REPAIRING OF REINFORCED CONCRETE (RC) MEMBERS IS TO USE EXTERNAL CARBON FIBER REINFORCED POLYMER (CFRP) SHEETS. CFRP CAN GREATLY IMPROVE THE FLEXURAL AND SHEAR CAPACITY OF DETERIORATED MEMBERS AND THEREFORE EXTENDS THEIR USEFUL LIFE. THE MAIN PROBLEM OF EXTERNAL CFRP IS THE DEBONDING OF THE SHEETS FROM THE CONCRETE SURFACE AT SOME POINT OF LOADING, WHICH NEGATIVELY AFFECTS THE EFFICIENCY OF STRENGTHENING AND MAY CONSEQUENTLY LEAD TO AN UNANTICIPATED FAILURE OF THE STRENGTHENED MEMBERS. THE MAJOR REASON FOR THIS EARLY DEBONDING IS LIKELY DUE TO THE LOW ACCURACY OF THE PREPARATION AND THE HIGH STRESS CONCENTRATION AT THE FLAT CONTACT AREA EXISTS BETWEEN CFRP SHEETS AND THE CONCRETE. THE PROBLEM HAS BEEN EXTENSIVELY DISCUSSED IN THE LITERATURE AND SOME CFRP APPLICATION TECHNIQUES SUCH AS “EXTERNALLY BONDED REINFORCEMENT ON GROOVES (EBROG)” AND “EXTERNALLY BONDED REINFORCEMENT IN GROOVES (EBRIG)” HAVE BEEN PROPOSED AS ALTERNATIVES TO THE CONVENTIONAL APPLICATION METHODS. ALTHOUGH SOME RESEARCH HAS BEEN CARRIED OUT, THERE HAVE BEEN FEW EXPERIMENTAL INVESTIGATIONS THAT PROVIDED QUANTITATIVE DISCUSSION OF THE EFFICIENCY OF THE NEW DEVELOPED TECHNIQUES. THIS RESEARCH WAS AIMED TO EXPERIMENTALLY ASSESS THE EFFICIENCY OF GROOVING TECHNIQUES AND TO PROVIDE A QUANTITATIVE DATA REGARDING THE BEHAVIOUR OF BONDING BETWEEN CFRP AND CONCRETE. THE EFFECTS OF SHAPE AND DIRECTION OF THE GROOVES AND CFRP LAYERS ON THE LOAD CARRYING CAPACITY, MID-SPAN DEFLECTION AND FAILURE MODE OF THIRTEEN RC BEAMS HAVE BEEN INVESTIGATED AND DISCUSSED. IN GENERAL, CFRP HAS SIGNIFICANTLY IMPROVED THE FLEXURAL CAPACITY OF STRENGTHENED BEAMS ESPECIALLY WHEN GROOVING TECHNIQUE HAS BEEN EMPLOYED