Experimental Research On Flexural Performance Of Reinforced Concrete Beams Strengthened With Prestressed Carbon Fiber Reinforced Polymer

Concrete structures deteriorate for various reasons and upgrading has been achieved for over 20 years by bonding steel plates using epoxy resins. Disadvantages of this method include transporting, handling and installing heavy plates and corrosion of the plates. The use of composite materials such as carbon fiber reinforced polymer(CFRP) overcomes these problems and provides equally satisfactory solution well suited to the rehabilitation demand of concrete structures.Further advantages are gained by prestressing the plate before bonding to the concrete. The benefits of external prestressing using CFRP have been investigated only relatively recently and further work in this field is needed in order to understand the behavior of members prestressed with CFRP, thereby allowing full advantage to be gained from the ease with which CFRP can be handled and applied, and from their excellent durability. This article is concerned specially with the flexural behavior of reinforced concrete beams strengthened with CFRP.Thirteen reinforced concrete beams of 2.5m lengths were tested in this paper. These beams were divided into four groups, considering the comparison of non-prestressed with prestressed CFRP sheets, the different areas of CFRP, variety of plate end anchorage systems and prestressing levels. The non-prestressed beams failed by separation of the plate from the beam or concrete crush, while all of the prestressed beams failed by plate fracture. It was showed that beams prestressed with carbon fiber sheets combine the benefits of excellent stiffness and structural improvement in terms of serviceability and ultimate conditions. Meanwhile, Prestressing produced significant increases in the load which causes yield of the internal steel over a non-prestressed specimen and effectively restricted the development of crack.Based on the mechanical performance of reinforced concrete beams prestressed with CFRP, the method for calculating the normal section flexural load-bearing capacity is proposed, which can match the data from experiment well. The process of the stiffness performance was analyzed and corresponding expressions were suggested which can basically meet the design requirement.