A New Practical Mechanical Prestressing System for Strengthening Reinforced Concrete Members by Using Carbon Fiber Reinforced Polymer (CFRP) Sheets

A new practical mechanical prestressing system was developed to prestress the carbon fiber reinforced polymer (CFRP) sheets. The system is used for strengthening reinforced concrete members. The main features of the system are 1) the prestressing forces are applied manually without using hydraulic jacks; 2) prestressing level of the CFRP sheets can be controlled by using an electronic load cell; 3) light weight system which can be installed without using heavy lifting equipments; 4) the CFRP sheets are extended to the ends of the member where high shear stresses occur; and 5) releasing of the prestressing CFRP sheets are accomplished under slow strain rate. An experimental program was conducted to check the validity and efficiency of the prestressing system by testing three reinforced concrete beams. One of these beams was used as a control beam, while the others were strengthened with prestressed CFRP sheets. Results show that the system is efficient and practical for prestressing CFRP sheets to strengthen reinforced concrete beams. The cracking and yielding loads increased with an increasing the prestressing level.