Analysis of prestressed concrete beams experimentally utilizing steel strands and CFRP bars

Abstract

This research seeks to improve the performance behavior of reinforced concrete (RC) beams by examining their load-deflection diagrams using ordinary and prestressed carbon fiber-reinforced polymer (CFRP) bars in place of standard steel reinforcement instead. Using CFRP bars as prestressed tendons to replace the bottom steel rebars, eight 1800-mm long RC beams with a 200 mm×300 mm cross-section were evaluated and split into three groups, evaluating critical loading phases (i.e., cracked, ultimate, and mid-span deflection). Relative to the reference beam, beams reinforced with CFRP had far higher load-carrying capacities and ductility. One beam, reinforced with regular CFRP bars, exhibited a mid-span deflection of 21.2 mm and an ultimate load of 157.2 kN, resulting in a cracked load of 57.7 kN. Another beam using regular CFRP bars also demonstrated improved performance with a mid-span deflection of 21.2 mm, an ultimate load of 160.6 kN, with a cracking load of 57.5 kN. Prestressed CFRP bars led to a significant decrease in mid-span deflection (7.3 mm), a rise in the ultimate load (254.2 kN), and a cracking load of 137.6 kN. Furthermore, the use of two different prestressed CFRP bars showed notable improvements. CFRP bars with these enhancements were employed instead of steel reinforcement in the tension zone, thereby greatly increasing the beam strength with respect to the bonding materials (cement grout and epoxy resin). Thus, using regular and prestressed CFRP bars in traditional steel reinforcement may significantly improve the load-carrying capacity and ductility, producing more robust reinforced concrete buildings.

Keywords

• ordinary cfrp bars
• prestressed cfrp bars
• steel stands
• fatigue and corrosion resistance
• bonded beam
• prestressing concrete beam
• harped and straight strands