Torsional Behavior of RC Beams with Opening Using (CFRP - GFRP - Steel) Stirrups

This paper presents the torsional behavior of R.C. beams strengthened with externally steel stirrups, steel links and Fiber Reinforced Polymers (FRP) systems, R.C beams with web opening subjected to pure torsion. A total six rectangular beams were tested. Two un-strengthened specimens without and with web opening, which considered as control specimen, the rest four beams with web opening which one specimens strengthened with external steel stirrups, one specimen strengthened with steel links, one specimen strengthened with external stirrups made from Glass Fiber Reinforced Polymer (GFRP), and one specimen strengthened with external stirrups made from Carbon Fiber Reinforced Polymer (CFRP). All the beams were subjected to pure torsion till failure. The type of strengthening material and system is the basic parameter in this study. The experimental results showed a noticeable increase in torsion resistance for the strengthened specimens compared to control specimen. In comparison with control beam, the ultimate torsional moment increased up to 287% for beam strengthened with steel links, up to 134 % for beam strengthened with CFRP and increase capacity of beams with, and up to 100% for beam strengthened with GFRP stirrups.

An analytical model was proposed and applied to predict the torsional strength of the tested RC beams, the predicted strengths were found to be in good agreement with the experimental results.