**Shear Behavior of Concrete Beams Reinforced with a New Type of Glass Fiber Reinforced Polymer Reinforcement: Experimental Study**

#### **Czesław Bywalski \*, Michał Drzazga, Maciej Ka ´zmierowski and Mieczysław Kami ´nski**

Faculty of Civil Engineering, Wroclaw University of Science and Technology, Wybrze ˙ze Wyspia ´nskiego 27, 50-370 Wrocław, Poland; michal.drzazga@pwr.edu.pl (M.D.); maciej.kazmierowski@pwr.edu.pl (M.K.); mieczyslaw.kaminski@pwr.edu.pl (M.K.)

### **\*** Correspondence: czeslaw.bywalski@pwr.edu.pl; Tel.: + 48-71-320-3397

Received: 6 February 2020; Accepted: 3 March 2020; Published: 5 March 2020

**Abstract:** The article presents experimental tests of a new type of composite bar that has been used as shear reinforcement for concrete beams. In the case of shearing concrete beams reinforced with steel stirrups, according to the theory of plasticity, the plastic deformation of stirrups and stress redistribution in stirrups cut by a diagonal crack are permitted. Tensile composite reinforcement is characterized by linear-elastic behavior throughout the entire strength range. The most popular type of shear reinforcement is closed frame stirrups, and this type of Fiber Reinforced Polymer (FRP) shear reinforcement was the subject of research by other authors. In the case of FRP stirrups, rupture occurs rapidly without the shear reinforcement being able to redistribute stress. An attempt was made to introduce a quasi-plastic character into the mechanisms transferring shear by appropriately shaping the shear reinforcement. Experimental material tests covered the determination of the strength and deformability of straight Glass Fiber Reinforced Polymer (GFRP) bars and GFRP headed bars. Experimental studies of shear reinforced beams with GFRP stirrups and GFRP headed bars were carried out. This allowed a direct comparison of the shear behavior of beams reinforced with standard GFRP stirrups and a new type of shear reinforcement: GFRP headed bars. Experimental studies demonstrated that GFRP headed bars could be used as shear reinforcement in concrete beams. Unlike GFRP stirrups, these bars allow stress redistribution in bars cut by a diagonal crack.

**Keywords:** GFRP; FRP reinforcement; shear; capacity; reinforced concrete beams
