1 Shear strength of FRP reinforced concrete beams without stirrups: 1 verification of fracture mechanics formulation 2 3 Fabio Matta 1 , Paolo Mazzoleni 2 , Emanuele Zappa 3 , Michael A. Sutton 4 , Mohamed ElBatanouny 5 , 4 Aaron K. Larosche 6 , Paul H. Ziehl 7 5 6 1 Dept. of Civil and Environ. Engr., University of South Carolina, Columbia, SC, USA, fmatta@sc.edu 7 2 Dept. of Mechanics, Politecnico di Milano, Milan, Italy, paolo2.mazzoleni@mail.polimi.it 8 3 Dept. of Mechanics, Politecnico di Milano, Milan, Italy, emanuele.zappa@mecc.polimi.it 9 4 Dept. of Mechanical Engineering, University of South Carolina, Columbia, SC, USA, sutton@sc.edu 10 5 Dept. of Civil and Environ. Engr., University of South Carolina, Columbia, SC, USA, elbatano@email.sc.edu 11 6 Dept. of Civil and Environ. Engr., University of South Carolina, Columbia, SC, USA, larosche@email.sc.edu 12 7 Dept. of Civil and Environ. Engr., University of South Carolina, Columbia, SC, USA, ziehl@cec.sc.edu 13 14 15 16 SYNOPSIS: 17 The size effect in shear in reinforced concrete (RC) one-way members without shear reinforcement becomes more 18 of concern when using glass fiber reinforced polymer (GFRP) reinforcement. In fact, the lower stiffness of GFRP 19 reinforcement typically results in wider flexural cracks with respect to steel RC counterparts. This issue is 20 especially relevant for the case of flexural members without stirrups, such as retaining walls and slab bridge 21 superstructures. Little evidence has documented the extent of such effect. Cognizant of this knowledge gap, ACI 22 Committee 440 (FRP Reinforcement) introduced the current nominal shear strength algorithm, which was calibrated 23 in a conservative fashion based on test results from small beams. This algorithm assumes that the shear strength at 24 the critical section is resisted predominantly through the uncracked concrete above the tip of the shear crack. Based 25 on the same fundamental assumption, a fracture mechanics algorithm for steel RC beams was recently proposed by 26 ACI Committee 446 (Fracture Mechanics of Concrete). In this paper, the ACI 440 and 446 algorithms are verified 27 and discussed based on experimental evidence from tests on scaled GFRP RC beams without stirrups. The latter 28 algorithm is modified to account for the smaller elastic modulus of GFRP, under the hypothesis that its relevant 29 parameters and the shear failure mechanism are similar irrespective of the reinforcement material. 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 Keywords: design, fiber-reinforced polymers, fracture mechanics, reinforced concrete, shear, size effect, strength 54 55