Effective shear design of FRP reinforced concrete

This thesis presents the results of an experimental study designed to investigate various aspects of the shear behavior of concrete beams and slabs reinforced with fiber-reinforced polymer (FRP) laminates. Specifically, the interacting roles that the reinforcement ratio (rho) and span-to-depth ratio, aid, have on shear strength of members without stirrups are investigated.;The experimental study consisted of load testing fifteen shear critical, FRP reinforced concrete members without stirrups to examine the accuracy of shear design methods, in particular to investigate the effect that the M/rhoVd ratio has on the shear strength of members without stirrups. For this purpose the specimens are grouped into four different categories based on the test variables: shear span to depth ratio (aid) and reinforcement ratio rho. All fifteen members were shear-critical, simply supported, subjected to point loads with rectangular dimensions 400mm wide by 280mm deep and the length of the specimens varied between 2200mm and 4600mm. All were constructed in the Carleton structures lab. All specimens were loaded monotonically and failed in shear. The ratio of experimental shear stress for each specimen to predicted shear stress of the seven prominent codes (nuexp/nupred ) was compared.;It was found that the modified CSA equations for shear strength (Hoult's Equation) produce conservative, but accurate, estimates of shear strength with an average nuexp/nupred of 1.14, a coefficient of variation of 9.9% and a 1st percentile of 0.88. This method offers more accurate predictions of the shear strength for FRP-reinforced members than the other methods. In particular, the ACI 440 method (Frosch's Equation) offers extremely conservative and inaccurate predictions.;The experimental results indicated that the failure shear stress of members without shear reinforcement is a function of strain in the longitudinal reinforcement which is a function of M/rhoVd. That is, the failure shear stress of a concrete member without shear reinforcement is not a function of reinforcement ratio rho or aid solely, but rather is a function of M/rhoVd. Higher reinforcement strains will result in wider cracks and these wider cracks in turn result in decreased shear strength due to reduced aggregate interlock capacity.;A background review of FRP materials is presented, focusing on the various types of fibers and resins, manufacturing techniques, material properties and practical strengths and weaknesses. Shear behavior of reinforced concrete beams and slabs without stirrups is discussed, with an emphasis on members constructed without stirrups. The roles that different variables have on shear strength are discussed, in particular the strain effect and its role on shear strength. Different prominent shear design methods for FRP-reinforced concrete members are presented, including the general method of shear design used in the CSA A23.3-04 code for design of concrete structures and a modification to the general method designed for FRP reinforced members. The different shear design methods are discussed and evaluated in terms of their generality and rationality.