The differences in mechanical and bond properties of Fiber Reinforced Polymers (FRP) bars when compared to those of traditional steel reinforcement for reinforced concrete (RC) structures may affect the cracking and deformability behaviour of FRP RC members. This study investigates the bond behaviour between FRP reinforcement and concrete through experimental and numerical analysis. Experimental results on pull-out tests and direct tension tests are presented and discussed. A general procedure, derived from a cracking analysis based on slip and bond stresses, is used to study the deformability of FRP RC elements under tension. The tension stiffening effect is included via experimental nonlinear bond-slip law obtained from a laboratory pull-out test. The comparison between experimental data and numerical predictions of the reinforcement strain profile along the reinforcing bar during a tensile test confirms that the bond-based model adequately reproduces the redistribution of stresses after crack formation. Because the numerical model is flexible enough to include any "user-defined" bond-slip law and variable materials' properties, a parametric study is conducted.

Due to the mechanical properties of Fibre Reinforced Polymers (FRP), serviceability limit states (SLS) often govern the design of FRP reinforced concrete (RC) structures. This study investigates the short-term serviceability behaviour of FRP RC beams through theoretical and experimental analysis. The experimental results on deformations, cracking and deflections are discussed. Prediction models provide adequate values of the experimental response up to the service load; however, an increment of the experimental deflection is obtained with respect to that provided by cracked section analysis when the load increases beyond the service condition. A discussion on the main aspects of the SLS of FRP RC is introduced, including the influence of the different parameters affecting the stresses in materials, maximum crack width and the allowable deflection. A methodology for the design of FRP RC at the serviceability requirements is presented. This procedure allows optimizing the overall depth of the element with respect to more generalised methodologies, since it takes account of the specific properties of materials and the loading conditions.