International Concrete Abstracts Portal

Fiber-reinforced polymer (FRP) composite materials been widely used in civil engineering new construction and repair of structures due to their superior properties. FRP provides options and benefits not available using traditional materials. The promise of FRP materials lies in their high-strength, lightweight, noncorrosive, nonconducting, and nonmagnetic properties. ACI Committee 440 has published reports, guides, and specifications on the use of FRP materials for may reinforcement applications based on available test data, technical reports, and field applications. The aim of these document is to help practitioners implement FRP technology while providing testimony that design and construction with FRP materials systems is rapidly moving from emerging to mainstream technology.

This volume represents the thirteen in the symposium series and could not have been put together without the help, dedication, cooperation, and assistance of many volunteers and ACI staff members. First, we would like to thank the authors for meeting our various deadlines for submission, providing an opportunity for FRPRCS-13 to showcase the most current work possible at the symposium. Second, the International Scientific Steering Committee, consisting of many distinguished international researchers, including chairs of past FRPRCS symposia, many distinguished reviewers and members of the ACI Committee 440 who volunteered their time and carefully evaluated and thoroughly reviewed the technical papers, and whose input and advice have been a contributing factor to the success of this volume.

Two full-scale interior beam-column joints reinforced with Glass Fibre Reinforced Polymers (GFRP) were constructed and tested under reversal cyclic loading. Two levels of joint shear ratios were investigated; 1.3 and 1.5 times the square root of the concrete compressive strength (√f’c.). The specimens were isolated from assumed points of contra-flexure at mid-height of the columns and mid-span of the beams. Based on the obtained results, it was concluded that interior beam-column joints reinforced with GFRP bars and stirrups can withstand joint shear stress ratio of 1.5√f’c when the column is reinforced according to the confinement requirements of the Canadian standards for FRP-reinforced concrete (RC) building structures. Due to high tensile strength and low modulus of elasticity of GFRP, GFRP-RC beam-column joints can withstand large lateral deformations without exhibiting sudden failure due to bar rupture. This deformable behaviour indicates that GFRP-RC frames can be used in seismically active regions.

An analytical model is proposed in this study to predict the flexural behavior of reinforced concrete (RC) beams strengthened with near-surface mounted (NSM) fiber reinforced polymer (FRP) reinforcements due to debonding failure. In modeling the RC beam-NSM FRP system, a trilinear bond-slip relation is adopted for the interfacial stress between the two components. A closed-form solution is obtained by imposing appropriate boundary conditions for bond stress, FRP strain and deflection of the strengthened beams. The results are verified by the comparison with experimental data from different studies, where satisfactory correlation is obtained such as flexural deflection and tensile strain of FRP reinforcement. A parametric study is further conducted, which shows that the diameter of the FRP reinforcement and the steel rebar significantly affects the flexural performance of the NSM-strengthened RC beams. The Young’s modulus, the compressive strength of concrete and the bond strength of FRP reinforcement improve the performance to a lesser extent.

Confinement of concrete using glass fiber reinforced polymer (GFRP) spirals was evaluated using small-scale concrete cylindrical specimens with a 254 mm (10 in.) diameter and 762 mm (30 in.) height under concentric axial compression. The contribution of longitudinal GFRP bars to confinement was excluded by using wood dowels as longitudinal reinforcement to maintain a constant spiral pitch. Thus, concrete confinement was provided exclusively by the GFRP spiral. An ultimate hoop strain of 1.0 to 1.5% was achieved for the GFRP spirals of well-confined small-scale concrete specimens. Expressions were developed for the confined compressive strength and ultimate axial compressive strain of concrete confined with GFRP spirals. The resulting confinement model is compared to axial column tests of reinforced concrete columns with GFRP spirals and GFRP longitudinal bars from the present study and the literature. This research investigates confinement of concrete obtained purely due to GFRP spirals. The contribution of the vertical reinforcement to confinement was avoided by using wooden dowels which did not provide appreciable strength under compression. In addition, this research investigates the ultimate tensile hoop strain of GFRP spirals. The equation derived for the confinement of concrete and axial strain of confined concrete can be used for design; additional research should be carried out for columns with a larger diameter and greater height than the columns used in this research.

Fiber reinforced plastics (FRPs) have become a first choice for strengthening/repairing concrete members deficient in shear, flexure or torsion. However, oftentimes, the desired increase in capacity of FRP repaired/strengthened member is not achieved due to premature failures that occur at loads lower than the loads associated with failure of constituent materials (concrete, steel, FRP). Examples of premature failures in FRP retrofitted concrete applications include (1) plate-end debonding, (2) intermediate crack induced debonding (ICID), and (3) concrete cover separation (CCS). This paper present three-dimensional finite element (FE) models developed mainly to demonstrate the capability of FE models in predicting such failures, and to serve as reference for future FE studies concerning the behavior of RC members bonded to FRP reinforcement. Five RC beams, tested in previous experimental study by the authors, are modeled. The beams include a control beam; beam strengthened with spliced CFRP rod panel, beam strengthened with spliced CFRP rod panel, anchored at panel’s ends with CFRP wraps; beam strengthened with one (full-length) CFRP laminate, and beam strengthened with lap-spliced CFRP laminate system. Results, including load mid-span deflection response, strain profile along FRP length, and failure modes, showed that the presented FE models can replicate the experiments and predict the various premature failures oftentimes observed with FRP retrofitted concrete members.