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.

The bond between external bonding (EB) of fiber reinforced polymer (FRP) composite materials to concrete is the weakest link in the strengthened concrete flexural members. There are three mechanisms to transfer the interfacial shear between FRP and the concrete substrate, i.e., adhesion, interlocking and friction. This paper proposes a new approach by grooving on the concrete surface before applying epoxy to make epoxy ribs to increase interlocking. An experimental program was conducted to verify the effectiveness of the proposed epoxy ribs. Six grooves perpendicular to the fiber direction were cut on the bonding surface of the concrete blocks. The grooves were filled by wax in the unfilled specimens and with epoxy primer in the epoxy filled specimens before CFRP plate was installed. The experimental results show that epoxy-filled grooves can significantly improve the bond between FRP and concrete.

This paper discusses the effects of member geometry (size effect) on shear behaviour of glass fibre reinforced polymer reinforced concrete (GFRP RC) beams with and without FRP shear reinforcement. The experimental programme comprised 6 beams with no shear reinforcement and 6 beams reinforced with closed external FRP shear links providing a minimum amount of shear reinforcement (calculated according to ACI440.1R-15). The beams were similar in mechanical properties, albeit varied in overall depth from 260mm to 460mm. All of the beams were tested in 3-point bending keeping the shear span-to-depth-ratio typical as for the beams failing in diagonal shear (about 2.65). Along with conventional instrumentation, a three dimensional digital image correlation system was employed in this study to gain an additional insight into the shear cracks development and their influence on shear strength. The experimental results showed that shear strength of GFRP RC beams is size-dependent, notably for beams without shear reinforcement. It was found that size effect is related to the shear crack opening and relative stiffness of the members. In addition, DIC measurements yielded meaningful information on diagonal cracks initiation and development along the shear span, and helped to better understand how shear cracking affects the shear resisting mechanisms in FRP RC beams.

This paper evaluates the influence of the key parameters on the shear behavior of reinforced concrete (RC) beams retrofitted in shear using near-surface mounted (NSM) fiber-reinforced polymers (FRP) laminates and rods. The commonly observed debonding failure is considered in the study. The principal bond related parameters are examined, including the FRP effective bond length, the NSM FRP to concrete bond relation and the pull-off force of NSM FRP bonded from concrete surface. It is found that unlike the beams strengthened with externally bonded (EB) FRP, the effect of the existing transverse steel shear reinforcement on the shear contribution of FRP is not significant and should not be considered by the design models. The existing experimental results in the open literature also show that the internal steel shear reinforcement and the strengthening NSM FRP do not diminish each other’s contributions to the shear resistance of the RC beam. To precisely predict the shear contribution of NSM FRP of the strengthened RC beams corresponding to the debonding failure, a new prediction method is proposed in this study to consider the most influencing factors on the shear contribution of NSM FRP (Vf). The accuracy of the proposed equations is verified by comparing the predictions with the shear strength of a series of experimentally tested RC beams from the literature. Moreover, a comparison with other existing models shows that the proposed model achieves a better correlation with the experimental data than the other existing equations.

This paper presents a parametric analysis of the ACI 440 (2015) and AASHTO (2009) algorithms governing the flexural design of a one-way concrete member internally reinforced with glass fiber-reinforced polymer (GFRP) bars. The influence of specific design parameters on the required amount of reinforcement is investigated. The aim is to identify variables and requirements governing the design of a large-section GFRP reinforced concrete (RC) member. The member considered for this case-specific analysis is the reinforced concrete pile cap of the Halls River Bridge (Homosassa, FL), which is deemed representative of large-section GFRP-RC members operating as bent caps in short-span bridges. The influence of four critical parameters on the required amount of reinforcement is assessed. Salient analysis and design implications are discussed with respect to creep and fatigue rupture stress limits, minimum amount of flexural reinforcement, and applicable strength reduction factors. The outcomes of the parametric analysis highlight an untapped potential to reduce the required amount of reinforcement, and prioritize research areas to advance the development of rational design algorithms. Cyclic fatigue and creep rupture are identified as governing mechanisms.