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.

There are large numbers of existing buildings around the world and in North America especially in California have been constructed with reinforced masonry since 1930s. These old reinforced masonry walls have not been improved to meet the current standards. Current ACI 440.7R reported as Guide for Design & Construction of externally bonded FRP System for Strengthening Unreinforced Masonry Structures. This document does not address strengthening of existing reinforced masonry structures (i.e. with steel reinforcement). The principle objective of this study was to determine and discuss the failure mechanism as well as to investigate the flexural behavior of reinforced masonry walls strengthened with externally bonded system and subjected to out-of-plane cyclic loading. This will be evaluated by comparing the flexural capacity and ability to sustain large deflection of specimens strengthened with different strengthening systems. In addition, the effect of specific parameters on the flexural response of reinforced masonry wall was investigated including: type and amount of fiber and masonry bond pattern. This study aimed to develop a database of experimental test results to validate the design model presented in next version of ACI 440.7R document. The performance of twelve strengthened masonry specimens was investigated. The strengthening systems that used in this study are fiber reinforced cementitious matrix (FRCM) and fiber reinforced polymer (FRP) technique. These simply supported walls were tested in four-point bending with an effective span of 1.12 m (44-in.) between the supports under an out-of-plane cyclic load at a rate 1.27 mm/min (0.05-in./min). The test results indicated that the flexural behavior of reinforced masonry walls strengthened externally by FRP may be controlled by either FRP rupture or debonding (intermediate crack or plate end debonding failure). The flexural behavior of reinforced masonry walls strengthened externally by FRCM may be controlled by either fiber slippage or debonding.

The current state of North America’s infrastructure system is in dire straits. The cost of repair is estimated at over $3.6 trillion in the United States alone. As an alternative to the current strengthening methods, fabric reinforced cementitious mortar (FRCM) is proposed to aid the civil engineering industry in removing the infrastructure spending gap. This research initiative set out to determine the flexural strength improvement on RC beams with different textile ratios, different fabric materials and different anchorage methods. Five full-scale (200 x 300 x 4000 mm) (8 in x 12 in x 13 ft) reinforced concrete beams (1 control, 4 strengthened) were cast and tested under monotonic four-point bending conditions. Ultimate flexural capacity, pseudo-ductility, stiffness, and failure mode were taken as performance indicators. The study found that flexural strength was improved by up 81% over the control value.

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 is part of an on-going research project on the behavior of damaged Reinforced Concrete (RC) beams repaired and strengthened with Externally Bonded Fiber Reinforced Polymer (EB-FRP). A total of seven full-scale rectangular beams; fully-damaged in a previous study, were repaired and retested to failure. The repair methodology consists of filling the cracks with epoxy, and then wrapping the beams with FRP discrete strips with two different thicknesses (1 layer and 2 layers). Out of the seven beams, four beams were strengthened using 2 layers of EB-FRP discrete strips; two beams were strengthened with 1 layer of EB-FRP; and the remaining beam was only repaired by crack injection with epoxy without wrapping with FRP. The beams were instrumented and tested to failure in three-points loading setup. The measured test parameters were the beams deflection and the maximum load-carrying capacity. Furthermore, the mode of failure was also observed and reported in this study. The test results revealed that the use of EB-FRP strips along with epoxy injection is an effective repair method that not only recovers the original strength (strength of the beams tested in previous study, considered as the reference beams), but also significantly increases their shear capacity. Comparing the shear capacity of the repaired beams to that of the reference beams, revealed that 2 layers of EB-FRP increased the shear strength by up to 95%, while the use of 1 layer of EB-FRP increased the shear strength by up to 66%. Moreover, comparison of the test results with existing predictive models (ACI 440.2R and fib TG-9.3) showed that both models reasonably predict the EB-FRP contribution to the shear strength of repaired and strengthened damaged beams.