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.

In recent research, the use of the near-surface mounted (NSM) technique has been proven to increase the torsional strength of reinforced concrete (RC) members. In this paper, an investigation into the torsional deformation characteristics of the ten RC beams strengthened using the NSM technique is reported and evaluated using photogrammetry. The experimental results of two control beams and eight beams strengthened using CFRP laminate embedded into pre-cut grooves using epoxy and mortar are evaluated. The Digital Image Correlation Photogrammetry (DIC) is used to determine the three-dimensional displacement of targets placed on the north and south faces of the beams at selected load levels up to failure. The main aim of this study was to measure the propagation of torsional crack width with increasing torque for each beam. The torsional deformations of the beams are evaluated and verified with the photogrammetry measurements and the differences in the width of the large torsional cracks across the tested beams are highlighted and compared. The width of the torsional cracks for the strengthened beams was smaller than that that of the control beams at the same load level. Similar deformation mechanisms were observed for the strengthened and control beams.

The use of Fibre Reinforced Polymer (FRP) reinforcement has been widely adopted in the construction industry. This paper presents the findings of an experimental program undertaken to examine the use of small-diameter Carbon Fiber Reinforced Polymer (CFRP) strands for shear strengthening of concrete beams, not in a U-shape form confinement, but in a discrete form; sheets are applied to beam sides only. Nine concrete beams were constructed and tested to evaluate the effectiveness of the strengthening scheme. The considered parameters included the width and spacing of the CFRP strands strips. The research was extended to examine the feasibility of additional anchorage system, in form of longitudinal strips, to better resist the shear diagonal cracks in both components directions (vertical and horizontal), to delay premature failure due to delamination of the strands. Test results revealed that the use of small-diameter CFRP strands for shear strengthening of concrete beams is simple, easy to install and efficient in increasing the shear capacity by around 23% compared to the control specimen. It was also shown that presence of the longitudinal CFRP strands enhanced the shear behavior of the beams by providing more resistance to the induced diagonal tension and delayed delamination of the strands.

One of the main reasons for the degradation of our infrastructure is steel corrosion in reinforced concrete. To com- bat that issue, alternative non-corrosive materials, such as fiber reinforced polymer (FRP) rebars, were developed and implemented as internal reinforcement for concrete structures. Because of significant physio-mechanical advantages (magnetic transparency, high strength, corrosion resistance, etc.), the adoption of FRP rebars increased rapidly through- out the last decades. Due to an increased material demand, the number of FRP rebar manufacturers grew, but each manufacturer started to develop proprietary products, with wide ranging properties — the industry is in need for guidance and unification. Therefore, this study aims to centralize the relevant information by (i) summarizing the globally available regulations, (ii) providing background data for the present production status, and (iii) listing the currently produced FRP rebars in an effort to compare their physio-mechanical properties. Analysis of the market showed that 27 manufacturers produce FRP rebars in 14 countries with diverse output quantities and different distribution logistics. The various production approaches lead to different rebar types with dissimilar surface properties and significant strength differences.

The objective of the work presented in this paper is to develop an image analysis methodology for evaluating the fracture surfaces of concrete-epoxy interfaces (CEI). The CEI is formed at the interface between epoxy and concrete and is influenced, as is the interface between fiber reinforced polymer composite bonded to concrete, by environmental and loading conditions in service. The developed image analysis methodology was used to characterize CEI debonding failure by one of three possible modes: cohesive failure in the concrete (CC), interfacial failure (IF), and cohesive failure in the epoxy (CE). Quantitative digital image analysis coupled with a set of rules for failure mode classification enabled the correlation of CEI failure mode with bond performance metrics such as fracture energy and lap shear pull-off force. The results show a strong correlation between failure mode and bond performance. Extended periods of sustained loading decrease bond performance and shift the dominant failure mode from CC to IF.