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.

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.

Strengthening using carbon fiber reinforced polymers (CFRP) provides a valuable addition to available structural preservation and life extension techniques. Damaged bridges can be repaired efficiently while structurally deficient bridges can be effectively retrofitted to higher load capacities using CFRP materials. A large research program has been ongoing since 2008 in Texas to demonstrate the effectiveness of using anchored CFRP sheets in shear strengthening of reinforced concrete bridge beams and girders. The research program has encompassed three main thrusts: 1) over 70 large-scale tests of concrete bridge sections strengthened using externally applied anchored CFRP sheets, 2) small-scale tests aimed at developing CFRP anchor design criteria as well as a simple test procedure for quality control of materials and installation, and 3) developing design specifications for CFRP anchors and sheets in shear strengthening applications. An overview of the experimental findings of the program is presented.

In design of structures, both the ultimate limit state (ULS) and the serviceability limit state of the structure must be verified. Carbon fiber reinforced polymer (CFRP) materials have high strength, and large amounts of CFRP are not needed for ULS. On the other hand, CFRP may be needed to introduce enough stiffness for meeting the serviceability design criteria and reduce the crack of concrete. The effects of externally bonded composite plates on the mechanical behavior of a cracked RC beam, loaded in flexure, are obtained by an experimental approach. The problem of crack width prediction is addressed. The model values are compared to experimental data obtained using a digital image correlation method. The crack width and spacing is measured as a function of load to analyze crack propagation. Finally, the study focuses on the validation of the codes model for calculating crack widths and curvatures in strengthened beams.