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.

FRP is customarily used to wrap concrete columns to increase their strength and strain capacities by providing extra confinement. Typically, steel hoops or spirals are used in constructed columns as mandated by codes. The behavior of retrofitted columns becomes thoroughly different because there are two systems with different mechanical response and interaction engaged in confinement. While most of the literature addressed concrete confined with FRP only, a limited number of studies and experimental cases accounted for both actions. This paper developed an axial stress-strain model which utilized geometric and mechanical properties of concrete, steel and FRP. The proposed work adopted Lam and Teng model for concrete confined with FRP, originally implemented in ACI 440.2R-17 guide, and calibrated its parameters against experimental curves. The proposed model correlates well with experimental cases that were collected from the literature.

This paper presents an investigation on deterioration of tensile and shear properties of GFRP bars. Composite bars, contrary to conventional steel, when used in structures exposed to aggressive environments can significantly increase their durability and lifetime. However, the use of GFRP bars in concrete structures is still limited due to unspecified durability properties of this relatively new material. Since long-term durability data are not readily available, accelerated aging tests have been used in this research to study GFRP bar degradation. GFRP bars were kept in a highly alkaline solution heated to 50, 60 and 70°C for 1, 3 and 5 months, respectively, and after each immersion period, bars were taken out and tested in tension and shear. The test results show that the high pH of the alkaline solution has an adverse influence on GFRP properties, and the speed of degradation depends on the temperature of the solution. Also, the effect of bar size and surface finishing on the degradation speed was analyzed, and the results are presented in the paper.

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.