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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 917 Abstracts search results
October 1, 2022
Alvaro Ruiz Emparanza, Francisco De Caso, and Antonio Nanni
In reinforced concrete (RC) structures, a proper bond between the reinforcement and the concrete is key for appropriate composite action. To date, limited studies exist that evaluate the bond of fiber-reinforced polymer (FRP) bars in concrete members under flexure and its effect on the development length required to ensure a full stress transfer. In this paper, the bond strength developed by glass FRP (GFRP) and steel rebars is evaluated and compared by testing 16 RC beams under three-point bending. The beams were 1.83 m long and had a section of 150 x 360 mm. Different embedment lengths were evaluated as a function of the bar diameter (db): 30 db, 40 db, and 50 db for GFRP reinforced specimens, and 20 db, and 30 db for steel reinforced beams. Two different GFRP rebar types (six beams for each) and conventional steel (four beams) were used as reinforcement; all the rebars had a nominal diameter of 12.7 mm. Based on the results presented herein, GFRP rebars have a lower bond capacity than steel rebars. Also, the development lengths as suggested by actual code provisions for GFRP rebars (ACI 440.1R-15) appear to be over-conservative: the theoretical development length values were around 110% - 188% higher than the experimental results for the tested GFRP rebars, while the predicted development length for steel rebars according to ACI 318 was about 83% higher than the experimental results.
Imad Eldin Khalafalla and Khaled Sennah
This paper investigates the use of glass fiber reinforced polymer (GFRP) bars to reinforce the jointed precast bridge deck slabs built integrally with steel I-girders. In addition to a cast-in-place slab, three full-size, GFRPreinforced, precast concrete slabs were erected to perform static and fatigue tests under a truck wheel load. Each slab had 200 mm (7.9 in) thickness, 2500 mm (98.4 in) width normal to traffic, and 3500 mm (137.8 in) length in the direction of traffic and was supported over a braced twin-steel girder system. The closure strip between connected precast slabs has a width of 125 mm (4.9 in) with a vertical shear key, filled with ultra-high-performance concrete (UHPC). Sand-coated GFRP bars in the precast slab project into the closure strip with a headed end to provide a 100 mm (3.9 in) embedment length. A static test and two fatigue tests were performed, namely: (i) accelerated variable amplitude cyclic loading and (ii) constant amplitude cyclic loading, followed by static loading to collapse. Test results demonstrated excellent fatigue performance of the developed closure strip details, with the ultimate load-carrying capacity of the slab far greater than the demand. While the failure in the cast-in-place slab was purely punching shear, the failure mode in the jointed precast slabs was punching shear failure with incomplete cone-shape peroration through the UHPC closure strip, combined with a major transverse flexural crack in the UHPC strip. This may be attributed to the fact that the UHPC joint diverted the load distribution pattern towards a flexural mode in the UHPC strip itself close to failure.
Piotr Wiciak, Maria Anna Polak, and Giovanni Cascante
The long-term durability of glass fiber-reinforced polymer (GFRP) in concrete remains an unresolved issue. The necessity of reliable NDT techniques for GFRP bars is critical for in-situ testing of concrete members with GFRP reinforcement. Such bars embedded in concrete show no visual deterioration and cannot be cut out of a structure to test in a traditional way. This paper presents a study of progressive damage of GFRP bars subjected to accelerated aging in alkaline solution and elevated temperature. The study offers four sections: (i) ultrasonic evaluation based on wave velocity and amplitude attenuation approaches, including characterization of ultrasonic transducers using the laser vibrometer, (ii) numerical simulations adding a more comprehensive understanding of wave propagation and investigating other testing methods, (iii) a destructive shear test carried on the bars, which investigates the level of damage in the bars and verifies the ultrasonic evaluation, and (iv) ultrasonic evaluation of bond loss for GFRP bar embedded in concrete beams. The comparison of ultrasonic evaluation, destructive shear test, and numerical simulations shows that ultrasonic techniques can successfully predict the degradation of shear strength (and ultimately tensile strength) of GFRP bars (with a maximum error of 7%). The amplitude-based ultrasonic technique is also capable of bond loss between concrete and GFRP bars.
Nancy Torres, J. Gustavo Tumialan, Antonio Nanni, Richard M. Bennet, and Francisco J. De Caso Basalo
This article presents a protocol for the flexural design of masonry walls reinforced with FRP bars. The proposed design methodology is based on the results of a research program on masonry walls reinforced with FRP bars subjected to out-of-plane (flexural) loads. The research program included testing full-scale masonry walls with different thicknesses, widths, and amounts and types of FRP reinforcement. The research program also included testing of full-scale masonry wall specimens to evaluate the effect of i) different bar lap splice lengths, ii) FRP bar diameter; iii) position of the FRP; iv) masonry strength and v) masonry material. Forty-seven masonry walls, 2.19 m high, were subjected to out-of-plane loads, and tested under quasi-static loading cycles. The test specimens included walls constructed using concrete and clay masonry units, reinforced with glass FRP (GFRP) in different configurations. All the FRP-reinforced masonry walls showed a bilinear moment-deflection curve with one steep slope up to the cracking of masonry and a decrease in stiffness after cracking. After failure occurred and as the out-of-plane load was progressively removed, the walls returned to a position close to the initial vertical position. The flexural design approach for FRP-reinforced walls provided good agreement with the experimental results.
Wael Zatar, Hai Nguyen, and Hien Nghiem
Fiber-reinforced polymer (FRP) materials provide an excellent alternative for shear, flexure, and confinement retrofitting of deteriorated infrastructure. Despite the advanced technology employed in fabricating FRP materials, the monitoring and quality control of the FRP installation still present a challenge. For externally bonded FRP-rehabilitated structures, the existence of undesirable defects, including surface voids and debonding, on the concrete surface should be evaluated, as these defects would adversely affect the durability and capacity of the FRP-rehabilitated structures. Nondestructive testing has the potential to provide a fast and precise means to assess these FRP rehabilitated structures. This paper presents an experimental and theoretical investigation of the use of ground-penetrating radar (GPR) and infrared tomography (IRT) methods to evaluate reinforced-concrete (RC) slabs externally bonded with glass fiber-reinforced polymer (GFRP). Four externally bonded GFRP RC slab specimens were fabricated. Surface voids, interfacial debonding, and vertical cracks were artificially created on the concrete surface of the RC slabs. Test variables include the location and size of surface voids, interfacial debonding, and diameter of steel reinforcement. Improved two-dimensional and three-dimensional image reconstruction method, using the synthetic aperture focusing technique (SAFT), was established to effectively interpret the GPR test data. The results showed that an in-house developed software, that employed the enhanced image reconstruction technique, provided sharp and high-resolution images of the GFRP-retrofitted RC slabs in comparison to those images obtained from the device’s original software. The data suggests that the GPR testing could effectively be employed to accurately determine the size and location of the artificial voids as well as the spacing of the steel reinforcement. The GPR, however, could not well predict the debonding and concrete cracking, as the GPR signals were corrupted because of the direct wave and coupling effect of the antennae and background noise. Results obtained from the IRT testing showed that this technique can detect and locate near-surface defects including surface voids, interfacial debonding, and cracking with acceptable accuracy. The study suggests the combined use of the GPR and IRT imaging to accurately detect possible internal defects of FRP-rehabilitated concrete structures.
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