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International Concrete Abstracts Portal

Showing 1-5 of 931 Abstracts search results

Document: 

SP-360_02

Date: 

March 1, 2024

Author(s):

John J. Myers

Publication:

Symposium Papers

Volume:

360

Abstract:

The American Concrete Institute (ACI) 440.1R-15 Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars linearly reduces the bar stress and thereby pull-out capacity of FRP bars to zero from an embedment length at 20 bar diameters (db) or less. Most experimental research and data examine the development length of various FRP bars at longer, more traditional, embedment lengths. A database was created from select available data in literature to compare to empirical standards. This investigation examines the bond performance of short embedded FRP bars into concrete considering a pull-out failure mode to expand the understanding of short embedded FRP bars into concrete. Based upon the database collected, for the glass fiber-reinforced polymer (GFRP) rebars, the current 440.1R appear quite conservative. For the basalt fiber-reinforced polymer (BFRP) rebar database collected, the current ACI 440.1R-15 provisions appear unconservative for a statistically significant number of the specimen test results within the database. In the case of the carbon fiber-reinforced polymer (CFRP) database, which is quite limited, the data appears to develop considerably less bond strength than the current 440.1R provisions might suggest which requires deeper investigation for the case of short embedment length bonded CFRP bars.

DOI:

10.14359/51740614


Document: 

SP-360_07

Date: 

March 1, 2024

Author(s):

Jaeha Lee, Kivanc Artun, Charles E. Bakis, Maria M. Lopez and Thomas E. Boothby

Publication:

Symposium Papers

Volume:

360

Abstract:

Small-scale plain concrete precracked beams strengthened with glass fiber reinforced polymer (GFRP) sheets underwent testing in 3-point flexure to assess variations in the FRP-concrete Mode II interfacial fracture energy after 6 and 13 years of sustained loading in indoor and outdoor environments. The Mode II fracture energy of the interfacial region, GF, was determined by analyzing strain profiles along the length of the FRP sheet, which were obtained using digital image correlation and photoelastic techniques. In the experiments conducted after conditioning, higher GF values were observed as the debonded zone progressed from the region of sustained shear stress transfer to the unstressed section of the interfacial region, particularly in beams subjected to outdoor conditioning. In the interfacial region near the notch, GFRP beams showed reductions in GF in both indoor and outdoor environments. For outdoor beams with GFRP sheets, there was no additional degradation in GF when the FRP was exposed to direct sunlight, in comparison to beams with the FRP exposed to indirect sunlight.

DOI:

10.14359/51740619


Document: 

SP-360_27

Date: 

March 1, 2024

Author(s):

Alessio Cascardi, Salvatore Verre and Luciano Ombres

Publication:

Symposium Papers

Volume:

360

Abstract:

his paper presents an experimental study on the discontinuous confinement of small-scale masonry columns using a FRCM system. The study aims to investigate the effectiveness of the FRCM in enhancing compressive strength and ductility under axial loading condition. In detail, the adopted FRCM system was composed of a cementitious matrix reinforced with PBO mesh. It was applied to the masonry columns using a discontinuous wrapping technique, which involved wrapping the FRCM material around the column in segments, leaving gaps between the segments itself.

More in deep, the experimental program included twelve specimens, ten (i.e. five couples) of which were wrapped with the PBO-FRCM system using the discontinuous wrapping technique, while the remaining two columns were left unconfined and served as the control group. The columns were measured concerning the load-displacement behavior, ultimate strength and failure mode and then compared between the FRCM-confined and unconfined columns. In particular, the amount of fiber in the vertical direction was kept constant, while the scheme of confinement was varied by both changing the strip width and spacing. In total, five different schemes of discontinuous confinement were proved. The performed research aims to contribute to the knowledge in the field of FRCM-masonry confinement, mainly focusing on the influence of the mentioned parameter.

DOI:

10.14359/51740639


Document: 

SP-360_16

Date: 

March 1, 2024

Author(s):

Ahmed Khalil, Rami A. Hawileh, and Mousa Attom

Publication:

Symposium Papers

Volume:

360

Abstract:

This study explores technological advancements enabling the utilization of GFRP bars in concrete structures, particularly in coastal areas. However, GFRP bars often encounter reduced bend strength at specific bend locations, which may pose a challenge in their practical application. Various properties such as the strength of bent GFRP bars are crucial for quality assurance, yet existing testing methods stated in ASTM D7914M-21 and ACI 440.3R-15 have limitations when applied to different GFRP bent shapes. Furthermore, those methods require special precautions to ensure symmetry and avoid eccentricities in specimens. To address these challenges, CSA S807:19 introduced a simpler standardized testing procedure that involves embedding a single L-shaped GFRP stirrup in a concrete block. However, the specified large block size in CSA S807:19 Annex E may pose difficulties for both laboratory and on-site quality control tests. Therefore, CSA S807:19 Annex E (Clause 7.1.2b) permits the use of a customized block size, as long as it meets the bend strength of the FRP bars without causing concrete splitting. To date, very few prior research has explored the use of custom block sizes. Therefore, this study aims to thoroughly investigate the strength of bent FRP bars with custom block sizes and without block confinement. Such an investigation serves to highlight the user-friendliness and efficiency of the CSA S807:19 Annex E method. The study recommends two block sizes: 200x400x300 mm (7.87x15.75x11.81 in) for bars <16 mm (0.63 in) diameter and 200x200x300 mm (7.87x7.87x11.81 in) for bars <12 mm (0.39 in). Additionally, the study cautions against using confinement reinforcement, especially with smaller blocks, as it could interfere with the embedded bent FRP bar. Furthermore, the study suggests incorporating additional tail length to mitigate the debonding effects resulting from fixing the strain gauges to the bent portion of the embedded FRP bar. By exploring these modifications, the study seeks to enhance the effectiveness of the testing procedure and expand its practical application for both laboratory and on-site quality assurance. The findings hold implications for the reliable testing of GFRP bars' strength, advancing their use as reinforcement in concrete structures.

DOI:

10.14359/51740628


Document: 

SP-360_13

Date: 

March 1, 2024

Author(s):

Girish Narayan Prajapati, Shehab Mehany, Wenxue Chen, and Brahim Benmokrane

Publication:

Symposium Papers

Volume:

360

Abstract:

This paper presents an experimental study that investigated the physical and mechanical properties of the helical wrap glass fiber-reinforced polymer (GFRP) bars. The physical tests are conducted to check the feasibility and quality of the production process through the cross-sectional area and evaluation of the fiber content, moisture absorption, and glass transition temperature of the specimens. While the mechanical tests in this study included testing of the GFRP specimens to determine their tensile properties, transverse shear, and bond strength. Four bar sizes (#3, #4, #5, and #6), representing the range of GFRP reinforcing bars used in practice as longitudinal reinforcement in concrete members subjected to bending, are selected in this investigation. The GFRP bars had a helical wrap surface. The tensile failure of the GFRP bars started with rupture of glass fibers followed by interlaminar delamination and bar crushing. The bond strength of the GFRP bars satisfied the limits in ASTM D7957/D7957M. The test results reveal that the helical wrap GFRP bars had physical and mechanical properties within the standard limits.

DOI:

10.14359/51740625


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