International Concrete Abstracts Portal

This paper describes the Joffre Bridge project where Carbon Fiber Reinforced Polymer (CFRP) was used as reinforcement for a portion of the concrete deck-slab is reinforced with reinforcement. The Joffre bridge, located over the St-François River in Sherbrooke, Quebec, Canada, consists of five longitudinal spans with length varying from 26 to 37 meters. Each span consists of a concrete deck supported by five steel girders at 3.7 meters. This spacing constitutes the highest span using FRP reinforcement. A Part of the concrete deck slab (7.3 m x 11.5 m) and a portion of the traffic barrier and the sidewalk was reinforced with Carbon and Glass Fiber Reinforced Polymer (FRP ) reinforcement. In addition, four FRP reinforced full-scale one-way concrete slabs were laboratory tested under static and cyclic loading, in order to optimize the design process. The bridge was extensively instrumented with different types of sensors, including integrated fiber optic sensors in FRP reinforcement that were integrated into the FRP reinforcement. The results of the laboratory study, in terms of deflection and crack-width versus applied load, as well as the results of calibrated loads, using heavy trucks, are also presented in this paper.

A total of 15 concrete columns were cast and tested to investigate the influence of replacing longitudinal and/or tie steel bars by an equal volume of amount of glass fiber reinforced polymers (GFRP) bars on the behavior of concrete columns. The columns were subjected to concentric monotonic axial loading. The concrete block for all columns was 450 ¥ 250 ¥ 1200 mm. The results indicated that replacing the longitudinal steel bars by GFRP bars reduced the axial capacity of the column by 13%. The results also showed that regardless of the type of the longitudinal bars, replacing the steel ties by GFRP ties reduced the axial capacity of the column by 10%. However, the study revealed that replacing the steel ties by GFRP had, up to about 80% of the ultimate load, no influence on the load-axial shortening curve. Furthermore, the results indicated that the currently used ACI formula to estimate the axial capacity of the column overestimated the actual capacity of the column reinforced longitudinally and or transversely by GFRP bars.

While ductile behavior of a reinforced concrete member can be given by flexural longitudinal steel bars, high strength continuous fibers can contribute as shear and confining reinforcement, which can provide excellent durability as well. Composite R/C members encased by fiber-mesh-mortar tubes seem to be therefore one of the most effective systems. In this research, the following aspects of the system were investigated by experimental studies: (a) Tensile behavior of fiber-mesh-mortar plate—Tensile properties of the fiber-mesh-mortar plates were investigated. The test results showed tension stiffening effect, which reduced crack spacing. (b) Compressive capacities of concrete columns with fiber-mesh-mortar tubes—Uniaxial compressive tests of concrete columns cast in fiber-mesh-mortar permanent forms were conducted. Improvements in strength and ductility were obtained. The confining effect was governed by fiber type, mesh directions and number of mesh layers. (c) Shear and flexural behavior of composite R/C beams encased by fiber-mesh-mortar tube—Composite R/C beams fully encased by fiber-mesh-mortar tubes were tested. The fiber-mesh-mortar tube reduces surface crack spacing on the lateral sides of the beams and improved shear/flexural capacities.

Concrete-filled fiber reinforced polymer (FRP) tubes provide an alternative to conventional reinforced and prestressed concrete columns. The tube helps turn normal strength concrete core into a high performance concrete, i.e., one with high strength, ductility, and durability. The over-reinforcement in concrete-filled tubes helps avoid split rupture of the FRP reinforcement in tension, which is catastrophic in nature. A total of 8 concrete-filled FRP tubes were tested as beam-columns under a combination of axial and flexural loads. The tubes were 9 feet long, and had an outside diameter of 13 11/16 in. with a wall thickness of about 0.55 in.. The study showed that over-reinforced concrete-filled FRP tubes generally behave well as beam columns. They deflect to a lesser extent than the corresponding under-reinforced sections. They are also more efficient than under-reinforced sections, because a smaller portion of their sectional capacity is consumed by secondary moments and P-D effects. Their failure, while in compression, is considered to be gradual and progressive.

In this paper, a new approach predicting the punching shear capacity of FRP reinforced concrete flat slabs without shear reinforcement is introduced in the light of the results of an experimental program conducted at the Centre for Cement and Concrete of the University of Sheffield. The new approach is found to accurately predict the punching shear capacity of the tested slabs. Verification of this new approach is undertaken through comparisons with other test results ensures its validity. Comparisons of the new approach with the ACI 318-95 equation calculating the punching shear capacity of reinforced concrete slabs without shear reinforcement show that the current ACI equation is unconservative in case of FRP reinforcement with low reinforcement ratios. A modification is proposed to the current ACI 318-95 code equation for punching shear in order to accommodate low stiffness FRP reinforcement. Comparisons with test results show that the proposed modification of the ACI code equation leads to good predictions.