Brahim Benmokrane

Flexural response of concrete beams reinforced with FRP reinforcing bars

The authors conducted an experimental and theoretical comparison between flexural behaviors of concrete beams reinforced with fiber reinforced plastic (FRP) reinforcing bars and identical conventionally reinforced ones. Comparisons were made in relation to cracking behavior, load-carrying capacities and modes of failure, load-deflection response, flexural rigidity, and strain distribution. The results revealed that perfect bond exists between FRP reinforcing bars and the surrounding concrete. Also, American Concrete Institute (ACI) Code formulas for predicting deflection response, cracking-ultimate moments, and cracked-effective moments of inertia can easily be adapted for modeling the flexural behavior of concrete beams reinforced with FRP reinforcing bars if appropriate modifications are made.

Structural health monitoring of innovative bridges in Canada with fiber optic sensors

This paper describes the development and application of fiber optic sensors for monitoring bridge structures. Fiber Bragg gratings (FBGs) have been used to measure static and dynamic loads on bridge decks and columns, including composite repairs for rehabilitation purposes. A new long gage concept that permits overall average strains to be measured has also been developed with gage lengths varying from 1-20 m. These gages can be bonded to the concrete structure or imbedded in the composite repair patch. Six projects undertaken by ISIS Canada to incorporate fiber optic sensing to monitor the structural health of bridges in Canada are described. Data will be presented for several bridges that indicate a measure of system reliability over several years in a hostile environment. The benefits of fiber optic sensors will be highlighted.

INVESTIGATION OF BOND IN CONCRETE MEMBER WITH FIBRE REINFORCED POLYMER (FRP) BARS

Abstract Bond strength of fibre reinforced polymer (FRP) rebars was experimentally investigated in this study and compared to that of steel rebars. A total of 64 concrete beams reinforced with two types of FRP rebars, respectively, were tested. Four nominal diameters of FRP and steel rebars, namely, 12.7, 15.9, 19.1 and 25.4 mm and three embedment lengths, six, 10 and 16 times the rebar diameter were used. Moreover, three concrete depths of 200, 600 and 1000 mm were investigated in the 18 pullout specimens. Results of the tests indicated that the applied tensile load approached the tensile strength of rebars as the embedment length increased and the GFRP rebars showed lower bond strength values compared to steel rebars. The average maximum bond strength of the FRP rebars varied from 5.1 to 12.3 MPa depending on the diameter and the embedment length. The GFRP rebars showed lower bond strength values compared to steel rebars. A modification factor of 1.30 is recommended for computing the development length, to account for the top bar effect. A new model is proposed for the ascending branch of the bond–slip law.

Shear Strength of FRP-Reinforced Concrete Beams without Transverse Reinforcement

This paper studied the behavior and shear strength of concrete slender beams reinforced with fiber-reinforced polymer (FRP) bars. Nine large-scale reinforced concrete beams without stirrups were constructed and tested to failure. The beams measured 3250 mm long, 250 mm wide, and 400 mm deep and were tested in 4-point bending. Test variables were the reinforcement ratio and modulus of elasticity of the longitudinal reinforcing bars. The test beams included 3 reinforced with glass FRP bars, 3 reinforced with carbon FRP bars, and 3 control beams reinforced with conventional steel bars. Test results were compared with predictions provided by the different available codes, manuals, and design guidelines, indicating that the relatively low modulus of elasticity of FRP bars results in reduced shear strength compared to that of control beams reinforced with steel. The current ACI 440.1R design method offered very conservative predictions, particularly for beams reinforced with glass FRP bars. Based on obtained experimental results, a proposed modification to the current ACI 440.1R design equation is given and verified against test results from other research.

FLEXURAL BEHAVIOR OF CONCRETE BEAMS REINFORCED WITH DEFORMED FIBER REINFORCED PLASTIC REINFORCING RODS

Fiber reinforced plastic (FRP) reinforcing bars are being used as an alterntative to steel reinforcement to overcome the corrosion problem in bridge decks, parking garages, water and wastewater treatment facilities, marine structures, and chemical plants. This paper presents test results of concrete beams reinforced with FRP and conventional steel reinforcement. The beams were tested under static loading to investigate the effects of reinforcement ratio on cracking, deflection, ultimate capacities, and modes of failure. Based on this investigation, theoretical correlations for the prediction of crack width, maximum deflection, and ultimate load-carrying capacity are proposed.

BOND STRENGTH AND LOAD DISTRIBUTION OF COMPOSITE GFRP REINFORCING BARS IN CONCRETE

The objective of this investigation was to examine the bond strength of glass fiber reinforced plastic (GFRP) reinforcing bars in concrete. Twenty concrete beams reinforced with four nominal diameters from 12.7 to 25.4 mm of GFRP and steel reinforcing bars were tested to determine the bond strength of GFRP reinforcing bars in comparison with steel reinforcing bars. Additionally, the distribution of tensile and bond stresses along the embedment length of GFRP reinforcing bars was studied by five pullout tests using instrumented 19.1-mm-diameter GFRP reinforcing bars compared with steel reinforcing bars in concrete. Only one type of GFRP reinforcing bar was used in this study. Test results reveal that the diameter effect on bond observed for steel reinforcing bars is also present for GFRP reinforcing bars. The bond strength of GFRP bars is lower than that of steel reinforcing bars. The bond strength from beam tests is lower than that from pullout tests. Furthermore, it was found that the distribution of bond stress along the embedment length of GFRP reinforcing bars is nonlinear.

Glass fibre reinforced plastic (GFRP) rebars for concrete structures

Abstract The study described is a part of a large-scale experimental and theoretical programme on the application of fibre reinforced plastic ( frp ) reinforcement for concrete structures initiated at the Universite de Sherbrooke (Sherbrooke, Canada). The programme is being carried out to gain an insight into the flexural behaviour of concrete beams reinforced with glass fibre reinforced plastic ( gfrp ) rebars. Results of experimental study on 3.3 m long beams reinforced with two different types of gfrp rebars are presented and compared to that of conventional steel reinforced concrete beams. Three series of reinforced concrete beams were tested in flexure. The beams were 200 mm wide and respectively 300, 450 and 550 mm high. The paper also attempts to present the properties of gfrp and its components and to give an oversight of relevant research activities involving gfrp rebars as reinforcement for concrete units.

LABORATORY EVALUATION OF CEMENT-BASED GROUTS AND GROUTED ROCK ANCHORS

Abstract The paper reports the findings of a laboratory study on six different types of cement-based grouts and two types of steel rock anchors. The physical and mechanical characteristics of cement grouts employing silica fume, aluminium powder, superplasticizer or sand are compared with those of conventional cement grouts. Pullout tests of grouted, 7-strand steel cable and solid steel thereadbar were conducted under similar conditions for different grouts and embedment lengths. From the results obtained, an empirical equation is derived for the estimation of anchor pullout resistance for a given embedment length. A simple trilinear constitutive model for shear bond stress-slip relation at the anchor-grout interface is proposed and discussed.

FLEXURAL BEHAVIOR OF ONE-WAY CONCRETE SLABS REINFORCED BY FIBER REINFORCED PLASTIC REINFORCEMENTS

Fiber Reinforced Plastic (FRP) reinforcements are currently used for special concrete structures in areas sensitive to magnetic fields and severe environmental conditions that accelerate corrosion of the steel reinforcements, and consequently leads to deterioration of the structure. This paper presents test results of eight one-way concrete slabs reinforced with glass-fiber, carbon-fiber, and conventional steel reinforcements. The slabs were tested under static loading conditions to determine their flexural and shear limit states, including the behavior prior to cracking, cracking, ultimate capacities, and modes of failure. Based on this investigation, design recommendations and guidelines are proposed.

Influence of Coarse Aggregate on Elastic Properties of High-Performance Concrete

The paper resports tests carried out on high-strength concrete made with differnt types of crushed rocks. These tests highlight the role played by coarse-aggregate through the elastic properties of the parent rock. The results obtained open an opportunity to review the present formulas relating E sub c to F sub c recommended by some codes.