Radhouane Masmoudi

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.

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.

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.

Axial Load Capacity of Concrete-Filled FRP Tube Columns: Experimental versus Theoretical Predictions

This paper presents the experimental and theoretical results of small and medium-scale concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) columns. A total of 23 CFFT specimens were tested under axial compression load. Five different types of new FRP tubes were used as stay-in-place formwork for the columns. The effects of the following parameters were examined: the FRP-confinement ratio, the unconfined concrete compressive strength, the presence of longitudinal steel reinforcement, and the height-to-diameter ratio. Comparisons between the experimental test results and the theoretical prediction values by the three North American codes and design guidelines (ACI 440.2R-08, CSA-S6-06, and CSA-S806-02) are performed in terms of confined concrete strength and ultimate load carrying capacity. The results of this investigation indicate that the design equations of the ACI 440.2R-08, CAN/CSA-S6-06, and CAN/CSA-S806-02 overestimate the factored axial load capacity of the short CFFT columns as compared to ...

Effect of Sustained Load and Environment on Long-Term Tensile Properties of Glass Fiber-Reinforced Polymer Reinforcing Bars

Glass fiber-reinforced polymer (GFRP) bars are gaining popularity as reinforcement for concrete bridge deck slabs and other concrete structures. This article reports on a study of the creep behavior of GFRP bars in different environments under sustained load. Twenty GFRP bars (E-glass in vinylester matrix) 9.5 mm in diameter in four series were tested for over 417 days (10,000 h) under combinations of different sustained load levels and surrounding mediums in ambient temperature. The bars were subjected to two levels of sustained tensile stress at 25% and 38% of guaranteed tensile strength while being surrounded by either alkaline solution (pH 12.8) or de-ionized water (pH 7.0). Axial strain in the central conditioned part of the bars was monitored with time to evaluate the creep behavior. Following the extended creep test, the GFRP bars were tested in axial tension until failure for residual tensile strength, elastic modulus, and axial strain. Results showed that the tested GFRP bar performed very well under these extreme loading and environmental conditions. Creep strain in the GFRP bars is less than 5% of the initial value after 10,000 h of sustained tensile loading. The average residual tensile strength was found to be 139% and 144% of the design tensile strength for bars conditioned in de-ionized water at 25% and 38% stress level, respectively. Alkaline solution tends to have more harmful effects on the bars than de-ionized water at higher stress levels. In alkaline solution, this range was 126% and 97% at 25% and 38% stress level, respectively. More importantly, the modulus of elasticity of the bars is very stable and almost unaffected by the conditions and sustained stress levels used. The authors note that this finding is critical in the design of concrete elements reinforced with FRP bars because the modulus is directly related to the crack width, deflection, and other serviceability concerns.

CONCRETE BRIDGE BARRIERS REINFORCED WITH GLASS FIBER-REINFORCED POLYMER COMPOSITE BARS

Recent expansion of highway networks has increased the need to provide corrosion-free reinforced concrete components for highway bridges. This paper describes an extensive research program that investigated the behavior of 2 types of bridge barriers--PL-2 and PL-3--reinforced with glass fiber-reinforced polymer (GFRP) bars. The geometry, concrete dimensions, and reinforcement of both PL-2 and PL-3 barriers were based on the new Canadian Highway Bridge Design Code. Sand-coated GFRP bars and conventional steel bars were used in the experimental study. The performance of barriers reinforced with GFRP bars was evaluated and compared with that of their counterparts reinforced with steel. Results indicate that the behavior of PL-2 and PL-3 concrete bridge barriers reinforced with GFRP bars is very similar to their counterparts reinforced with conventional steel in terms of cracking, deflections, strains, energy absorption, integrity, and ultimate strength.

Bond Performance of Basalt Fiber-Reinforced Polymer Bars to Concrete

This paper presents the test results of a study on the bond behavior of basalt fiber-reinforced polymer (BFRP) bars to concrete. Thirty six concrete cylinders reinforced with BFRP bars and twelve cylinders reinforced with glass fiber-reinforced polymer (GFRP) bars were tested in direct pullout conditions. Test parameters included the FRP material (basalt and glass), the bar diameter, and the bar embedment length in concrete. Bond-slip curves of BFRP and GFRP bars revealed similar trends. BFRP bars developed average bond strength 75% of that of GFRP bars. All BFRP specimens failed in a pullout mode of failure along the interfacial surface between the outer layer of the bar and the subsequent core layers. The influence of various parameters on the overall bond performance of BFRP bars is analyzed and discussed. The well-known BPE and modified-BPE analytical models were calibrated to describe the bond-slip relationships of the bars. Test results demonstrate the promise of using the BFRP bars as an alternative to the GFRP bars in reinforcing concrete elements.

Thermal effect on fiber reinforced polymer reinforced concrete slabs

The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar - concrete interface, which induces tensile stresses within the con- crete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insuf- ficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from -30 to +80 8C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 8C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 8C. Also, the first cracks appear in concrete at the FRP bar - concrete interface at temperatures around +40 8C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.

Finite Element Modeling for Deflection and Bending Responses of GFRP Poles

The use of the tapered glass fiber-reinforced polymer (GFRP) poles are well recognized as an alternative for traditional materials such as wood, steel, and concrete, in overhead power lines and distribution aerial networks. The current research work aims to assess the general behaviors of lightweight GFRP poles structures. A nonlinear finite element (FE) analysis is carried out to address the nonlinear behavior of tapered GFRP poles under lateral loads. The numerical results of the program are verified with the experimental results conducted on full-scale GFRP poles. The GFRP poles are fabricated using the filament winding technique; E-glass fiber and Epoxy resin are utilized for manufacturing these poles. There is very satisfactory agreement between the numerical results and the experimental results in terms of load-deflection relationship and ultimate load carrying capacity. The FE model was used to detect the performance of GFRP poles having service openings (holes). Several FE simulations with different combinations of parameters, such as fiber orientation, number of layers and thickness of layers, were employed. Evaluation of the deflection and bending strength characteristics of GFRP Poles (20, 33, 35 and 40 ft height) are presented. Optimum new designs for three zones along the height of the GFRP poles are proposed, under equivalent wind load. The ultimate load carrying capacity and flexural stiffness are improved with a significant saving in the weight by utilizing this design.

Nonlinear Stability Analysis of Concrete-Filled Fiber-Reinforced Polymer-Tube Columns: Experimental and Theoretical Investigation

Few studies have been conducted on the buckling modes of failure of concrete-filled fiber-reinforced polymer (FRP)-tube (CFFT) columns. This paper seeks to fill this research gap by presenting both experimental results and theoretical analysis for buckling responses of CFFT columns. The effect of three parameters (FRP tube thickness, concrete compressive strength, and slenderness ratio) and the parameters’ interaction on the buckling behavior were investigated. The experimental program consisted of testing 22 circular CFFT columns with a total height ranging from 305 to 1520 mm (12 to 60 in.) and an internal tube diameter of 152 mm (6 in.). The experimental results showed that uniaxial compressive strength of CFFTs was reduced by 13-23% as the slenderness ratio increased from 4 to 20, depending on the concrete compressive strength and the thickness of FRP tubes. Both the axial strength and stiffness of slender columns were increased as a result of the confining effect of the FRP tubes. The enhancement of the axial strength of the slender column was more pronounced for lower-strength concrete than for higher-strength concrete. Increasing the thickness of the glass-FRP tubes significantly improved the ultimate load capacity of the tested specimens. Predicted slenderness limit was slightly affected by both the concrete compressive strength and FRP tube thickness. A simplified formula for the limit slenderness ratio was proposed for the design of CFFT columns.