Ahmed Sabry Farghaly

Concrete columns reinforced longitudinally and transversally with glass fiber-reinforced polymer bars

The use of glass fiber-reinforced polymer (GFRP) reinforcing bars is being widely investigated as an alterative to conventional steel reinforcement in reinforced concrete (RC) structures exposed to harsh environments. This experimental study investigates the behavior of concrete columns reinforced with GFRP bars under axial loads. The effect of FRP bars as longitudinal and lateral reinforcement on the concrete column response is estimated, focusing primarily on the strength and strain capacities of RC members. Tie spacing, tie configuration and spalling of concrete cover were considered. The experimental results also were compared to different design formulas provided by the ACI Building Code and Canadian Standards Association S806-02 code. Results showed that columns reinforced with GFRP withstood loads similar to or higher than the columns reinforced with steel. Gains in strength, toughness and ductility were found for the concrete cores of well-confined columns. Setting the FRP compressive strength at 35% of the FRP maximum tensile strength resulted in a reasonable estimate of ultimate capacity compared to the experimental results.

Experimental Investigation of Concrete Shear Walls Reinforced with Glass Fiber–Reinforced Bars under Lateral Cyclic Loading

AbstractThe present study addresses the applicability of reinforced concrete shear walls totally reinforced with glass fiber–reinforced polymer (GFRP) bars to attain reasonable strength and drift requirements as specified in different codes. Four large-scale shear walls—one reinforced with steel bars (as reference specimen) and three totally reinforced with GFRP bars—were constructed and tested to failure under quasistatic reversed cyclic lateral loading. The GFRP-reinforced walls have different aspect ratios covering the range of medium-rise walls. The reported test results clearly show that properly designed and detailed GFRP-reinforced walls could reach their flexural capacities with no strength degradation and that shear, sliding shear, and anchorage failures were not major problems and can be effectively controlled. The results also show recoverable and self-centering behavior up to allowable drift limits before moderate damage occurs and achieving a maximum drift meeting the limitation of most build...

Prediction of Punching Shear Strength of Two-Way Slabs Strengthened Externally with FRP Sheets

Strengthening two-way slabs by using fiber-reinforced polymer (FRP) is experimentally and analytically evaluated. Results show that the punching capacity of two-way slabs can increase to up to 40% greater than that of a reference specimen. A three-dimensional FEM program called 3D CAMUI, which was developed at Hokkaido University, was used to simulate the experimental slabs. Very good agreement is obtained in load-carrying capacity and modes of failure. An analytical model based on the numerical simulation, which discloses the mechanism of punching shear strength enhancement by FRP strengthening, is proposed to predict the punching shear strength of two-way slabs externally strengthened with FRP sheets. DOI: 10.1061/(ASCE)CC.1943-5614.0000177.

Flexure and Shear Deformation of GFRP-Reinforced Shear Walls

AbstractExperimental results of midrise RC shear walls under quasistatic cyclic loading were used to investigate the interaction of flexural and shear deformations. Four large-scale shear walls—one reinforced with steel bars and three totally reinforced with glass fiber–reinforced polymer (GFRP) bars—were tested to failure where the behavior was dominated by flexure. It was found that relying on the diagonal displacement transducers tended to overestimate shear deformations by 30 to 50%. To correct the shear deformations, the center of rotation of the tested shear walls was evaluated. Based on experimental results, the fundamental equation of flexural deformation obtained values of the center of rotation (α). Using the suggested values of α produced consistent results for the flexure and shear deformations. Decoupling the total deformation of the tested shear walls into flexural and shear deformations was discussed. Using elastic materials (GFRP bars) gave uniform distributions of shear strains along the ...

Strut Efficiency-Based Design for Concrete Deep Beams Reinforced with Fiber-Reinforced Polymer Bars

In this paper, a strut-and-tie-based model is proposed to predict the shear strength of fiber-reinforced polymer-reinforced (FRP) deep beams. An assessment of the available strut-and-tie models (STMs) in ACI and CSA provisions was conducted, identifying the important parameters affecting the strut efficiency factor. The tendency of each parameter (concrete compressive strength, shear span-depth ratio, and strain in longitudinal reinforcement) was assessed against the efficiency factor. The data from the 28 specimens with and without web reinforcement, including 12 tested FRP-reinforced concrete deep beams in our study and 16 FRP-reinforced deep beams taken from the literature, were used to assess the proposed model. The model was capable of capturing the failure mode and predicting the ultimate capacity of the tested FRP-reinforced deep beams. The proposed model was verified against a compilation of databases on 172 steel-reinforced deep beams, resulting in an acceptable level of adequacy.

Laboratory Testing of GFRP-RC Panels with UHPFRC Joints of the Nipigon River Cable-Stayed Bridge in Northwest Ontario, Canada

AbstractThis study investigates the behavior of ultrahigh-performance fiber-reinforced concrete (UHPFRC) joints between precast concrete panels reinforced with glass-fiber-reinforced polymer (GFRP) bars that are being used in the first cable-stayed bridge in northwest Ontario, Canada (Nipigon, Nipigon River Bridge). The test panels, which simulated the deck panels of the Nipigon River Bridge, were fabricated at the same precast facility in Ontario and delivered to the University of Sherbrooke for flexural testing until failure. The test matrix included eight panels measuring 3,000 mm long × 1,000 mm wide × 220 mm thick. The tests included three reference specimens without structural joints (one reinforced with steel bars and two reinforced with GFRP bars) and five jointed specimens (one reinforced with steel bars and four reinforced with GFRP bars). The structural joint width was a constant 220 mm for all jointed specimens. The specimens were tested in a cantilever-panel setup with the UHPFRC joint subjec...

Aspects of Deformability of Concrete Shear Walls Reinforced with Glass Fiber–Reinforced Bars

AbstractThe ACI and CSA design codes offer no unified method for evaluating the deformability of fiber-reinforced polymer (FRP) reinforced-concrete (RC) structures, although numerous experimental results for such elements are available. This study discusses the methods for quantifying the deformability in FRP-RC structures. The methods were assessed based on the experimental results of four full-scale RC shear walls: three reinforced with FRP bars and one with steel bars. The objective was to contribute to the development of a method for verifying the deformability of FRP-RC structures. The curvature ductility index (μϕ) and deformability index (J) were found to be the most appropriate methods when calculated at a concrete strain equal to 0.0035.

Experimental Behavior of Glass Fiber-Reinforced Polymer- Reinforced Concrete Columns under Lateral Cyclic Load

The present study addresses the feasibility of reinforced concrete columns totally reinforced with glass fiber-reinforced polymer (GFRP) bars achieving the drift requirements specified in various codes. Eleven full-scale concrete columns—two reinforced with steel bars (as reference specimen) and nine totally reinforced with GFRP bars—were constructed and tested to failure under quasistatic reversed cyclic lateral loading and simultaneously subjected to constant compression axial load. The reported test results clearly show that properly designed and detailed GFRP-reinforced concrete columns could reach high deformation levels with no strength degradation. The results also show that the achieved drift satisfies the limitation in most building codes. Acceptable levels of energy dissipation and ductility parameters, compared to the steel-reinforced columns, were observed. The promising results can provide impetus for constructing concrete columns reinforced with GFRP and constitute a step toward using GFRP reinforcement in lateral-resisting systems such as reinforced concrete frames.

Effect of Vertical and Horizontal Web Reinforcement on the Strength and Deformation of Concrete Deep Beams Reinforced with GFRP Bars

AbstractTen full-scale concrete deep beams reinforced with glass fiber-reinforced polymer (GFRP) with a cross section of 1,200×300  mm were tested to failure under two-point loading. The test varia...

Beam-Testing Method for Assessment of Bond Performance of FRP Bars in Concrete under Tension–Compression Reversed Cyclic Loading

AbstractThis paper presents a novel beam-testing method to assess the bond performance of fiber-reinforced polymer (FRP) bars in reinforced-concrete resisting systems subjected to tension–compression reversed cyclic loading. Special attention was paid to ensuring the stability of the proposed test setup, limiting all unwanted forces generated in the system and allowing for the application of tension and compression forces to the FRP bar without premature bar buckling. Preliminary test results are presented specifically for the cyclic bond stress-slip relationship under different loading conditions—tension–tension and tension–compression cyclic loading—in addition to the monotonic-tension loading to assess the suitability of the novel testing method.