Hamdy M. Mohamed

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 ...

Performance Evaluation of Concrete Columns Reinforced Longitudinally with FRP Bars and Confined with FRP Hoops and Spirals under Axial Load

AbstractNowadays, AASHTO LRFD Bridge Design Specifications and the Canadian Highway Bridge Design Code contain flexural and shear provisions for the design of concrete bridge members reinforced with fiber-reinforced polymer (FRP) bars. Because of a lack of research, these standards do not recommend using FRP bars to resist compressive stresses in compression members. This paper reports on 14 full-scale circular RC columns tested under concentric axial load. The columns were reinforced with longitudinal FRP bars and confined with circular FRP spirals or hoops. Sand-coated glass-FRP (GFRP) and carbon-FRP (CFRP) reinforcement was used. The test parameters included configuration of the confinement reinforcement (spirals versus hoops), hoop lap length, volumetric ratio, and FRP reinforcement type (glass versus carbon). The test results indicate that the GFRP and CFRP RC columns behaved similarly to columns reinforced with steel. Using GFRP and CFRP spirals or hoops according to the provisions of the Canadian S...

Axial Capacity of Circular Concrete Columns Reinforced with GFRP Bars and Spirals

AbstractSeveral codes and design guidelines are now available for the design of concrete structures reinforced with fiber-reinforced polymer (FRP) bars under flexural and shear loads. Yet, because of a lack of research, North American codes and design guidelines do not recommend using FRP bars as longitudinal reinforcement in columns to resist compressive stresses. This paper reports on 12 full-scale circular reinforced concrete (RC) columns that were tested under concentric axial loads. The columns were reinforced with longitudinal glass FRP (GFRP) bars and newly developed GFRP spirals. The 300-mm diameter columns were designed according to code requirements. The test parameters included reinforcement type (GFRP versus steel); longitudinal FRP reinforcement ratio; and the volumetric ratios, diameters, and spacing of spiral reinforcement. The test results indicated that the GFRP and steel RC columns behaved in a similar manner. The average load carried by the longitudinal GFRP bars ranged between 5% and 1...

Strength and Axial Behavior of Circular Concrete Columns Reinforced with CFRP Bars and Spirals

AbstractThe behavior of concrete members reinforced with fiber-reinforced polymer (FRP) bars has been the focus of many studies in recent years. However, limited research work has been conducted to examine the axial behavior of concrete columns reinforced with FRP bars. In this paper, the behavior and compression strength of 11 full-scale circular concrete columns reinforced with carbon fiber–reinforced polymer (CFRP) bars and spirals were investigated. The test variables included reinforcement type (CFRP versus steel); longitudinal CFRP reinforcement ratio; and the volumetric ratio, size, and spacing of CFRP spirals. The test results indicated that the CFRP and steel reinforced concrete (RC) columns behaved in a similar manner up to their peak loads. The CFRP bars were effective in resisting compression until after crushing of concrete, and contributed on average 12% of column capacity. The design equation is modified to accurately predict the ultimate load capacities of CFRP RC columns. A new factor (αc...

Durability Assessment of Glass FRP Solid and Hollow Bars (Rock Bolts) for Application in Ground Control of Jurong Rock Caverns in Singapore

AbstractThis study was conducted to investigate the durability of two types of vinyl-ester/glass fiber-reinforced polymer (GFRP) rock bolts [solid and hollow (tubular) GFRP bars] that were subseque...

Axial Load–Moment Interaction Diagram of Circular Concrete Columns Reinforced with CFRP Bars and Spirals: Experimental and Theoretical Investigations

AbstractNorth America’s current design codes and guidelines allow the use of fiber–reinforced polymer (FRP) bars as the primary reinforcement in concrete structures and provide design recommendations for using these bars. Because of a lack of experimental data, however, FRP bars have not been recommended for resisting compression stresses as longitudinal reinforcement in columns or compression reinforcement in flexural elements. This paper presents test results of an experimental program to investigate the structural performance of 10 full-scale circular concrete columns reinforced with carbon fiber–reinforced polymer (CFRP) bars and spirals subjected to combined axial compression loads and bending moments. The test variables include different eccentricity-to-diameter ratios and two types of reinforcement (CFRP and steel). The test results show that the CFRP- and steel-reinforced concrete columns behaved similarly up to their peak loads. The failure of the test specimens under different levels of eccentri...

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.

Confinement Model for Concrete Columns Internally Confined with Carbon FRP Spirals and Hoops

AbstractRecent years have seen valuable research work and widespread applications of fiber-reinforced polymer (FRP) bars as flexural and shear reinforcement for concrete structures. Nonetheless, the axial compression behavior of FRP reinforced concrete (RC) columns has not yet been defined. This study introduces equations and a confinement model to predict the stress-strain envelope responses of RC columns reinforced with carbon-FRP bars (CFRP) and confined by CFRP spirals or hoops. The model takes into account the effect of many parameters such as transverse reinforcement configuration, longitudinal reinforcement ratio, volumetric ratio, and the size and spacing of spirals or hoops. Results of analysis using the proposed confinement model were verified by means of a series of experiments with full-scale circular CFRP-RC columns. The proposed equations have been shown to predict accurately confined concrete core stress, corresponding concrete strain, and prepeak and postpeak stress-strain relationships fo...

Experimental Study of Circular High-Strength Concrete Columns Reinforced with GFRP Bars and Spirals under Concentric and Eccentric Loading

AbstractIntegrating fiber-reinforced polymer (FRP) reinforcement into high-strength concrete (HSC) would effectively contribute to enhancing the stiffness of cracked concrete sections when the FRP ...

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.