Ehab A. Ahmed

Bend Strength of FRP Stirrups: Comparison and Evaluation of Testing Methods

This paper provides a comparison and evaluation of the current test methods used to determine the strength of fiber-reinforced polymer FRP bent bars/stirrups at the bend location bend strength. The available methods depend on applying tensile forces through the straight portion of the bent bar/stirrup and keeping the bend zone restrained to generate a stress perpendicular to the bend direction in addition to the stress in the longitudinal direction. This could be achieved through the ACI 440.3R-04 B.12 test method for U-shaped bare FRP bars. Another possible method is the ACI 440.3R-04 B.5 which evaluates the bend strength of FRP stirrups by embedding them in two concrete blocks, which are pushed apart until the rupture of the FRP bent bars. Both methods were employed in testing FRP stirrups and bent bars and the bend strength was compared. The test results showed that the ACI 440.3R-04 B.12 test method consistently underestimates the bend strength of FRP stirrups. On the other hand, B.5 test method is more reliable and representative to the actual state of stresses in real concrete structural elements.

Flexural Behavior and Serviceability of Normal- and High-Strength Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars

This paper investigated the flexural behavior and serviceability performance of glass fiber-reinforced polymer (GFRP)-reinforced concrete (GFRP-RC) beams fabricated with normal- and high-strength concretes (NSCs and HSCs). The beam specimens measured 4250 mm long x 200 mm wide x 400 mm deep (167.0 x 8 x 16 in.). Three GFRP products with moduli of elasticity ranging from 48.7 to 69.0 GPa (7100 to 10,000 ksi) with sand-coated and helically grooved surface textures were employed. A total of 12 full-scale beams reinforced with GFRP bars and two reinforced with steel bars, serving as control specimens, were tested to failure in four-point bending over a clear span of 3750 mm (148 in.). The test parameters were: 1) type and ratio of the GFRP reinforcement; 2) surface configuration of the GFRP bars; 3) concrete strength; and 4) bar diameter. The test results were reported in terms of deflection, crack width, strains in concrete and reinforcement, flexural capacity, and mode of failure; they were also employed to assess the accuracy of the current deflection and crack-width prediction equations in the FRP-RC codes. The test results revealed that the crack widths were affected by the bar diameter and surface configuration while the deflections were not significantly affected. In addition, the bond coefficient kb value of 1.4 was very conservative for both of the sand-coated and helically grooved GFRP bars in NSC and HSC.

Shear Performance of RC Bridge Girders Reinforced with Carbon FRP Stirrups

One of the main components in girder-type bridges is bridge girder. This paper presents experimental data on the behavior and shear strength of concrete bridge girders reinforced with carbon fiber-reinforced polymer CFRP stirrups. A total of four large-scale reinforced concrete beams with a total length of 7,000 mm and a T-shaped cross section were constructed and tested up to failure. The test variables were the type and ratio of shear reinforcement stirrups. The test beams included three beams reinforced with sand-coated CFRP stirrups of 9.5-mm-diameter spaced at d /2, d /3, and d /4 where d is the beam depth and a control beam reinforced with conventional steel stirrups of 9.5-mm-diameter spaced at d /2. The geometry of the test prototypes were selected to simulate the New England Bulb Tee NEBT beams that are being used by the Ministry of Transportation of Quebec, Canada. As designed, three beams failed in shear due to CFRP stirrup rupture or steel stirrup yielding. While, the forth one, reinforced with CFRP stirrups spaced at d /4, failed in flexure due to yielding of longitudinal reinforcement. The test results were compared to predictions provided by different codes and design guidelines. The current ACI 440.1R-06 design method provides conservative predictions; however, the CAN/CSA S6-06 and JSCE 1997 underesti- mate the contribution of the FRP stirrups due to low strain limits.

Performance Evaluation of Glass Fiber-Reinforced Polymer Shear Reinforcement for Concrete Beams

Using fiber-reinforced polymer (FRP) reinforcing bars as the main reinforcement for concrete structures in severe environments is becoming a widely accepted solution to overcome the problem of steel corrosion and the related deteriorations. Due to the relatively lower cost of glass FRP (GFRP) bars compared to the other commercially available FRP bars, the use of GFRP bars in reinforced concrete (RC) structures has been widely investigated in the last few years. This paper reports experimental data on the shear strength of concrete beams reinforced with GFRP stirrups. A total of four large-scale RC beams with a total length of 7000 mm (276 in.) and a T-shaped cross section were constructed and tested up to failure. The test variables were type and ratio of shear reinforcement (stirrups). The test beams comprised three beams reinforced with sand-coated GFRP stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2, d/3, and d/4 (where d is the beam depth), and a reference beam reinforced with conventional steel stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2. As designed, the beams failed in shear due to GFRP stirrup rupture or steel stirrups yielding. ACI 440.1R-06 and the updated version of CAN/CSA S6-06 are able to predict the shear strength of beams reinforced with GFRP stirrups with a reasonable accuracy. The analytical approach using Response 2000 (R2K), which is based on the modified compression field theory (MCFT), predicted well the shear capacity of the beams reinforced with GFRP stirrups, but overestimated their shear crack width.

Construction and Testing of GFRP Steel Hybrid-Reinforced Concrete Bridge-Deck Slabs of Sainte-Catherine Overpass Bridges

AbstractHybrid reinforcement for concrete bridge-deck slabs is being investigated through a collaboration project between the Ministry of Transportation of Quebec (MTQ) and the University of Sherbrooke. This paper presents design concepts, construction details, and results of live-load field tests of the twin hybrid-reinforced bridges (P-15502N and P-15502S) on Sainte Catherine Road in Sherbrooke, Quebec (Canada). These hybrid-reinforced slab-on-girder bridges are simply supported over a single span of 43,415 mm. Their 200-mm-thick concrete deck slabs are continuous over four spans of 2,650 mm each, with an average overhang of about 1,000 mm on both sides (measured perpendicular to the girder axis). The deck slabs were reinforced with glass fiber–reinforced polymer (GFRP) reinforcing bars in the top mat and with galvanized steel bars in the bottom mat. One of the two bridges (P-15502S) was instrumented with fiber-optic sensors (FOSs) in the bridge-deck slab (over and between the girders). The instrumented...

Punching Shear Behavior of Flat Slabs Reinforced with Glass Fiber-Reinforced Polymer Bars

Results from an experimental study aimed at investigating the behavior of full-scale two-way flat slabs reinforced with glass fiber-reinforced polymer (GFRP) bars and subjected to monotonically increased concentrated load are presented. A total of 10 interior slab-column prototypes measuring 2.5 x 2.5 m (98 x 98 in.) were constructed and tested up to failure. The test parameters were: 1) reinforcement type (GFRP and steel) and ratio (0.34 to 1.66%); 2) slab thickness (200 and 350 mm [7.9 and 13.8 in.]); and 3) column dimensions (300 x 300 mm [11.8 x 11.8 in.] and 450 x 450 mm [17.7 x 17.7 in.]). All test prototypes showed punching shear failure and the crack patterns at failure were almost the same regardless of reinforcement type or ratio. Besides, the GFRP-reinforced prototypes showed lower punching capacity compared to that of the steel-reinforced ones when the same reinforcement ratio was employed due to the lower modulus of GFRP bars compared to steel. Predictions using different design guidelines were compared to the experimental results obtained herein. The comparisons showed that the ACI 440.1R equation yielded very conservative predictions with an average Vtest/Vpred equal to 2.10 ± 0.30.

Experimental Testing of Concrete Bridge-Deck Slabs Reinforced with Basalt-FRP Reinforcing Bars under Concentrated Loads

AbstractAdvances in fiber-reinforced polymer (FRP) technology have led to the introduction of new basalt-fiber-reinforced-polymer (BFRP) bars. This paper presents a research project investigating the behavior of edge-restrained concrete bridge-deck slabs reinforced with BFRP bars. The tests included six full-scale edge-restrained concrete deck slabs simulating a slab-on-girder bridge deck commonly used in North America and one full-scale unrestrained concrete deck slab. The deck slabs measured 3,000 mm long × 2,500 mm wide × 200 mm thick. The test parameters investigated were (1) reinforcement type (BFRP and steel); (2) BFRP bar size (12 and 16 mm); (3) reinforcement ratio in each direction (0.4–1.2%); and (4) edge-restraining [restrained or unrestrained (free)].The slabs were tested up to failure over a center-to-center span of 2,000 mm under a single concentrated load acting on the center of each slab over a contact area of 600 × 250 mm to simulate the footprint of a sustained truck wheel load (87.5-kN ...

Steel Post-and-Beam Barrier with GFRP-Reinforced Concrete Curb and Bridge Deck Connection

This paper discusses the crashworthiness of prototype steel post-and-beam barriers [Ministry of Transportation of Quebec (MTQ) Type 210] whose concrete curb-to-bridge deck connection is reinforced with corrosion-resistant glass fiber-reinforced polymer (GFRP). Experimental evidence is obtained from proof tests on five full-scale barrier and overhang subassemblies. The text matrix includes three GFRP RC and two steel RC specimens. The steel RC benchmark system is currently used as specified in the Canadian Highway Bridge Design Code (CHBDC). The objective is to verify whether (1) the resistance to out-of-plane quasi-static loads and the associated transverse deflection of the GFRP RC curb and steel barrier system are comparable to those of the steel RC counterparts; (2) the transverse strength exceeds the CHBDC equivalent static load demand; and (3) failure at the curb-deck connection is attained at safe transverse loads, and premature failure at the curb-deck connection is prevented. The GFRP and steel RC systems exhibit comparable strength, with the former undergoing greater deformations. For both systems, premature brittle failure of the curb-deck connection is prevented, and the equivalent static load requirements are satisfied. A larger capacity is attained when closed GFRP stirrup connectors are used at the curb-deck connection in lieu of C-shaped stirrups. An analytical model is used to predict the lower-bound strength of the GFRP RC curb-deck connection, and relevant design implications are discussed. It is recommended that the adoption of the proposed GFRP RC design relies on conclusive evidence from crash testing to verify safety against vehicle rollover because of the greater deformations compared with steel RC systems having the same amount of reinforcement.

Case Study: Design, Construction, and Performance of the La Chancelière Parking Garage’s Concrete Flat Slabs Reinforced with GFRP Bars

AbstractParking garages are among the concrete structures that suffer from corrosion and deterioration due to exposure to deicing salts. The 40-year-old La Chanceliere parking garage in Quebec (Canada) showed severe corrosion-related deterioration and was in need of costly rehabilitation. As its structural system consisted of two-way flat slabs and the steel reinforcement was severely corroded in most of the slabs, the City of Quebec (structure’s owner) decided to replace the structure’s flat slabs (a total area of about 3,160  m2) with new ones, while maintaining the main supporting elements (columns and retaining walls). The consulting firm produced two designs with steel reinforcing bars and glass-fiber-reinforced polymer (GFRP) reinforcing bars. Based on the comparative cost analysis of the steel-reinforced and GFRP-reinforced designs, the city opted for GFRP bars. The flat-slab system was designed according to CAN/CSA S806-12 with GFRP bars as main reinforcement, the world’s first application of its ...

Testing of Large-Scale Two-Way Concrete Slabs Reinforced with GFRP Bars

Few studies were conducted to investigate the structural behavior of GFRP-reinforced concrete two-way slabs. This paper presents preliminary results of an extended research project aims to developing the FRP technology reinforcing bar for parking garage structures and to introducing design guidelines for such structures. The results of five full-scale isolated interior parking flat slabs which are part of a 20-specimen experimental program are presented and discussed. Four slabs were reinforced with GFRP bars and one reference slab was reinforced with steel. The test parameters are: (i) reinforcement type and ratio; (ii) slab thickness; (iii) column size; and (iv) compressive reinforcement. The test results showed that there was no significant difference between the specimens in term of general behavior and mode of failure.