الفهرس 
صفحة العنوانOnly 14 pages are availabe for public view
 |  | from | 164 |  |  |
| | | from | 164 | | |
Abstract
Fiber-reinforced polymer (FRP) composite materials have been used in the field of civil engineering constructions especially in corrosive environment. They can be used as internal reinforcement for beams, slabs, and pavements, or as external reinforcement for rehabilitation and strengthening different structures. One of their innovative applications is the concrete-filled FRP tubes (CFFTs) which are becoming an alternative for different structural members such as piles, columns, bridge girders, and bridge piers due to their high performance, durability and resistance to corrosion. In such integrated systems, the outer FRP tubes act as stay-in-place forms, protective jackets for the embedded concrete and steel, and as external reinforcement in the primary and secondary direction of the structural member.
This study investigates the flexural behaviour of square filament-wound FRP tubes filled with concrete. The FRP tubes have different percentages-of-axial-and-transverse E-class glass fibers and were fabricated by filament winding process and hand lay-up technique in Department of Civil Engineering at Helwan University. Several test variables were chosen to investigate the effect of the tubes thickness, fibers laminates structure of FRP tubes, and the different percentages-of-axial-and-transverse-fibers. To fulfil the objectives of the study, seven beam specimens, 2000 mm long, and 200×200 mm2 cross section, were tested under a four-point bending load. These specimens include FRP tubes with wide range of tube thickness of 2 mm to 5.8 mm, and the ratios of axial fibers to transverse fibers range from zero to 0.7, approximately. All the beams were cast with the same concrete patch with low compressive strength to highlight the effect of confinement of the FRP tubes on the concrete core. Details of experimental program, fabrication process of FRP tubes, test method and results are discussed in this study.
The results of the tested CFFT-beams indicate significant gain in strength, stiffness, cracking moment, ultimate flexural capacity and energy absorption, according to the manufacturing method for the laminated structure of FRP tubes and according to the axial fibers percentages. The CFFT-beams that contain a helical fiber at angle [±55°], show greater resistance than the CFFT-beams manufactured with E-glass fiber sheets at angles [0°, 90°], while the CFFT-beams that manufactured with E-glass fiber sheets, show greater stiffness than the CFFT-beams that contain a helical fiber.
The overall behaviour of the CFFT-beams is considered as bilinear. Before cracking, the beams start with a great flexural stiffness due to the massive gross sectional inertia. After the first crack, the flexural stiffness decreased, because of the low modulus of elasticity of the FRP tubes material and the cracked inertia. Nevertheless, the flexural strength of the CFFT beams was increasing gradually until failure. There was a difference in the flexural stiffness among the CFFT beams at the region after the first crack and until ultimate failure, due to the different thickness and different axial stiffness of the FRP tubes.
Keywords: Fiber-Reinforced Polymer, Filament Winding, Concrete-Filled FRP Tube, Beams, Flexural behaviour.