Behavior of two-way slabs reinforced with GFRP bars

El-Tom, Ehab (2007) Behavior of two-way slabs reinforced with GFRP bars. Masters thesis, Memorial University of Newfoundland.

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Abstract

In this thesis, the performance of GFRP bars used as the main reinforcement for high strength concrete two-way slabs is investigated. A total of six interior slab-column connections, were cast and tested to failure at the structural laboratory of MUN. The dimensions of the simply supported tested slabs were 1900 X 1900 mm square and the thicknesses were 150 and 200 mm. -- The reinforcement ratio and the clear concrete covers were the main variables in this investigation. A transverse central load was applied to the slabs through a central column stub. The structural behavior of the test specimens was investigated in terms of load-deflection, crack pattern and spacing, deflection profile, concrete and GFRP strains, failure mode and ultimate carrying capacity. Six slabs made of high strength concrete were constructed and reinforced with 16 mm GFRP bars. One slab was cast as a reference specimen using high strength concrete reinforced with traditional steel rebars. -- The test results revealed that the slabs reinforced with GFRP bars exhibit higher deflection and wider crack width compared to similar slabs with conventional steel rebars. The load carrying capacity of the tested slabs was lower than the reference slab reinforced with steel rebars. However, slab performance can be improved by increasing slab depth. -- The use of high strength concrete improved the slab ultimate load capacity and reduced the total deflection of the slab. High strength two-way slabs reinforced with GFRP show more ductility than the slabs reinforced with tradition steel; however, in terms of energy absorption, the slab reinforced with steel rebars shows higher values than the GFRP slabs. -- The existing code limitations for serviceability limit state for crack width and spacing expressions were compared with the experimental results to verify their applicability in predicting crack width and spacing. -- An existing numerical model and related expressions to calculate the crack width and spacing were adopted and modified to account for the low modulus of elasticity and weak bond properties associated with the use of GFRP rebars. The modified model and expression results were compared to the experimental recorded data. The modified crack model and expressions provide excellent agreement with the experimental results. -- Finally, a finite element ABAQUS model was modified and adapted to predict the structural behaviour of high strength two-way slabs reinforced with GFRP. The finite elements model provides useful agreement with the experimental results in terms of ultimate load and maximum deformations.

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