Concrete slabs reinforced with GFRP bars

Rashid, Mohammad Imtiaz (2004) Concrete slabs reinforced with GFRP bars. Masters thesis, Memorial University of Newfoundland.

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Abstract

The performance of non-ferrous reinforcing material, in the form of GFRP bars, as the primary reinforcement of flat plates is investigated. In total, nine interior slab-column connections, that represent full scale specimens, were made and tested to failure at the structural laboratory of MUN. The 1900 x 1900 mm square slabs were simply supported along the four edges. The reinforcement ratio, concrete strength and effective depth were the main variables. Transverse central load was applied to the slabs through a central column stub. The load was applied in displacement control. The structural behaviour of the test specimens was investigated in terms of load-deflection relationship, crack pattern and width, deflection profile, concrete and FRP strains, failure mode and ultimate failure load. The effects of those variables on the behaviour were examined. Eight slabs were made with GFRP bars commercially known as ISOROD®. One slab was made with traditional steel bars. Two slabs were with high strength concrete, over 85 MPa. The rest of the slabs were made with normal strength concrete. Two slabs were 200 mm thick with an effective depth of 150 mm. The other slabs were 150 mm thick with an effective depth of 100 mm. All GFRP slabs were designed with over reinforced section capacity. -- The test results revealed that slabs reinforced with GFRP bars exhibit higher deflection and greater crack width compared to similar slabs with traditional steel bars. The failure loads are also lower than those of slabs with traditional reinforcement. Nevertheless, the structural performance of the GFRP reinforced slabs can be improved by increasing the slab depth. High strength concrete increases the ultimate failure load but does not significantly improve the serviceability of the slabs. -- The existing code formulas were examined to check their applicability in predicting the shear capacity of two-way slabs reinforced with GFRP bars. Elastic plate theory was used in an attempt to calculate the flexural capacity of such slabs. The results revealed that, with proper modifications, the equations that use a cubic root relationship for concrete strength and include the effect of the reinforcement ratio are able to predict the capacity of the slabs with reasonable accuracy. -- An existing mechanical model was adopted and modified. That model had an unidentified limitation. The limitation is described and removed by modification of model geometry. Further modification is made to incorporate FRP's properties and structural behaviours and thus the model is made applicable for slabs reinforced with FRP as well as for slabs reinforced with traditional steel bars. The model results were compared to the slab test results available in literature with both steel and FRP reinforcement. The model gives a fairly good agreement between the predicted and experimental punching failure loads.

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