Behaviour of two-way slabs reinforced with CFRP bars

An experimental program was carried out to investigate the behaviour of two-way slabs reinforced with carbon fibre-reinforced polymer (CFRP) bars at Memorial University of Newfoundland. In total, seven interior slab-column connections, which represent fullscale flat plates, were prepared and tested to failure under a central load. The main variables were the reinforcement type, the reinforcement ratio, the concrete strength, and the slab depth. The reinforcement ratio varied between 0.36% and 0.75%. The concrete strength was in the range of 23 MPa to 98 MPa. The slabs had two different thicknesses of 150 mm and 200 mm. The test slabs had an equal side dimension of 1900 mm. A central load was applied on each slab through a 250 x 250 mm column stub using a closed-loop hydraulic actuator in a displacement control mode. The structural behaviour of the slabs with regard to ultimate capacity, serviceability, deflections, strains, and crack patterns was investigated.; According to the test results, the load-deflection curve of the CFRP reinforced slabs consisted of two linear parts with a small transition stage after the initial crack formation. The tests revealed that slabs reinforced with CFRP bars had punching shear strength that is very similar to those with steel reinforcement. The reinforcement ratio had a small effect on the strength of the CFRP reinforced slabs, while the slab depth had a pronounced effect on both the load-carrying capacity and deflection. The use of high strength concrete resulted in some enhancement of the punching shear strength of the slabs. In addition, CFRP bars are capable of offering bond performance that is close to steel reinforcement according to the bar force gradients of the test slabs. However, the concrete tension stiffening may play a more significant role in the slab behaviour that could be more pronounced in slabs reinforced with CFRP bars than in slabs with steel reinforcement. The results also revealed that the strain of the CFRP bars when limited to 2000 muepsilon is a reasonably good criterion for CFRP reinforced slabs to ensure that the allowable crack width is acceptable within the serviceability limits. At the end of each test, a punching cone was formed in all test slabs. The results indicated that punching shear failure occurred in all slabs The CFRP reinforced slabs showed a ductile punching failure mode. There was no clear evidence of concrete crushing at the compression side of the slab. Also, no rupture of the CFRP bars was detected in any of the tests.; The existing code equations for two-way slabs with steel reinforcement and the expressions that were recently proposed in the literature for FRP reinforced slabs were examined to check their ability to accurately predict the punching shear strength of two-way slabs reinforced with FRP reinforcement. A statistical analysis was performed to investigate the effect of the different parameters on the punching shear strength. It was found that the proposed equations that were based on the BS8110 code adequately presented the contribution of each parameter. In addition, these equations gave good predictions of the punching shear strength of the CFRP reinforced slabs that were tested in the current program as well as all test slabs that are available in the literature. A novel empirical approach that considers both the concrete and reinforcement contribution to the shear strength was proposed. The approach gave good predictions of the punching shear strength of slabs with FRP reinforcement.; A finite element analysis of the current test slabs was carried out using the general finite element program ANSYS. The numerical model was able to capture the behaviour of the test slabs. The numerical investigation provided predictions that were in good agreement with the test results.; Finally, a rational design model was developed to predict the punching strength of FRP reinforced slabs. The model incorporated reasonable assumptions to model the...