The design of concrete members reinforced with fiber-reinforced polymer reinforcement (FRPRC members) is typically governed by serviceability-limit-state requirements rather than ultimate-limit state requirements. ACI 440.1R deflection design equations were introduced and assessed based on experimental work on FRPRC members with rectangular sections. These equations have not been assessed for circular sections for inclusion in an anticipated FRPRC design code currently being prepared by ACI Committee 440. This research program was designed to evaluate the deflection predictions of circular FRPRC flexural members using the available design equations. A total of eight full-scale circular RC flexural members measuring 500 mm (20 in.) in diameter and 6000 mm (236.22 in.) in length were constructed and tested up to failure under four-point bending load. The test parameters included the type of FRP reinforcing bars and the reinforcement ratio. Three specimens were reinforced with glass FRP (GFRP) bars, three were reinforced with carbon FRP (CFRP) bars, and two were reinforced with basalt FRP (BFRP) bars. The measured deflections and experimental values of the effective moment of inertia (Ie) were analyzed and compared with those predicted using models in the literature as well as those in design guidelines and codes. Based on the analysis of the test results, a new equation was developed to accurately predict the deflection of the tested circular specimens. Moreover, an analytical model was developed using a layer-by-layer curvature analysis approach based on cross-sectional analysis satisfying strain compatibility and equilibrium conditions. The load-deflection relationship for circular FRPRC flexural members can be generated based on the calculation of curvature with an incremental strain technique. The comparisons with the experimental results indicate the model’s capability of reproducing the experimental load-deflection responses of the tested circular specimens. |
