Reliability analysis and calibration for flexural design provisions of GFRP-RC beams

This study aims to conduct reliability assessment and calibration of the design provisions for flexural capacity in existing design codes for glass fiber reinforced polymer bar reinforced concrete (GFRP-RC) beams. Firstly, model uncertainties for three design codes including GB 50608-2020, ACI 440.1R-15 and CSA S806-12 were evaluated using the statistical analysis methods. Subsequently, the reliability analysis of flexural capacity in three design codes was investigated based on Monte Carlo Simulation (MCS) method, considering stochastic factors such as material properties, geometric parameters, model uncertainties and load effect combinations. Moreover, the influences of tensile strength of GFRP bar, the ratio of reinforcement ratio to balanced reinforcement ratio (rho(f)/rho(fb)) and the live-to-dead load effect ratio (theta) on reliability index were explored. Meanwhile, the calibration of GFRP material partial factor (gamma(f)) for GB code was performed with the target reliability index of 3.7, based on the least squares analysis. Finally, the flexural capacity provisions of GFRP-RC beams in the GB code was revised for improving the reliability index under a relatively low live-to-dead load effect ratio theta by re-calibrating parameter gamma(f )for GFRP bar tensile failure and introducing revision coefficient xi for concrete compressive failure, achieving target reliability index over 3.7.