Resistance Factors for Ductile FRP-Reinforced Concrete Flexural Members

Abstract

To prevent damage caused by corroding reinforcement, fiber-reinforced polymer (FRP) reinforcing bars have been used in place of steel in a relatively small but increasing number of structures in civil infrastructure. A concern with the use of traditional FRP bars, however, is the resulting lack of ductility. This problem has been overcome with the development of a new generation of composite reinforcement, ductile hybrid FRP (DHFRP) bars. However, standards that address the design of DHFRP bars are unavailable, and appropriate resistance factors for the use of DHFRP reinforcement are unknown. In this paper, a reliability analysis is conducted on tension-controlled concrete flexural members reinforced with DHFRP with the intent to estimate potential strength-reduction factors. Flexural members considered include a selection of representative bridge decks and building beams designed to meet strength requirements and target reliability levels dictated by relevant engineering standards. Nominal moment capacity is calculated from standard analytical models and is taken as first DHFRP material failure. Statistical parameters for load and resistance random variables in the reliability model are consistent with previous code calibration efforts. The resulting resistance factors ranged from 0.61-0.64 for tension-controlled sections, which indicates a potential increase in allowed strength with respect to flexural members using nonductile bars.