Environmental reduction factors for GFRP bars used as concrete reinforcement: New scientific approach

This paper presents a new approach that incorporates the effects of temperature, design life, and relative humidity (RH) of exposure into the environmental reduction factor (RF) for glass fiber reinforced polymer (GFRP) bars used as concrete reinforcement. The environmental RFs for GFRP bars that are adopted in various guidelines are presented and discussed. By using time extrapolation and time-temperature shift approaches, a new equation for design strength of GFRP bar under various exposure time and temperature was proposed. The effect of moisture, in the form of RH, was incorporated into the new equation by investigating the degradation mechanism of GFRP bar owing to alkali attack and the relationship between the RH and concrete pore water. Design examples for strength RFs linked to service life, temperature, and RH were presented on the basis of reported durability data for E-glass/vinyl ester (VE) GFRP bars embedded in concrete.