인발성형 GFRP H형강 보의 휨 거동 분석과 통계적 신뢰도 기반 공칭 휨 강도 산정

초록

In the construction industry, pultruded glass fiber reinforced polymer (pGFRP) H-beams are emerging as innovative, lightweight, and corrosion-resistant alternatives to steel. However, establishing load and resistance factor design (LRFD) standards requires characterization of the inherent uncertainties of these materials. This study conducted four-point bending tests on pGFRP H-beams with varying shear span-to-depth ratios (a/d = 7.5, 5.0, and 2.5) to analyze their failure modes and ultimate loads. The experimental results revealed a clear transition in failure mechanisms as the span length decreased. Specimens with a/d ratios of 7.5 and 5.0 exhibited flexure-dominated failure, while short-span specimens (a/d = 2.5) experienced premature failure primarily due to shear and local crushing. To reflect these failure characteristics, this study employed maximum likelihood estimation and goodness-of-fit tests to identify the Weibull distribution as the most suitable model for describing the material’s weakest-link failure behavior. In addition, to address the statistical uncertainties due to a limited sample size, the ASTM D7290 standard was applied to derive LRFD-based nominal design strengths satisfying the 80% lower confidence bound. These strengths conservatively account for the pGFRP variability, providing foundational data for future LRFD structural design standards.

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