Experimental study on shear performance of ultra-high-performance concrete beams at elevated temperatures

Abstract

Ultra-high performance concrete (UHPC) is a novel concrete with ultra-high strengths and favourable durability, and it possesses broad application prospects. Given the lower cross-sectional dimensions and unique thermo-mechanical properties, UHPC beams have a higher risk of shear failure when exposed to fire, restricting their range of application. This study investigates the under-fire performance of shear-dominant UHPC beams. Ten full-scale UHPC beams fabricated with varying load ratios, shear span to effective depth ratios, stirrup ratios and longitudinal reinforcement ratios were tested under ISO 834 fire exposure. The shear failure modes of beams exposed to fire are different from those observed at ambient temperatures with the same shear span to effective depth ratio. Additionally, the fire resistance increases significantly with the decrease of load ratio and shear span to effective depth ratio. Higher longitudinal reinforcement ratio and stirrup ratio are beneficial to prevent crack development and reduce brittleness of shear failure. This paper further discusses the feasibility of using current fire resistance standards for shear-dominant UHPC beams.