Flexural Performance and Design of Steel-UHTCC Composite Bridge Decks with Different Composite Degrees under Hogging Moments

Abstract

Due to the excellent tensile properties and long-term durability, using ultrahigh-toughness cementitious composite (UHTCC) at the hogging moment regions of long-span composite bridge decks is a new solution to the cracking issue. Composite degrees and the longitudinal reinforcement ratio have been suspected of influencing the flexural performance of steel-UHTCC composite bridge decks under hogging moments, but the extent of the influence remains unclear. This study aims to investigate the influence of these two core design parameters. Six specimens with different stud spacings and longitudinal reinforcement ratios were designed to investigate the failure modes, flexural capacity, deformation behavior, and cracking characteristics. The results show that the cracking stresses σ0.05 and σ0.1 in the steel-UHTCC composite bridge decks were 58.6%–216.8% and 58.9%–213.5% higher than those in the steel-normal-strength concrete (NSC) composite bridge decks. As the longitudinal reinforcement spacing reduced from 125 to 75 mm, the growth of the crack width was effectively restrained, and the cracking stresses σ0.05 and σ0.1 increased by 36.6% and 71.2%, respectively. Finally, a modified theoretical model is established to evaluate the influence of composite degrees on the elastic flexural performance of steel-UHTCC composite bridge decks. The dimensionless composite degree η is defined as a core parameter in this model. For practical elastic design, the threshold value of the dimensionless composite degree can be determined as 0.005.