Experiment study on flexural performance of steel concrete composite beams under salt freeze-thaw cycles in negative moment sections

Abstract

Bridge structures in cold climates face significant challenges due to freeze-thaw cycles and salt-induced corrosion. This study investigates the degradation mechanisms of the negative bending behavior of steel-concrete composite beams using normal concrete (NC) and ultra-high performance concrete (UHPC) under salt freeze-thaw cycles (SFTC), considering the impact of different stud arrangements. The results indicate that UHPC significantly enhances the cracking performance in the negative bending region of the composite beams and demonstrates high resistance to SFTC. Before undergoing SFTC, the cracking moment of the UHPC beams increased by an average of 210.5%, and stiffness by 37.3%, compared to the NC composite beams. After 150 SFTCs, the NC beams showed a significant decline in performance, with a 62.1% reduction in cracking moment, a 6.2% decrease in load-carrying capacity, and a 5.6% reduction in stiffness. In contrast, the flexural performance of the UHPC beams was almost unaffected, with only a 17.5% reduction in cracking load. Moreover, beams with a double-row stud configuration exhibited better negative bending resistance compared to those with a single-row stud configuration. Based on experimental results and data from reference, a reasonable formula for predicting the composite beams under the effect of SFTCs was proposed and proved to have satisfactory accuracy.