Experimental study on flexural behavior of steel-concrete composite girders under salt freeze-thaw cycles

Steel-concrete composite girders in cold regions are highly vulnerable to freeze-thaw cycles and de-icing salt corrosion, which substantially compromise their long-term durability. This study explored the flexural performance degradation of six composite girders with different numbers of shear connectors under salt freeze-thaw cycling (SFTC). The specimens were exposed to combined action of freeze-thaw cycling and de-icing salts prior to static flexural testing. The results show that both yield and ultimate moments decreased as the number of cycles increased. After 100 cycles, the ultimate moments of single-row and double-row stud specimens decreased by 13.3% and 13.6%, respectively, accompanied by stiffness reductions of 17.6% and 18.9%. A greater number of shear connectors effectively mitigated interfacial slip, thereby alleviating the adverse effects of SFTC. The initial slip difference between double-row and single-row stud specimens was 6.8% and expanded to 57.6% after 100 cycles. The empirical formula developed in our previous research exhibits strong applicability for predicting the flexural capacity of composite girders subjected to SFTC. These findings provide valuable insights for the design and maintenance of composite girders in cold regions.