Experimental Case Study on the Fatigue Behavior of Steel–Concrete Composite Beams after Chloride-Induced Corrosion and Cyclic Freeze–Thaw

In this paper, the fatigue performance of six steel–concrete composite beam specimens was tested following subjection to chloride-induced corrosion and cyclic freeze–thaw conditions. The specimens included cast-in-place concrete slab composite beams with uniformly distributed studs and precast concrete slab composite beams with a cluster distribution of studs. According to the climatic characteristics of large temperature differences between day and night in alpine and high-altitude areas of Qinghai Province of China, together with the working conditions of bridges under deicing salt after snow, corrosion tests and freeze–thaw tests of composite beam specimens were performed prior to fatigue testing. The test results show that the freeze–thaw cycle causes obvious frost heave damage to the concrete, which affects its strength and stiffness. When the composite beam specimens were subjected to fatigue loads, tearing failure of the steel plates at the welds and interface failure at the studs were observed. Furthermore, with the influence of stress amplitude, fatigue life was found to be related to the initial crack defect within the specimen itself. Reduction in the initial stiffness of composite beams was found to be affected by the freeze–thaw cycle, stud arrangement type (uniformly distributed or cluster distributed), and steel type (ordinary steel or weathering steel). However, the stiffness degradation rate of all specimens against loading times was essentially identical before fatigue failure.