Thin-walled galvanized helical corrugated steel tubes (HCSTs) filled with concrete are promising composite members, consisting of concrete, an anti-corrosion shell, and a multifunctional exterior corrugated steel tube. To investigate the synergistic working mechanism of concrete-filled HCSTs (CFHCSTs), six specimens were designed for axial compression tests, with the inner diameter of the column and the volumetric steel ratios of the longitudinal reinforcement as the variation parameters. The results show that HCSTs can better confine the concrete core and increase its strength. The failure mode of HCSTs is significantly influenced by the column’s diameter, and those with a smaller diameter are prone to slide failure and lock seam tearing. The strains and stresses on HCSTs are discussed in detail to elucidate the confinement effect. This paper proposes a suitable design method to predict the ultimate axial compression load capacity of CFHCST columns based on early studies on steel tube-confined concrete.

In this paper, the rib beam bridge slabs were taken as the research object. Static load and fatigue tests were carried out on the benchmark bridge slabs to determine the ultimate load capacity and fatigue life of the bridge slabs. Then, the bridge slab was pre-damaged and reinforced with polyurethane concrete. A fatigue test was carried out on the reinforced bridge slab to study the fatigue performance. Based on the damage theory, the fatigue damage reinforcement finite element models of the bridge slabs under different damage degrees were established. The fatigue performance of the reinforced bridge slabs was systematically studied. The results show that the fatigue damage of the reinforced bridge slab developed in stages. Compared to the unreinforced bridge slab, the fatigue damage of the reinforced bridge slab was significantly reduced at each stage. According to the least square method and numerical analysis results, a residual-bearing-capacity model including damage degree and fatigue cycles of the reinforced bridge slabs is proposed, which can be used as a reference in bridge slab reinforcement design.

The purpose of this paper is to study the development law of fatigue damage of the carriageway slab of reinforced concrete ribbed girder bridge and to provide theoretical support for carriageway slab design. The fatigue test of reinforced concrete rib beam bridge carriageway slabs was conducted. Based on the material fatigue damage theory, the fatigue damage model was established by ABAQUS software. The fatigue performance, failure mechanism, and the effect of fatigue level on the fatigue performance of the carriageway slab were studied. The experimental research results show that when the slab of the rib beam bridge was fatigued, and the radial crack appeared at the bottom of the slab, which belonged to punching shear failure. The fatigue failure process was divided into three stages as follows: in the initial stage of fatigue, the deflection and reinforcement strain increased linearly with fatigue times, and in the stable development stage, the bottom deflection and reinforcement strain increased steady progression. With the increase in fatigue cycles, the fatigue accumulation damage was gradually accumulated, and the stiffness of the carriageway slab gradually decreases. In the rapid development stage, the deflection, reinforcement strain, and crack growth speed were significantly increased. According to the fatigue damage model, the simulation analysis results show that the accumulated damage to the bridge carriageway was more serious with the increase in fatigue load level. The fatigue damage degree was lower when the design fatigue load level is not greater than 0.55.

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