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Concrete-filled double skin steel tubular columns with large hollow ratios (LHR-CFDST) have been commonly researched in the past few years. The excellent performance of this structure renders it promising as a novel form of wind turbine tower. Increasing the diameter-to-thickness ratio is one efficient way to reduce steel consumption as the size of this engineering structure continues to expand. There is a paucity of research on thin-walled LHR-CFDST. Meanwhile, these structures may be susceptible to local buckling without stiffening measures. Furthermore, the size effect of this type of structure is more complicated. This paper reports the first experimental investigation on super-sized thin-walled LHR-CFDST columns under combined compression-torsion-shear-bending loads. Two LHR-CFDST columns with varying stud spacings are discussed. Investigations are conducted into failure modes, local buckling behaviors, load-strain responses, and a few popular mechanical indices. According to the test results, the specimen with smaller stud spacing has an 8.1% greater ultimate bearing capacity. It is assumed that a more intensive stud arrangement can delay the onset of local buckling, thereby increasing the peak load. Besides, the arrangement of the studs leads to an obvious effect of section confinement, thus improving the overall performance of the specimens. The failure modes and load-displacement relationships simulated by the FE models agree well with the experimental results. Then, a modified method for predicting the ultimate strength of LHR-CFDST based on the previously summarized formulae for CFST under compression-bending-shear-torsion is proposed and utilized for the evaluation of two specimens in this research. Since the tested value of the specimen with narrower stud spacing is higher by 5.6% than the predicted value, it can be concluded that the large-scale thin-walled LHR-CFDST may be evaluated using this method, complemented by appropriate stiffened measures. • Two thin-walled CFDST columns were tested subjected to combined loads. • The stiffened studs greatly postpone the appearance of local buckling. • The studs produces a clear impact of section confinement, which enhances the specimen's overall performance. • This experiment utilizes a novel mutual verification model. • A modified method for CFDST under combined loads is proposed and utilized for the evaluation of two specimens. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) framed shear walls with steel sheathing are promising lateral-force-resisting members of mid-rise buildings in seismic regions. Previous studies have demonstrated that steel sheathed CFS framed shear walls have high shear capacity but some shortcomings, such as the low ductility caused by the premature damage of the frame and the shear buckling of the sheathing. This paper presents an experimental study on a novel type of CFS framed shear wall with slitted steel sheathing (CFS-SSWs), which uses longitudinal slits to change the failure mode of the sheathing so that the ductility of the wall can be improved; Meanwhile, stiffeners are utilized to enhance the out-of-plane stability of the slitted sheathing and the integrity of the wall. Six full-scale CFS-SSW specimens were tested under monotonic and cyclic lateral loading. Three types of stiffening approaches (Type I, Type II and Type III) were adopted for the walls. Test results were analysed to investigate lateral performances of walls under different stiffener arrangements, including failure modes, load-displacement hysteresis curves, backbone curves, stiffness and strength degradation, and energy dissipation capacity. The measured strengths of the walls in the tests were assessed using theoretical indexes. It is found that peak loads and energy dissipation capacity of stiffened walls are noticeably higher than those of the unstiffened wall. Type II and Type III are effective stiffening approaches that could mitigate the buckling of the slitted sheathing and enable the links between the slits to reach the full plastic strength. By connecting the stiffeners and studs through stiffener connectors, Type III has the most significant enhancement on the stiffness, strength and ductility of the wall. • A novel type of cold-formed steel framed shear wall, i.e., CFS-SSW, is presented. • Six full-scale CFS-SSW specimens are tested to investigate their lateral behavior. • The stiffened walls show improved performances compared to the unstiffened wall. • Type II and III are effective stiffening methods that can mitigate the buckling. • Type III has the most significant enhancement on the performances of the wall. [ABSTRACT FROM AUTHOR]

The precast concrete segments of wind turbine hybrid towers are usually lifted and installed using the pre-installed lifting anchors with supplementary reinforcements. The lifting anchors are made of steel plate and the supplementary reinforcements are often arranged near the lifting anchors to enhance their anchoring performance. This lifting system including the reinforcement configuration is presented in existing design codes, but the design recommendation and calculation method of ultimate capacity are not provided. It is necessary to explore the pull-out behavior of the lifting anchor considering the effects of reinforcements. Therefore, a comprehensive investigation on the pull-out behavior of the lifting anchor is conducted in this paper, by using the precast concrete segments of hybrid tower as a carrier. Four specimens based on the actual dimension of precast concrete segment of hybrid tower were tested under cyclic pull-out loading, and the failure modes as well as the ultimate capacity were analyzed. The verified finite element (FE) models were established based on the test results, and mechanical analysis were performed to reveal the pull-out mechanism of the lifting anchor. Subsequently, the parametric analysis was conducted to explore the sensitive parameters of the lifting anchor's pull-out performance. The accuracy and applicability of the calculation methods for ultimate pull-out capacity in existing design codes and literatures were evaluated based on the test results. Lastly, a practical calculation method for the ultimate pull-out capacity of lifting anchor was proposed based on theoretical model and regression analysis. The proposed method can provide a reference for the lifting design of precast concrete segments of wind turbine hybrid towers. • 4 specimens with the specialized lifting anchor based on the actual size of precast concrete segment were tested under cyclic pull-out loading. • The verified FE models were established, and mechanical analysis were performed to reveal the pull-out mechanism of the lifting anchor. • The parametric analysis was conducted to explore the sensitive parameters of the lifting anchor's pull-out performance. • The accuracy and applicability of the existing calculation methods for ultimate pull-out capacity were evaluated based on the test results. • A practical calculation method for the pull-out capacity of lifting anchor was proposed based on theoretical model and regression analysis. [ABSTRACT FROM AUTHOR]