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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]

Highlights • Experimental investigation was conducted on shear behavior of SSG in PC decks. • The interface shear force -slip non-linear relations of the specimens were obtained. • The effect of different parameters on behavior of specimens was investigated. • The failure modes, ductility, bearing capacity of test specimens were analyzed. • The existing design formulas may be utilized to calculate shear capacity of SSG. Abstract In order to study the shear behavior of a group of shear studs placed on a composite beam, a total of 16 pushout tests were conducted, including 4 specimens with cast-in-place (CIP) concrete decks and 12 specimens with precast concrete (PC) decks. The primary parameters considered include reserved hole shape, loading path, and deck casting method. Through the experiment, the interface shear force-slip curves and the failure modes of shear stud groups (SSGs) in both CIP and PC decks under monotonic and repetitive loads were obtained. The results show that the shear behavior of the SSGs in square reserved holes is more favorable than that in circular reserved holes, the shear strength of SSGs in PC decks is smaller than that in CIP decks under monotonic loads. The general failure modes for a SSG are the cutoff of stud shanks and the damage of root welds at studs. While the shear strength of a SSGs in PC decks is similar to that in CIP decks under repetitive loads, ensuring the ductile failure mode of stud fracture and the shear capacity not smaller than that stipulated in the design code for reinforced concrete (RC) structures, even without using any rebar in a reserved hole. The peak interface shear force and the trend of interface shear force-slip curves under repetitive loads are also similar to that under monotonic loads, although the interface slip corresponding to peak force under monotonic loads is smaller than that under repetitive loads. The study results indicate that the SSG in a PC deck can be fully utilized and the existing design formulas almost may be utilized to calculate shear capacity of shear stud groups. [ABSTRACT FROM AUTHOR]

• Experiment and numerical analysis of built-up hot-rolled steel sections were carried out. • The design rules for hot-rolled built-up section stub columns under compression were proposed. • The design rules of the stability bearing capacity of columns have been developed. In this paper, a new type of steel section is proposed comprising adjacent H-sections linked together by intermediate steel plates welded along their flanges. Experiments on three hot-rolled steel built-up H-sections and five columns infilled with concrete are conducted, with results showing that both variants having much better ductility compared to conventional columns (i.e. hollow section columns and concrete filled steel tube (CFST) columns). Experimental results showed that the bearing capacity of the built-up hot-rolled steel hollow section column improved by 45.1% to 55% after it was filled with concrete. A finite element software ABAQUS is used for parametric study. The newly developed finite element models were validated against test results in terms of failure modes and load-displacement curves. A total of 482 numerical results, 132 hot-rolled steel built-up section columns and 350 concrete-filled built-up section columns, have been generated. Based on the experimental and numerical results, the compressive behaviours of hot-rolled steel built-up section columns and concrete-filled built-up section columns are studied. A new design method for the compression capacity of these two types of columns is proposed. It is found that the newly proposed design method could provide accurate and consistent predictions – the mean value of experimental to predicted results are 0.963 for hollow section columns (with coefficient of variation being 0.061) and 1.04 for composite section columns (with coefficient of variation being 0.043). [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]

• Two large-scale thin-walled CFDST columns with different stud spacing were tested under axial compression. • The stiffened studs delayed the occurrence of local buckling in these specimens significantly. • The arrangement of the studs leads to a obvious effect of section confinement, thus improving the overall compressive performance of the specimen. • The variability of the Poisson's ratio of concrete and steel during loading resulted in different stresses on the studs. • The current design specifications for calculating the peak load of CFDST columns are modified and used for the evaluation of the two large-scale thin-walled CFDST specimens in this study. Wind turbine towers offer good application potential for concrete-filled double-skin steel tubular columns with large hollow ratios (LHR-CFDST). With the increasing size of this engineering structure, the requirement to reduce construction expenses can be met by enhancing the diameter-to-thickness ratio of steel tubes. Few studies have been conducted to report on thin-walled LHR-CFDST columns. Meanwhile, local buckling and size effect shall be considered for this type of structure. Based on this, the first experimental investigation on large-scale stiffened thin-walled LHR-CFDST columns under axial compression is reported in this paper. Two large-scale thin-walled LHR-CFDST columns with different stud spacings are discussed. Failure modes, local buckling behaviours, load-strain responses, and some common mechanical indexes are investigated. According to the test results, adding studs was an effective method to increase the ultimate capacity of LHR-CFDST columns, as evidenced by the 16.6% increase in peak load for the specimen with smaller stud spacing than the other. Besides, the arrangement of studs leads to an obvious effect of section confinement, thus improving the overall compressive performance of the specimens. Then, four existing specifications all give a conservative prediction for the ultimate capacity of the specimen with smaller stud spacing, indicating that the large-scale thin-walled LHR-CFDST can be evaluated utilizing the present specifications with suitable stiffening measures. [ABSTRACT FROM AUTHOR]

• A novel prefabricated shear wall with double-corrugated steel plates (DCSPs) was introduced. • Quasi-static cyclic tests were conducted on DCSPs to investigate the shear behaviour. • DCSPs have a superior performance owing to the combination effect of the cross-section. • Corrugation height has considerable effects on the out-of-plane stability and the shear resistance. • Reasonable connecting bolts' spacing is important for DCSPs to maintain a good performance. Double-corrugated plate shear wall (DCPSW) is a new member developed based on the single-corrugated plate shear wall (CPSW). Due to its improved stability and shear resistance, it has good application potential in buildings subjected to large shear loads. Up to now, the reported experimental data of DCPSWs under cyclic loading are limited and the shear behaviour of double-corrugated steel plates in DCPSWs is needed to be further understood. This paper presents an experimental study on the double-corrugated steel plate under cyclic in-plane shear loading. Ten specimens were tested and the varied parameters included the height of corrugation, the width of subpanels in corrugation, the spacing of connecting bolts and the number of bolt columns at each valley region. The experimental results in terms of failure modes, load versus deformation hysteretic curves, skeleton curves, energy dissipation and stiffness degradation were discussed. By analysing the effects of important parameters, the mechanism of the double-corrugated steel plate under pure shear loads was revealed. It is found that the specimens failed with shear buckling which behaved as either global buckling or local buckling. Due to the combination effect, the shear resistance of the double-corrugated plate was higher than that of the single-corrugated plate with the same steel volume. Increasing the corrugation height is beneficial to improving the shear buckling load and maintaining the energy dissipation capacity. It is suggested that the ratio of corrugation height to thickness is higher than 15 in the design of the double-corrugated plate. [ABSTRACT FROM AUTHOR]