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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]

Reinforced ultra-high-performance concrete (RUHPC)-encased concrete-filled steel tubular (CFST) columns in composite construction have exceptional fire and corrosion resistance, superior load-bearing capacity, and enhanced ductility compared to standalone RUHPC and CFST columns. However, research on their behavior is limited. This paper presents a 3D finite element (FE) simulation model for accurately predicting the behavior of axially loaded RUHPC-encased CFST short columns. The model accounts for the effects of the concrete confinement provided by the steel reinforcement and circular steel tube. The existing experimental data is used to validate the FE model. The validated model is then utilized to investigate the performance of RUHPC-encased CFST columns with various geometric and material properties. The range analysis technique is applied to an orthogonal design to assess the relative significance of the factors affecting the structural behavior. The findings reveal that RUHPC-encased CFST columns have high ultimate strength and ductility. The range analysis identifies the importance order of parameters as: the compressive strength of UHPC, the steel fiber concentration, tube diameter, stirrup spacing, tube thickness, and confined concrete's compressive strength. Lastly, a simplified design model is developed to estimate the compressive capacity of RUHPC-encased CFST stub columns, providing accurate results that are verified by tests and numerical analysis. • Finite-element simulation model for UHPC-encased CFST stub columns is developed. • The behavior of UHPC-encased CFST stub columns is parametrically studied. • A range analysis is carried out to specify the importance of design key factors. • The proposed finite-element simulation and design models provide accurate predictions. [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]

Highlights • Partial composite beams were fabricated and tested statically. • The use of precast concrete (PC) deck enhances the moment capacity and stiffness of the composite beam. • The ductility of steel block shear connector is similar to the shear stud group. • The composite beam with PC deck makes good use of the current design theory and standard. Abstract This study aims to investigate the static behavior of a simply-supported assembled monolithic steel-concrete composite beam (SCCB). A total of ten composite beams were tested considering the parameters of shear connection degree, reserved hole shape, concrete deck width, and deck casting method. Based on the test results, failure mode, stiffness, ductility, and moment capacity were obtained and are discussed in this paper. Compared to the conventional SCCBs with wide flange beams and headed shear connectors, the composite beam considered in this study has favorable flexural performance, while reducing the excessive cost and potential construction challenge due to the use of precast concrete (PC) deck. The flexural behavior of the new assembled monolithic SCCBs was investigated through the one-point bending tests on the ten specimens. The study results indicate that: (1) The assembled monolithic SCCB with shear stud group (SSG) or steel block shear connector (SBSC) has higher moment capacity and ductility, with the ductility factor ranging from 3.4 to 6.8; (2) the higher the degree of shear connection, the greater the moment capacity; (3) the SBSC has higher moment capacity and stiffness and is suggested for practical use for better welding quality and convenient construction; (4) the nonlinear calculation formula specified in GB50017-2017 (Code for Design of Steel Structures) predicts more accurate ultimate moment strength for the composite beams with partial shear connection than Eurocode 4, in comparison with the experimental results; (5) the SCCB with PC deck shows respective 50% and 174% higher elastic stiffness when using SSG and SBSC, compared to the SCCB with cast-in-place concrete (CIPC) deck. [ABSTRACT FROM AUTHOR]

• Based on the test results, a refined finite element model was established for the push-out test of SSGCs. • Parametric analysis was carried out through the finite element model, and the factors affecting the static performance of the specimen were analyzed. • The stiffness of the SSGCs at the elastic stage was theoretically analyzed by using the thrust pile comprehensive stiffness method. A refined finite element (FE) model was established to simulate the push-out test of shear stud group connectors (SSGCs). The failure phenomena and interface shear-slip curves obtained by the FE model were compared with the test results and found to be in good agreement. The verified FE model was then used in a parametric analysis, considering the concrete strength, stud diameter, stud height, stud spacings (longitudinal and transverse), strength of grouting material, and number of shear studs in a SSGC. Based on the Winkler foundation model and the comprehensive stiffness principle of thrust piles, a theoretical calculation formula for the stiffness of SSGCs was obtained, considering the concrete material, stud diameter, and number of shear studs in a SSGC. The calculation formula was verified with the test results and fitted with the FE analysis results. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular (CFST) columns are widely utilized in structures owing to their cost-effectiveness, high strength, ductility, and proven fire resistance. Despite these advantages, concerns persist regarding the performance of CFST columns with locally corroded steel tubes, impeding their widespread adoption in offshore structures. This research employs three-dimensional finite element (FE) simulations for circular CFST stub columns subjected to axial compression, validated against experimental data. Verification includes full load-displacement histories, ultimate axial strengths, and failure modes. The validated FE models are then employed to assess and compare the structural behavior of CFST columns with various shapes of localized corrosion, analyzing overall load-deformation curves, interaction stress-deformation responses, and composite actions. To acquire critical data for understanding stub column behavior, 81 specimens underwent non-linear finite element analysis, with local corrosion represented by artificial notches in steel tubes. Test parameters, such as notch orientations, lengths, depths, widths, and concrete compressive strength, are varied. Results elucidate the impacts of these parameters on different aspects of stub column responses with corroded steel tubes. Furthermore, the accuracy of existing design models in predicting the ultimate axial strengths of CFST columns with corroded steel tubes is assessed. Finally, through parametric analysis of test results, a practical model is proposed and verified for computing the peak resistance of a CFST stub column with a locally corroded steel tube. • Finite-element simulation model for circular CFST stub columns with locally corroded steel tubes is developed. • The influence of different shapes of localized corrosion on the performance of circular CFST stub columns is investigated. • The behavior of circular CFST stub columns with locally corroded steel tubes is parametrically studied. • The proposed finite-element simulation and design models provide accurate predictions. [ABSTRACT FROM AUTHOR]

• The hat-section cold-formed steel plate shear wall was proposed. • The cyclic pure shear behavior of the shear walls was investigated. • The effect of arrangement of hat-section cold-formed steel constraint was studied. • The reliability of the bearing capacity calculation formula was evaluated. The hat-section cold-formed steel member buckling-restrained steel plate shear wall is a new type of lateral force resisting system that uses hat-section cold-formed steel member to restrain out-of-plane buckling deformation of the steel plate shear wall. Additionally, the integration of building function and structural function can be realized by externally pasting OSB sheet and filling sound insulation material. In order to investigate the cyclic pure shear behaviour of the hat-section cold-formed steel member buckling-restrained steel plate shear wall, the lateral force resistance contribution of the edge rigid connection frame was removed and the quasi-static tests of seven hat-section cold-formed steel member buckling-restrained steel plate shear wall specimens under reciprocating shear load were carried out. The test results indicated that the hat-section cold-formed steel members blocked the diagonally full-length tension band of the steel plate shear wall and reduced the out-of-plane deformation degree of the steel plate shear wall; In addition, the reinforcement of the restraint construction of hat-section cold-formed steel member could gradually improve the deficiency of the hysteresis curve pinching of pure steel wall and promote the energy consumption of structure; Furthermore, the hat-section cold-formed steel member restraint had different degrees of improvement on the initial stiffness of the steel plate shear wall, enhancement of post-yield shear capacity, ultimate shear capacity and ductility, and evidently inhibited the stiffness degradation of the specimen; The externally attached OSB sheet exhibited significant applicability under reciprocating shear load. Finally, the test ultimate shear capacity results of each specimen were compared with the theoretical formula calculation values, and the reliability of the shear capacity calculation formula was evaluated. [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]

• A concrete-filled steel tube-gusset plate joint with ring stiffener plates is proposed. • The mechanical properties of the specimens were derived and analysed. • The equivalent interaction method (EIM) was introduced to predict the ultimate strength of CFST-gusset plate joint with ring stiffener plates under tension. Tube-gusset plate joints are increasingly adopted in large lattice towers for wind power, due to the advantages of simple fabrication and clear force transmission path. To investigate the mechanical performance of CFST-gusset plate joints with ring stiffener plates, tensile bearing capacity tests of three tube-gusset plate joints were performed in this study. The test results showed that setting ring stiffener plates and filling concrete could effectively improve the stiffness and tensile bearing capacity of tube-gusset plate joints. In addition, the finite element (FE) models were established in this study, and the accuracy of the FE models was verified by comparing it with the test results. Parameter analysis showed that the increase of the width ratio (R / D) and thickness ratio (t r / t) of the ring stiffener plate and the width ratio (L GP / D) of the gusset plate was a significant method to improve the ultimate strength of tube-gusset plate joints under tension. But when the width ratio and thickness ratio of ring stiffener plates exceeded the limit relationship, the ultimate strength of joints would not be further improved, which was easy to cause waste of materials. Finally, to simplify the calculation of CFST-gusset plate joints with the ring stiffener plates, an equivalent interaction method (EIM) was proposed in this study, which could accurately predict the ultimate strength of CFST-gusset plate joints with ring stiffener plates under tension. [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]

• Typical failure patterns of TLHR-CFDST columns for wind turbine towers are investigated. • Coupled mechanisms of columns under compression-bending-torsion loads and parameter effects are analysed. • Ultimate strength correlations of TLHR-CFDST columns for wind turbine towers are revealed. • A strength prediction method of TLHR-CFDST columns under combined loads is proposed. Concrete-filled double-skin steel tubular (CFDST) tower has emerged as a promising type of wind turbine support structure with excellent strength and stiffness. As the basic member in CFDST towers, tapered concrete-filled double-skin steel tubular columns with large hollow ratios (TLHR-CFDSTs) are frequently subjected to complex combined compression-bending-torsion loads. This paper presents a comprehensive analytical study on the coupled behaviour of the TLHR-CFDST column under combined loads and the relevant ultimate strength prediction method. A FE model was established to conduct numerical analyses and extensive parameter studies while the data from the previous experimental research was used to provide a verification basis. It is found that the column subjected to combined loads has three typical failure patterns, which are mainly governed by the bending-to-torsion ratio (m t). Columns with moderate m t undergo the bending-torsion failure and show obvious coupled performances. The load-deformation relation, the ultimate characteristics and the effects of important parameters, including axial compressive ratio (n), tapered angle (θ), hollow ratio (χ) and height-to-diameter ratio (λ) were discussed. The ultimate strength correlations of the column were revealed by analysing strength data within the parameter scopes commonly used in wind turbine towers. Lastly, a practical and accurate prediction method for the ultimate strength of the TLHR-CFDST column under combined compression-bending-torsion loads was proposed. [ABSTRACT FROM AUTHOR]

Highlights • Full-scale angle-encased CFST members under axial tension are investigated experimentally and numerically. • Load-transfer mechanism between components is assessed. • Component interactions that help to achieve high tensile performance are evaluated. • Design method based on load-transfer mechanism and component interactions is proposed. Abstract Load-transfer mechanism of concrete-filled steel tubes (CFSTs) with encased built-up angles under concentric tension is assessed experimentally and numerically in this paper. Seven full-scale angle-encased CFST test specimens with the length of 4000 mm were tested. The test parameters were the diameter-to-thickness ratio (D / T), connecting type, and configuration of encased-angles. Finite element analyses (FEA) were performed to further investigate the tensile behaviour of the composite members. The load distribution, load-transfer mechanism, and interactions between components, i.e. the tube, inner concrete, and encased-angles, were extensively evaluated. All these components could synergistically work under axial tension, though the encased angles were disconnected from the endplates. The strength of the angles could be effectively used through the load-transfer from the concrete, owing to the interactions between each component. In addition, the connecting types exerted minor effects on the ultimate tensile strength despite the existence of an insufficient confining region within the connecting area. The tensile strength design method was proposed for the angle-encased CFST member, based on experimental and numerical analyses on the load-transfer mechanism and component interactions. The comparisons between the calculated predictions and the results from the tests and simulations demonstrated the proposed design method was accurate and reliable. [ABSTRACT FROM AUTHOR]

• A multi-class Boosting method is proposed for the multi-class imbalanced problem. • Parametrized division of exposure zone is achieved using RMS, C r , C s , and D cl , etc. • Field chloride profile data with time span of 18 years validates proposed method. • The distribution of exposure zone satisfies the Weibull distribution. The analysis of marine reinforced concrete structures using chloride profile data is a commonly used exposure zone classification method. However, chloride profile data is multi-class, unbalanced and non-parametric, which makes it difficult for the commonly used machine-learning methods to construct an appropriate classification model. To solve this problem, chloride profile is parametrized by the minimum redundancy maximum relevance algorithm and a multi-class Boosting method using F-measure as inductive bias indicator to evaluate the weight of base classifiers is put forward. The method is based on field test data of the chloride profile over a period of 18 years in Hangzhou Bay, China. The method outperforms the original Boosting method with an average F-measure improvement of 6.2 %. The results show that parametric partitioning of the exposure zone is achieved and the distribution of the exposure zone satisfies the Weibull distribution. [ABSTRACT FROM AUTHOR]

• Six steel–concrete composite adapter (SCCA) specimens and one reinforcement concrete adapter (RCA) specimen were tested under axial compression. • The superiority of SCCA over RCA was proved. • The effects of stud spacing, the thickness of stiffened plates, and the amount of bottom circumferential rebars on SCCA were reveal. • Finite element models were established and validated by the test results. • Parametric analysis was conducted and the prime sensitive parameters affecting the ultimate compressive capacity were presented. Adapter is one of the most important components in wind turbine hybrid towers. It allows the upper steel segments to connect reliably with the lower concrete segments and thus they can work well as a whole structure. However, traditional reinforced concrete adapters (RCAs), which have been commonly used in engineering practice, encounter many shortcomings such as complicated construction processes and strength/stiffness degradation after the concrete cracking. In this paper, a novel type of steel–concrete composite adapter (SCCA) was proposed. Experimental and numerical studies on its compressive behavior were conducted. Six SCCA specimens and one RCA specimen were tested under axial compression. The tested parameters include the stud spacing, the thickness of stiffened plates, and the amount of bottom circumferential rebars. By revealing the failure modes, load–displacement relations, ultimate strength, deformability, and strain relations of SCCA, the superiority of SCCA over RCA was proved. To extend the scope of the experiment and conduct parametric analyses, finite element models were established and validated with test results. Sensitive parameters related to the ultimate capacity of SCCA were investigated. Additionally, reasonable studs spacing which is beneficial for enhancing the ultimate capacity of SCCA was obtained. [ABSTRACT FROM AUTHOR]

• 1) Completing the monotonic axial loading test on the STCLAC stub columns. • 2) Proposing a formula that calculated the equivalent lateral confining stress. • 3) Proposing formulae that calculated the compressive stress and the corresponding strain for confined LAC. • 4) Proposing the constitutive model for confined LAC. To study the constitutive model of lightweight aggregate concrete (LAC) constrained by the circular steel tube, the monotonic axial loading test was carried out on steel tube confined LAC (STCLAC) stub columns, considering the effects of the diameter-to-thickness (D / t) ratio (30.4, 19 and 12.7) and steel grade (Q235 and Q355). The test results showed that the steel tubes of STCLAC columns were bulging outward as a whole without local buckling during the loading process. The D / t ratio for the STCLAC column is recommended that be greater than 19.0. Due to friction stress accumulating at the interface between the steel tube and the LAC core, the steel tube is subjected to longitudinal stress. When the confinement factor (ξ) is less than 2.313, the transverse stress of the steel tube reached its yield strength before the peak load, otherwise it reached the proportional stress without yielding. Using the average transverse stresses along the height of the steel tube, this study calculated the equivalent lateral confining stress of the STCLAC column. The calculation formulas of the compressive stress and corresponding strain of confined LAC were proposed based on the test results. And the constitutive model was also proposed, which is more capable of predicting the stress–strain relationship of the constrained LAC by a circular steel tube. [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]

• Seismic performance of H-CFST columns under cyclic torsional and compression–cyclic torsional loads is investigated. • Two types of H-CFST columns under cyclic pure torsion and compression-torsion are tested. • Shear capacity of steel and concrete under combined normal and shear stress conditions is firstly studied. • Design methods of torsional capacities of H-CFST columns under cyclic pure torsion and compression-torsion are proposed. Concrete-filled steel tube (CFST) columns have been widely used in the construction industry because of their excellent compression capacity and torsion resistance. Regarding traditional CFST columns, the H-CFST column with an additional H-section steel member embedded in the core concrete provides improved fire and compression resistance. In this study, the seismic performance of nine H-CFST columns under cyclic torsional and compression–cyclic torsional loads was experimentally analysed. In the experiments, the failure mode, torque versus torsional angle hysteresis, torque versus torsional angle skeleton, torsional stiffness degradation, and energy dissipation capacity were determined. The hysteretic curves of the H-CFST columns under torsion were relatively plump in shape and exhibited no 'pinching' phenomenon, and the torsional stiffness of the H-CFST columns under unloading and reverse loading was approximately equal to the initial torsional stiffness. In addition, the applied compression had remarkable effects on the torsional capacity, torsional ductility, torsional stiffness, and hysteretic loop energy dissipation of the H-CFST columns. The shear capacities of the steel and concrete under normal stress or combined normal and shear stress were determined based on the latest theories and test results. Moreover, design method for the determination of the torsional capacity of H-CFST columns under compressive torsion is proposed based on the test results, and the theoretical contribution ratio of the H-section steel, steel tube, and concrete in the H-CFST columns to the torsional capacity was determined. [ABSTRACT FROM AUTHOR]