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• A novel cold-formed thin-walled steel beam-column joint entirely using self-tapping screws. • Influence of different connection modes on static load carrying effect. • Seismic behavior of H-section beam-square steel column joints connected by self-tapping screws. • The calculation method for yielding moment strength based on the improved component method. This paper proposes a novel thin-walled steel beam-column joint entirely using self-tapping screws. Compared to bolted and welded connections, its advantages of easy construction, low precision requirements, and fast construction are suitable for low-rise steel structures. Four full-scale H-section beam-square steel column joints connected by self-tapping screws were tested and the force transfer mechanism was investigated. Three of the specimens were loaded monotonically at the beam ends. The effects of the L-shaped connecting plate thickness and the arrangement of stiffening ribs on the bending performance of the joints are analyzed. Monotonic loading tests have demonstrated that the increased thickness and the arrangement of stiffening ribs enhance the common forces in the clusters of self-tapping screws, thereby increasing the bending stiffness of the joints. One of the specimens was tested with cyclic loads. The cyclic loading test revealed that the hysteretic curve of the self-tapping screws connection is relatively full, with high energy dissipation capacity and low degradation of strength and stiffness. Finally, the improved component method proposed the calculation method of bending resistance of self-tapping connection joints. The calculation accuracy is within 10 %, which can be used as a reference for the design of bending resistance. [ABSTRACT FROM AUTHOR]

In this paper, the eccentric compression test of seven specimens was conducted to explore the application possibility of recycled aggregate concrete (RAC) in L-shaped columns composed of concrete-filled steel tubes (CFST). The main parameter is the replacement ratio of recycled coarse aggregates (RCA), and an L-shaped column of composed hollow steel tubes was set as a control. The test results indicated that the bearing capacity and stiffness of the L-shaped column composed of RAC-filled steel tubes (RACFSTs) are better than those of the L-shaped column composed of hollow steel tubes. The compressive strength of concrete is reduced by 73.1% as the replacement ratio of RCA increases from 0 to 100%, while that of the column is merely reduced by 23.9%. The strength disadvantage of RAC is compensated by the confinement of steel tubes. Besides, the result of the eccentric compression test (80 mm eccentricity) was compared with the axial compression test (0 mm eccentricity). The increase in eccentricity reduced the bearing capacity and ductility due to additional bending moments. The finite element model (FEM) was established by software ANSYS to compare with the experimental results. The bearing capacity deviation of FEM is 4.23~6.56%. The parametric analysis was carried out to summarize the influence of parameters such as eccentricity, material strength, and steel tube thickness. With the increase of eccentricity, the bearing capacity of the RACFST decreases gradually. In engineering design, the bearing capacity of the RACFST can be improved by increasing the strength and thickness of the steel. [ABSTRACT FROM AUTHOR]

The quasi-static experiments and finite element analysis of three groups of special-shaped concrete-filled steel tube (SCFST) column chevron braced frames (two groups of eccentrically braced frames and one group of concentrically braced frame) were carried out. The differences of quasi-static mechanical properties between the three groups frame were compared. The damage mechanism of the concentrically and eccentrically braced frames was significantly different, and the eccentrically braced frame could significantly improve the energy-dissipation ability and ductility. When the single limb of columns was connected by double-steel-plate, the stiffness of eccentrically braced structure could be improved around 10.4% and showed better energy-dissipation capacity. The finite element simulation was built on the basis of experiments, and parametric analysis was examined. The analysis results showed that section forms of the SCFST column and the thickness of brace have significant impacts on the quasi-static properties of such type of structure. [ABSTRACT FROM AUTHOR]

Based on the low cyclic loading test results of vertical stiffener connections between L-shaped columns composed of concrete-filled steel tubes and steel beams, a simplified trilinear model to predict the shear strength versus the shear deformation response in panel zone is presented in this article. Considering the characteristics of the panel zone, the strength of the joints is determined by contributions from the web of steel tubes and internal short beams, core concrete diagonal struts and the steel frame yield hinge mechanism. Existing calculation methods, which are applicable to the vertical stiffener connection to L-shaped columns composed of concrete-filled steel tube, are summarized and modified in this article. In addition, the use of the proposed design equations led to excellent agreement with experimental shear strength for both corner and exterior vertical stiffener connections to L-shaped columns composed of concrete-filled steel tube. [ABSTRACT FROM AUTHOR]

To promote special-shaped concrete-filled rectangular steel tubular (SCFRT) columns in high-rise buildings, this study proposes the innovative SCFRT column chevron concentrically braced frame. To study the seismic performance of the braced frame, this paper experimentally investigated the behavior of SCFRT column chevron concentrically braced frames subjected to constant axial load and cyclically flexural load. The braced frames exhibited rational failure mechanism, favorable ductility, and high deformation capacity. The hysteretic curves of the specimens were smooth and spindle indicating the good energy dissipation capacity of the braced frames. Stiffness and strength degradation were not obvious. Hence, the SCFRT column braced frame has good anti-seismic performance. The load carrying capacity and the stiffness increased with the increase of axial compression ratio, whereas, the energy dissipation ability and ductility decreased. The lateral stiffness, horizontal bearing capacity, energy dissipation capacity, and ductility could be improved significantly when the columns were strengthened from L-shape to combined T-shape and cross-shape. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation of L-shaped columns composed of concrete-filled steel tubes (LCFST columns) connected by steel linking plates. As a new kind of composite column, the fundamental structural behavior of LCFST columns connected by steel linking plates is discussed in this paper. Eight large-scale LCFST columns were constructed and loaded under either concentric axial compression or biaxial eccentric compression up to failure. Slenderness ratio, thickness of the steel linking plates and load eccentricities were all studied within the experimental program. The relationships of load versus longitudinal displacement, lateral deflection at mid-height, longitudinal strain at mid-height etc. are presented. It is demonstrated that specimens with larger slenderness ratios or eccentricities have lower ultimate load capacities, as expected. It is also demonstrated that the steel connection plates, also as expected, have a considerable influence on confining lateral deflections of the mono CFST columns and that they significantly contribute to the columns' ultimate carrying capacity. Predictive formulas for calculating the ultimate loads of LCFST columns connected by steel linking plates are proposed based on modifications of the ANSI/AISC 360-05 guidelines. [ABSTRACT FROM AUTHOR]

L-shaped column composed of concrete-filled steel tube mono-columns connected by double vertical plates (LCFST-D) is widely used in high-rise buildings because it can be embedded into walls and is flexible for architectural design. Due to the asymmetrical cross-section of the LCFST-D, the traditional form of one side of the H-beam and LCFST-D connection is the widen-flange plate joint and other sides are vertical stiffener joints. However, the strength and stiffness of the former are relatively low. Thus, in this study, the π-shaped joint was introduced to make the flexural capacity of both sides of the connection are close. Five full-scale specimens were casted for pseudo-static tests, and finite element models (FEM) calculation by Abaqus was introduced to provide a supplementary calculation. The results showed that the whole connection had a good seismic performance. The strength and stiffness of the vertical stiffener joint and the π-shaped joint were closed. Subsequently, parameter analysis was performed for further study of the factors of the flexural capacity. Finally, the calculation formulas for the flexural strength of the connection were derived, and the formulas of the shear strength were quoted. The calculation results were conservative and the errors were acceptable, thus, these calculation methods could be used in actual projects. [Display omitted] • A new connection between L-shaped concrete-filled steel tube column and H-beams. • The asymmetry of L-shaped connection is optimized. • The introduction of pi-shaped joints optimizes the mechanical properties. • The calculation formula of the flexural strength and shear strength. [ABSTRACT FROM AUTHOR]

This paper experimentally investigated the behavior of specially shaped columns composed of concrete-filled steel tube frames (SCFST frames) subjected to constant axial load and cyclically varying flexural load. Three specimens with two storeys and a single span were tested. The effects of axial compression ratio and the beam-to-column stiffness ratios on the behavior (i.e., stiffness, strength, ductility, and energy dissipation) of SCFST frames were studied. The failure modes of the frames were studied. The hysteretic curve shapes of these three specimens were smooth and full, and the skeleton curves both have gently descending stages, which represent suitable ductility and energy dissipation ability. The load carrying capacity and stiffness decreased with the decrease in axial compression ratio, but the energy dissipation ability and ductility increased and the stiffness degeneration decreased. The load carrying capacity and stiffness decreased with the increase in beam-to-column stiffness ratio, but the energy dissipation and deformation abilities increased. Furthermore, a finite element analysis was conducted to simulate the behavior of SCFST frames. Test results agreed with the results of the finite element analysis. [ABSTRACT FROM AUTHOR]

A flat concrete-filled steel tubular column (FCFST) is a concrete-filled steel tubular column (CFST) with a section length-width ratio greater than or equal to two. In this study, the vertical stiffener joint was appropriately modified, and a new type of rigid joint suitable for the width-side direction (weak axis direction) of the FCFST and H-beam was proposed. Four specimens were designed for pseudo-static experiments, and Abaqus was used to establish finite element models (FEM) to provide a supplementary calculation. The results showed that the π-shaped joints had a clear load path, sufficient energy consumption, and good seismic performance. When the beams were eccentrically arranged, the stiffness and ultimate strength of the joints were improved, whereas the ductility was reduced. Subsequently, a parameterized analysis was performed for the π-shaped joint of the FCFST. It was determined that the thickness of the π-shaped part, length of the corbel, thickness of the steel tube, and width of the FCFST have prominent influences on the stiffness and ultimate strength of the joint. Finally, a calculation formula was derived for the joint based on the yield-line theory. The calculation results of the formula were compared with the experimental results. These errors were found to be acceptable, confirming that this approach can be used in actual projects. [Display omitted] • A new type of joints suitable for the flat concrete-filled steel tubular column (FCFST) and the H-beam was proposed. • Experiments, finite element analysis, and parametric analysis were used to study the mechanical property of the π-shaped joint. • The calculation formula of the π-shaped joint was derived. [ABSTRACT FROM AUTHOR]

This paper proposes a new structure suitable for high-rise buildings that combines specially shaped columns composed of concrete-filled steel tube (SCFST) frames and double steel concrete (DSC) composite walls. To investigate the quasi-static behavior of the structure, three 1:2 specimens with two stories were tested. The failure modes and effects of the form of boundary elements on the behavior of the structure were studied. The experimental results indicate that the structure exhibits good hysteretic behavior, energy dissipation capacity, and ductility. The form of boundary elements has a significant influence on the quasi-static behavior of the structure. A finite element analysis model with the function of deleting failure elements was proposed based on the experimental results. The analysis of the model shows that the aspect ratio, thickness of the steel plate, and form of the boundary element have a significant influence on the lateral bearing capacity and deformation of the structure, whereas the axial compression ratio has less influence. A skeleton curve model was proposed based on the finite element analysis results. [Display omitted] • The structures have good quasi static behavior. • The failure modes of the structures were shear failure. • The form of boundary elements has great influence on the quasi static behavior. • The function of deleting failure elements was used in finite element analysis. • The skeleton curve model can reflect the load displacement law of the structure. [ABSTRACT FROM AUTHOR]

Special-shaped concrete-filled steel tube (SCFST) columns have been extensively used in residential buildings owing to their excellent mechanical properties and architectural benefits. In this study, five groups of eccentric compression tests were conducted to study the mechanical properties of SCFST columns with respect to the axial force and bending moment around the centroidal principal axis, using the eccentric distance and eccentric direction as the parameters. ABAQUS software was used to construct finite element models. The model results fit well with the experimental results. Based on the experimental study and finite element simulation with reference to the standards of different countries, a formula for calculating the in-plane stability of SCFST columns under the axial force and bending moment around the centroidal principal axis was derived. The findings of this study could provide guidance for future engineering design. • Eccentric compression tests of Special-shaped concrete-filled steel tube (SCFST) columns were carried out. • Finite element models of SCFST columns were constructed by the ABAQUS software. • The calculation formula of in-plane stability of SCFST columns under axial force and bending moment was deduced. [ABSTRACT FROM AUTHOR]

To study the uniaxial eccentric compression properties of slender L-shaped column composed of concrete-filled steel tubes (CFST) connected by steel linking plates, a compression test on four L-shaped CFST columns with different eccentricities was designed in this study. The ultimate bearing capacity, ductility, and deformation capacity of the L-shaped CFST columns were obtained by analyzing the failure phenomenon, load–axial displacement curves, load-lateral deflection curves and load–strain curves. Experimental results were verified by ABAQUS finite element analysis software, and the N–M correlation curves of the L-shaped CFST columns were calculated by using a full-section plasticity method. The calculation formulas of eccentric compression ultimate bearing capacity of L-shaped CFST columns was proposed, which provided a reference for engineering design. • Four L-shaped CFST columns connected by steel linking plates subjected to uniaxial eccentric compression were tested. • FEA models were built for verifying the experimental results. • Full-section plasticity method was used to obtain N-M correlation curves. • Calculation formulas of eccentric compression ultimate bearing capacity of L-shaped CFST columns was proposed. [ABSTRACT FROM AUTHOR]

• SCFRT column frame-buckling restrained steel plate shear wall structure. • The connection form determines the failure mode of the structure. • The structure with the four-side connection form has the best bearing capacity. • The groove connection has prominent ductility and deformability. • In engineering, the groove connection is recommended for this structure. To promote the application of special-shaped concrete-filled rectangular steel tubular (SCFRT) columns in high-rise residential buildings, this paper proposed innovative SCFRT column frame-buckling restrained steel plate shear wall structure. Three sets of 1:2 scale structural model specimens with a single span and two stories were designed and tested under the quasi-static load. The connection form between the frame and the shear wall includes four-side connection, four-corner connection, and groove connection. The hysteretic performance of the specimens was evaluated, and the mechanical properties were analyzed. The parametric analysis was carried out by the verified finite element model. The results revealed that the SCFRT columns frame-buckling restrained steel plate shear wall structure has favorable seismic performance, and the connection form significantly affects the mechanical properties of the structure. The bearing capacity and stiffness of the four-side connection form are relatively prominent, while the groove connection and four-corner connection have better ductility. The results can guide the engineering application to choose the proper connection form between the frame and the shear wall. [ABSTRACT FROM AUTHOR]

The behaviour of unusual composite column sections is difficult to examine owing to their asymmetric geometry. In this study, seven L-shaped columns fabricated using concrete-filled steel tubes connected via double-vertical steel plates (LCFST-D columns) were tested under axial compression. The failure modes, load–deformation relationship, strain distribution, ductility, and strength index of the columns were studied. Test results demonstrated that the local buckling of the vertical steel plates was delayed by filling with concrete. The bearing capacity and ductility ratio increased by 21.1% and 8.1%, respectively, compared with the specimen without concrete in the vertical steel plates. Transverse stiffeners were used to increase the axial stiffness by restraining the deformation of the vertical steel plates. However, the effect of the transverse stiffeners on the bearing capacity was negligible. The behaviour of the LCFST-D columns with concrete filled in between the two vertical steel plates, without the transverse stiffeners, was more favorable than the LCFST-D columns with the transverse stiffeners, and thus recommended for practical engineering application. The mono-columns worked more cooperatively in this connecting pattern. 3D nonlinear finite element models were developed and verified to analyze the mechanical properties and bearing capacity of the LCFST-D columns. The approach is verified by the experimental results and the available current design codes to be reasonably conservative. EC4 showed the best agreement with the experimental values. The results of this study provide a basis for the application of LCFST-D columns in high-rise composite structures. [ABSTRACT FROM AUTHOR]

In this paper, special-shaped columns composed of concrete-filled steel tube mono-columns connected by double vertical steel plates (LCFST-D) are proposed. Five specimens were tested under a constant axial force and cyclic lateral loading. The variables studied in the experiments include the axial compression ratio, sectional dimensions of the mono-column, and the width and thickness of the vertical steel plates. The specimens behaved in a ductile manner and experienced stable hysteresis behaviour before failing in a sequence involving local buckling at the base of the side mono-column, compressive crushing of concrete at the base of the side mono-column, and fracture propagation at the boundary between the side and central mono-column. The seismic behaviour of the specimens was evaluated in terms of strength, stiffness, deformation, ductility, energy dissipation capacity, and strain distribution. Based on the experiments conducted on these LCFST-D columns under cyclic loading, 3-D nonlinear element models were used to analyse the mechanical properties and seismic behaviour of LCFST-D columns. The results of this finite element analysis showed good agreement with the experiment results. Overall, the seismic behaviour of the LCFST-D column was significantly better than the behaviour of L-shaped columns composed of concrete-filled steel tube mono-columns connected by a single vertical steel plate (LCFST-S). Additionally, it was found that the mono-columns worked more cooperatively in the LCFST-D column arrangement. The research presented in this paper provides a basis for the application of LCFST-D column structural systems in high-rise steel buildings. [ABSTRACT FROM AUTHOR]

Both concrete-filled steel tube (CFST) column and buckling-restrained steel plate shear wall (BRSPSW) have the advantages of high load-carrying capacity and superior seismic performance. The structural system composed of CFST columns and BRSBSWs will have the superior mechanical performance and be more suitable for high-rise buildings. In this study, the pseudo-static tests were carried out on the specimens of unstiffened steel plate shear wall and cold-formed steel (CFS) BRSPSW which were infilled in the single-span two-story 1/3 scaled composite frame respectively. The test results show that the CFS stiffeners have the obvious effect of restraining the outward buckling deformation on the steel plate, improving the lateral stiffness and resistance of the steel plate, and reducing the deflection deformation of the steel plate to the surrounding composite frame. The finite element (FE) model was established and validated, and the interaction between the BRSPSW and the composite frame was analysed. In combination with the theory and the FE analysis results, the maximum deflection limits of CFST column and steel beam were proposed to ensure the strength of the infill BRSPSW to give full play. Considering the separation of the steel tube wall of square CFST from the core concrete in the process of loading, the deflection limit of square CFST is proposed considering the separation effect of the steel tube wall of square CFST from core concrete under the action of infilled steel plate. • A novel buckling-restrained SPSWs with composite structure was investigated. • The interaction behaviour of buckling-restrained SPSW and boundary composite frame were discussed. • The deflection limit of square CFST and steel beams is proposed under the action of infilled steel plate. [ABSTRACT FROM AUTHOR]