International Journal of Steel Structures最新文献

The socket joint are commonly employed in large-span spatial structures; however, its bending stiffness is limited. Based on the socket joint, this paper proposes an improved and novel sprayer joint that features a more rational force transmission mechanism and have larger bending stiffness. Firstly, the joint is designed, followed by verification of numerical model and bending stiffness comparison with socket joint. Secondly, the bending performance of the sprayer joints with various surrounding bolt radii under load conditions is investigated, and the resulting bending moment-rotation curves are obtained. The research findings demonstrate that the force transmission mechanism of the sprayer joint with larger bending stiffness is more rational. When the surrounding bolt radius is excessively small or the axial tension is excessively high, the bolt prematurely yields, leading to a significant decrease in joint stiffness. Despite a mere 15% increase in material cost, the bending stiffness of the new joint is 21.71 times higher than that of the traditional socket joint, and the ultimate bending moment is 5.42 times higher.

This state-of-the-art review comprehensively evaluates the seismic design and performance assessment of concentrically braced frame (CBF) systems, specifically focusing on special concentrically braced frames (SCBFs). SCBFs have shown remarkable effectiveness in providing seismic resistance for various building types, including residential, commercial, and industrial structures. However, it is crucial to acknowledge that natural disasters can lead to significant losses in human lives, economic impact, social disruption, and damage to industrial facilities. Therefore, this review concentrates on the seismic design and performance assessment of SCBFs developed for complex industrial buildings. Despite significant research efforts in SCBF performance assessment, there remains a notable gap in comprehensive critical reviews focused on studying SCBFs in the context of irregular and complex industrial structures. Identifying this research gap and conducting an updated review incorporating recent advancements, particularly the integration of Artificial Intelligence (AI) techniques, becomes necessary. The major goal of this study is to assess existing research efforts and identify areas that need further inquiry. Furthermore, AI methods, such as Machine Learning (ML) techniques, are highly recommended to enhance the performance of SCBFs and effectively identify damaged structures after severe earthquakes. The review identifies the need for further investigation in this specific area. By addressing these research gaps and leveraging AI advancements, the resilience of industrial buildings can be enhanced, thereby mitigating the losses resulting from seismic events.

Abstract

This paper aims to study the experimental and analytical behaviour of cold-formed steel (CFS) T-joint members with or without external ring stiffeners under combined axial compression and bending. The parameters varied in the study include the type of T-joints (with and without ring stiffeners), spacing of the stiffeners (100 mm and 200 mm from the central axis of the T-Joint), and thickness of the ring stiffeners (4 mm and 6 mm). The load–deflection and load-strain behaviour were studied by measuring the overall deflection of the T-joints and strain using dial gauges and strain indicators, respectively. The load-carrying capacity of the T-joints with external ring stiffeners was compared, and the results of a numerical investigation showed good agreement. An extensive parametric study was carried out for different geometric parameters of the ring stiffener, chord, and brace member using the FE model to obtain the ultimate strength of the stiffened T-joints, and strength was also compared and obtained using the published equation. From the results of this investigation, it was found that the T-joints with external ring stiffeners can resist more strength and deformation when compared to the T-joints without external ring stiffeners.

Abstract

So far, several studies have been conducted on progressive collapse of tall buildings, of which a few have been on the buildings with diagrid structures, however, in none of them the effect of the building’s plan geometry has been a concern. In this study the progressive collapse of a set of 50-story steel buildings with diagrid structures in three different plan geometries of square, rectangular, and octagonal was investigated by nonlinear static and dynamic analyses. First, the considered buildings were designed according to ASCE 7 and AISC design provisions, trying to be close as much as possible to the optimal design, based on the demand to capacity ratios. Then, five damage scenarios were considered including removal of columns and/or diagonal elements of the diagrid structure in the lowest, the 25th, and the top story of the building according to UFC provisions. Nonlinear static and dynamic analyses were conducted by Perform-3D software. Results show that robustness index, calculated by using the stiffness method would be smaller for the cases of member removal in upper stories, and that the lowest robustness index corresponds to removal of two corner columns, and bracing element connected to them, in the first and second stories. Results also show that removal of interior column in the first story leads to progressive collapse in all three plan shapes. However, yielding and ultimate load factors in building with octagonal plan are more than other two buildings, implying that this type of buildings have more resistance against progressive collapse.

Abstract

The construction of the cross-sea steel box girder bridge is gradually advancing and integrating, which particularly reflects in the size of the bridge. The length of a single installation segment often exceeds 100 m. The alignment of the steel box girder is significantly affected by the temperature effect during manufacturing. This paper investigates the impact of temperature gradient on corresponding alignment at the manufacturing stage for the large-segment steel box girder taking a large-span continuous steel box girder bridge as a case study. The inspection of temperature during the assembly procedure was carried out. After obtaining the data during welding, the influence of the temperature was evaluated using a finite element model. The results show that with the temperature gradient measured, the deflection of the second suspension of the mid-span reaches 10.9 mm and the deflection of the cantilever end reaches 17.1 mm, respectively. The deformation conforms to the code specifications when considering the influence of the temperature gradient effect. The corresponding pre-camber value should be set for the large segments assembled outdoor. At the same time, welding operation should be carried out under the preset temperature difference to partially eliminate the impact of temperature gradient.

This paper presents a study on the performance of two types of fully bolted connections in relation to progressive collapse. Two specimens were specifically designed and fabricated to represent these connections. One specimen utilized the traditional double web angle connection (DWA), while the other employed a new type of connector, resulting in a new fully bolted connection (NFB). The study thoroughly investigated various aspects of the specimens, including failure modes, load–displacement responses, and resistance mechanisms. The findings revealed that the flexural behavior and ultimate behavior of the NFB connection were superior to those of the DWA connection, particularly in terms of flexural behavior. However, the rotational behavior of the NFB connection was slightly inferior to that of the DWA connection. Additionally, refined numerical models were used to simulate the failure modes and load–displacement responses of both connections, and a strong correlation was observed between the test results and the numerical analysis. Furthermore, a parametric analysis of the NFB connection was conducted, leading to the discovery that modifying the structural type of the new connector, specifically adjusting the form of part C from flush to extended, was the most effective measure for enhancing the anti-progressive collapse capacity of the NFB connection. Moreover, the rotational capacity and ultimate load-carrying capacity of the NFB connection could be improved by adjusting the thickness of the new connector and increasing the diameter of the bolts within the steel beam.

The existing flexural analysis methods of corrugated steel web composite box girders are either inaccurate due to thoughtlessness of the influencing factors, or complicated due to excessive consideration of the influencing factors. In this study, a flexural displacement model of composite box girder considering both the accordion effect and shear deformation of web and the shear lag effect of flange is proposed. According to the internal force balance condition, the complex flexural models of a composite box girder are decoupled into three independent simple flexural states: Euler–Bernoulli beam flexure satisfying the quasi-plane assumption, flexure of equivalent web deformation, and flexure of shear lag of flange. Based on the flexural theory of the thin-walled beam, the generalized internal force system and beam-type finite element model was established corresponding to each flexural state. The results of numerical examples show that the proposed method has high solution accuracy and can directly obtain the displacement and internal force of each flexure deformation. The moment results show that the generalized moment has a peak value at the point of shear discontinuity, and increases or decays rapidly near it.

Abstract

In this paper, authors propose a novel type of light weighted steel buckling restrained brace (LWSBRB) made with two hollow rectangular sections used as restrainers, thus making the all-steel buckling restrained braces additionally light-weighted fulfilling the Euler’s buckling criteria as well. The proposed LWSBRB is cyclically tested and compared with conventional all-steel buckling restrained brace specimen for hysteretic behavior, failure pattern, energy dissipation capacity, cumulative plastic deformation, ductility, compression strength adjustment factor and equivalent viscous damping factor. The tested specimen is also numerically validated by non-linear finite element analysis. It was seen that LWBRB showed higher ductility with optimum energy dissipation. It was also observed that LWBRB induced quite stable hysteretic behavior with higher values of maximum compressive and tensile forces, and can be loaded beyond 2% axial strain to dissipate more energy.

A key component of steel structural design is the careful selection of structural modeling joints in steel structures, as the behavior of the joints affects the structure's strength and displacement characteristics. According to the capacity for transferring moment, connections in the analysis of frames are categorized as rigid, semi-rigid, or pinned. Also, the response modification factor (R-factor) is an effective parameter used in the seismic design of structures. However, the influence of the beam-column connection's stiffness factor on the response modification factor did not seem to have been considered in seismic design codes. Consequently, the R-factor under static pushover and dynamic loading is being studied for moment-resisting steel frames (MRSFs) with 3-, 6-, and 12-story using three different forms of beam-column connections depending on the connections' stiffness (m). The rigidities of the connections are taken 20, 10, and 5 for rigid, stiff semi-rigid, and flexible semi-rigid connections, respectively. The MRSFs are subjected to ten records with varying frequency contents and ground motion durations. The ductility reduction factor (R_μ), the over-strength reduction factor (R_o), and the R-factor were determined. The results indicated that the beam-column connection rigidity factors affected the R₀, R_μ, and R-factors. Also, the R-factors were more affected by the rigidity factors for the beam-column connections and the number of story frames.

To enhance the structural connectivity of prefabricated steel frame systems and augment their construction efficiency, this study introduces an innovative prefabricated joint design tailored for square steel columns and H-beams characterized by varying beam heights. This study includes both static loading tests and seismic tests performed on full-scale joints featuring two different beam heights. This investigation involved a comprehensive analysis of the static and seismic performance of the joints, employing various performance metrics such as ultimate load capacities, ultimate rotation angles, hysteresis curves, skeleton curves, stiffness degradation curves, and ductility coefficients, in alignment with established structural codes and standards. The results indicate that the plasticity of the H-beam is fully developed, exhibiting a relative slip phenomenon. Additionally, the joints demonstrate commendable rotational capacity, with hysteresis curves consistently manifesting an inverse S-shape and exhibiting noteworthy stiffness degradation. Furthermore, the comparison with the unimproved joint shows that the novel joint, in addition to being easy to construct, has better ductility and energy dissipation capacity. The results of the study will provide a technical reference for further optimization and application of prefabricated beam-column joints.