International Journal of Steel Structures最新文献

Numerous studies have been conducted regarding the fatigue strength of longitudinal welded gusset joints. Most studies employed relatively small specimens. Thus, this study aims to evaluate the variation of fatigue life of longitudinal welded gusset joints by using the probabilistic fracture mechanics approach, particularly for larger specimens. Although some studies claimed that lower fatigue strength is found in the thicker main plate specimens, however only a limited number of fatigue test was conducted. A probabilistic approach was employed to conquer the shortfall. In this study, fatigue crack propagation analysis was performed on the main plate thicknesses of 12, 40, and 60 mm to evaluate the effect of main plate thickness on the fatigue life of the joints. Then, a probabilistic approach is given to investigate the variation of fatigue life of the joint. In addition, fatigue tests were carried out to investigate the crack propagation behavior on larger specimens. A significant decrease in fatigue life was observed by the increase of the main plate thickness from 12 to 40 mm, however, no further decrease thereafter. The fatigue strength of longitudinal welded gusset joints with the main plate thickness of 12 mm was appertained to category F in the JSSC design curve. Meanwhile, the fatigue strength of longitudinal welded gusset joints with the main plate thickness of 40 and 60 mm falls into category G in JSSC. This condition was also confirmed by the fatigue test results, where both specimens were classified as category G in JSSC.

Steel structures are commonly used in engineering projects and infrastructure. Steel structures should have high bearing capacity and be able to resist fire, earthquake, and corrosion. A new type of Q235 refractory steel has recently been developed in China, and the residual mechanical properties of steel structures are key indicators for estimating structural damage and reusability. Therefore, in-depth research is urgently needed. The yield stress, residual elastic modulus, ultimate tensile strength, and ultimate strain at room temperature to 900 °C and under air and water cooling conditions were detected. The residual mechanical properties of Q235FR steel were compared with other structural steels, and it was confirmed through experiments that they are closely related to temperature and cooling methods. In the case of the above cooling methods, the loss of mechanical properties can be negligible when exposed to temperatures up to 600 °C. When the temperature exceeds 600 °C, the high temperature and cooling method significantly impact the residual mechanical properties of Q235FR steel. The advantages of Q235FR steel are high strength, good ductility, strong corrosion resistance, and fire resistance. The suggested predictive equations could be used to accurately evaluate the residual mechanical properties of Q235FR steel at high temperatures.

Premature failure of transmission towers due to extreme weather conditions and inadequate design methods have severe socio-economic implications. This study presents a state-of-the-art review of the research work related to failure of self-supported lattice steel transmission towers. Selected articles from literature were divided into broad categories namely—failure analysis techniques, joint slippage effects, retrofitting and investigations of failure due to earthquakes and high intensity winds. The former three aspects mentioned above are chosen for review in this paper since the latter two are very broad aspects by themselves. A systematic literature review has been conducted based 76 research articles after filtering from reputed journals. Advanced analysis involving computational models based on nonlinear formulations and modern finite element software and their potential to reduce the need for full-scale prototype testing have been highlighted. A description of the studies available on retrofitting techniques for transmission towers for intervention against impending tower failures—diaphragm and leg member retrofitting techniques and studies on retrofitting connections are also discussed. Key conclusions from the study that highlight the most useful findings from the various studies, limitations of the current study and directions for future research have been established.

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.

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.

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.

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.