International Journal of Steel Structures最新文献

This research investigates the compressive and flexural strengths of cold-formed steel (CFS) members with channel and Z-profiles. The study includes a comprehensive analysis of 500 CFS members. Finite-element (FE) models in ABAQUS, validated by experimental results, assess the influence of various parameters on the capacities of these CFS members. The parameters analyzed include the member length-to-depth ratio, section depth-to-width ratio, plate slenderness ratio, lip-to-flange width ratio, and material yield stress. Results from FE models were compared with those from the Effective Width Method (EWM) and the Direct Strength Method (DSM). A graphical user interface (GUI) was developed to streamline EWM and DSM calculations, enhancing efficiency and accuracy. This study provides valuable insights into the performance of innovative CFS channels and Z-profiles, facilitating a deeper understanding of their structural capacities and offering a foundation for potential applications in modern engineering design and construction practices.

Previous studies have rarely investigated stochastic robustness of flexible cable dome structures under impact loads. In this study, the dynamic responses and failure modes of a Geiger cable dome structure were analysed under impact loads. The number of components damaged by impact and the loss of internal force in components were used to establish a structural damage index and an equation of failure mode control. Following this, by establishing the impact resistance failure limit state equation and combining the probabilistic and statistical characteristics of each design parameter of the structure, the probability of disproportionate failure of the structure undergoing disproportional damage under the impact load was calculated. Then, the stochastic robustness index ({I}_{text{rob}}) based on the probability of structural failure was proposed, and the key factors affecting the structural robustness were analysed through parameter analysis. The research results indicated the following. First, cable dome structures exhibited three types of failure modes under impact loads. Second, the stochastic robustness index fully reflected the probability of a cable dome structure sustaining disproportional damage under impact loads. Increasing the mass or speed of the impactor both increased the probability of the structure sustaining disproportional damage. An impact occurred closer to the centre of the structure, both the probability of overall structural failure and structural robustness performance increase, but the probability of the structure sustaining disproportional damage decreases. Third, increasing the prestress and cross-sectional area of the components might increase their impact resistance and structural robustness performance.

Concrete-filled steel tube (CFST) columns exhibit remarkable structural performance due to the combined effects of lateral confinement provided by the steel tube and the capacity of the core concrete to delay steel local buckling. This interaction enhances the axial capacity, peak-load strain, and ductility behavior of CFST columns. However, accurately modeling CFST stub columns using finite element (FE) simulations is a challenging task, requiring accurate representation of concrete behavior under tri-axial stress conditions. The concrete damaged plasticity (CDP) model in ABAQUS software is commonly used but has limitations, particularly for confined concrete. In addition, most introduced confinement models are constrained by the type of confining material and column dimensions. This study addresses these limitations by introducing an enhanced CDP model that properly accounts for the hardening/softening rule, yielding surface, and flow rule. In addition, a new confinement ratio is proposed for steel-confined concrete columns to calculate the dilation angle. The suggested model was validated through FE analysis on 1041 previously tested CFST stub columns. It was found that the proposed model successfully predicts load–strain curves and axial capacity for various cross-section shapes and confinement levels.

To ensure the fire resistance performance of modular construction, various methods such as spray-applied fire resistive material (SFRM), intumescent paint, and gypsum board can be used. Rectangular steel tube columns, commonly used in modular construction units, are fireproofed by attaching fireproofing boards. The required thickness of the fireproof board increases with the duration of fire exposure, which in turn increases the self-weight. To address these issues, this study proposes two conditions for improving fire resistance: (1) SFRM application, and (2) mortar filling or finishing on both the inside and outside of small-sized rectangular steel tube columns in modular units. Experimental and analytical approaches were employed to evaluate the behavior of these columns over time under fire exposure and to analyze the required sheathing thickness according to the fire-resistant sheathing method. The results indicated that mortar filling suppressed the temperature rise due to its thermal storage effect. The application of fireproofing spray after mortar filling extended the fire resistance time by approximately 143 to 146% compared to the unfilled specimen. It was also found that SFRM provided a 149% higher fireproofing performance compared to finishing mortar.

The joints of cold-formed steel (CFS) portal frames with box sections are primarily formed either through stiffened welded connections or by bolted end plates, which typically involve costly full penetration butt welds. In New Zealand, CFS portal frames with nested tapered box beam (NTBB) sections are popular, and the joints of these portal frames are also formed through a bolted end plate system. In literature, it was found that welds in these joints are prone to cracking in the heat-affected zone (HAZ) under bearing opening moments (tension). Therefore, this paper focuses on proposing an alternative connection system (bolted-side plate) for eaves joints without any weld, aiming to reduce the overall cost of construction and increase construction speed. The performance (strength and stiffness) of these joints is mainly dependent on the geometric details of the bolted-side plate, which is limited in Australia/New Zealand standards (AS/NZ 4600). Herein, a non-linear finite element (FE) model was developed for the NTBB portal frame and validated against the experimental test results from the literature. Firstly, the validated FE model was used to investigate the feasibility of using bolted-side plates for NTBB portal frames and found that the bolted-side plate can increase the ultimate capacity of NTBB portal frame by 9%. A parametric study was then conducted by considering different geometric details of the bolted-side plates under both closing (gravity) and opening (wind uplift) moments. Finally, unified design equations for the moment capacity of bolted-side plates were proposed based on the results of the parametric study, and their accuracy was assessed through reliability analysis.

In this paper, an innovative configuration for steel braced frames, incorporating an energy absorption system proposed. The proposed bracing system features a dual-level slotted bolted connection (SBC) dampers with slipping performance and a horizontal shear panel system (H-SPS) integrated into eccentrically braced frames (EBF), referred to as CS-EBF. Consequently, the fuses within this system, allowing controlled slip in the first fuse and inelastic deformation in the second fuse. Hence, the proposed system concentrate damage within the fuses, preventing harm to other components. Numerical results demonstrate that the CS-EBF system exhibits greater ductility and energy dissipation compared to similar single-level systems. Additionally, the slip of the SBC fuse at low earthquake levels initiates the energy absorption process earlier than in other comparable dual-level systems, ultimately leading to smaller dimensions for the bracing frame sections.

Transmission line towers designed based on the provisions of different standards may fail during mandatory testing for many reasons. Two different types of premature failures observed during full-scale testing at Tower Testing and Research Station, Structural Engineering Research Centre, Chennai (CSIR-SERC), are studied in this paper. These towers failed prematurely due to improper design assumptions secondary to the primary bracing connection. The failures are modelled using general-purpose finite element software. The test and analytical results are compared with various codal provisions. Hip bracing connected to primary bracing with a single bolt acts as a hinge and fails to provide adequate restraint. The assumption that hip bracing provides restraint to the primary bracing against the in-plane deformation is invalid, and it can only prevent the primary member’s displacement along the hip’s axis due to its axial stiffness. This study recommends a double bolt connection for redundant members.

Local buckling of steel plates is a major concern, as it dominates the plastic mechanism and reduces the ultimate strength of the steel plates depending upon their slenderness. At elevated temperatures, material nonlinearities result in a further reduction in the stability, stiffness, and strength of thin steel plates. Numerical simulations have been performed on stiffened and unstiffened steel plates at elevated temperatures under uniaxial compression load for different slenderness using commercially available FE software ABAQUS. The established finite element model, which depicts the local buckling behaviour and ultimate post-buckling strength of square and rectangular steel plates, has been the basis for a number of parametric investigations, all of which have been conducted using shell finite elements. The designed specification offered by North American Standards (ANSI/AISC 360-16) and European Standards (EN 1993-1-2), which employ a stress-based method to determine the ultimate post-buckling strength of steel plates for local buckling at elevated temperature, has also been compared with the obtained results. According to this investigation, EN 1993-1-2 produces results that are excessively conservative at higher temperatures. To overcome this, an attempt has been made by replacing the normal temperature parameter by a temperature-dependent non-dimensional slenderness ratio for predicting the ultimate strength of steel plates in fire exposure conditions. Further, this study provides some critical highlights on the behavior of steel plates of two different aspect ratios at elevated temperatures under compressive loads. The design formulations have also been proposed for estimating the ultimate strength of thin square and rectangular steel plates under compression. A good correlation has been observed in predicting the strength of the new design approach compared with existing experimental and computational results. The reliability and accuracy assessments of the proposed approach have been illustrated in brief.