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This paper presents an arch structure called the circular box arch with sinusoidal corrugated webs (CBASCW). This study investigates the out-of-plane elastic buckling behavior and elastoplastic stability capacity of the arch through a combined approach of theoretical derivation and finite element simulation. The section stiffness of the arch, including flexural stiffness, shear stiffness, and torsional stiffness, is achieved through theoretical derivation. Additionally, the elastic buckling load in both pure compression and pure bending states is derived. A simplified model is also introduced, which can conveniently simulate the internal force and deformation of the arch. The elastoplastic instability mechanism and failure mode are studied under various loading conditions, including uniform radial load, end bending moment, vertical load uniformly distributed in full-span, and vertical load uniformly distributed in half-span. Furthermore, the stability curves of the arch under conditions of pure compression and pure bending are graphed by incorporating stability coefficient and regularized slenderness ratio. According to the simulation results obtained from the simplified model and the analysis of stability curves, a design formula for stability capacity is proposed. [ABSTRACT FROM AUTHOR]

Due to their thin‐walled nature and complex geometry, cold‐formed steel purlins are prone to a variety of instabilities. In most applications, purlins rely on the attached sheeting to restrain member buckling and hence their cross‐section is optimized to maximize their cross‐sectional resistance to local and distortional buckling caused by sagging bending moments under the action of a uniformly distributed load. Sigma purlins are a family of cold‐formed steel members with folding‐lines along their webs. The non‐straight geometry of their web is beneficial in terms of reducing the local slenderness of the web, however it increases their susceptibility to web crippling in case the purlins are subjected to concentrated transverse loads and hence it may reduce the overall moment resistance. This study reports a series of experimental tests on sigma purlins interior‐one‐flange (IOF) loading condition. The tested specimens employ two different section geometries and three different bearing plate widths. The test results show that all the specimens failed by web crippling, however two distinct failure modes and corresponding load‐deformation curves are observed depending on the section geometry. To investigate further the effect of web geometry on the IOF web crippling strength of sigma sections, an FE model was developed and validated against the reported test results. Following successful replication of the experimental observations, a comprehensive parametric study was performed and several sigma sections were numerically tested. Furthermore, the applicability of a novel slenderness‐based design approach previously proposed by Duarte and Silvestre for the web crippling design of channel sections is assessed and design recommendations are proposed. [ABSTRACT FROM AUTHOR]

• A mathematical model for buckling and post-buckling under different torsion-bending ratios were established. • The buckling stability and load carrying capacity of the wing box were analyzed by the experiments. • By establishing a refined simulation model, the impact of different torsion-bending ratio on failure mode of the wing box. In this paper, a mathematical model for the effect of different torsion-bending ratios on buckling and failure loads under complex operating conditions was proposed, and the buckling, post-buckling and failure behavior and mechanism of carbon fiber composite wing box were studied by combining experiments and simulations. A high-precision computational simulation model was established by considering detailed bolt arrangement information, as well as damage and failure of composite materials. The predicted buckling loads, failure loads, and damage modes are in good agreement with the experimental results. The results show that, under the condition of constant bending moment, as the torque increases, the linear strain of the box section remains consistent, while the shear strain increases significantly, leading to a change in the buckling mode and failure distribution. When the torsion-bending ratio is less than 2.0, the loading form of the structure is greatly affected by the torque. On the contrary, the buckling and failure loads are exponentially close to the pure torsional state. The mathematical model and simulation model in this study can provide an important reference for the structural design and failure mechanism analysis of large composite wing boxes. [ABSTRACT FROM AUTHOR]

An assessment method is developed for the panel reliability of ship-shaped Floating, Production, Storage and Offloading units (FPSO). Not only axial compressive loads but also internal and external lateral pressures are taken into account in the reliability assessment. Beam-column buckling and flexural-torsional buckling are regarded as two primary failure modes of stiffened panels. Variability of corrosion wastage and material properties are accounted for in modelling the panel’s time-dependent ultimate strength. Uncertainty of axial compressive loads induced by hull girder bending is evaluated based on probabilistic characteristics of still-water bending moment (SWBM) and vertical wave-induced bending moment (VWBM). A case study is performed to demonstrate this method and the effects of the lateral pressure, the return period of the extreme value of VWBM, the environmental severity factor, and the corrosion wastage on the panel reliability are investigated. Sensitivity measures for random variables are also carried out. [ABSTRACT FROM AUTHOR]

Flange edge stiffeners increase the ultimate moment capacity of cold-formed channel sections. At the same time, they cause complexity to the buckling failure mode of the section. There is a lack of experimental research on the failure mode of sections with a partially stiffened element, such as channel sections with edge stiffeners, in which a distortional buckling mode can be observed. The focus of recent studies is mainly on the behaviour of the whole section as one member under bending without any concern about the relationship between the web and flange ratio. In this study, an extensive experimental analysis of 42 cold-formed channel sections was used to explore the failure behaviour of cold-formed channel sections under pure bending. The sections were made from cold-formed G450 steel with a nominal thickness of 1.6 mm. The results of the pure bending experimental investigations are used to describe the relationship between the web and flange ratio and the failure deformations. It is also shown that the current international cold-formed steel specifications over-predict the buckling coefficient of partially stiffened elements with high aspect ratio values. The experimental results are used to propose revisions to current international cold-formed steel specifications. [ABSTRACT FROM AUTHOR]

To determine the load-bearing capacity of cold-formed steel (CFS) beam–column members, closed formed interaction formulas are generally used in most current design guidelines by linearly combining axial load and biaxial bending moment effects. However, this approach ignores the nonlinear interactions between these actions. To evaluate this issue, in this research the structural behaviour of eccentrically loaded beam–column CFS lipped and sigma channel profiles are investigated experimentally and analytically under simultaneous effects of axial loads and biaxial bending moments. Detailed Finite Element (FE) models are developed using ABAQUS software by considering geometric imperfections and actual material properties obtained from coupon tests, and validated against experimental data to estimate the strength and buckling behaviour of CFS beam–column elements. A total of 4480 FE analyses are then performed on 500 mm and 2000 mm long CFS members with different lipped and sigma channel sections subjected to a wide range of eccentricity values in various directions. The results of the analyses indicate that the failure modes are mainly dependent on the stress distribution of the cross-section generated by the combined actions. It is also demonstrated that regardless of the selected load combination, using sigma sections for the short beam–column members generally results in higher strength by up to 42% compared to those with lipped channel sections. It is shown that AISI and Eurocode underestimate the capacity of CFS beam–column members, on average, by around %50 and %25, respectively. However, the recently proposed extended Direct Strength Method (DSM) can generally provide more accurate strength predictions, especially in the case of short beam–column elements. • Buckling behaviour of CFS beam–columns investigated under axial load & biaxial bending interaction. • 4480 FE models of lipped and sigma channels developed and validated against experimental results. • Effects of element length, thickness and load eccentricity in various directions were investigated. • Sigma sections showed up to 42% higher capacity than lipped channels especially in shorter members. • Extended DSM provided more accurate strength predictions by 50% compared to AISI and EC3. [ABSTRACT FROM AUTHOR]

• Tests and numerical analysis of specimens with large width-thickness ratios. • Elastic-plastic local buckling and its effects on hysteretic behaviour of beam-columns. • Design formula for bearing capacity of Q690 high strength beam-columns. To evaluate local buckling and its effect on the hysteretic performance of high-strength Q690 thin-walled H-section beam-columns, cyclic testing was carried out on four H-section columns composed of plates with a nominal yield strength of 690 MPa. Based on China's standard for the design of steel structures (GB 50010-2017), the four H-section columns are categorized as S4 and S5 sections, and the axial load ratio of the columns is 0.2 and 0.35. After the test, the failure mode, second-order effect of bending moment, hysteresis curve, bearing capacity, backbone curve, energy dissipation, ductility and stiffness degradation of the specimens were investigated. The failure mode of the specimens is elastic–plastic local buckling of the column bottom flange and web. The ductility coefficient of the specimens is 2.08–3.04, and they have certain specific deformation and energy dissipation capacities. Following this, a finite element model was established to simulate the hysteretic performance of the Q690 thin-walled H-section beam-columns. The failure mode and hysteresis curve obtained by the finite element simulation corresponded well with the tests. Based on this agreement, a parametric study was carried out to investigate the influence of the flange width-thickness ratio, web width-thickness ratio, and axial load ratio on the local buckling and hysteretic performance of H-section beam-columns. The variation trend of the backbone curve and the bearing capacity were further investigated by the finite element parametric analysis. Finally, a prediction formula for the beam-column bearing capacity was proposed based on the finite element results. The comparison with the test results shows that the proposed formula has sufficient accuracy and can be used in engineering design. [ABSTRACT FROM AUTHOR]

Tubed-reinforced-concrete columns are gaining increasing usage in engineering practices, whereas research on their fire behaviour is still limited and mainly concentrated on unrestrained columns. Since end-restrained columns might behave differently in fire as compared to the unrestrained columns, the fire behaviour of square tubed-reinforced-concrete columns with end restraints was investigated via numerical modelling in this study. The axial and rotational restraints were modelled using linear springs and then validated against fire test results. The effects of end restraints on the failure mode, axial force and buckling length at failure and fire resistance, and on the evolution of deformations, internal force and bending moment during heating, of end-restrained columns were systematically analysed through parametric studies. The axially-restrained columns mostly undergo axial contraction only in fire; their typical failure mode is uncontrolled overall axial deformation, except for those columns of relatively high axial restraints. An increase in axial restraint leads to a nearly linear decrease of axial force at failure and a linear increase of fire resistance. For rotationally-restrained columns, the typical failure mode is also uncontrolled overall axial deformation. As the rotational restraint increases, the bucking length at failure decreases and the fire resistance increases, which is particularly significant when the rotational restraint is relatively low. A practical design method is proposed for the fire resistance design of square tubed-reinforced-concrete columns with either axial, or rotational, or combined axial and rotational restraints. Both constant and temperature-dependent end restraints have been adopted and the outcome is that they provide very similar results. [Display omitted] • An effective FEA model was built for the simulation of restrained columns in fire. • Paramatric studies on the fire performance of restrained TRC columns were conducted. • A structural fire design method was proposed for end-restrained TRC columns. [ABSTRACT FROM AUTHOR]

A systematic finite element based approach is presented to characterize the interaction between the bending moments and axial forces coming from the connected beams in 2D welded steel joints. The modelling technique is described in the paper, as well as the description of the interaction diagrams between axial forces and bending moments for a series of commercial steel sections. An initial imperfection is included in the finite element model to capture the possible buckling failure modes in the column web and the beam flanges. The approach predicts moment capacities that are very similar to those predicted by Eurocode 3 in the absence of axial forces. Interaction diagrams and moment rotation curves are shown for different levels of axial forces, as well as axial force versus displacements for different levels of bending moments. An investigation is also carried out that shows that the approach leads to axial-bending interaction curves that are path independent. Finally, a nonlinear exponential curve fitting is proposed for the axial-moment interaction diagram. • Finite element method to accurately model the resistance of 2D welded joints with axial force and bending moment interaction • Initial imperfection to capture the possible buckling failure modes in the column web and the beam flanges • Generation of axial force versus bending moment interaction diagrams • Path independent limit surfaces [ABSTRACT FROM AUTHOR]