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In Eurocode 3 (2005) the buckling curve approach is adopted for verification of prismatic columns and beams. It has the flexibility of adjusting imperfection factors according to their sections, steel grade and other relevant parameters. However, for generic single members, built-up or not, uniform or not, with complex support conditions or not, the available possibilities for such cases are the General Method given in clause 6.3.4 of Eurocode 3 (2005) or advanced numerical simulations. The applicability of the general method, however, is limited and in some aspects inconsistent (Simões da Silva et al., (2010)). As an alternative, the stability of non-uniform members can be analysed using numerical GMNIA which is a time-consuming procedure and the output is highly dependent on the experience of the user. In this paper, a novel general formulation for stability design of steel columns, beams and beam-columns with variable geometry, loads and complex support conditions is presented. The verification is based on the buckling mode as shape of the initial imperfection with an amplitude previously calibrated for the standard prismatic simply-supported columns and beams in Eurocode 3. The verification is performed as an interaction equation where the first and second order contributions to the longitudinal stress utilization are added for each cross-section along the member length. Several aspects regarding the member behaviour in the context of a specific buckling mode are discussed and finally, validation of the approach is carried out to show its consistency and accuracy. [ABSTRACT FROM AUTHOR]

The prediction of the behaviour of joints relies on experimental and numerical tests that provide accurate information for the characterization of the various joint components. This paper presents the calibration and validation of a parametric FE model of a beam-to-column double extended end-plate steel joint, using test results, and characterizes the web panel components using the validated FE models. The model implemented in the ABAQUS FE package which takes into account the non-linear geometrical and material behaviour, non-linear contact and slip. The calibration/validation of the model is based on results from an experimental research programme on three double-extended end-plate partial-strength beam-to-column joints. The behaviour of the joints is characterized both globally and in terms of the critical components. The experimental and numerical results are compared, revealing good agreement, allowing their further use in the more detailed components assessment. Thus, based on the validated stress and deformation fields of FE results, a procedure is proposed to extract the force-deformation behaviour of the column web components. The results are compared with those obtained from Eurocode 3 and from the literature. [ABSTRACT FROM AUTHOR]

Highlights: [•] Numerical calibration of mechanical problems involved in steel-to-concrete joints. [•] Validation of numerical models by means of benchmark examples. [•] Calibration of slab longitudinal rebars model (governing component of the joint). [•] Reinforcement–concrete interaction approximating the real bond–slip behavior. [•] Composite beam simulated applying solid and spring elements. [Copyright &y& Elsevier]

• Data on residual stresses measurements were collected. • Experimental tests on residual stress distribution were carried out. • Numerical welding simulations were performed for the tested specimens. • Statistical characterization of the measured and collected data is proposed. Residual stresses have major influence on the stability of steel members. It is well-known that, due to the differences in manufacturing procedures, the residual stresses for welded and hot – rolled members are rather different. In the same way, despite several studies on residual stresses distribution and magnitude for hot-rolled members were already done, for prismatic and tapered welded I section steel members the investigation is still very scarce. In the current work, an experimental programme on the buckling resistance of tapered members, with different tapering ratios and section heights, was conducted and residual stress measurements were carried out using the sectioning method. Numerical simulations of the heat input during welding were also performed in order to predict the residual stress fields. A statistical analysis of the residual stresses distribution for welded I section members was performed, using the experimental and numerical results, as well as literature data. Systematized information on residual stresses distribution and magnitude was generated and some guidelines for the statistical characterization of residual stresses in welded members were proposed. [ABSTRACT FROM AUTHOR]

Tapered steel members offer a better cross-section utilization along the member, which makes them an interesting and more economical alternative to prismatic ones. Yet, the design methodologies available do not provide a clear and sufficient guidance for the stability verification of such members. Alternatively, nowadays, the existing computer capacity and software programs provide an accessible and rapid means of reproducing the structural performance of members and systems, although they require beforehand validation to assure the plausibility of their predictions. For that, a full-scale experimental programme on non-uniform members was carried out, covering column, beam and beam-column tests. The test results are used to validate a numerical model commonly used for the assessment of stability design rules. In this paper, firstly, a global overview of the experimental tests is presented, which covers the test layout, member dimensions and the supplementary tests, essentially characterization of material properties, geometrical dimensions and imperfections, and residual stresses. The key results from each experiment are presented and discussed, they are further compared with numerical and analytical estimations of the member resistance. Finally, the experimental results provide physical validation of the design method proposed in Marques et al. (2012) for web-tapered columns. [ABSTRACT FROM AUTHOR]

Tapered steel members are often chosen instead of prismatic due to a better cross-section utilization along the member, which makes them an interesting and more economical alternative. Although EN1993-1-1 offers several methodologies for the stability verification of steel members and frames, it does not provide a clear guidance for the stability design of such members. Recently, the research group has provided simplified stability verification methodologies for tapered columns and beams. The developed methodologies are based on analytical derivations which were validated with advanced numerical simulations. In order to improve the accuracy of the proposed procedures, full-scale experimental tests on tapered columns, beams and beam-column were carried out. The experiments are used to calibrate a numerical model, incorporating all relevant parameters, such as: geometrical imperfections (local and global) and material imperfections (residual stresses). In this paper, firstly a global overview of the experimental programme on web-tapered steel members is given. The key results from each experiment are summarized; they are further used for the calibration of an advanced numerical model. [ABSTRACT FROM AUTHOR]

• Novel insights into bolted connections to I-section webs and tubular column chords under out-of-plane loads via experimental testing. • Calibration of numerical models with experimental results for improved accuracy. • Extensive analysis of single and double bolt row connections in a parametric study to identify key parameters affecting face plate behavior. • Comparative analysis of existing methods for initial stiffness estimation using parametric analysis data, revealing their limitations. • Proposal of a refined analytical method for initial stiffness prediction, validated by experimental data. This paper presents a comprehensive investigation into the behavior of column webs/faces under out-of-plane loading within steel joints. The experimental component of the study involves testing five profiles, encompassing both open and closed sections with varying web slenderness and steel grade, subjected to direct out-of-plane tensile loads through bolted connections, utilizing both single and double rows of bolts. Concurrently, numerical simulations are conducted using finite element models, thoroughly calibrated with the experimental results. Drawing upon the calibrated numerical models, the paper systematically explores the influence of key parameters, including web slenderness, bolt arrangement, and analysis methods, through a parametric study involving 167 cases. A careful comparison of the observed behavior of the component from experimental tests, numerical models, and analytical models for initial stiffness is presented. Finally, the initial stiffness formulation derived from a recent model developed by the authors is improved to align with the observations from the experimental and numerical results. [ABSTRACT FROM AUTHOR]

An experimental investigation of eight statically loaded extended end plate moment connections was undertaken at the Delft University of Technology to provide insight into the behaviour of this joint type up to collapse. The specimens were designed to confine failure to the end plate and/or bolts without development of the full plastic moment capacity of the beam. The parameters investigated were the end plate thickness and steel grade. The results show that an increase in end plate thickness results in an increase in the connection flexural strength and stiffness and a decrease in rotation capacity. Similar conclusions are drawn for the effect of the end plate steel grade, though no major variations in the initial stiffness are observed. The failure modes involved weld failure in two test specimens, nut stripping in four tests and bolt fracture in the remaining, always after significant yielding of the end plate and bolt bending. Comparisons of the joint ductility and the corresponding equivalent T-stub for the end plate side are drawn. [Copyright &y& Elsevier]

In this paper, an extensive numerical study is performed with the aim to investigate the post-buckling behavior of simply supported cylindrically curved steel panels subjected to a pure shear load. The main objective is to understand the influence of geometrical parameters, such as curvature and aspect ratio, but also it is aimed to examine how the level of the constraint of the edges affects the ultimate shear resistance. Finally, a new set of formulas are numerically derived, which allow estimation of the ultimate shear reduction factor of unstiffened curved panels with three different types of edge constraints, for various curvatures (up to 50) and various aspect ratios (up to 5). Moreover, the formulas use a similar base form as the one available in EN 1993-1-5 for the prediction of the ultimate shear load of a flat panel. • Cylindrically curved panels subjected to shear load may exhibit a highly unstable initial post-buckling behavior. • Ultimate shear strength depends on geometry of panel (Z and α), boundary conditions and initial imperfections. • Proposed formulas predict the reduction factor χ w , as a function of slenderness parameter, similar to EN 1993-1-5. • The buckling curves (χ w - λ ¯ w ) can be easily calculated for Z ≤ 50, 0.5 < α ≤ 5, and three different in-plane edge constraints. • Formulas cover the most common ranges of the curvature parameter used in bridge, offshore and airplane applications. [ABSTRACT FROM AUTHOR]

Curved steel panels are increasingly used in several engineering fields yet, design provisions to predict their strength are mostly empirical and with a limited range of application. Consequently, the aim of this paper is to propose expressions for the prediction of the ultimate load of curved panels under uniaxial compression based on a physically robust approach, using semi-analytical methods (SAM). The formulation is based on large deflection theory incorporating initial imperfections and geometric nonlinearity and a first yield criterion applied to the von Mises' stresses is employed. The ultimate load is calculated for a wide parametric variation of geometries considering different amplitudes and patterns of imperfections and boundary conditions. In order to assess the influence of the geometry on the resistance of the curved panels, the curvature parameter, Z , the aspect ratio, α , and the width over thickness, a / h , are varied with the objective to cover most cases of unstiffened curved panels with practical applicability. The influence of these parameters is calculated and validated with the results of the FEM showing good agreement. • The ultimate resistance of curved panels is established based on semi-analytical methods. • Expressions for the elastic non-linear large-displacement behaviour are presented. • Accurate expressions to predict the ultimate load are proposed. • Validation with FEM simulations is performed for a wide parametric variation. [ABSTRACT FROM AUTHOR]

In this paper, an extensive numerical study is performed with the aim to investigate the elastic buckling behavior of simply supported cylindrically curved steel panels subjected to a pure shear load. The main objective is to understand the influence of geometrical parameters, such as curvature and aspect ratio, but also of the edge in-plane constraints. Finally, a new formula is proposed, which allows simple and accurate estimation of the critical shear stress of unstiffened curved panels with three different types of edge constraints, for various curvatures (1 < Z ≤ 100) and various aspect ratios (up to 5). • Cylindrically curved panels subjected to shear load show very complex behavior. • Buckling mode depends on curvature Z , aspect ratio α and in-plane edge constraints. • Proposed formulae enable accurate prediction of the shear buckling coefficient k τ. • Formulae can replace the outdated and impractical NASA monographs. • Formulae extend EN1993-1-5 to a wide range of the curvature parameter (Z ≤ 100). [ABSTRACT FROM AUTHOR]

Highlights • A semi-analytical method for the post-buckling behaviour of stiffened curved panels is proposed. • The large deflection model accounts explicitly with the number and geometry of the stiffeners. • The results obtained by the proposed procedure are compared with FEA yielding good results. • Closed-form analytical expressions are derived based on SDOF approximations. Abstract Stiffened curved steel panels are increasingly used in structural applications in civil, naval and offshore engineering. Due to the incorporation of stiffeners these elements are able to withstand substantial loads with low material usage. However, design provisions to predict the strength of these elements are practically non-existent. The aim of this paper is to present a robust semi-analytical procedure for the prediction of the post-buckling behaviour of stiffened cylindrically curved steel panels under uniform uniaxial compression. The semi-analytical procedure is based on an orthotropic model with the number and geometry of the stiffeners properly taken into account. The procedure is based on nonlinear stability models based on large deflection theory incorporating initial imperfections and geometric nonlinearity. The problem is solved and the equilibrium paths are obtained through the Rayleigh-Ritz method. The validity of these computational models is assessed with the results of finite element analyses for different curvatures, aspect ratios, number and geometry of stiffeners yielding good results. Finally, a design-oriented closed-form expression is derived for the second-order elastic behaviour of the stiffened panels. [ABSTRACT FROM AUTHOR]

This paper presents a design proposal for the out-of-plane buckling resistance of prismatic beam-columns subject to axial compression and uniaxial major-axis bending that was developed based on the well-known Ayrton-Perry format. Firstly, the relevant theoretical background is summarized, closely following the theoretical derivation performed by Szalai and Papp (2010). Secondly, the required transformations for the engineering application of the design procedure are detailed and extended to arbitrary bending moment distributions. Appropriate generalized initial imperfection factors for the out-of-plane buckling of beam-columns are defined so as to achieving complete consistency across the stability verifications for columns, beams and beam-columns. The proposed procedure is subsequently validated against a large set of advanced numerical simulations. A good agreement was found between the numerical results and the estimates provided by the proposed design procedure, both in terms of the overall trend and the specific quantitative results. Based on a statistical assessment, the comparison with the interaction expression of Eurocode 3 (2005) (method 2) showed that this proposal slightly outperforms the Eurocode procedure, both in terms of average values and dispersion of results. [ABSTRACT FROM AUTHOR]

This paper analyses the microstructural and mechanical properties of carbon steel coupons produced by CMT-WAAM. The strategy adopted in the fabrication of the test specimens using a robotised facility is explained. Then, the results of the mechanical characterization performed using as-built and machined samples, extracted in several directions (0°, 45°, 90°) relative to the material deposition trajectory, are analysed. The yield and ultimate tensile strengths were determined by performing tensile tests and the Young's modulus was determined using ultra-micro hardness measurements. A deep microstructural characterization was also performed by optical microscopy for establishing a direct relationship between the manufacturing procedures and the registered mechanical properties. The failure micro-mechanisms associated with the building orientation and the surface condition was also examined by scanning electron microscopy. It was found out that the additive manufactured material has isotropic tensile properties, which result from the formation of an annealed microstructure upon cooling from the successive CMT-WAAM thermal cycles. The machined specimens exhibit higher strength and ductility than the as-built ones. The fracture surfaces of both machined and as-built coupons showed ductile failure. The results of the uniaxial tensile tests indicate that the machined and as-built WAAM steel walls satisfy the requirements of a structural steel grade as specified by Eurocode 3. • Mechanical characterization of CMT-WAAM carbon steel in different directions with respect to the build direction. • Characterization of as built and machined specimens. • Microstructural analyses and hardness study of CMT-WAAM carbon steel. • Analyses of the fracture surfaces by SEM. [ABSTRACT FROM AUTHOR]