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High strength steels (HSS) are becoming more common in engineering practice due to their improved qualities. They are standardized by the specific parts of product standard EN10025 and soon they will be also codified in the execution standard EN1090. Regarding design using HSS, EN 1993 − 1 − 1 gives stability design rules for columns, beams and beam–columns up to S460, whereas EN 1993 − 1 − 12 gives additional guidance for S500 up to S700 (based mainly on numerical work available at the time). Existing studies on flexural buckling of welded H, I and box columns in steel grades S460 to S960, even though limited, show that improved curves can be used for members in high strength steel (HSS). Recently, within the European Project STROBE, evaluation of the European stability design rules was carried out covering columns, beams, and beam–columns. The research was based on experimental programme covering 20 full-scale tests, residual stress measurements, advanced numerical models, analytical derivations, and statistical evaluation. Finally, it was possible to justify new, more accurate recommendations for the buckling curve selection for HSS members. This paper provides a summary of the project conclusions regarding the stability design of steel members in high strength steel. • Stability design using high strength steel. • Reliability of design rules using Eurocode 3. • Non-linear analyses with imperfections for welded I-section columns in high strength steel. [ABSTRACT FROM AUTHOR]

• 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]

Abstract: This paper presents an evaluation of the accuracy and safety of the design rules from Eurocode 3, for the fire resistance of stainless steel beam-columns, with and without lateral-torsional buckling. These evaluations are carried out performing an extensive numerical parametric study on beam-columns with equivalent welded H-cross-sections. In this study the influences of the residual stresses, the cross-sectional slenderness, the shape of the bending moment diagrams and the stainless steel grade are considered. New proposals for the design equations of stainless steel beam-columns in case of fire are presented. These proposals revealed to be safer than the design equations of Eurocode 3 when compared with numerical results. Additionally, the lateral-torsional buckling of stainless steel beams subjected to combined end moments and transverse loads in case of fire is also studied. [Copyright &y& Elsevier]

• Full-scale experimental tests on high strength steel columns. • Residual stresses and geometrical imperfection measurements. • Non-linear analyses with imperfections for welded I-section columns in high strength steel. • Comparison with design resistance according to Eurocode 3. The use of high strength steel (HSS) has been consolidated around the world because of its numerous advantages mostly for high-rise buildings and large span bridges. As it provides the possibility of a design with slender sections, substantial reduction in the structure weight is expected, but special attention should be given to the stability of the HSS compression members. However, the existing design codes for HSS columns are limited and based on experimental data related to normal strength steel (NSS) materials, which is responsible for an inaccurate resistance prediction. In this sense, the present paper aimed to investigate the buckling behavior of S690 HSS welded I-section columns failing by flexural buckling around the both principal axes and beam-columns failing by lateral torsional buckling. The experimental campaign contemplated 4 pin-ended columns, in which 2 were tested about their major-axis and the other 2 about the minor-axis, and also 2 beam-columns, including supplementary experimental to measure the geometric imperfections, residual stresses and material properties of the S690 welded I-section columns and beam-columns. In the following, a numerical model was built and validated against the experimental results and afterwards employed to perform a sensitivity study considering different membrane residual stress patterns. Finally, the European [1,2] , American [3] , and Australian [4] codes were assessed by comparing the design resistances with the results from the experimental tests and the collected test data of relevant studies, showing in general a considerable level of conservatism. [ABSTRACT FROM AUTHOR]

EN 1993-1-1 gives stability design rules for columns, beams and beam–columns up to S460, whereas EN 1993-1-12 gives additional guidance for S500 up to S700. Recent studies show that high strength steel members may be designed using improved buckling curves, where the enhanced behaviour is usually attributed to the improved material properties but mainly due to the more favourable residual stress distribution. The behaviour of unrestrained beams in HSS has not been widely studied. At present in EN 1993-1-1, the design rules for lateral-torsional buckling of beams are not dependent on the steel grade, meaning that the code does not distinguish between beams in conventional strength steel or HSS. In pursuit of an answer to the mentioned shortcomings, the present research is based on the experimental programme covering 12 full-scale tests, residual stress measurements, advanced numerical models and analytical derivations. The experiments cover different steel grades up to S690, welded and hot-rolled sections, homogeneous and hybrid (flanges in HSS and web in mild steel), double and mono-symmetric sections as well as variations in the cross-section class. This paper provides an overview of the experimental programme, discusses the results for lateral-torsional buckling of beams, and presents an advanced numerical model that was calibrated to the experimental results including the measured residual stress distribution and geometrical properties of the members. The numerical model was explored to assess various assumptions for the member imperfections, and these are further compared with code recommendations. • Full-scale experimental tests on high strength steel beams hybrid and homogeneous. • Lateral-torsional buckling of beams with doubly and monosymmetric cross-section. • Residual stresses and geometrical imperfection measurements. • Non-linear analyses with imperfections for welded I-section beams in high strength steel. • Comparison with design resistance according to Eurocode 3. [ABSTRACT FROM AUTHOR]