This paper proposes the use of existing European buckling curves to check the resistance of heavy wide flange quenched and self-tempered (QST) sections made from high-strength steel, failing by flexural buckling. The buckling curves are evaluated according to the statistical procedure given in Annex D of EN 1990 using finite element analyses. The residual stress model as described in a related paper was used to define the initial stress state of the column in the finite element model. A large database was created containing the ratio between the elasticplastic buckling resistance obtained from finite element analysis and the buckling resistance obtained from the proposed buckling curve for a wide set of column configurations from which a partial factor γ Rd was deduced. Two different section types were investigated: the stocky HD and more slender HL type, featuring a height-towidth ratio (h/b) of approximately 1.23 and 2.35, respectively. Based on the criterion that the partial (safety) factor γ Rd should not exceed 1.05 it is suggested to check the buckling response of a heavy HD section according to buckling curve "a 0 " or "b" when failing by strong-axis or weak-axis buckling, respectively. HL sections are to be designed according to buckling curve "a" for strong-axis buckling and buckling curve "b" for weak-axis buckling.

This paper proposes a new method to build a probabilistic fire demand model (PFDM) to investigate the structural behaviour of a steel pipe-rack located within an industrial installation and exposed to a localised fire. The PFDM will serve to develop fire fragility functions to be used either in a fire risk assessment or in a fully probabilistic structural fire engineering (PSFE) framework. The cloud analysis (CA) was exploited to build a PFDM based on different engineering demand parameters (EDP) -intensity measures (IM) pairs. In particular, the analysis was applied to a prototype steel pipe-rack integrating an industrial plant in Italy. In order to cover a wide range of plausible fire scenarios and to introduce uncertainties in the fire model, 539 fire scenarios were examined by varying the fire diameter, the fire-structure distance and the fuel. The selection of the fire diameters was based on parametric analyses quantifying liquid flow through orifices and pipes. The thermal impact of the pool fires on the structure was analysed using the LOCAFI localised fire model and the thermo-mechanical response of the pipe rack was evaluated by means of finite element analysis. Based on the structural analysis outcomes, it was found that the interstorey drift ratio (ISDR) -average heat flux impinging the structure (HFavg) EDP-IM pair was the most efficient and was also characterised the highest relative sufficiency among the other pairs. Moreover, it has to be noted that for this type of case study, the CA revealed to be a suitable and versatile tool to build a PFDM.

Document VersionAuthor's version before peer-review Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Simoes da Silva, L., Tankova, T., Marques, L., Kuhlmann, U., Kleiner, A., Spiegler, J., ... Popa, N. (2017). Safety assessment across modes driven by plasticity, stability and fracture. In 8th European Conference on Steel and Composite Structures (EUROSTEEL 2017), September 13-15, 2017, Copenhagen, Denmark (pp. 3689-3698). (CE/Papers; Vol. 1, No. 2-3). DOI: 10.1002/cepa.425 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. ABSTRACTThe European design rules for steel structures in EN1993 cover various failure modes that were developed using different methodologies in terms of accuracy and safety. Consequently, the safety level of these design rules is not homogeneous throughout their own field of application, as well as in comparison between different rules. Safety is regulated by partial factors for the various loads and resistances, respectively. EN 1990 -Annex D offers a procedure for the reliability assessment of resistance functions, based on a semi-probabilistic approach. However, its application is not straightforward in many cases concerning steel design rules and several additional assumptions are necessary to ensure that a target probability failure is achieved. Moreover, the design rules are calibrated using certain variability values for the relevant parameters, such as material properties, geometric properties and imperfections. It is therefore required to appropriately characterize the statistical distributions of these basic variables in order to comply with the safety assessment procedure. The present research work, carried out in the ...

Recently completed experimental steel beam-column connection tests on the largest specimens of reduced-beam section specimens ever tested have shown that such connections can meet current seismic design qualification protocols, allowing to further extend the current AISC Seismic Provisions and the AISC Provisions for Prequalified Connections for Special and Intermediate Steel Moment Frames. However, the results indicate that geometrical and material effects need to be carefully considered when designing welded connections between very heavy shapes. Understanding of this behavior will ease the use of heavier structural shapes in seismic active areas of the United States, extending the use of heavy steel sections beyond their current use in ultra-tall buildings. To better interpret the experimental test results, extensive detailed finite element analyses are being conducted on the entire series of tests, which comprised four specimens with beams of four very different sizes. The analyses intend to clarify what scale effects, at both the material and geometric level, influence the performance of these connections. The emphasis is on modeling of the connection to understand the balance in deformation between the column panel zones and the reduced beam section, the stress concentrations near the welds, the effects of initial imperfections and residual stresses and the validity of several damage accumulation models. The models developed so far for all four specimens have been able to accurately reproduce the overall load-deformation and moment-rotation time histories.

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