This article provides an overview of the various support structures for offshore wind turbines and addresses the challenges that arise for the different design variants. First of all, the existing types of support structures are explained and their benefits and shortcomings discussed. Following that, the focus is on material fatigue and its analysis, which is of great importance due to the cyclic loading on the structures. A central topic of this article is the experimental evaluation of fatigue strength using large-scale test setups and state-of-the-art measurement methods. Critical and complex design details such as welds for extremely thick plates, tubular joints, grouted connections, large HV bolts and ring flanges are investigated to improve methods of analysis. Further, the new series of German standards (DIN 18088) for support structures for wind energy turbines and platforms is addressed. Finally, these topics are summarized and the importance of offshore wind energy for the transition to cleaner energy is emphasized.

The research into an innovative steel-concrete-steel composite (SCSC) plate presented here is being carried out in the Steel Structures Research Unit of the Institute of Structural Engineering at TU Wien. The aim of the research is to use the SCSC plate for single-track, short-span railway bridges in Austria. The SCSC plate is designed to be a loadbearing structure in the transverse direction, transferring the loads to the main steel girders of the bridge cross-section. An engineering model will be presented in this paper to reproduce the results of the ABAQUS finite element analysis software [1]. Using this simple framework model, which includes springs, it is possible to consider cyclic loading and inelastic slip, too. This results in an increase in the global vertical displacements and a change to the internal forces, which are discussed in the paper.

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Different post-weld treatment methods have been developed to enhance the fatigue strength of welded steel structures and extend the service lives of their components. High-frequency mechanical impact (HFMI) treatment and tungsten inert gas (TIG) remelting are two methods that have attracted considerable interest in recent decades. This paper presents the results of a study of fatigue life extension for pre-fatigued welded steel details which can be achieved using HFMI treatment and TIG remelting. More than 250 fatigue test results were collected - including different details such as butt welds, longitudinal attachments, transverse attachments and cover plate attachments. HFMI treatment was found to extend the life considerably when the specimens treated were free from cracks or when existing cracks were < 2.25 mm deep. TIG remelting could extend fatigue lives even with cracks > 4 mm deep. In comparison to TIG remelting, HFMI treatment results in a longer fatigue life extension for pre-fatigued details, provided existing cracks are < 2.25 mm deep. Regarding TIG remelting, the depth of possible remaining cracks was found to be a substantial parameter when assessing the degree of life extension.

This study presents a numerical investigation into the cyclic performance of skewed special moment frame (SMF) connections that include composite concrete slabs. The study uses advanced finite element simulations to investigate the behaviour of shallow (W14×), medium (W24×) and deep (W33×) steel column sections with three levels of beam skew (10, 20 and 30 degrees) for both bare-steel and composite (steel-concrete) construction. To account for complex torsional boundary conditions that may affect the skewed connection response, prequalification-type analyses were conducted considering the middle storey of a three-storey, two-way moment frame configuration. In the analyses, all skewed configurations achieved at least 0.04 rad of connection rotation during the cyclic loading protocol prior to a 20 % reduction in moment capacity. When a composite concrete slab was added, column twisting and column flange yielding increased at large skew angles (30 degrees) during positive moment cycles.

This article presents a comprehensive review of the state of the art in composite cold-formed steel flooring research over the past couple of years. The most relevant and significant literature references were reviewed to provide some insights into trends and developments in composite cold-formed steel floors. Advantages of this type of composite flooring system are also highlighted. A broad description of mainly two types of composite floor - mainly consisting of cold-formed steel and concrete, and cold-formed steel and timber-based floorboards - are outlined in this study. The experimental and numerical investigations that have been carried out worldwide are likewise discussed in the paper. The most important aspects covered are shear connection behaviour and the flexural and dynamic behaviour of the floors. There is also a brief description of fire testing.

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This paper investigates the design of steel-concrete composite beams, with an emphasis on the shear connectors as specified in Eurocode 4-1. A structural safety inaccuracy is identified and analysed. Improvements for the future design code are proposed.

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In memoriam
PHD-THESIS: Design of cast steel components under cyclic loading

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The building of the San Giorgio bridge in Genoa re-establishes the connection between autoroutes A10 and A7 after the tragic event of the Morandi bridge collapse of 14 August 2018.
The bridge deck layout required the use of a torsionally rigid section. This was achieved, in particular, with two longitudinal beams spaced 7.00 m apart, a curved, calendared soffit and a top slab made of composite concrete.
The new bridge was opened on 3 August 2020, finally revealing the idea of the architect, Renzo Piano: A big, white vessel moored in the valley, a bridge that enters a dialogue with the sea, with the wind, with light, a structure that encourages builders to continue building bridges as links between territories and symbols of union. (Sarcina, G. et al., pp. 14-21)

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Extended keynote paper of Eurosteel 2021
This paper provides an overview of recent work regarding the revision of Eurocode 3 on the European level. Selected scientific and technical issues are described and there is a summary of the activities executed within European Standardization Committee CEN/TC250/SC3 “Design of Steel Structures” chaired by Prof. Dr.-Ing. Ulrike Kuhlmann. This includes the description of current normative developments for the 2nd Generation of Eurocodes, which aim at evolution through improvements and harmonization of the existing codes. In addition, a technical review of selected rules is given for several issues, which support the code revision and reflect well the recent tendencies in steel structures.

A bridge that slowly crosses Polcevera Valley, step by step, in silence, almost asking for permission; a bridge that will be like a ship, a big white vessel moored in the valley; a bridge that can't be banal in its simplicity; a bridge made by Italian excellences who, through an intense activity of coordination, planning and the work of expert professionals, had to carry out the work as soon as possible. It is through the words of its designer, architect and senator for life Renzo Piano, that we want to introduce the new Genova San Giorgio Bridge. The steel contractor's approach to the realization of the work is summed up in the words of the CEO Giuseppe Bono: “The bridge must be an expression and a symbol of the country all over the world. All this is Fincantieri, what we have done so far and what we will do. Fincantieri represents something unique in our country, with introduction of its unparalleled integration model.” The steel contractor has made the replacement of former Morandi bridge possible only two years after the tragic events of 14 August 2018, bringing the road system of the Autostrada dei Fiori motorway back to normal.

This paper presents the analytical results of six steel bolted T-connection models and four steel bolted beam-to-column connection models with top and seat angles. This study was undertaken to analyse the influence of bolted T-connections instead of welded connections and the influence of angles with and without stiffeners on the behaviour of the beam-to-column connections under hysteretic loading. The aim was to compare the energy dissipation of different connections with each other. The energy dissipation characteristics are obtained from the main characteristics of moment-rotation hysteresis curves. This study shows that the energy dissipation decreased by about 2-29 % and 2-13 % for bolted T-connection and top-and-seat-angle connection models respectively after switching from one cycle to another in five hysteretic loadings.

Steel plate shear walls (SPSW) are being increasingly used in steel or concrete structures as lateral load-resisting systems. Shear buckling is one of the major shortcomings of the SPSW and so to address this issue, buckling-restrained steel plate shear walls (BRSPSW) have started to appear. Owing to the novel concept of this structural system, this paper aims to investigate the effect of factors influencing the response of BRSPSWs. For this purpose, a parametric study was conducted using ABAQUS software. Based on the results acquired from the hysteretic curves, an increase in the concrete compressive strength does not markedly affect the ductility and energy dissipation capacity. Moreover, it was observed that as the width of the gap between concrete panel and steel plate grows, the energy dissipation and response modification factor are reduced. Besides, the results indicate that as steel strength increases, so energy dissipation increases from 0.7 to 11.7 %. Accordingly, based on a comparison between the rate of improvement in shear capacity arising from an increase in the strength of the concrete panels, frame and steel plate, it is concluded that it would be much more rational to increase the concrete strength so that a high shear capacity can be achieved for the BRSPSW. Lastly, in all models, as the gap width increases from 0 to 20 mm and 20 to 35 mm, ductility decreases by 41 and 30 % respectively.

This paper describes how a wavelet model comprised of a linear combination of sine terms is capable of representing the cross-section inertia variation along the length of cellular beams. This allows the efficient computation of deflections of cellular beams when these are deployed as a part of steel-concrete composite flooring systems. This method does not involve purely statistical approaches or piece-wise integration of moment-curvature relationships that lead to cumbersome matrix approaches and complicate the assessment of deflections. Despite its simplicity, the proposed approach is found to be reliable as it successfully predicts displacements obtained through finite element model representations of more than 260 cases with errors smaller than ±5 %. Furthermore, the proposed analytical description of cross-section inertia along the beam length is defined by only three parameters that can be inferred through linear expressions considering the geometrical characteristics of a perforated beam, namely, the ratio of flange to web thickness, the second moment of inertia of the steel beam and the ratio between beam length and depth, making it easy for widespread application by practitioners.

The Committee on the Design, Construction and Production of Aesthetic Architecture, established by the Japanese Society of Steel Construction (JSSC), has for a long time stood for the promotion of appealing architecture - particularly in steel-glass structures. Such aesthetic architecture, despite being very modern, often expresses the tradition of the particular location and its culture. The choice of structural configuration is one of the tools for achieving relevant architecture. This paper, introducing attractive and innovative steel structures combined with glass, shows several examples typical of this trend in Japan.

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International Colloquium on Stability and Ductility of Steel Structures 2022 in Aveiro, Portugal
STCO Online Live Seminar #2 with Prof. Knobloch, Prof. Kuhlmann and Prof. Taras: Structural member stability in the second generation of Eurocode 3
New European Bauhaus: European Commission launches design phase

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A 2 stories, 15 m cantilever, called the “Effet Wow” being erected in the 8th floor in Issy-Les-Moulineaux near Paris. An exceptional space is created to accommodate 700 m2 of restaurant and bar amenities on the new Orange's Headquarters (Foto: Bouygues Bâtiment Îles de France. S. paper pp. 264 ff).