In 2002, construction work for the largest combined railroad/road bridge in India started. The Bogibeel Bridge owes its name to a secluded village in the tri-border region of India, Myanmar, and the PR China, where the Brahmaputra leaves the Himalaya. MAURER supplied 164 spherical bearings to be placed between the bridge deck and the piers. The bearing specialists from Munich were awarded the contract because they succeeded in designing bearings capable of transmitting the extreme structural loads of 2,800 t, yet fitting into the confined space on the piers. (© MAURER SE)

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Extended version of the Tomá Vraný SDSS Award 2019
The method of the equivalent compression flange simplifies the verification of lateral torsional buckling of steel beams to flexural buckling of an equivalent part of the cross-section that is in compression. The current simplified method is based on outdated normative rules and the design results may be both, uneconomic and non-conservative. To remedy these shortcomings, the simplified method is modified based on the basic structural behaviour of steel beams taking into account the effects of material, cross-sectional geometry and residual stresses. This paper presents a comprehensive experimental study on the lateral torsional buckling behaviour and residual stresses of welded doubly- and mono-symmetric I-shaped steel beams. Moreover, an improved simplified method of the equivalent compression flange is proposed for design purposes.

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
This work reports on the results of an ongoing investigation of the direct strength method (DSM) design of hot-rolled steel equal-leg angle columns with pinned (spherically hinged) supports and short-to-intermediate lengths, i.e. buckling in flexural-torsional modes. It extends the scope of similar studies involving cold-formed steel angle columns with the same characteristics (but higher leg width-to-thickness ratios). After collecting the experimental and numerical failure loads available in the literature concerning columns with several geometries, the paper addresses the mechanical reasoning behind a DSM-based design approach proposed in the context of fixed-end and cylindrically hinged cold-formed and hot-rolled steel short-to-intermediate angle columns, which must be modified to handle spherically hinged supports. After that, the failure loads gathered are used to assess the quality of their estimates using this design approach, namely, by determining LRFD resistance factors. It is shown that this approach can be successfully applied to predict hot-rolled steel simply supported angle column failure loads, leading to LRFD resistance factors above 0.90.

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Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
Preliminary numerical and experimental investigations by the authors have highlighted the fact that the stiffness of the rotational restraints at the gusset plates near the ends of members are crucial for the prediction of the compression member capacities of bolted angles. Consequently, analytical models for estimating appropriate spring stiffness values have been developed for several practical applications in buildings and two-bolt connections at both ends of a member. The connection details investigated comprise a simply fixed gusset plate, a connection to the flange of an I-shaped section and a connection to the web of an I-shaped section via a gusset plate. In this paper, the formulae developed are presented alongside the detailed background to their derivation. The stiffness values formulated can in future be used to improve the accuracy of the prediction of the compression member capacities of single steel angles with bolted end connections.

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
The stability design of members and structures based on a geometrically nonlinear analysis with equivalent initial geometric imperfections (GNIA) is a commonly used method. In the case of lateral torsional buckling (LTB) of members, the regulations in EN 1993-1-1 are unsatisfactory. With the current code, but also with the new draft prEN 1993-1-1 results are achieved, some of which are significantly too conservative as well as lacking in terms of safety. The reasons for this are the specified shape of imperfection as bow imperfections e0 out of plane, an inappropriate differentiation related to the cross-section shape and yield strength, as well as neglecting the influence of the moment distribution over the member lengths. Parameter studies have shown that a distinction is required due to the different structural behaviours of members loaded with pure bending, pure compression, or a combination of bending and compression. This article presents current research results that consider the case of pure bending of I- and H-profiles. The dependencies of the profile shape, the cross-sectional resistance model and the influence of steel grades are analysed with respect to the height of the equivalent geometric imperfection to be applied.

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
Cable-stayed columns offer several advantages among traditional solutions. Owing to the additional restraint given by the prestressed cables and cross-arms, they can provide enhanced buckling resistance in comparison to conventional columns. They are also aesthetically appealing, combining a strong architectural effect with a top-notch engineering solution. This paper presents a design approach for the stability design of prestressed cable-stayed columns. This method is based on the well-known Ayrton-Perry format, combining first- and second-order effects. The imperfection factors were calibrated on the basis of experimental results. This method is consistent with design rules for uniform columns in Eurocode 3 and is easy to apply.

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
This paper discusses the simplified method for the lateral-torsional buckling design of I-shaped beams with discrete lateral restraints. This popular method, also adopted in Eurocode 3, Part 1-1:2005, consists of verifying the resistance of the compressed “flange” of the beam subjected to major-axis bending. In this case the compressed flange is considered to be composed of the flange itself plus 1/3 of the compressed part of the web. This paper summarizes the analytical derivation of the simplified method and its key assumptions. It then presents inconsistencies arising if the simplified method is compared with the more generally applicable design methods for lateral-torsional buckling given in Eurocode 3, Part 1-1:2005. In addition, the design methods are compared with numerical simulations to reveal the lack of conservatism in the simplified method in some cases. The final part of the paper discusses how the simplified method may be modified in order to ensure a sufficient level of safety.

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Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
The cross-sectional strength of square (SHS) and rectangular (RHS) hollow sections loaded in compression and various degrees of uniaxial or biaxial bending are governed by local instabilities in the elastic or plastic range. Common design checks for cross-sectional strength, e.g. those found in the Eurocodes, regularly penalize these sections through a conservative omission of various mechanical effects and a categorization of cross-sections into distinct classes with corresponding, markedly different, design rules. This leads to discontinuities and inaccuracies in the strength representation. Such conservatism is particularly detrimental to the introduction of high-strength steel hollow sections, which often fall into the semi-compact and slender cross-section classes for which local buckling is more relevant. This paper discusses the results of extensive research work carried out during the RFCS research project HOLLOSSTAB. In this project, new design rules were developed for the cross-sectional and member design checks of hollow sections with various shapes and slenderness ratios, termed the “Generalized Slenderness-based Resistance Method - GSRM”. This paper summarizes the experimental and numerical campaign carried out within HOLLOSSTAB and describes the new GSRM design rules and their background for the case of the cross-sectional strength of SHS and RHS.

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 - Structural Stability
This paper presents the development and assessment of an innovative cross-section design method for structural steel circular and elliptical hollow sections (CHS and EHS) - the generalised slenderness-based resistance method (GSRM). A numerical simulation programme was first conducted to expand the data pool for CHS and EHS. Finite element (FE) models were established, validated against existing test data and then utilised for parametric studies, where a total of over 3 700 cross-section resistance data were numerically generated. The development of the GSRM for CHS and EHS is then presented. Key design parameters, including the reference resistances and the generalised local slenderness, are initially defined. The general design procedure is subsequently introduced. Two design alternatives for CHS and EHS - a strength-based approach, and a deformation-based approach based on the continuous strength method (CSM), are developed and presented. Finally, the proposed GSRM is assessed using the previously collected test results and freshly generated FE data, where excellent accuracy and consistency in the resistance predictions are clearly revealed for all loading scenarios. Subsequent reliability analyses demonstrate that the current partial safety factor used in EN 1993-1-1 can be applied to the GSRM, achieving an appropriate level of reliability.

Kurita-Albrecht Best Technical Paper Award - Steel at 12th Japan German Bridge Symposium, September 2018 in Munich
The bridge across the Schorgast Valley is based on a competition-winning design. It comprises an overhead structure consisting of six pylons each with 10 stay cables and a slender composite cross-section with a torsion-resistant steel box as the bridge superstructure.
The jury concluded that the competition submission was a self-assured accomplishment integrating harmoniously into the sensitive landscape of the Schorgast Valley. The substructure solution shows great transparency, emphasizing the significance of the superstructure. All in all, the design is a convincing contribution to the region's building culture characterized by innovative spirit and creative power.
The structural analysis of the cross-girders and the supporting frame structures is explained in this article. To this end, the section forces from the global model were applied to a local finite element model.

The installation of solar (or photovoltaic, PV) panels (also arrays) on flat roofs is becoming increasingly popular. Experimental investigations have not only provided qualitative results for snow load distributions, but also quantitative results that enable snow load shape coefficients to be derived for flat roofs with elevated PV arrays. Small-scale water flume tests were carried out to analyse how the presence of PV arrays can influence wind-induced snow accumulations. The laws of physical similarity between model and climatic data were used for this. The tests were carried out at the Institute for Hydraulic Engineering and Water Management at the Technical University of Darmstadt. Recently, design models for snow loads on flat roofs with elevated solar arrays have been published in draft versions of the Eurocode prEN 1991-1-3, currently under review. They are based on regulations soon to be published in a new German National Annex to the existing Eurocode DIN EN 1991-1-3/NA:2019. In this paper it is shown that these draft models are not suitable for every climatic condition. Research results and alternative criteria are discussed on the basis of the investigations.

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The mission, rich history and numerous achievements of the Technical Committee TC8 “Stability of Steel Structures” of the European Convention for Constructional Steelwork (ECCS), which is active since 1958, are highlighted by present and former chairpersons.

ECCS News:
ECCS R&D activities
News from ECCS Members
European Steel Design Awards 2019
Austria: The New ÖAMTC Headquarters, Vienna
Czech Republic: Replacement bridge over the Dam Hracholusky
Denmark: K.B. Hallen, Copenhagen
France: Simonne-Mathieu Tennis Court, Roland Garros
Germany: Adidas Arena, Herzogenaurach
Norway: PAN Treetop Houses, Gjesasen
Portugal: Hippodrome de Longchamps, Paris
Sweden: Kristallen, Kiruna
Switzerland: Jet deau Movable Footbridge, Geneva
The Netherlands: Station E-line, Den Haag
Turkey: Sveti Stephan Bulgarian Church Restoration, Istanbul
Winners, The Awards of Excellence

News: Tomá Vraný SDSS Award for experimental study on lateral torsional buckling of welded sections
Bernt Johansson Outstanding Paper Award for studies on the influence of imperfections on the post-buckling behaviour of square hollow sections
Professor Eduardo de Arantes e Oliveira Award at XII Conference on Steel and Composite Construction in Coimbra

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monatliche Gesamtausgabe

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Jahrelang erregte das leerstehende Hertie-Kaufhaus die Gemüter der Lüner Bevölkerung. Aus dem markanten Betonklotz im Herzen der Stadt wurde ein Prestigeobjekt mit 24 barrierearmen Mietwohnungen und 6 Gewerbeeinheiten. Beim Umbau der Großimmobilie setzte die Bauverein zu Lünen Bewirtschaftungs-GmbH auf nachhaltige Produkte und Lösungen: Wohnungsstationen von AEG Haustechnik übernehmen die dezentrale Raumheizung und Warmwasserbereitung. So bleiben die Nebenkosten langfristig niedrig und das Trinkwasser fließt stets hygienisch einwandfrei. (Foto: AEG Haustechnik)

Obwohl vor Jahrzehnten der Energiebedarf von Gebäuden noch eine untergeordnete Rolle gespielt hat, wurden bereits früh die thermischen Vorteile von Dachbegrünungen genutzt. Beispielsweise lassen Funde von Grassodenhäuser in Island auf das Jahr 1000 n. Chr. schließen. Auch findet sich immer wieder der spezielle Baustil dicker Grasplatten als Dach an Orten mit extremen Klimaschwankungen.
In der hier vorliegenden Studie werden Moosmatten auf ihre Wärmeleitfähigkeit (&lgr;) und den thermischen Widerstandswert (R-Wert) untersucht. Im Fokus stehen dabei sowohl der strukturelle R-Wert ohne Änderung des Wassergehalts als auch der effektive R-Wert, der insbesondere durch die Änderung der latenten Energie gekennzeichnet ist. Die Ergebnisse werden mit den Resultaten ähnlicher Dachbegrünungen von Studien anderer Autoren der letzten Jahre verglichen und in Beziehung gesetzt. Damit sollen die Berechnung der thermischen, energetischen Aktivität der Gebäudehülle unterstützt und die Transmissionswärmeverluste quantifizierbar werden.

Thermal analysis of a roof greening with moss mats.
Although the energy needs of buildings played a minor role decades ago, the thermal benefits of green roofs have already been exploited. For example, finds from turf houses in Iceland date back to the year 1000 A. D. The special architectural style of thick grass slabs as a roof in places with extreme climatic fluctuations can also be found again and again.
In the present study, moss mats are examined for their thermal conductivity and thermal resistance (R value). The focus is on both the structural R-value without changing the water content and the effective R-Value, which is characterized in particular by the change in latent energy. The results are compared and correlated with the results of similar green roofs from studies of other authors in recent years. The aim is to support the calculation of the thermal, energetic activity of the building envelope and to quantify transmission heat losses.

The present paper reports on an experimental study performed in a seminar room of the University of Luxembourg in a building of the 1970ies without a major renovation. This lecture room is typical for this building period and has a capacity of 60 seats. It is equipped with a mechanical ventilation system that is normally in operation on workdays for 11 hours a day in semester periods (8:00-19:00h), while windows can be opened manually. A blower-door test revealed that the room is not airtight. During a year, the ventilation system was shut “on” and “off” in periods of some weeks and the consumed final-energy was measured, as well as the indoor climate assessed by physical and psychological measurements. For instance, the measured CO2 concentrations are marginally better with the ventilation system “on”, which was not perceived in any way by the occupants during the investigations. It was not possible to properly identify the impact of ventilation on the consumed heat-energy, as the room could not be thermally separated from the rest of the building. But with the system “on”, there was a clear increase in consumed primary energy due to the electric consumption of the fans. No relationship between the perceived percentage of dissatisfied and perceived climate could be observed. It is concluded that the typical normal operation modus is questionable for seminar rooms in older buildings with variable occupancy and that a simple shut down or semi-automatic user-controlled modus by low-cost retrofit seems advantageous.

Energieeffizienz und Raumluftqualität von Seminarräumen im Bestand mit und ohne mechanische Belüftung.
Der vorliegende Artikel berichtet über eine experimentelle Studie, die in einem Seminarraum der Universität Luxemburg in einem Gebäude der 1970er Jahre ohne größere Renovierung durchgeführt wurde. Dieser für diese Bauzeit typische Hörsaal hat eine Kapazität von 60 Plätzen. Er ist mit einer mechanischen Lüftungsanlage ausgestattet, die in den Vorlesungszeiten (8:00-19:00 Uhr) an Werktagen in der Regel 11 Stunden täglich in Betrieb ist, während Fenster manuell geöffnet werden können. Im Rahmen eines Blower-Door-Tests wurde festgestellt, dass der Raum nicht luftdicht ist. Während eines Jahres wurde die Lüftungsanlage in Zeiträumen von einigen Wochen ein- und ausgeschaltet und die verbrauchte Endenergie sowie das Raumklima durch physikalische und psychologische Messungen ermittelt. So sind beispielsweise die gemessenen CO2-Konzentrationen bei eingeschalteter Lüftungsanlage etwas besser, was aber von den Nutzern während der Untersuchungen in keiner Weise wahrgenommen wurde. Die Auswirkungen der Lüftung auf die verbrauchte Wärmeenergie konnten nicht eindeutig identifiziert werden, da der Raum nicht thermisch vom Rest des Gebäudes getrennt werden konnte. Aber mit eingeschaltetem System kam es zu einem deutlichen Anstieg des primären Energieverbrauchs aufgrund des Strombedarfs der Ventilatoren. Es konnte kein Zusammenhang zwischen dem wahrgenommenen Prozentsatz an Unzufriedenen und dem wahrgenommenen Raumklima festgestellt werden. Es wird die Schlussfolgerung gezogen, dass der typische Normalbetrieb für Seminarräume in Bestandsgebäuden mit variabler Belegung fragwürdig ist und dass ein einfacher Shutdown oder ein halbautomatischer benutzergesteuerter Modus durch kostengünstige Nachrüstung vorteilhaft erscheint.

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