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Im Stahlbau werden Schraubverbindungen entweder aus Gründen der Tragfähigkeit oder der Gebrauchstauglichkeit vorgespannt. Ein- und mehrschnittige Verbindungen in Brücken, Funkmasten und Turmbauwerken von Windenergieanlagen gehören zu den typischen Einsatzgebieten. Eine Spaltbildung, hervorgerufen durch fertigungs- und montagebedingte Imperfektionen, stellt ein Risiko z. B. für das kontrollierte Aufbringen des erforderlichen Vorspannkraftniveaus sowie zur Vermeidung von Spaltkorrosion dar. Dies kann die Tragfähigkeit sowie die Dauerhaftigkeit der Verbindung erheblich beeinträchtigen und sogar zu einem vorzeitigen Versagen führen. Die Spaltbildung ist daher auf ein Minimum zu begrenzen, wobei DIN EN 1090-2 dazu Maßnahmen wie z. B. den Einsatz von Futterblechen vorsieht. Eine mögliche Alternative für den Ausgleich von Spalten stellen Zweikomponenten-Reaktionsharzsysteme auf Epoxidharzbasis dar, die zur Verbesserung der mechanischen Eigenschaften mit speziellen metallischen Werkstoffen gefüllt sind. Im Rahmen des ZIM-Kooperationsprojekts “Bri-San-T - DuroFüllSta” wurden systematische Untersuchungen zum Einsatz des duroplastischen Spaltausgleichsmaterials MM1018 der Firma Diamant Polymer GmbH in vorgespannten geschraubten Verbindungen durchgeführt. Im vorliegenden Beitrag werden die experimentell bestimmten Haftreibungszahlen sowie die zu erwartenden Vorspannkraftverluste vorgestellt.

The application of duroplastic gap filling material DIAMANT MM1018 in preloaded bolted connections
In steel construction, bolted connections are preloaded either for load-bearing capacity reasons or for serviceability reasons. Single and multi-section connections of wind turbines, offshore plants, bridges etc. are typical application examples. Gap formation, caused by imperfections due to fabrication and assembly, poses a risk e. g. for the controlled application of the required preload level as well as for the prevention of cavity corrosion. This can significantly impair the load-bearing capacity and the durability of the connection and even lead to a premature failure. Therefore, the formation of gaps must be kept to a minimum, whereby DIN EN 1090-2 provides possible measures such as the use of packing plates for this purpose. Two-component reaction resin systems based on epoxy resins, which are filled with special metallic materials to improve the mechanical properties, are a possible alternative for gap filling. Within the framework of the ZIM cooperation project “Bri-San-T - DuroFüllSta”, systematic investigations were carried out into the use of the gap-filling material MM1018 of the company Diamant Polymer GmbH for use in preloaded bolted connections. In this contribution, experimentally determined slip factors as well as the expected preload losses over the service life are presented and discussed.

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Im Vorhaben “Zyklische Bemessung von Zugstäben mit Endgewinden” sind umfangreiche Untersuchungen an Zugstäben verschiedener Herstellungsarten (geschnitten, gerollt, mit und ohne Feuerverzinkung) durchgeführt worden. Dabei wurden die Durchmesser M16, M48, M68 und M100 untersucht. Die Ergebnisse der 214 Ermüdungsversuche zeigen erhöhte Ermüdungsfestigkeiten für gerollte Zugstäbe. Für geschnittene Gewinde wird der Kerbfall 50 bestätigt. Der Einfluss von Produktions- und Montagetoleranzen wurde mit dem Kerbdehnungskonzept untersucht. Auf Basis der Untersuchungen wird ein Vorschlag der Einordnung des Kerbdetails “Zugstäbe mit Endgewinden” aus Baustahl unter Berücksichtigung des Herstellungsverfahrens und einer Feuerverzinkung formuliert.

Fatigue strength of tension rods with threads
In the project “Zyklische Bemessung von Zugstäben mit Endgewinden”, extensive fatigue tests have been carried out on tension rods of different manufacturing types (cut, rolled, with and without hot-dip galvanizing). The diameters M16, M48, M68 and M100 were investigated. The results of the 214 fatigue tests show increased fatigue strengths for tension rods with rolled threads. Fatigue detail category 50 is confirmed for cut threads. The effect of production and assembly tolerances were investigated using the strain notch concept. A proposal for the classification of the fatigue detail “tension rods with threads” made of structural steel is provided as an outcome of the research project. Fatigue detail categories dependent on the manufacturing process type of thread and on whether hot-dip galvanization is performed or not are proposed.

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Im Zuge der Errichtung eines Ersatzneubaus des Luisenturms auf dem Atzelberg bei Kelkheim-Eppenhain im Taunus löst eine Stahlkonstruktion den bisherigen Aussichtsturm in Holzbauweise ab. Das 27 m hohe Bauwerk zeichnet sich durch schlanke Tragelemente aus geradlinigen und gekrümmten Stahlrohren aus, die in Off-Knot-Bauweise hergestellt und gefügt sind, wobei sich die Stoßstellen außerhalb der Stabwerksknoten befinden und so die komplett geschweißten Knoten frei bleiben von zusätzlichen Laschen, Stoßdeckungen und Verschraubungen. Die Rohrfügungen bestehen aus vierteiligen, passgeformten Laschen aus Rundrohrausschnitten, die im Inneren angeschraubt werden und nur an der Stoßfuge und den außenliegenden Schraubenköpfen erkennbar sind. Die neuartige Konstruktionsweise unterstreicht die Filigranität des Tragwerks und setzt einen eleganten Akzent in die umgebende gebirgige Taunuslandschaft.

The Luisenturm on the Atzelberg
In the context of the construction of a replacement for the Luisenturm tower on the Atzelberg near Kelkheim-Eppenhain in the Taunus region, a steel structure is replacing the previous wooden observation tower. The 27 m high structure is characterized by slender load-bearing elements made of curved steel tubes, which are manufactured and joined using the off-knot construction method, whereby the joints are located outside the beam intersections, leaving the fully welded knots free of additional plates, joint parts and bolted connections. The pipe joints consist of four-part, fit-formed plates made from round pipe sections, which are screwed on internally and can only be seen by looking at the butt joint and the screw heads on the outside. The novel construction method emphasizes the filigree of the supporting structure and sets an elegant accent in the surrounding mountainous landscape of the Taunus.

Aktuelles:
Erzeugerpreisindex Stahl (2015 = 100)
Durchschnittliche BDSV-Lagerverkaufspreise für Stahlschrottsorten in Deutschland
Ingenieurbaukunst 2023 an Staatssekretär Rolf Bösinger übergeben
Das neue bauingenieur24

Persönliches:
Markus Knobloch neuer Chairman CEN/TC 250/SC 3 Eurocode 3

Tagungen & Veranstaltungen:
4. Symposium Ingenieurbaukunst - Bauen mit und im Bestand

Wettbewerbe:
Deutscher Ingenieurbaupreis 2022 verliehen

REVIEWER

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Thin-walled cold-formed steel elements represent an attractive structural solution due to the fast manufacturing and erection time on-site. Their small thickness leads to imperfection and sensitivities to eccentricities. An experimental programme was performed on short members with lipped channel cross section, subjected to eccentric compression about the minor and major axes, in a large range of eccentricities. Siehe article: Ungureanu, V. et al, p. 44.

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Better and simpler possibilities of structural optimization due to increasing computational power but also for reasons of environmental sustainability, the use of materials and their reusability lead to greater acceptance towards more advanced numerically intensive, so-called ‘design by analysis’ methods like geometrically and materially non-linear analyses with imperfections (GMNIA). The general choice of imperfections and their combination in such models, especially for slender cross sections of intermediate length prone to an interaction between a global and local plate buckling, is crucial in terms of the reached load-bearing capacity. Annex C of EN 1993-1-5:2010 makes use of the ‘70 %-rule’ for the combination of imperfection modes and amplitudes. This rule postulates that two GMNIA calculations should be conducted when local and global interactive buckling may be dominant; one with 100 % + 70 % of the maximum specified amplitude in either case. In addition, extended information is provided on the choice and combination of imperfections in the newly introduced and currently available draft of the prEN 1993-1-14:2020 (design assisted by finite element analysis). Although information is provided on how the local and global imperfections should be combined, it is not stated when it is relevant to consider those. Based on conducted GMNIA simulations on SHS/RHS (square and rectangular hollow sections) and I-shaped sections, this article presents general decision support on the choice of equivalent imperfections. On the basis of numerical analysis, the developed flow chart and design routine allow for the decision whether the consideration of the interaction of local and global imperfections is required or not.

There is currently no reliable and simple design method available in international literature for the determination of the patch loading resistance of slender plate girders having multiple longitudinal stiffeners. The current research focuses on the patch loading resistance of girders having multiple longitudinal stiffeners. An advanced numerical model is developed and verified by own laboratory test results. A numerical parametric study is executed to investigate the load-carrying capacity of girders having typical bridge geometries. Analysing the numerical simulation results, the structural behaviour obtained is classified based on the stiffener stiffness. Effect of the different geometrical parameters on the patch loading resistance is evaluated with special focus on the stiffener stiffness and distance between the longitudinal stiffeners. The failure modes depending on stiffener stiffness are investigated and the local buckling type failure is characterised by minimum stiffness. For this specific failure mode, an improved design method is developed, giving reliable resistance within the analysed parameter range. The presented resistance model is consistent with the design philosophy of EN 1993-1-5. The applicability of the improved design equation has been investigated for multiple stiffener places in unequal distances, which is the common case in praxis, and for bending and transverse force (M-F) interaction.

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Owing to the new rules of the German National Annex to EN 1998-1, the relevance of the seismic action has increased, materialising in extended seismic areas and higher spectral accelerations. This may lead to seismic loading being decisive on the design of steel and composite frames. However, the demand is lower in Germany than in other seismic areas. Consequently, these challenges are addressed in an ongoing German national research project, by developing joints with dissipative connections, classified as semi-rigid and partial-strength, for steel and composite frames that could allow for the use of behaviour factors in the range of 1.5 to 3. The development started with typical connections from the German catalogue, designed to withstand static loads in the elastic range, followed by performance and detailing improvements. Developments (e.g., increase in sagging/hogging bending: 125 %/18 % of steel joints and 70 %/40 % of partially composite joints) resulted from pre-test finite element analyses (FEA) on joints and frame models. Improvements to joint detailing were made according to the provisions of the newest draft of Eurocode 8. The optimised joints were integrated in frame specimens, which are currently being tested under monotonic and cyclic loads at RWTH-Aachen University. This article introduces the developed joint solutions, describes the experimental and numerical programs and presents the monotonic response of frame specimens based on the results of FEA, as well as the main conclusions.

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Thin-walled cold-formed steel elements represent an attractive structural solution due to the fast manufacturing and erection time on-site. Their small thickness leads to imperfection and sensitivities to eccentricities. An experimental programme was performed on short members with lipped channel cross section, subjected to eccentric compression about the minor and major axes, in a large range of eccentricities. The specimens were manufactured on a folding machine. Before testing, the dimensions of all specimens were measured. Shortening of all specimens was measured in two ways, i.e., 1) using the displacement gauge integrated with the machine crosshead beam and 2) from deformation fields obtained using digital image correlation (DIC) system. The quantitative results, presented as the ultimate loads versus the eccentricity curve, emphasise the influence of the eccentric load on the capacity of the element. Finite element (FE) analyses were performed to simulate the behaviour of short members in eccentric compression using the commercial FE software ABAQUS/CAE and ANSYS. Static non-linear analyses were conducted in displacement control. Both geometrical and material nonlinearities were included. An isotropic linearly elastic-perfectly plastic constitutive model was considered, with von Mises yielding the criterion and associated flow rule. Failure modes were identified due to numerical and experimental tests. Plastic mechanism models were derived, resulting in the derivation of post-ultimate, rigid-plastic curves, characterising a post-ultimate structural behaviour.

A Lego-like steel-framed structural system has been developed within the frame of an RFCS project, REDUCE, to facilitate 1) deconstruction of composite structures, 2) circularity at structure and element levels, and 3) serial production in construction by promoting a greater standardization of structural elements. The system utilizes innovative demountable shear connections for composite flooring solutions with precast concrete elements, and adjustable steel connections for use in both beam-to-beam and beam-to-column connections. The first use case of the structural system has been realized in the Petite Maison project which is a demonstration project for circularity and contributes to the event ESCH2022. Each construction element is linked to a digital database and remains available for future reuse, as a result of the plug-and-play, demountable and robust features of the developed system. This paper presents the proposed demountable system, the results from experiments and finite element analyses on the behaviour of shear connections, composite beams, and steel connections, and indicates the analysing methods for structural engineers to open a pathway for full implementation of the structures built into digital tools, fabrication, and construction.

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ECCS News:
Save The Date: ECCS webinar sessions in spring 2023
Eurosteel 2023 - 12 to 14 September 2023 in Amsterdam (NL)
13th Pacific Structural Steel Conference (PSSC'22)
11th International Conference on the Behaviour of Steel Structures in Seismic Areas
Nordic Steel Construction Conference 2024 - Save the date
In Memoriam: Dr. Per-Olof Thomasson
In Memoriam: Prof. Dr. Nesrin Yardimci

Reviewers

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Zum Titelbild:
Im Norden Berlins wird derzeit ein Quartierprojekt mit einem vollständig neuen Anspruch an Nachhaltigkeit und Wohnkomfort realisiert. Auf knapp 7.000 m2 Dachfläche kommt hierbei die preisgekrönte Ganzdachlösung für Photovoltaik des Magdeburger Unternehmens Ennogie zum Einsatz. Marktführer VELUX baut auf das flexible Ennogie-Solardach, das sich mit Hilfe von Anpassungsmodulen an jede Dachfläche anpassen kann. Bewusst wird dabei auf spezielle Dachfenster im Rastermaß verzichtet. Planer und Architekten begrüßen diese Innovation. Sie genießen vollständige Freiheit bei der Auswahl und Platzierung der Fenster im Dach. Auch die Bewohner profitieren, denn lichtdurchflutete Räume und hohe Stromproduktion können nur gemeinsam erreicht werden. (Abb.: Ennogie Deutschland GmbH)

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