Extended keynote paper of Eurosteel 2021
Automated production is finding its way into the fabrication of structural steel. One robot holds attachments (stiffeners, end plates, etc.) on a steel beam or column and another robot produces weld seams. However, welding robots can also be used for Additive Manufacturing (Wire and Arc Additive Manufacturing, WAAM). The wire electrode serves as a printing material. The Institute of Steel Construction and Materials Mechanics in Darmstadt is investigating how typical connecting elements for steel structures can be printed directly on steel beams using Additive Manufacturing with arc welding and robots. Furthermore, structural elements such as nodes for space frames can be printed and even complete structures, e.g. columns and a little bridge, have already been manufactured additively. The main focus is on determining suitable welding and process parameters. In addition, topology optimization is necessary in order to achieve good structures using a small amount of material. This is possible due to the free design prospects of WAAM, which opens up new design and production strategies.

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Extended keynote paper of Eurosteel 2021
The robustness of steel structures during severe earthquakes is largely based on the calibration of stiffness, strength and ductility. Such a robust system dissipates the energy by plastic deformations in the plastic members (fuses) made from mild carbon steel (MCS), while the other members remain elastic. In the case of concentrically braced frames (CBF), the fuses can be in the form of buckling-restrained braces (BRB), while for eccentrically braced frames (EBF), the short links could take on this role. In the case of shear walls (SW), slender steel plates can be used. To avoid oversized elastic members, they can be made of high-strength steel (HSS). Structures made from HSS and MCS are called dual steel (DS) structures. In order to ease the post-earthquake intervention, the fuses can be detachable. Furthermore, their replacement is less costly if the structure is re-centred using moment-resisting frames (MRF) connected to the main dissipative system, i.e. a dual frame (DF) structure. This paper presents the concept of DS DF structures and some examples.

Extended keynote paper of Eurosteel 2021
This two-part paper provides a state-of-art report on the most recent findings concerning the behaviour, strength and Direct Strength Method (DSM) design of cold-formed steel (CFS) columns and beams affected by mode coupling phenomena not adequately covered by the current specifications for CFS members, namely local-distortional (L-D), local-distortional-global (L-D-G), distortional-global (D-G) and global-global (flexural-torsional/flexural - FT-F) interaction. The paper addresses experimental tests, numerical simulations and DSM-based design approaches that are intended to i) acquire in-depth knowledge on the non-linear behaviour (elastic and elastic-plastic), load-carrying capacity and failure mode nature of the members under consideration, and ii) make use of that knowledge to develop, propose and assess the merit of efficient DSM-based design approaches to estimate their failure loads/moments. Initially, illustrative column results are briefly presented to help grasp some fundamental concepts, namely the characterisation of i) the aforementioned mode coupling phenomena, ii) different sources of mode interaction that may lead to failure load/moment erosion, and iii) the most detrimental initial geometrical imperfections. The DSM design curves currently codified and two strength curves recently developed for column flexural-torsional and beam distortional failures are presented next. The two-part paper then addresses separately each mode coupling phenomenon dealt with, for columns, but only L-D and D-G interaction for beams - while L-D interaction (in columns and beams) appears in Part 1, the remaining column and beam coupling phenomena (all involving global buckling) are dealt with in Part 2 [1]. For columns undergoing L-D and L-D-G interaction, beams experiencing L-D interaction and angle columns susceptible to FT-F interaction, the work reported includes experimental studies, numerical simulations and DSM-based design considerations and/or guidelines. For the remaining coupling phenomena, only numerical results are reported, but they unveil interesting (and unexpected) behavioural features that will help plan future test campaigns and achieve efficient design approaches. Finally, the two-part paper closes with a few concluding remarks and an outlook regarding future developments in this field.

Extended keynote paper of Eurosteel 2021
This is Part 2 of a two-part paper providing a state-of-art report of the most recent findings concerning the behaviour, strength and Direct Strength Method (DSM) design of cold-formed steel (CFS) columns and beams affected by mode coupling phenomena not adequately covered by the current specifications for CFS members. This second paper covers interactions involving global buckling modes, namely local-distortional-global (L-D-G), distortional-global (D-G) and global-global (flexural-torsional/flexural - FT-F) interaction - note that local-global (L-G) interaction, already well mastered by the technical/scientific community, is not dealt with. Like Part 1 [1], this paper also addresses experimental tests, numerical simulations and DSM-based design approaches, intended to i) acquire in-depth knowledge on the non-linear behaviour (elastic and elastic-plastic), load-carrying capacity and failure mode nature of the members under consideration, and ii) make use of the above knowledge to develop, propose and assess the merits of efficient DSM-based design approaches to estimate their failure loads/moments. Taking into account the fundamental concepts and DSM design curves presented in Part 1 [1], the paper addresses separately each mode coupling phenomenon dealt with, for columns, and only D-G interaction for beams - recall that L-D interaction (columns and beams) was covered in Part 1 [1]. For columns undergoing L-D-G interaction and angle columns susceptible to FT-F interaction, the work reported includes experimental studies, numerical simulations and DSM-based design considerations and/or guidelines. For columns and beams experiencing D-G interaction and channel columns prone to FT-F coupling, only numerical results are reported - they reveal surprising behavioural features that will be very useful in planning future test campaigns and achieving efficient design approaches. Finally, the two-part paper closes with a few concluding remarks and a perspective about future developments in this field.

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This two-part article gives an overview of the developments of the structural member verification in prEN 1993-1-1:2020 “Eurocode 3: Design of steel structures - part 1-1: General rules and rules for buildings”, one of the second generation of Eurocodes. These developments were undertaken by Working Group 1 (WG1) of Subcommittee CEN/TC250/SC3 and by Project Team 1 (SC3.PT1) responsible for drafting the new version of EN 1993-1-1. In the past, WG1 collected many topics needing improvement, and the systematic review conducted every five years also yielded topics needing further development. Based on this, the current version of EN 1993-1-1 has been developed into a new draft version prEN 1993-1-1:2020 enhancing “ease of use”. The technical content of this new draft was laid down at the end of 2019. Many improvements to design rules have been established with respect to structural analysis, resistance of cross-sections and stability of members. This two-part article focuses on member stability design rules and deals with the basis for the calibration of partial factors, the introduction of more economic design rules for semi-compact sections, methods for structural analysis in relation to the appropriate member stability design rules, new design rules for lateral torsional buckling plus other developments and innovations. This second part of the article is dedicated to illustrating the most relevant changes to member buckling design rules.

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Many mechanical joints in steel structures use conventional bolts. Nevertheless, this proven joining technology has some significant disadvantages. These basically include the high levels of scatter during application of the assembly preload using the torque-controlled tightening process, the risk of loosening during cyclic loads due to transverse displacement of the components and the low fatigue resistance under axial loading. Lockbolt technology was invented as long ago as the 1930s and mainly used for the aviation and space industry because of its evident advantages. This joining technology has been constantly further developed in response to the most diverse demands from sectors such as aviation, commercial vehicles, rail vehicles, agricultural machinery, defence technology and steel structures. The application of lockbolt technology, which is primarily used in mechanical engineering, was in most cases based on individual studies, since no consistent rules and guidelines were available for the design and execution of lockbolt connections in steel structures. Within the scope of several public research projects funded by the AiF (German Federation of Industrial Research Associations) and conducted by the iGF (Industrial Collective Research) organization as well as through approval investigations, the Fraunhofer Institute for Large Structures in Production Engineering (IGP) has successively developed the necessary design rules according to the EN 1993 standard (Eurocode 3) for use in structural connections. These design rules will be presented within the context of this article in order to make the benefits of this joining technology available to other users. In addition, insights into the use of technical approvals will be presented together with some current applications.

Nominated for the Professor Eduardo de Arantes e Oliveira Award at XII Conference on Steel and Composite Construction in Coimbra 2019
This paper presents the results of a numerical parametric study that investigated the M-V interaction behaviour of box-girder bridge deck specimens. The study made use of an advanced numerical model that was previously verified against the experimental results. Based on the numerical results and the current rules for trapezoidal box girders, new design models are proposed for predicting the bending and shear resistance of cross-sections with a curved bottom flange. Additionally, the force-based M-V interaction equation proposed by Jáger et al. [1], adopted in the new version of EN 1993-1-5 [2], was verified and slightly modified to fit this type of cross-section.

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PHD-Thesis:
Fatigue Assessment of Large-Size Bolting Assemblies for Wind Turbine Support Structures

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Zum Titelbild:
Im Norden von Bonn wurde die Kindertagesstätte “Rhein-Dampfer” nach dem sogenannten “Bonner Modell” des Städtischen Gebäudemanagements Bonn (SGB) errichtet. Bei der Planung legten das Büro rheintreuearchitekten, Köln und der Bauherr besonderen Wert auf Nachhaltigkeit. Die Gebäudeeinheiten wurden in Holzbauweise mit vorgefertigten Bauelementen realisiert. Mit einem energetischen Gesamtkonzept nach der aktuellen Energieeinsparverordnung (EnEV) wurde der Standard KfW-Effizienzhaus 55 erreicht, siehe Meldung S. 205 (©Foto: P. Prior).

Das Wasseraufnahmeverhalten von Fassadenkonstruktionen historischer Gebäude spielt für deren Dauerhaftigkeit eine wesentliche Rolle. Für die Bestimmung des Wasseraufnahmeverhaltens von Fassadenbaustoffen können nach dem Stand der Technik lokal Proben entnommen und im Labor untersucht werden. Im Hinblick auf den Denkmalschutz oder den Einfluss von Mörtelfugen bei Sichtmauerwerk ist diese Vorgehensweise nicht immer sinnvoll. In-situ-Messgeräte arbeiten zerstörungsfrei und direkt am Gebäude, liefern jedoch häufig nur beschränkt aussagekräftige Ergebnisse. Dieser Aufsatz enthält Teile der Ergebnisse der Dissertationsschrift Stelzmann [1] und Ansätze für die Abschätzung verschiedener Effekte, die In-situ-Prüfungen zum Wasseraufnahmeverhalten beeinflussen können. Hierzu zählen die Korrektur dreidimensionalen Saugens im Bereich des Randes der Benetzungsfläche, abweichende Wassertemperaturen oder vorhandene Startfeuchtegehalte der Fassadenbaustoffe. Nach physikalischer Herleitung wurden drei Fassadenkonstruktionen in einer umfangreichen Studie mit dem in [1] entwickelten Wasseraufnahmemessgerät insgesamt 274 In-situ-Einzelprüfungen untersucht. Die statistische Auswertung der Daten gibt einen Eindruck der jeweiligen Anteile der verschiedenen Effekte an der Messunsicherheit bei In-situ-Messungen.

In situ-measurement of the water absorption behaviour of facades - Evaluation of measurement results on three façade constructions.
The water absorption behaviour of façade constructions of historical buildings is an important aspect for their durability. To determine the water absorption coefficient of façade construction materials, samples can be taken on site and examined in the laboratory according to the state of the art. With regard to the protection of historical buildings or the influence of mortar joints in fair-faced masonry, this procedure is not appropriate in all cases. In situ measuring instruments work non-destructively and directly at the building, but often provide only limited results. This paper contains parts of the dissertation Stelzmann [1]. It contains approaches for the estimation of various effects that can influence in situ tests on water absorption behaviour. These include the correction of three-dimensional suction in the area of the edge of the wetting surface, varying water temperatures or initial moisture content of the facade materials. After physical derivation, three façade constructions were examined in a comprehensive study with the water absorption measuring instrument developed in [1]. The statistical evaluation of the data gives an indication of the respective proportions of the various effects of in situ measurements.

No short description available.

Die Berechnung des bewerteten Norm-Trittschallpegels im Bau L'n, w erfolgt aktuell in der DIN 4109-2:2018 sowohl für den Massivbau als auch für den Holz-, Leicht- und Trockenbau unter Berücksichtigung relativ pauschaler Korrekturen für die flankierende Schallübertragung. Darüber hinaus unterliegen die derzeitigen Verfahren einigen weiteren gravierenden Beschränkungen des Anwendungsbereiches, die eine Überarbeitung der Verfahren wünschenswert erscheinen lassen. Basierend auf dem neuen vereinfachten Verfahren der DIN EN ISO 12354-2:2017 werden deshalb Berechnungsverfahren auf der Basis von Einzahlangaben vorgestellt, mit denen die direkte und die flankierende Trittschallübertragung, wie beim Luftschall, getrennt berechnet und anschließend aufsummiert werden. Hierdurch ergeben sich deutlich bessere Möglichkeiten, die tatsächliche Bausituation im Rechenmodell abzubilden und somit eine bessere Übereinstimmung zwischen dem prognostizierten und einem gemessenen Wert zu erhalten. Im Massivbau kann beispielsweise eine Vorsatzkonstruktion im Empfangsraum vor dem trennenden oder dem flankierenden Bauteil entsprechend ihrer schalltechnischen Wirkung berücksichtigt werden. Weiterhin können auch horizontale oder diagonale Übertragungssituationen oder die Trittschallübertragung von Treppen abhängig von der jeweiligen baulichen Situation berechnet werden. Die neuen Berechnungsverfahren ermöglichen damit eine wirtschaftlichere Dimensionierung der Bauteile.

New calculation method for impact sound transmission
In Germany, the weighted normalized impact sound pressure level, L'n, w, in both massive and lightweight buildings, is currently calculated according to DIN 4109-2: 2018. Although this approach takes flanking sound transmission into account, it only does so by applying general correction terms, which lead to serious limitations. In a more modern approach, based on the simplified model in DIN EN ISO 12354-2:2017, single number quantities are calculated for the direct and for each flanking impact sound transmission path separately and are then added up energetically. This later approach has many advantages over the former, and is therefore proposed here to be used in Germany as the “new calculation method" for impact sound transmission. This proposed approach leads to a significantly greater understanding and more accurate mapping of impact sound transmission in the actual building situation and thus results in an improved match between the predicted and the measured results. In massive construction, for example, a wall or floor lining applied on the separating or a flanking building element in the receiving room can be taken into account according to its acoustical properties. Furthermore, horizontal and diagonal transmission of floor impact sound and impact sound transmission from stairs can be calculated dependent on the actual construction details. The new calculation model thus enables dimensioning the building components more economically.

Mit ehrendem Gedenken an Prof. Dr.-Ing. Wolfgang Fasold geschrieben
Für Räume, die eine mühelose und ungestörte Sprachkommunikation ermöglichen sollen, gelten erhöhte akustische Anforderungen. Als besondere Herausforderung hat sich hierbei eine Dämpfung der tieffrequenten Schallanteile erwiesen. Hierfür geeignete, genügend breitbandig wirksame Absorber wie Verbundplatten-Resonatoren belegen jedoch eine große Wand- oder Deckenfläche und sind für viele Anwendungen zu sperrig und teuer. Das hier vorgestellte, neuartige Modul, das allseitig stabil von einem nur teilweise perforierten Metallgehäuse umschlossen ist, weist demgegenüber nicht nur eine höhere Wirksamkeit auf, sondern eignet sich aufgrund seiner modularen Bauweise und geringer Herstellungskosten für eine Vielzahl von Raumtypen, auch für eine Nachrüstung bei laufendem Betrieb. Messwerte aus dem Hallraum und von ersten raumakustischen Sanierungen bestätigen die theoretischen Erwartungen und stellen eine praktikable Lösung für ein allgegenwärtiges Problem der Bauphysik in Aussicht.

Broadband sound absorber for rooms with special acoustic requirements
For rooms that should allow effortless and undisturbed speech communication, increased acoustic requirements apply. The damping of low-frequency sound components has proven to be a particular challenge. However, suitable absorbers with sufficient broadband effectiveness such as composite panel resonators occupy a large wall or ceiling area and are too bulky and expensive for many applications. In contrast, the new module presented here, which is enclosed on all sides by a partially perforated metal housing, is not only more effective but, due to its modular design and low manufacturing costs, is also suitable for a large number of room types, including acoustic renovation during ongoing operation. Measured values from the reverberation room and from the first room acoustic refurbishments confirm the theoretical expectations and hold out the prospect of a practicable solution to an omnipresent problem of building physics.

No short description available.

In dieser Studie wird auf Grundlage einer Literaturanalyse der aktuelle Forschungsstand zu autochthonen Bauten und deren Beitrag zur klimagerechten Gestaltung der gebauten Umwelt auf globaler sowie regionaler Ebene ausgewertet und zusammengefasst. Dabei wird insbesondere der Einsatz und die Auswirkung von Vegetation im Außenraum, zur Anpassung an das Klima, analysiert. Laut diversen Studien zeichnen sich autochthone Bauten nicht nur durch einen schonenden Umgang mit Ressourcen aus, sondern tragen durch die sensible Eingliederung in den geographischen und topographischen Kontext auch einer bioklimatischen Gestaltungsdoktrin Rechnung. Zusätzlich werden anhand der Literaturauswertung bestehende Forschungslücken hinsichtlich der Themenstellung, insbesondere für den regionalen Kontext, identifiziert und formuliert. Die wissenschaftliche Analyse autochthoner Bauten ist im deutschen Raum noch unterrepräsentiert und erfordert weitere Untersuchungen.

Use and effect of vegetation in autochthonous buildings
Based on a literature analysis, this study evaluates and summarizes the current state of the art of autochthonous buildings and their contribution to a climate-responsive design of the building environment on a global and regional level. The use and the effect of green structures in outdoor spaces for climate adaption is analyzed in a focused way. According to various studies, autochthonous buildings are not only characterized by a responsible resource management, but also take into account a bioclimatic design doctrine through a sensitive integration into the geographical and topographical context. Furthermore, existing research gaps, especially for the regional context, will be identified and formulated on the basis of the literature evaluation. In Germany the scientific analysis of autochthonous buildings is still underrepresented and requires further research.

In dem vorliegenden Beitrag wird die Anwendung von VOC-Sensoren zur luftqualitätsgeführten Volumenstromregelung bei Dunstabzugshauben untersucht. Bei Koch- und Garprozessen müssen die VOC-Sensoren hohe Verunreinigungen sowie schnelle und teilweise sprunghafte Signaländerungen detektieren. Untersucht werden fünf unterschiedliche VOC-Sensoren von vier Herstellern. Durch Messungen werden die spezifischen Eigenschaften der VOC-Sensoren analysiert und untereinander verglichen. Die durchgeführten Messungen zeigen, dass ein Vergleich der absoluten Sensorsignale nicht zielführend ist. Werden die Messsignale der einzelnen VOC-Sensoren als Prozentwerte bezogen auf die Differenz von maximalem und minimalem Messwert einer Zeitreihe dargestellt (normiert), weisen vier der fünf Sensoren bei gleicher Verunreinigungslast ähnliche Signalverläufe auf. Zwei VOC-Sensoren werden detailliert untersucht und zeigen einen plausiblen Signalverlauf bei Koch und Bratvorgängen, aber auch in einem Vorlesungssaal und in einem Büro.

Comparative investigation of VOC sensors:
In this article the use of VOC sensors for air quality-controlled volume flow control in extractor hoods will be examined. In cooking processes the VOC sensors have to detect high levels of contamination as well as rapid and sometimes sudden signal changes. Five different VOC sensors from four manufacturers are examined. The specific properties of the VOC sensors are analyzed and compared with each other by measurements. The measurements carry out that a comparison of the absolute sensor signals is not expedient. If the measurement signals of the individual VOC sensors are represented as percentages based on the difference between the maximum and minimum measurement values of a time series (standardized), four of the five sensors have similar signal curves with the same contamination load. Two VOC sensors are examined in detail and show a plausible signal course during the cooking processes, but also in a lecture hall and in an office.

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