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Item type:Publication, Access status: without files , Verknüpfung von Nano mit Makro – Chancen für den StahlbauLinking nano with macro – opportunities for steel construction. Nanostructured metallic multilayers have significantly higher strength, fatigue resistance and ductility than monolithic homogeneous metal cross sections. The superior structural properties of these nanostructured cross sections are known, and so it is surprising why no attempt has been made to date to use nanostructured cross sections in macro cross sections in structural engineering to improve the cross section properties. This paper links the advantages of nanostructured multilayers with the needs of homogeneous metallic macro-cross sections and examines the question of the extent to which the high-performance material nanolaminate can compensate for the structural weak points of metallic infrastructure. The following weak points of metallic infrastructure are addressed: 1) the welded connection subjected to fatigue and corrosion, 2) additively printed metallic cross sections exposed to fatigue and corrosion. The article provides food for thought on how nanostructured multilayer can potentially contribute to the future of steel construction. As an example, the design and maintenance of cyclically loaded metallic infrastructure structures, such as bridges and offshore wind turbines, are discussed and it is shown how sustainability, resource conservation, reduction of the CO2 footprint, availability, security of supply and economic viability of steel infrastructure structures can potentially be achieved.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Das Nanolaminatpflaster – Schweißnahtnachbehandlung für bisher unerreichte Lebensdauerverlängerung(2021-09); The nanolaminate patch – a post-weld treatment for unmatched lifetime extension. Maintenance of dynamically loaded steel infrastructure is expensive. The frequency of inspections increases towards the end of the lifetime. The weak link of a structure is often the structural joint. Economical maintenance methods for fatigued structural components, which make expensive inspection intervals obsolete, have not been transferred to engineering practice yet. This article introduces a new post-weld treatment method using a nanolaminate coating, also called nanolaminate patch, on the welded joint. A tension-tension fatigue testing study of welded steel specimen shows the potential of this post-weld treatment compared with other existing post-weld treatment methods in respect to lifetime extension. Nanolaminate coating applied in this study shows promising first results: At an applied stress range close to the yield strength, the lifetime of the weld can on average be extended by a factor of 3 or 4.5, respectively. The nanolaminate coating is discussed in comparison with other post-weld treatment methods. The post-weld treatment using nanolaminate coating seems to be of interest across industries and is applicable on new or existing structures.Publicationtype: Journal Article102 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 63 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Die Auswirkungen von Diffraktion und Multi-Reflexion auf zylindrische Stützen(2020-01-01); ; The effects of diffraction and multi-reflection on cylindrical columns. The surrounding topology of a column potentially has a significant impact on a blast wave and the following design procedure. Effects like diffraction or multi-reflection does not seem to be included in design codes or technical literature. This issue shall be addressed within this paper. The paper addresses three main topics. First, the paper answers the question whether the area behind the column is protected, constituting a shadowed area. For the column itself, this is not of significant influence, but shall clarify if the load on a backwards-placed structure, e. g. a façade, can be determined correctly by using current technical codes. Second, a secondary shock-front, which originally initiates by diffraction and then distributes diagonally in space, shall be investigated. The correct load assessment on e. g. a second-row-column is discussed. Third, directly coupled with the assessment of incident pressure build-up behind the column due to diffraction is the quantification of pressure increase due to (multi-)wave reflection at a facade, leading to a significant pressure scale up, which might be relevant for design of column and/or façade.Publicationtype: Journal Article161 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Vorschläge zum Bau von Verbundbögen an StabbogenbrückenSuggestions for the construction of composite arches at tied arch bridges. The arches of tied arch bridges are predominantly under compressive loading and are most often constructed out of steel. This contradicts the basic engineering knowledge to use concrete for compressive loading and steel for tension loading. The simple assembly of steel arches compared to the time-consuming falsework for concrete arches, the large degree of prefabrication and a smaller self-weight compared to a heavy concrete arch are reasons for choosing to use a steel arch. As an alternative to steel or concrete arches, suggestions for composite arches on ”normal“ tied arch bridges are made. A composite tied arch combines, like a composite column, the advantages of steel and concrete construction. Calculations show that rolled sections encased in concrete can be used as tied arches for common effective spans. Such arches have economic advantages and the rolled sections can be additionally used as formwork or formwork girder. Concrete filled hollow sections allow for particularly slender arches and the hollow section functions also as formwork. Furthermore, possible arch supports are specified and analyzed. Tied arch bridges are often assembled at a preassembly area and subsequently launched into their end position. For such cases, composite arches have, when compared to pure steel arches, a lighter steel construction during the bridge launch.Publicationtype: Journal Article120 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Laserstrahlgeschweißte T-Stoß-Verbindungen in Stahlhohlplatten(Wiley, 2015-09-02); ; ; ; Fricke, WolfgangLaser‐stake welding enables an economic production of all‐steel sandwich panels that can be used for steel bridges as well as for decks in ro/ro ships. Deck plates of 10 mm thickness can be joined to interior web plates ensuring a weld throat thickness of 2 to 3 mm. Up to now the thickness of cover plates which could be stake welded in acceptable quality was limited to 4 mm. For this reason these sandwich panels could be used only for secondary structures in shipbuilding or similar only static strained structures. In the frame of FOSTA project P869 “Laser beam welded T‐joints“ (IGF 16935 BG) reliable welding parameter and technologies were developed to join cover plates up to 10 mm thickness to enable the use of sandwich panels in higher strained, fatigue loaded structures. Fatigue tests were performed with laser‐stake welds subjected to axial, shear and multiaxial in‐phase loading and assessed by the nominal and the notch stress approach. In addition to possible effects of gaps between deck and web plates or of the steel strength, the application of interaction formulae to laser‐stake welds is checked as contained in Eurocode 3 and the IIW recommendations for the fatigue assessment of multiaxial loading. In this way, the basis is provided for a safe design of laser‐stake welded T‐joints. A technology for tractor‐based assembly of these panels using laser beam and laser beam GMA welding was developed simultaneously.Publicationtype: Journal Article75 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Ein angepasstes Ermüdungslastmodell für stählerne Stabbogenbrücken mit freistehenden BögenLateral arch vibrations are frequently observed at existing steel bowstring bridges. These result from critical axle arrangement loads of crossing trucks and resonance. A long post oscillation is often detected. Hence, a large fatigue load for the arch and the adjacent construction components exists, which is included in the actual standards insufficiently. An extended fatigue load model for structural design is presented to incorporate the large fatigue load while planning such bridges. It is called ELM 3a and is based on the fatigue load model 3 given in DIN Fachbericht 101. An adjustable distance between axles and an adjustable speed are introduced for the ELM 3a to maximize the lateral arch vibrations. A simplified impulse form is given for the wheel loads in this context, which can be used in an FEM calculation for example. © Ernst & Sohn;.Publicationtype: Journal Article68 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effiziente Dimensionierung von Tragbohlen kombinierter StahlspundwändeEfficient verification of king piles of combined steel sheet walls. This contribution deals with the optimization of the stability verification according to DIN EN 1993‐1‐1 for the design of combined steel walls built‐up by H‐sections as king‐piles and infill steel sheeting. In addition to the king piles’ embedment in the soil advantage can be taken from the torsional stiffness of partially welded double king piles. Since lateral torsional buckling does not need to be considered for cross sections with a sufficient torsional stiffness, it is possible to simplify the stability verification significantly by considering the partial welding and the resulting increased torsional stiffness. In order to determine the real torsional stiffness, two large‐sized king piles with three degrees of welding were tested. Based on a numerical model the test results were simulated and a parameter study was carried out. For a given example it is shown how the consideration of partial welding allows an efficient design verification of the king piles.Publicationtype: Journal Article50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Flatternachweis von Brücken mittels Finiter BalkenelementeWind-induced flutter of bridges with streamlined, plate-like cross-section occurs as coupled torsional and vertical oscillation. Prediction can possibly be facilitated by representing the spatial system by a generalized 2-DOF system. This, however, may be unadmissible or extremely conservative if the modes of torsional and vertical vibration differ strongly. In this case, flutter prediction should be based on spatial modeling. Classical methods of aircraft engineering for solving the spatial problem proceed from partial differential equations of motion. For applications in bridge engineering, the finite-element concept proves more efficient. In this paper, two beam elements of differenct complexity are defined, and correspondend matrices are given. Formulation and solution of the resulting MDOF equations of motion is described. Results of a numerical study are presented and discussed.Publicationtype: Journal Article336 339