P 1043 - Optimised dimensioning of high lattice towers for wind turbines under realistic consideration of aerodynamic effects, fatigue behaviour and the influence of steel grades

P 1042 - Fatigue strength of hot-dip galvanised composite dowel bars in composite bridge construction Studies in recent years have shown that the hot-dip galvanisation of steel components in bridge structures has economic and ecological advantages. It has been shown that the corrosion protection provided by hot-dip galvanising can last for the service life of a bridge of 100 years, even in an environment with high corrosivity, so that no major corrosion protection maintenance measures are required. At the same time, another innovative solution was developed to increase the efficiency of composite bridges. Based on several research projects and an initial application in 2003, composite dowel bars have been proven to offer an economical solution for shear connections between steel girders and concrete slabs in composite bridge structures. Continuous improvements and further developments ultimately led to FOSTA applying for a general technical approval from the DIBt in Germany. Numerous bridges using this new technology have since been built in Germany and abroad. However, hot-dip galvanising cannot yet be used for bridges with composite dowel bars, as the effects of hot-dip galvanising on the fatigue strength of flame-cut composite dowel bars are not yet known. The required verification of fatigue in accordance with DIN EN 1993-1-9 can therefore not be carried out at present. In order to be able to combine the advantages of the composite dowel bar with those of hot-dip galvanising in bridge construction, the basis for technical regulations for the use of hot-dip galvanised composite dowel bars was developed as part of this project. For this purpose, the galvanising process with the process-related and geometric influences was examined in detail with regard to possible pre-damage to the composite dowel bar. It was found that the resulting plastic strains in the most unfavourable configuration of geometry and galvanising process of a maximum of 0.5% were below the limit value of 2% specified in DASt Guideline 022, Annex 4 for the requirements of detail class A. Furthermore, the influence of hot-dip galvanising on the fatigue strength of the composite dowel bar was investigated by means of cyclic tests. Comparative fatigue tests were carried out on galvanised and non-galvanised small component samples, push-out bodies and component-like beams. The tests consistently showed that, as regulated for the non-galvanised composite dowel bar in the general design approval, the proof of fatigue strength can also be carried out for the hot-dip galvanised version with notch case 125 in accordance with DIN EN 1993-1-9. This made it possible to achieve the research objective and provide a practicable basis for design in practice. Publication: May 2020 Authors: Prof. Dr.-Ing. M. Feldman, R. Kühne, M.Sc., Prof. Dr.-Ing. D. Ungermann, S. Holtkamp, M.Sc.

P 1041 - Optimisation of the principle of operation and energy utilisation for sandwich construction with energy accumulation, energy distribution and insulation Industrially manufactured sandwich elements with additional trapezoidal steel sheets on the outside were joined together in the FOSTA project P 779 to form the so-called SEA air collector (SEA = Sandwich Energy Accumulation). Due to the cross-section of the trapezoidal steel sheets, channels through which air can flow are created when the individual components are joined together on the outside. With solar radiation on the south façade and on the roof surface, the SEALuftkollektor can generate an annual energy yield of approx. 160 kWh/m² in the form of heated air. This project investigated the extent to which the energy yield of this collector can be further improved by optimising physical and design parameters. In order to investigate the individual optimisation aspects, a research approach consisting of measurement, simulation and calculation was chosen. Laboratory measurements were used to quantify the positive influence of a transparent cover in the form of a solid polycarbonate panel on the efficiency and temperature level of the SEA collector. Changing the profile geometry of the absorber and adapting various design aspects to increase heat transfer also proved successful. Ultimately, this resulted in an aesthetically pleasing collector in which all variants continue to fulfil the principle of using only components that are available on the market as individual parts. Laboratory measurements were used to precisely clarify the mass flow dependency for the analysed collectors and efficiency curves were generated for three SEA collector variants. The accompanying simulation and calculations were used to show the range of optimum air duct heights for flat or trapezoidal absorbers, how the angle of incidence, different degrees of absorption and the collector lengths affect the efficiency and temperature level of the collectors. Finally, a sample hall was used to show the contribution that collectors can make to the energy utilisation concepts of heating and cooling using different system variants of secondary energy generators and the integration of an energy storage unit in an hourly-resolved annual analysis with reference weather data. With regard to cooling, for example, it was shown that even without an energy storage system, full solar coverage can be assumed. In the case of energy utilisation for heating, however, this only appears possible with the integration of an energy storage system. Publication: March 2020 Authors: Dr Michael Hermann, Timo Altan, Frederik Böhm, Sofía Camarena Covarrubias, Paolo Di Lauro, Stefan Fortuin, Muhammad Haris, Dr Korbinian Kramer, Manuel Lämmle, Axel Oliva, Max Reinhardt, Christoph Thoma, Christian Welz, Rolf Koschade, Gabriele Deisenroth-Bröcker, Donald Greiner, Klaus Pilsner

P 1040 - New application possibilities for ventilated metal curtain wall façades through the use of composite sheets with stainless steel Stainless steels are often used in the design of ventilated metal façades. They impress with their characteristic appearance and high durability. However, challenges arise with large-area façade elements. High rigidity requires greater material thicknesses and higher resource consumption. Increasing material thickness limits the individual design of the façade elements. The current requirements in modern façade design intensify this challenge. Individually shaped, three-dimensional façade elements with sharp-edged contours or organic free-form surfaces with soft transitions between individual moulded elements are often desired. The solution approach chosen in this research project addresses the realisation of these requirements and tests the use of new composite sheets with stainless steel for ventilated curtain wall façades. The composite sheet allows shaping with lower forming forces while maintaining the same rigidity, and its own weight is also significantly lower. Following a basic characterisation of the material, evidence is provided for the use of typical joining, cutting and forming processes. The possibility of using other forming processes, such as the milling edge technique for composite sheets with stainless steel, is also positively demonstrated. Another result is a catalogue of possible element geometries, as well as a presentation of the effect of static strengthening through component folding. The realisation of pneumatic stretch forming as a new forming process for the design of façade sheets is successfully implemented, and current requirements in façade construction are given additional design potential as a result. As proof of feasibility, a demonstrator was created to show the potential of the composite sheet as a façade sheet. An additional innovative side effect is the option of inserting welding studs, which allow the panels to be fastened on the back and concealed. To summarise, the composite sheet investigated represents a very good alternative to elements made of single-layer metal panels for the design of rear-ventilated metal façades. Composite sheets with stainless steel are characterised by very good formability and are also suitable for the application of established façade design methods. The research project was carried out by the Department of Architecture and Metal Construction at Dortmund University of Applied Sciences and Arts and the Institute of Production Engineering at Dresden University of Technology with technical support and funding from the Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, with funds from the Stiftung Stahlanwendungsforschung, Essen. Publication: April 2019 Authors: Prof. Dr.-Ing. H. Hachul, Dipl.-Ing. (FH) J. Bach M.Sc., Dipl.-Ing. (FH) H. Rößling M.Sc., Y. Tekinbas M.Sc., Prof. Dr.-Ing. A. Brosius, Dipl.-Ing. M. Tulke, Dipl.-Ing. J. Watzke

P 1049 - Development of evaluation methods and guidelines for the bonding of ZnMgAl-alloy coated steel sheets To improve corrosion protection and abrasion resistance in the forming process, +ZM (ZnMgAl) alloy coatings are a further development of conventional +Z coatings. In combination with structural adhesives for automotive body-in-white applications, high bond strengths are achieved for this type of coating, although macroscopic adhesive failure components can occur in some cases. Due to the nevertheless high bond strengths achieved, the categorisation into adhesive for a poorly executed bond and cohesive for a well executed bond is not sufficient. As part of screening tests, a 1-component EP adhesive system and one +ZM and +Z coated material per material group were selected using ESZ and T-Peel tests based on the bond strength and failure behaviour. The mechanical bond properties and the resulting failure behaviour were determined under different test conditions and sample geometries. To develop an understanding of the interface, the surface condition of the substrates was determined before and after mechanical testing using XPS, AFM, SEM and EDX. This demonstrated that the resulting failure takes place in the interface and that elements of the coating, as well as adhesive residues, are present on both substrates after mechanical testing using XPS. The targeted variation of the composition of the oxide layer by means of different surface modifications did not improve the fracture pattern depending on the type of load, but did have an effect on the mechanical properties of the interface. The maximum bond strengths are significantly influenced by the properties of the joining parts. A method was therefore developed to reduce the influence of the joining parts on the peel resistance of the composites. This allows the peel resistance of the adhesives to be characterised as a function of the existing failure behaviour. It has been shown that the type of failure has a significant influence on the amount and time-dependent behaviour of the peel resistance in the boundary layer and the adhesive bulk. In order to determine the course of failure after the mechanical test, microspectroscopic images of the two fracture surfaces were taken as an extension to the fracture pattern evaluation, and carry-over on both sides was determined, the element assignment of which is possible using relatively simple and cost-effective IR spectroscopy. The results of this research project make it possible for small and medium-sized companies in particular to take a broader view of the failure behaviour of structurally bonded, +ZM-coated steel sheet and to assess it using the systematic procedure developed. Publication: 2017 Authors: Prof. Dr.-Ing. G. Meschut, Prof. Dr.-Ing. G. Grundmeier