P 297 - Determination of the long-term properties of similar weld metals of new high-temperature steels

P 298: Static and dynamic deformations of steel radio masts The subject of the research project was radio masts in steel and reinforced concrete construction, as they are currently used for the nationwide expansion of mobile phone networks. The static and dynamic deformation behaviour under the influence of wind was to be investigated up to the serviceability limit state. For long-term observations and measurements, five original masts were selected as examples from the variety of competing construction methods - in a steel, a spun concrete solid wall construction and in three different steel lattice designs. At the same time, model tests were carried out in the boundary layer wind tunnel. By analysing the measurement results with regard to the maximum twist angle at the top of the mast and the duration for which the permissible change in the deflection angle was exceeded, reliable frequency curves were to be obtained. They should also include strong wind events or allow conclusions to be drawn about their effect by extrapolation. Both original measurements and modelling tests showed that the stresses and deformations calculated on the basis of existing design concepts could not be achieved under any circumstances. On the basis of these investigations, a new concept was proposed which is orientated towards the design philosophy of the Eurocodes. For the design of radio masts in the serviceability limit state under the influence of wind, the previously valid arbitrary deterministic criterion of half the dynamic pressure without gust reaction is no longer used. Instead, the assessment is carried out on the basis of the frequency with which the operator authorises exceeding the radiation limit angle as a result of the probability of extreme wind situations. According to the newly gained knowledge, there is still potential for optimisation in the design of new structures for all construction methods in steel and reinforced concrete. It is also expected that design reserves can be demonstrated on existing radio masts, which the mast operators can utilise for retrofitting with additional antennas. Due to the planned development of areas with little infrastructure, capacity expansions and the addition of new network providers, a high demand for radio mast construction projects can be expected in the medium term. In the long term, the Europe-wide expansion of mobile communications networks will be at the centre of construction activity. Due to the large quantities of steel required, regardless of the chosen construction method, there is a large market for German steel construction. STUDIENGESELLSCHAFT STAHUNWENDUNG e.V. Publication: 1999 Authors: Dipl.-Ing. Ch. Kammel, Prof. Dr.-lng. G. Sedlacek, Dipl.-Ing. W. Langer

P 294: Investigation of the corrosion attack on components in enclosed composting plants with special consideration of stainless steels and the discharge of alloy components In environmental and disposal technology, steel is exposed to high mechanical and corrosive conditions. The aim of this research project was to develop quantitative statements on the corrosion resistance of selected steels and thus to provide information on material suitability according to application areas in enclosed composting plants. With regard to environmental protection, the significance of the alloy components for the composition of the compost was to be analysed in particular. As part of the research project, a corrosion register was compiled on the basis of literature research, surveys of operators and inspections of composting plants. The corrosion resistance of selected steel materials was analysed by means of ageing tests under practical conditions in various types of plant. With the help of a service life-cost analysis - PC programme: "Stainless steel in service life-cost comparison" from the Informationsstelle Edelstahl Rostfrei, Düsseldorf - various material alternatives were tested as models. Corrosion damage has occurred in all enclosed composting plants to date, which could have been avoided if the available expertise had been applied. Based on the information standard DIN 50 929, assessment standards for corrosiveness under the various conditions in composting plants are presented. Based on practical experience, theoretical considerations and observed material behaviour, material recommendations are given for various requirement profiles. Model calculations based on the corrosion rates determined show that the discharge of heavy metals from stainless steels is orders of magnitude lower than the average background load of composts in Germany. In view of the fact that up to now only sporadic and little systematic information has been published on corrosion in composting plants, the research project closes an information gap. The results can be used by designers and plant operators as a decision-making basis for the selection of materials when planning new plants or renovating existing plants. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 1998 Authors: Dr rer. nat. P. Dierschke, Dipl.-Chem. A. Tulke

P 293: Design rules for the assessment of the fatigue behaviour of crane structures - Classification of crane-specific notch details The aim of the research project was to identify and close normative gaps with regard to the fatigue analyses of crane structures. Therefore, in close contact with the industry, a selection of those crane-specific design details were investigated which frequently occur in practice but are not yet included in the notch detail catalogues of the various standards. In addition, the influence of the use of high-strength steels on certain notch details was investigated in more detail. On the basis of the investigations carried out, concrete proposals for categorisation in the notch classes according to EC 3 could be made for the notch details angle connections, box sections welded from L-sections and for eye bars with round sections. Rough classifications could also be made for the notch details dovetail plate, attached rectangular plate and for eye bars with rectangular profiles, which still need to be verified by further tests. The use of high-strength steels for the notch detail of stud welds does not change the classification in the existing notch tables, which were developed for normal-strength steels, due to the notch sharpness. For tack welds on high-strength fine-grain structural steels, the few results of the pilot tests are well above the highest notch class according to EC 3. For the detail of lamellae welded onto high-strength fine-grain structural steels, it is also evident that the base material has a clear positive influence on both the fatigue strength and the Wöhler line inclination. There is still a considerable need for research in this area of the general transfer of the rules for fatigue analyses for normal-strength steels to high-strength steels. This project makes a contribution to extending the existing notch case tables in the applicable standards to include some crane-specific notch details. Pilot tests were carried out on further details with positive results, which emphasise the need for further activities in this field. It has also been shown that certain notch details can be rated higher in terms of fatigue strength by using high-strength materials. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 2000 Authors: Prof. Dr F. Mang, Dr S. Herion, Prof. Dr G. Sedlacek, Dipl.-Ing. Ch. Müller, Dipl.-Ing. M. Kästner

P 291: Application-technical investigations into the buckling and folding structuring of thin-walled steel pipes Bulge structuring with the aid of hydraulic active media is a new deformation technique for processing semi-finished pipe products. Tubes receive raised or inwardly directed regular or irregular deformations of their jacket. Structured tubes have better strength and vibration properties than smooth tubes in many areas of application. The bulging structure also influences the external and internal flow and reflects sound and light waves in a special way. The material steel is particularly suitable for the production of the various structural shapes. The selection of grades suitable for the stresses in combination with a buckling structure adapted to the different requirements offers simple and often surprising, innovative solutions for known and new problems. The present research project served to define technical parameters on the way to an industrial, targeted and reproducible buckling structuring of steel pipes. Supplementary work was carried out to analyse the strength of these pipes under fatigue loading with regard to bending (point and line load), compression and torsion. The sound-absorbing effect of the structuring was demonstrated in acoustic tests. The present research work provides numerous indications of the many possible applications of this new type of deformation technology and thus opens up new technical possibilities for the use of steel pipes. A supplementary prospective market analysis examines and describes specific applications for the use of structured steel pipes. Selected examples are used to illustrate the market potential. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 1997 Authors: Prof. Dr.-Ing. U. Hellwig, Dipl.-Ing. T. Görlich, Dipl.-Ing. H. Nikolaus