
By utilising their cross-sectional and system reserves, continuous composite beams can be designed plastically if the indented parts of the steel sections fulfil the requirements of Class 1. In the case of slender …
By utilising their cross-sectional and system reserves, continuous composite beams can be designed plastically if the indented parts of the steel sections fulfil the requirements of Class 1. In the case of slender cross-sections assigned to class 2, only the plastic reserves could previously be utilised. This can be a disadvantage for composite beams, as the main load-bearing capacity is in principle determined by the span cross-section area. However, it cannot be fully utilised if the redistribution of the support cross-sections into the span sets a tracking limit. It was therefore desirable, despite the prevailing risk of buckling, to allow large plastic deformation on the internal supports even with Class 2 cross-sections.
This was achieved. However, it should be noted that the support cross-section must be reduced by calculation in such cases. One of the aims of this research project was to determine the effect of such a reduction on the load-bearing capacity. On a two-span beam with a centred concentrated load, it was shown that the reduction of Mpl,s to 80 % due to local instability reduces the ultimate load by only 4 %. In cases where the plastic zero line is high and thus the span cross-section becomes ductile, the ultimate load can even increase if the steel beam in the span is transferred to the hardening zone. The work has also shown that the yield hinge theory can be applied to continuous steel composite systems of the type presented here, even if the rolled sections only fulfil the requirements of class 2. If the beams are sufficiently deformable in the area of the support moments, the full moment redistribution can be taken into account - with a mathematical reduction of the column cross-section. Since the tests were carried out on rolled beams with complete dowelling and support stiffeners on both sides, it was also shown that the bending load-bearing capacity does not have to be reduced due to the simultaneously acting shear force. The tests apply specifically to the hot-rolled beams of the corresponding dimensions analysed here and under the other specified conditions. For higher beams, where lateral-torsional buckling may be expected, special tests must be carried out. STUDIENGESELLSCHAFT FüR ANWENDUNGSTECHNIK VON EISEN UND STAHL e.V.

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P 121 - Stabilisation of hot-rolled I-beams with gratings Gratings are used as easy-to-install load-bearing prefabricated elements, in particular as a covering material for walkable and drivable floor surfaces such as platforms, tegals or as a cover over horizontal openings. Of decisive importance in such applications are the good light and air permeability, high load-bearing capacity with low dead weight, easy installation and removal, the inherently slip-resistant surface and the fact that liquids and dirt cannot be deposited. The clear focus for the use of gratings is in industrial construction; however, they have also been increasingly introduced in the construction industry in general, for example as sun protection gratings and as façade walkways or as step elements for outdoor staircases. The present research work focusses on the interaction of steel girder scaffolding and mounted grating. By taking into account the stabilising effect of the grating element, the load-bearing capacity of the supporting steel girders is to be increased, thereby improving the cost-effectiveness of the overall structure. The work was carried out with financial support from the Federal Minister for Research and Technology at the Institute for Building Structures and Strength, TU Berlin, Prof.Dr.-Ing. J. Lindner, on behalf of the Studiengesellschaft für Anwendungstechnik von Eisen und Stahl e.V. (Study Association for Application Technology of Iron and Steel). STUDIENGESELLSCHAFT FÜR ANWENDUNGSTECHNIK VON EISEN UND STAHL e.V. Publication: 1985 Authors: Prof. Dr.-Ing. J. Lindner, Dipl.-Ing. I. Stickel
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P 100 - Development of characteristic values for the production of cold rolled profiles from the point of view of economical production of dimensionally accurate profiles Cold profiling using the roll forming process is a forming process that has been used industrially for over half a century. It allows the production of cold-formed profiles with consistent and high dimensional accuracy, some with sharp-edged bends, many curved sections, complicated double folds, with - if desired - targeted work hardening of the starting material and finally the combination of profile shaping with further processing steps such as punching, beading and bending. Although the diverse requirements and the general technical development of mechanical engineering have led to a wide variety of roll forming systems over the course of time, the technology of roll forming is still largely based on practical experience. This applies both to the dimensioning of production facilities and to the design of forming tools. This unsatisfactory situation can probably be explained essentially by the fact that the entire process - in addition to the rather difficult geometric relationships of forming - is governed by numerous working conditions which influence each other. For this reason, the Technical Committee of the German Cold Forming Association has been working closely with a well-known plant manufacturer for several years on the development and dimensioning of a machine and drive concept for research purposes. A machine and control technology solution was developed and realised which for the first time makes it possible to empirically investigate the interactions between the parameters of the production process and the properties of the product in a reproducible manner. This research work was carried out on behalf of the Studiengesellschaft für Anwendungstechnik von Eisen und Stahl e.V. by Prof. Dr.-Ing. D. Schmoeckel, Institute for Forming Technology at Darmstadt Technical University. In addition to confirming some of the results of earlier investigations, new findings of practical relevance were obtained. This applies in particular to the experiments on slip reduction, which resulted in a drastic saving in the energy used, and on the relationship between the quality of the finished product and the selected forming strategy. These results represent a step towards a better understanding of the complex manufacturing process, but at the same time demonstrate the need for further intensive efforts to conduct in-depth research into roll forming technology. The research project was funded by the Federal Ministry of Research and Technology (BMFT) and was supervised by Kernforschungsanlage Jülich GmbH (KFA) as the project sponsor for the raw materials research programme. STUDIENGESELLSCHAFT FÜR ANWENDUNGSTECHNIK VON EISEN UND STAHL e.V. Publication: 1986 Authors: Prof. Dr.-Ing. D. Schmoeckel, Dipl.-Wirtsch.-Ing. U. Eichler
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