P 767 - Residential and commercial buildings in modular construction - Design aids

P 766 - Technology and safety gains in hot-dip galvanising to expand the market position of galvanised steel construction In steel construction, structures are particularly economical and sustainable if they are hot-dip galvanised. In order to meet the growing demands of the market, further developments and economic efficiency measures have been implemented in the industrial sectors of steel production, steel construction and galvanising. These include in particular - the development of modern high-strength fine-grain steels in the sheet and profile area, - the realisation of complex component geometries in architecturally buildings and structures with large spans, - the use of larger boiler dimensions and improved processes in the galvanising process chain galvanising process chain, - the use of new zinc melts with modified composition for better control of the coating layer thickness and layer appearance. As a result of these further developments, the steel construction and galvanising industry suffered setbacks, as considerable crack damage was observed from 2000 onwards, particularly in structures galvanised with the new zinc melts mentioned above and mostly made of structural steels with strengths of 355 MPa and above. Investigations of damaged structures showed that the mechanism of liquid metal-induced stress corrosion cracking is the cause of the cracks. Although cracking due to liquid metal-induced stress corrosion cracking has been known for many decades, further research activities were required to clarify the problems at hand, and the large number and extent of damages observed since 2000 made new interdisciplinary investigations necessary. In particular, because it was found that interdisciplinary guidelines for crack-free galvanisation did not exist or were still under development. This research project was initiated against this background. The issues to be clarified were in particular the influence of pre-treatment (pickling), the material (toughness, strength), processing (welding, cold forming, drilling, cutting), the zinc alloy and the dipping speed on the formation of cracks as well as issues relating to the design of the construction (e.g. zinc pass-through openings). The results contributed to the development of new guidelines of the German Committee for Steel Construction DASt and the Association of German Engineers (VDI) for crack-free hot-dip galvanising and damage analysis. As a result, further developments of laboratory tests to determine the criticality of melts, the creation of input values for the numerical simulation of galvanising and for new metallographic preparation methods were also created for the practical implementation of the aforementioned guidelines. In addition, magnetic particle testing was further developed for constructions where cracks cannot be ruled out. The IGF project 265 ZBG of the Forschungsvereinigung Stahlanwendung e.V., Düsseldorf, was funded via the AiF as part of the programme for the promotion of joint industrial research and development (IGF) by the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag. The project was carried out at RWTH Aachen University by the Chair and Institute of Steel Construction and Light Metal Construction and the Institute of Ferrous Metallurgy, at Ruhr University Bochum, Institute for Materials, Department of Materials Testing, at the Institute for Corrosion Protection Dresden GmbH, at the Technical University of Darmstadt, Institute for Steel Construction and Materials Technology, Department of Materials Mechanics and at the State Materials Testing Institute Darmstadt, Department and Institute of Materials Science as well as by the Schweißtechnische Lehr- und Versuchsanstalt Duisburg GmbH. Authors: M. Feldmann, D. Schäfer, W. Bleck, A. Durst, M. Pohl, A. Luithle, A. Schütz, J. Triebert, M. Vormwald, C. Versch, C. Berger, R. Landgrebe, J. Adelmann, D. Körber, S. Keitel, H. Schmeink Publication: 2010

P 768 - Qualitative analysis of different methods for determining springback Sheet metal materials exhibit an individual springback behaviour after the forming process. This springback behaviour has a direct influence on the dimensional accuracy of deep-drawn parts. The springback of load-bearing body parts is particularly critical, as it has a greater influence on the accuracy of the entire assembly than large outer body parts, which can adapt to the structure within certain limits. High-strength and ultra-high-strength steels in particular tend to have a very pronounced springback due to their high yield strength Rp0.2. Different methods exist for determining the springback tendency in order to qualitatively differentiate the behaviour of different sheet metal materials. It should be noted that no measurement method is currently recommended as an international standard. One method widely used in practice to determine the springback tendency is to look at geometric shape deviations on hat profiles. Here, the deep-drawn component springs open after removal from the mould, as stresses are released in the material. The geometric shape deviation of the flange and frame of the deep-drawn part from the nominal contour is quantified by determining the tangent. In the second method, a hat profile is cut out of a deep-drawn rectangular mould. The springback is thus quantified using the original contour. Another method involves cutting a segment free in a radial direction to determine the springback tendency on a round cup. In all the methods presented, the springback tendency of the material is determined by comparing the actual and target contours of the respective component. The springback tendency was determined in this research project using the example of these three different methods with two materials as a quantitative comparison. The sheet materials HC340LA and HDT580X with a sheet thickness of s0 = 1.0 mm were selected for this purpose. The results obtained were then compared and contrasted. Authors: B. A. Berhrens, K. Voges-Schwieger Publication: 2009

P 769 - Detachable adhesive brackets for orthodontic tooth bonding - "PRODENT" The aim of this research project by the Kaiserslautern Materials and Surface Technology Working Group (AWOK) and INNOVENT Technologieentwicklung e.V. in Jena was to provide a new method for the tooth-friendly removal of adhesive brackets. The pliers commonly used today should no longer be used to exert forces on the bonded composite but to stretch a metal substrate in order to loosen the adhesive bond in the polymer-substrate interface. This necessitated a systematic investigation of the interactive effect of metal surface pretreatment and adhesive as well as the determination of the elongation values required for loosening. As part of the research project, test specimens were developed that enabled an experimental investigation of the residual strength as a function of the plastic strain previously introduced into the bonded part. The reduction in bond strength with increasing elongation of the bonded part was demonstrated using metal-to-metal and metal-to-tooth bonds, whereby adhesives, substrates and pre-treatment procedures commonly used in orthodontic dental bonding were used. In addition, an elongation value was identified that enables the bonded joint to be released without damaging the teeth for all adhesive systems analysed. This elongation value was used as the basis for the subsequent design of a functional model. The solution principle was implemented constructively in the form of a newly developed functional sample. After manufacturing the functional model in small quantities, orthodontic testing was carried out with the result that significantly less force was required for removal compared to conventional adhesive brackets. In addition to the intended reduced risk of enamel damage, this results in a more comfortable treatment procedure for the patient and orthodontist. Publication: 2010 Authors: Prof Geiß

P 764 - EUROBUILD in Steel Current developments in commercial construction The aim of this European research project "EUROBUILD in Steel" is to improve the level of information on the use of steel in building construction and thus to promote its increased use. To this end, both European and national construction methods were presented and analysed, particularly in the areas of office and administrative buildings and industrial construction. Furthermore, realised projects were selected that represent exemplary use of steel in the construction industry. The results of the research project were presented at the event "Presentation of new results from steel application research in the construction industry - current developments in commercial construction" on 27 November 2008 in Dortmund. This research report contains the "best practice documents" produced as part of the project for the areas of office and administrative construction and industrial construction. These documents illustrate the state of the art in Europe and are intended to serve as guidelines for architects and structural engineers. The most suitable and economical systems for certain building types are highlighted. Architects and engineers who are less familiar with steel and steel composite structures should be given a quick introduction to the use of steel in construction. The documents are organised as follows: Firstly, the most important design parameters are defined, taking into account special requirements from building utilisation as well as architectural aspects. This is followed by a discussion of design aspects, including both the main structure and the secondary components, the building envelope and the connecting elements. National specialities are then presented. In this way, for example, special systems that are currently only available nationally can also be publicised in other European countries. To illustrate the previously described constructions and design principles in realisation, a selection of case studies is presented in the final section. section presents a selection of case studies. These cover a range of designs and locations across Europe. This report is also available in English. Authors: M. Haller, N. Popa, M. Barendsz, P. Beguin, G. Nüsse, S. M. Iglesias, J. A. Chica, B. Åstedt, M. Lawson, N. Baddoo, D. Ungermann, J. Kalameya, I. Strohmann Publication: 2008