P 615 - Innovative steel construction solutions for primary and secondary structures of multi-purpose buildings in the public sector

P 613 - Laser-MSG hybrid welding of innovative steel materials The aim of the research project was to provide the crane, vehicle and plant construction industry with a tool that can be used to weld high-strength fine-grain structural steels economically and safely using the laser-MSG hybrid process. To this end, suitable welding consumables and the corresponding temperature cycles were qualified together with the process for these steels. The process is particularly interesting for the steel S1300QL, which has only recently been trialled and represents the current upper limit of water-quenched and tempered fine-grain structural steels suitable for welding in terms of strength. Its suitability for hybrid welding was demonstrated for the first time in this project. With the only representative of thermomechanically rolled steels analysed, the steel S700MC (1.8974), joints were produced together with a MoNi-type welding wire that met the requirements in terms of strength and toughness. In the tensile test, fracture occurred in the weld metal as the hardness of the weld metal was lower than that of the base material. The water-quenched and tempered fine-grained structural steels S690QL (1.8928) and S960QL (1.8933) proved to be comparable in terms of the behaviour of the welded joint. As the hardness of the heat-affected zone and weld metal was significantly higher than that of the base material, the fracture occurred in the unaffected sheet. A "hardness sag" in the heat-affected zone could not be observed either with extremely short or longer cooling times. The values for the impact energy required in the delivery conditions were also met at low temperatures down to -40°C. It was demonstrated that laser MAG hybrid welding is suitable for welding high-strength fine-grain structural steels in the sheet thickness range between 5 and 7 mm for vehicle and crane construction with nominal yield strengths of 690 MPa up to 1300 MPa. The solid and metal powder wires developed for MAG welding can be processed with the laser hybrid welding process without any problems. Authors: H. Haferkamp, O. Meier, B. Boese, R. Mittelstädt, G. Kuscher Publication: 2007

P 617 - Workshop repair concept for vehicle structures made of high-strength steel materials in automotive body construction The aim of this research project was to develop a repair strategy for vehicle components made of high-strength steel materials, taking into account practical transferability. A further objective was to achieve the component properties before damage occurs in order to guarantee the property profiles with regard to fatigue strength and crash behaviour after a repair. As part of the first and second project phases, various practically relevant repair joining methods were investigated with regard to their use for the repair of vehicle structures made of high-strength steel materials. The results of the load-bearing capacity tests under quasi-static, oscillating and impact loading of these repair joints were compared and evaluated with the corresponding results of the near-series production joints. Resistance spot welding, resistance spot welding bonding and laser beam welding were used as near-series production joining methods. The repair methods considered were adhesive bonding, blind riveting, blind rivet bonding, MIG soldering, resistance spot welding, MAG welding and hand-held laser beam welding. Parallel to these investigations, the possibilities of using various practical cutting techniques for cutting automotive structures made of high-strength steel materials were analysed. Building on this, the next phase of the project focussed on the development of repair concepts for various structures made of high-strength steel components. Here, a partial cut-out and a partial section repair on component-like Z-profiles were designed and realised using various repair joining methods. The profiles were then crash-loaded using a drop weight tester and the deformation behaviour of the repaired Z-profiles was compared with that of the non-repaired profiles. The repair concept developed for a partial cut-out repair on the Z-profile was verified in the final project phase on a sill with minor damage. verified. The repair joining methods of blind rivet bonding, hand-guided laser welding and MAG welding were used in the investigations on the real component. The repair strategy developed in this project created the basis for the repair of automotive structures made of high-strength steel materials. The results thus obtained already form a comprehensive basis for calculable workshop repairs with regard to the restoration of component properties. Authors: O. Hahn, M. Wibbeke, D. Böhme, S. Allmeier, H. Haferkamp, B. Boese, H. Matthiß, C. Schmid Publication: 2006

P612 - Development and design of a new modular antenna support structure For the new mobile phone networks, there is a very high demand for antenna support structures that can be erected quickly and economically. The aim of this research project was to develop a simple, type-tested system that can be used in series. The required features were a modular, unobtrusive design with shielding, which ensures that the radio radiation is well below the legally required limits. In its decision of 5 March 2003, the Münster Higher Administrative Court (OVG) already demanded higher requirements with regard to both the optical effects of the transmitters and radiation emissions. Against this background, the research results presented here gain additional topicality. A support structure system was developed that allows different construction heights with an otherwise identical design. It consists of standardised modules with identical connecting flanges for all system lengths. By installing one or two shielding modules, even stricter limits for radio radiation can be safely complied with. The antenna support structure can be brought to the construction site as a complete, finished delivery unit and attached directly to a pre-assembled substructure using a crane. The same support tube cross-section was selected for all planned construction heights when determining the load and dimensioning the antenna support structure. The verification against vortex-excited transverse vibrations is important. These can reach high numbers of load cycles transverse to the wind direction. The supporting structure must therefore be designed to be fatigue-resistant. The structural analysis was designed for wind load assumptions in accordance with E DIN 1055-4 and DIN 4131 or 4133 and already for the new E DIN 1055-4, whereby the decisive aerodynamic coefficients were determined in extensive wind tunnel tests. The system has been type-tested by the North Rhine-Westphalia Structural Testing Office. The tests have shown that the dynamic behaviour as a result of wind impact is largely determined by the substructure in addition to the antenna design. In order for the above-mentioned statics to be valid, a minimum rigidity of the existing substructure must therefore be ensured. This must also be verified by the site planner. The antenna system can be installed on almost all roof locations and any roof shape. The respective internal forces required on site for the substructure can be read from a simple table. This speeds up the production and assembly of the system considerably thanks to the possibility of prefabricating the modules and also makes it more cost-effective. STUDIENGESELLSCHAFT STAHLANWENDUNG e. V. Publication: 2003 Authors: Dr.-Ing. M. Hortmanns, Dipl.-Ing. S. Stark