P 487 - Load application for concrete-lined hollow section composite columns with normal and high-strength concretes

P 486 - Investigations on the ductility of composite materials when using high-strength steel and high-strength concrete Authors: J. Hegger, P. Döinghaus, G. Sedlacek, H. Trumpf Publication: 2003 Aim of the research projects are the determination of the load-bearing capacity and ductility of shear connectors in high-strength concrete as well as the development of shear connectors with a sufficient ductility in high strength concrete. Therefore various shear connectors have been tested with Push-Out test. The development of a new Push-Out test specimen enables tests on single headed stud shear connectors and its modification in high-strength concrete. Consequently an accurate analysis of the load-bearing behaviour as well as an efficient check of the various variants is achieved. So that a headed stud shear connector in high-strength concrete will exhibit ductile behaviour while retaining its ultimate load, its application can be modified by enlarging the weld collar, strengthening the connector shaft, e.g. with a sleeve made of metal, using a high-strength base material for fabricating a cold-formed headed stud shear connector (S460) or the arrangement of double connectors as close together as possible due to fabrication. At present the last procedure is the easiest to guaranty an application of headed stud shear connector as ductile shear connectors in high strength concrete. It has absolutely to be renounced on intermediate traverse reinforcement between the studs. The loadbearing capacity of the second stud has to be reduced to 80% of its design value. This possibility is directly applicable for small and medium companies.

P 488: Sliding connections in trusses under non-stationary loading A method regularly used in structural steelwork to connect bar-shaped load-bearing elements to each other is the gusset plate connection. Here, two or more profiles lying in one plane are connected to each other via a gusset plate. The profiles are connected to the plate using bolts or weld seams. One of the design variants is the sliding connection. Pockets are cut into the gusset plate to accommodate the profiles to be connected, the profiles are pushed into the pockets and then welded to the sheet metal. The weld seams can be made all round or only on the sides. The aim of the research project was to record the behaviour of the sliding ring connection with only lateral weld seams under cyclic loading in order to enable an evaluation with regard to the fatigue strength curves of EC 3. In the work, a plastically dimensioned gusset plate was investigated, the geometry of which was selected in such a way that the dominant fatigue-relevant areas are covered for as many practical construction designs as possible. The series of tests carried out included specimens left in the welded state, stress-relieved annealed specimens, galvanised specimens, gusset plates with angular cut-outs and gusset plates with rounded corners in the cut-outs. The load level of the test specimens subjected to cyclic tensile swelling was in the range of 60% to 100% of the calculated service load with reference to the measured material strengths. The method used to analytically determine the service life includes the crack initiation phase according to the local concept as well as the crack propagation based on linear-elastic fatigue fracture mechanics. Both the tests and the calculated service life predictions show that the investigated gusset plate connection is only suitable to a limited extent for structures under predominantly non-stationary loads with regard to its low load-bearing capacity. The gusset plate connection with angular plate cut-outs could not be categorised in the notch case according to EC 3. A classification in notch case 40 was proposed for the gusset plate connection with the rounded corners. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 2003 Authors: Prof. Dr.-Ing. J. Lange

In the steel producing and processing industry, labelling and marking of steel products is an important logistical tool. Marking that cannot be clearly assigned or is incomplete results in incorrect identification of steel materials, which can lead to mix-ups, incorrect deliveries and increased difficulties with liability issues. The reason for the frequent occurrence of such products that cannot be clearly identified is the fact that the marking technologies currently in use, such as the application of labels or spraying processes, only fulfil requirements such as machine readability, weather resistance or temperature resistance to a limited extent. This research project was initiated together with Salzgitter AG to improve the identifiability of steel products and to increase the competitiveness of steel manufacturers, distributors and end users. Fundamental investigations were carried out into the permanent labelling of semi-finished steel products using laser radiation and the possibilities of detecting such markings. Various laser labelling processes were used. The possibility of annealing and ablative marking was investigated. Based on these results, combined processes were developed that combine the actual marking process with cleaning of the steel surface, also using laser radiation. In addition, tests were carried out on painted steel samples. The applied paint layer is partially removed by the laser beam or its colour is changed, creating a contrast to the untreated paint. All of the aspects investigated as part of this project were used to draw up a catalogue of requirements, which was used as the basis for applying for a further research project to realise this system at European level. STUDIENGESELLSCHAFT STAHLANWENDUNG e. V. Publication: 2002 Authors: Dr.-Ing. A. Ostendorf, Dr.-Ing. M. Goede, Dipl.-Phys. A. von Busse

P 483 - Testing of metallic tool concepts for the thixoforming of steel Authors: D. Hartmann, U. Morjan, B. Nohn, M. Zimmer, A. Hoffmann, R. Braun Publication: 2002 Thixoforming of steel is in a very early state of development. Reduction of costs and higher freedom with lay outing the components, e.g. regarding the forged pieces, are expected. A hindering point for the industrial application is the up to now weak durability of tools. That is why research was focussed on the choice of a suitable metallic tool material as well as the development and the experimental testing of a material adapted tool-concept. The aim was to reach a standing time of the tools, which in consideration of later economical benefit makes thixoforming of steel possible. On the basis of meaningful component geometries different tool materials were investigated via numeric simulation about their suitability for thixoforming of steel. The chosen tool materials were the molybdenum based TZM (MoTi0,5Zr0,08C0,02) and the copper based Hovadur CCNB (Cu-Co1NiBe0,5). This facilitated a direct comparison to the heat resistant steel 1.2367 (X38CrMoV5 3), which was investigated in a previous project. The geometry of the testing component was selected according to a cylinder pump fabricated in mass production. Based on the chosen material a thixoforming tool concept was generated and tested in practical conditions. The research showed that the durability of the tool can be significantly extended by proper selection of tool materials and by an adapted shape concept.