Institut für Tragwerksentwurf  |  FK3 Architektur Bauingenieurwesen Umweltwissenschaften   |  Technische Universität Braunschweig

In:  Proceedings of the International Association for Shell and Spatial Structures (IASS) Symposium 2015, Amsterdam Future Visions 17 – 20 August 2015, Amsterdam, The Netherlands Bild1 Abstract The undirected distribution of steel fibres in pre-fabricate concrete elements is of substantial nature. The goal of this investigation is to increase the local mechanical properties of specific concrete elements by controlling the alignment of the fibres according to the flow of forces using robots. The paper will present theoretical consideration and experimental research of the robot controlled interaction between magnetisms and the steel fibre orientation in freshly cast fibre reinforced concrete. The predefined path of the robot was controlled via movement parameters acceleration and velocity. The end effector of the robot arm was implemented with ultra-strong neodymium magnets of different dimensions and polarity. The repeatable path of the end-effector ensured reproducible interaction between the force fields and field lines of the different magnets, the geometry of the tested fibers and the geometry of the mould. The desired micro-overlap of parallel-orientated fibres in the tensile zones could be achieved by using sets of magnets mounted on the end-effector of the robot: They were aligned due to their specific characteristics and the particular choice of the fibres. Using the effect of moving these sets on the outside of the moulds in a rotary way, the concentration of fibres affected by the magnets could be increased drastically. The initially chosen concrete was due to its convenient rheological properties an UHPFRC (Ultra-High Performance Fiber Reinforced Concrete) containing 1 to 2,5Vol% of fibres. UHPFRC as a composite consists of two components providing two properties: The high compressive-resistance of the matrix and the tensile strength of the fibers. Since every structural member is submitted to specific local forces, whereas the distribution of fibres is extensively undirected, conventional UHPFRC structural elements contain more fibers than structurally needed. Novel elements such as shells providing fibers aligned in zones where they are effectively needed would reduce the waste of fibers drastically. Accordingly, the entire member could be designed in a more effective, filigree and sustainable way. Furthermore the robotic post-modeling of reinforced areas before hardening could replace the complex pre-fabricated reinforcement structures. Keywords: Robotics, UHPFRC, magnetism, fiber orientation