A Digital Design Process for Bundling of Void Formers for Application in Functionally Graded Concrete

Minimizing resource consumption, greenhouse gas emissions and construction waste is essential to the construction industry. One comprehensive approach to addressing this in concrete construction is the technology of Functionally Graded Concrete (FGC) developed at the Institute for Lightweight Structures and Conceptual Design (ILEK). It is based on the purposeful placement of mineral void formers in the interior of concrete building elements in areas of low stress. This allows for significant mass reduction in FGC elements and enables mono-material recycling. Previous investigations dealt with the structural design and assessment of FGC building components. This contribution presents an interface prepared to link the developed design methods with the fabrication of FGC components. It focuses on the positioning of bundles of mineral void formers inside the given statical boundary conditions of the structure. This could reduce the effort in an industrialized process for human-assisted installation or a fully robotic pick-and-place process. The top-down design algorithm is implemented in a Rhino/Grasshopper 3D environment. Numerical optimization is used to generate a grid across all constrained areas in the floor plan. This grid enables the greatest number of void formers to increase the mass-saving performance and assures the continuity of the longitudinal reinforcement across areas. The designer can define hierarchical bundles in the input interface to account for fabrication restrictions from transportation, physical human limitations, or robotic gripping. The bundle placement can be optimized accordingly. The results of this process will be used in a real-scale case study, the Large-Scale Construction Robotics Laboratory (LCRL) of the Cluster of Excellence IntCDC at the University of Stuttgart.