The fundamental aim of the project is to develop a digital construction kit for the design of complex structural systems made from concrete. To this end, it is planned to develop and implement a comprehensive digital twin and associated methodologies for the complete design process. A special feature will be the application and enhancement of parametric methods for interactive computer-aided design (CAD) tools for design, sensitivity analysis and optimization.

Isogeometric analysis (IGA) [1], which aims at bridging the gap between design and analysis, has been selected as the methodological basis for the project. On the one hand, spline basis functions incorporated in CAD will be used as ansatz function for the Finite Element Method (FEM), making use of its superior properties (smoothness, continuity, etc.) to improve the quality of the solutions. While on the other hand, CAD models will be directly applied for the simulation, without discretising them beforehand. Hence, the bottleneck of discretising the model is circumvented a priori. IGA is the ideal technology to achieve these aims, as it supports interactive and parametric working methodologies.

The underlying emphasis of the programme is given by the maxim; “individuality in the bigger picture, similarity in the detail”. A suitable modular discretisation needs to be chosen to achieve this.

In view of serial production, regular discretisation is preferential. This is demonstrated using a modular planar structural system (plates and flat shells) made from concrete, which is divided into a patchwork of hexagonal modules (Fig. 1). It is further required to consider the detailed modelling of the individual elements, including their respective connections and the coupling of the system. The Isogeometric B-Rep Analysis (IBRA) data-format developed at the institute [2] needs to be expanded to include structural-mechanical aspects. It is planned to subsequently investigate the structural behaviour of the individual modules and the whole system. To achieve this, IGA needs to be expanded in order to detect and consider inherent stresses and deformations resulting from the time-dependent behaviour and loading history of the structure.

The Plug-In kiwi!3D [3], developed by the institute for the CAD software Rhinoceros3D [4], will be used for the implementation of the individual analysis and design procedures. In addition, the simulation software Kratos Multiphysics [5] will be utilized, which is being developed in conjunction with the International Centre for Numerical Methods in Engineering (CIMNE, Spain).

Literature
[1] Hughes, T. J. R.; Cottrell, J. A.; Bazilevs, Y.:  Isogeometric analysis: CAD, finite elements, NURBS, exact geometry and mesh refinement - Computer Methods in Applied Mechanics and Engineering, 2005, Vol. 194, Nr. 39-41, S. 4135-4195.
[2] Teschemacher, T.; Bauer, A. M.; Oberbichler, T.; Breitenberger, M.; Rossi, R.; Wüchner, R.; Bletzinger, K.-U.: Realization of CAD-integrated shell simulation based on isogeometric B-Rep analysis - Advanced Modeling and Simulation in Engineering Sciences, 2018, Vol. 5, Nr. 1, Art. Nr. 19.
[3] Kiwi!3D; URL: http://kiwi3d.com/
[4] Rhinoceros3D; URL: https://www.rhino3d.com/de/