Shells are some of the most effective means of creating load-bearing spatial structures because of their great load-bearing capacity and rigidity with accompanying low weight and material usage. The rigorous implementation of force adaptive design principles in constructing shell load-bearing structures is at present impeded by their very high planning and manufacturing costs. The aim with the current SPP 2187 sub-project “Adaptive Concrete Diamond Construction” (ACDC) is to develop new approaches for effectively manufacturing shell load-bearing entities on an industrial scale, and thus cost-effectively, by approximating them using numerous similar facets [1-3]. A discretised shell load-bearing structure comparable to a gridshell can be created in this way by preferentially applying quadratic faceting, see Fig. 1.
Parabolic framework structure with planar quadratic facets; D. Lordick
Computer-assisted algorithms, in which strategies will have been implemented for both architecturally and structurally processing the modules, are being developed in order to geometrically describe these freely shaped load-bearing structures and their faceting, see also [4]. This forms the basis for a universal digital model, with which the parametric modelling of the load-bearing structure and the shaping of the facets can be represented along with generating digital data sets for manufacturing the modules automatically.
The modules are divided into a peripheral zone and infill. The peripheral zone is composed of ultra-high-strength, highly ductile concrete with short polymer fibres [5] and defines the interlocking peripheral geometry to neighbouring modules in its cross-section and longitudinal axis. This type of concrete reacts in a good-natured way to local loading peaks and guarantees great robustness for the module periphery. The infill can be carried out in different ways, thus enhancing the module’s changeability. It is intended to carry this out initially with a thin layer of textile reinforced concrete. The textile reinforcement will be produced in function to loading by setting in carbon yarns along the main tensile stress trajectories [6, 7]. Alternatively, the textile reinforcement can be implemented structurally and tailor-made from semi-finished mesh products for this purpose.
The modules will be produced automatically in a continuous flow manufacturing process. The module periphery will be shaped with a changing cross-section but without formwork using the end effector of an extruder [8-10]. The reinforcement yarns will be impregnated inline with an ultra-fine mineral material suspension and set in place with the aid of a yarn positioning unit. A pouring or spraying procedure can be employed for filling out the infill. All tools are guided by robots controlled by the universal digital model. The digital geometric and material data sets from the model are additionally the testing criteria for ongoing quality management.
The freedom in design and variable selection of materials achieved on this basis of digital algorithms make it possible to manufacture individual construction components in varying shapes and dimensions, thus resolving the conflict in objectives between mass production and individuality.
Literature
[1] Hagemann, M., Klawitter, D., Lordick, D.: Force Driven Ruled Surfaces. Journal for Geometry and Graphics 17/2, 2013, S. 193–204.
[2] Osman Letelier, J. P., Goldack, A., Schlaich, M., Lordick, D., Grave, J.: Shape Optimization of Concrete Shells with Ruled Surface Geometry Using Line Geometry. In: Bögle, A., Grohmann, M. (Eds.): Proceedings of the IASS Annual Symposium 2017 »Interfaces: architecture.engineering.science« 25 - 28th September 2017, Hamburg, Germany. Paper #9199 1-10.
[3] Lordick, D.: Intuitive Design and Meshing of Non-Developable Ruled Surfaces. In: Proceedings of the Design Modelling Symposium, University of the Arts Berlin, 5-7 October, Berlin, Germany, 2009, S. 248-261.
[4] Bornemann, M., Melzer, S., Lordick, D.: Automated High Precision Texturing of 3D-Scans. In: Schröcker, H.-P., Husty, M. (Eds): Proceedings of the 16th ICGG. Innsbruck University Press, 2014, S. 93‑102.
[5] Curosu, I., Liebscher, M., Mechtcherine, V., Bellmann, C., Michel, S.: Tensile behavior of high-strength strain-hardening cement-based composites (HS-SHCC) made with high-performance polyethylene, aramid and PBO fibers. Cement and Concrete Research 98, 2017, S. 71-81.
[6] Schneider, K.; Michel, A.; Liebscher, M.; Mechtcherine, V.: Verbundverhalten mineralisch gebundener und polymergebundener Bewehrungsstrukturen aus Carbonfasern bei Temperaturen bis 500 °C. Beton- und Stahlbetonbau 113, 2018, S. 886-894.
[7] Mechtcherine, V.; Michel, A.; Liebscher, M.; Schneider, K.; Großmann, Ch.: Mineral-impregnated carbon fiber composites as novel reinforcement for concrete construction: Material and automation perspectives. Automation in Construction 110, 2020, Art. 103002.
[8] Ogura, H.; Nerella, V.N.; Mechtcherine, V.: Developing and testing of strain-hardening cement-based composites (SHCC) in the context of 3D-printing. Materials 11, 2018, 1375.
[9] Nerella, V. N.; Näther, M.; Iqbal, A. Butler, M.; Mechtcherine, V.: Inline quantification of extrudability of cementitious materials for digital construction. Cement and Concrete Composites 95, 2019, S. 260-270.
[10] Mechtcherine, V.; Nerella, V. N.: Beton-3D-Druck durch selektive Ablage: Anforderungen an Frischbeton und Materialprüfung. Beton- und Stahlbetonbau 114(1), 2019, S. 24-32.