Proceedings of the IASS Annual Symposium 2019 – Structural Membranes 2019 Form and Force 7 – 10 October 2019, Barcelona, Spain C. Lázaro, K.-U. Bletzinger, E. Oñate (eds.) Natural Form(s): case study of a spatial framework composed of naturally grown forked branches Lukas ALLNER * , Daniela KROEHNERT * , Andrea ROSSI a , Matthew TAM b *University of Applied Arts Vienna Vordere Zollamtsstraße 7, 1030 Vienna lukas.allner@uni-ak.ac.at, daniela.kroehnert@uni-ak.ac.at a Technical University Darmstadt b Bollinger + Grohmann Engineers, Vienna Abstract Wood as a construction material not only serves as a sustainable resource but also offers the potential to develop complex structural models (and architectural spaces) that are derived from its complex ma- terial logic. This paper proposes an experimental methodology for the design of spatial frameworks that utilize natural forked branches as structural components. Computational methods such as 3D- scanning and parametric structural analysis tools allow designers to cope with the irregular complexity of the natural material. This paper presents a comprehensive digital workflow leading to the robotic fabrication of a medium scaled demonstrator. Keywords: Naturally grown form, complex wood structures, spatial frameworks, discrete element aggregation, 3D Scanning, parametric engineering, structural optimization, digital fabrication 1. Introduction The structural system of trees responds to multiple forces forming a complex configuration of struc- tural members, resulting in an optimized form, with forking branches acting as optimized joints (Mattheck [1]) (Müller et al. [2]). Based on concepts previously presented (Allner and Kroehnert [3]), this paper expands the research with a design and fabrication process of an experimental spatial framework formed by tangentially joined branch parts. A digitized set of hornbeam branches is utilized as components in a synthetic for- mation. This is a project in the tradition of architectural research attempting to utilize wood in its natu- ral form (Mollica and Self [4]). It also explores how design control becomes relative to the constraints introduced by the available inventory, determining a dynamic design process in which constraints and design goals are negotiated in a feedback system. Adapting the structural logic of natural trees to architectural applications, originally cantilevering branches are reassembled to form closed loops constituting a cellular framework with improved struc- tural integrity and general bracing. For the purpose of this paper, the demonstrator represents a case study of a regular lattice of tetrahedron cells. 2. Digitization and Cataloging The workflow starts with a collection of 3d scan models of the physical branch parts, which have been prepared by flush cutting the ends and with marking of several reference points. In an automated process centerline models (Figure 1) are generated from the mesh geometries: Cen- troids of co-parallel section outlines define vertices of polylines. For an optimal matching of the indi- Copyright © 2019 by Lukas Allner, Daniela Kroehnert, Andrea Rossi and Matthew Tam Published by the International Association for Shell and Spatial Structures (IASS) with permission.