Naturally grown timber elements as basis for load-bearing building structures - structural analysis and growth simulation

我们的社会对人类对自然和环境的干预的影响越来越敏感，这刺激了对以自然为基础的产品的研究，导致建筑中木材的使用增加。传统的木结构建筑是基于预制的半成品，具有几何简单和适应性强的基本形状。预制技术，如胶合层压木材允许均质化，实现通用的机械特性。然而，制造木板、棒材和横梁中的木制建筑元素需要大量的后勤工作，其中只使用干木材，导致大量的铣削废料。树枝被完全处理掉了。因此，传统的木结构建筑和以线性元素为主的建筑系统被优化为一种普遍的应用，并为正交几何的建筑构件的建设。然而，它们并没有被优化为经济利用原始木材材料。基于替代木结构体系的发展，例如：“Off-Knot-Construction”，也可以使用自然生长的木材元素，稍加调整。为此，先进的数字方法，如基于图像的建模和形态分析和分类，允许从单个自然生长的木制部件及其相应的部分生成新结构的几何形状。先进的非线性模拟技术和数值模拟，如等几何分析，考虑层的极性排列，不同密度沿半径变化的强度特征，代表具有木材典型各向异性行为的纤维状材料的配置。在此分析工具的基础上，将发展一种综合方法，以模拟受简单的引力向性或一般施加力影响的树木的生长。为此，必须推导出木材在活态和变性（干燥）状态下的材料特性，以及影响机械特性的生物变化。最相关的生物影响因素，如纤维组织发育和密度必须被识别并传递到模拟参数。该项目旨在采用一种创新的方法，系统地利用自然生长的木材，并更深入地了解树木的生长。

The increasing sensitivity of our society to the effects of human intervention in nature and the environment is spurring research into nature-based products, leading to increased use of wood in construction. Timber constructions, traditionally based on prefabricated semi-finished products, are built with geometrical simple and adaptable basic shapes. Prefabrication techniques such as glue-laminated timber allow for homogenization achieving universal mechanical features. However, the manufacturing of wooden construction elements in boards, bars, and beams is associated with a considerable logistical effort, in which only stem wood is used, resulting in a big amount of milling waste. Branch wood is completely disposed of. So traditional timber construction and construction systems with mainly linear elements are optimized for an universal application and for the construction of building components of orthogonal geometry. However, they are not optimized for the economical utilization of raw wood material. Based on the development of alternative timber construction systems like e.g. 'Off-Knot-Construction,' also naturally grown timber elements with minor adaptations can be used. For that, advanced digital methods like image-based modeling and morphological analysis and classification allow to generate the geometry of new structures from individual, naturally grown wooden components as well as their corresponding sections. Advanced nonlinear simulation techniques and numerical modeling like e.g. isogeometric analysis consider a polar arrangement of layers, different densities along the radius with variable strength characteristics, representing the configuration of a fiber-like material with the typical anisotropic behavior of wood. Based on this analytical tool a synthetic approach will be developed in order to simulate the growth of a tree influenced by the simple gravitation tropism or by the imposition of forces in general. For this purpose, material properties in live and denatured (dry) state of wood as well as the biological alterations affecting the mechanical properties have to be derived. The most relevant biological influencing factors, such as fiber tissue development and density have to be identified and transmitted to simulation parameters. The project is aiming on an innovative approach to a systematic use of naturally grown wood as well as a deeper understanding of the growth of trees.