Simon Bechert

Abstract

Though capable of allowing multi-directional spans, timber products such as cross-laminated timber are primarily utilized uni-directionally using linear supports like walls or beam elements. Recent building designs increasingly show punctual supports but with narrow column grid layouts. Support beams and narrow grids limit the design space for multi-storey timber buildings. To overcome these design limits, an integrative design concept for punctually supported timber slabs is being developed that allows for large spans and irregular column layouts. Therefore, engineering methods are integrated in the architectural design of the building components, such as plates, columns, and their connections. The developed slab system combines hardwood and softwood materials in a sandwich construction. The plates have a tailored internal topology considering the force flow in the slab. A plate-to-plate connection design is evaluated through mechanical tests, which also serve as calibration for the global structural model. The research findings are validated through the design and construction of a large scale demonstrator: the ITECH Campus Lab.

Abstract

Recent development in research and practice for curved cross-laminated timber (CLT) opens up novel and interesting possibilities for applications of slender surface-active shell structures in architecture. Such typologies provide advantageous structural behaviour allowing for efficient and lightweight structures while simultaneously determine the envelope and space of a building. The high degree of prefabrication combined with a sustainable and renewable building material makes CLT an ecological and economic solution for future construction. This paper presents the design development and construction of the Urbach Tower for the Remstal Gartenschau 2019: a structure made from high curvature CLT components on a building scale. This research contribution illustrates a sophisticated integrative design to construction process emphasizing computational and structural design, fabrication and detailing for curved timber components in complex spatial structures. The authors further explore the structural potential of self-shaped curved CLT investigating the influence of curvature radius on the load-bearing behaviour of the tower structure. The Urbach Tower translates these technical developments into practice arising at the intersection of digital innovation and scientific research.

Abstract

This paper presents an agent-based method for the design of complex timber structures. This method features a multi-level agent simulation, that relies on a feedback loop between agent systems and structural simulations that update the agent environment. Such an approach can usefully be applied for the design of variable density timber slab systems, where material arrangements based on structural, fabrication, and architectural boundary conditions are necessary. Such arrangements can lead to multi-directional spanning slabs that can accept pointwise supports in unique layouts. We discuss the implementation of such a method on the basis of the structural design of a pavilion-scale multi-storey testing setup. The presented method enables a more versatile approach to the design of multi-storey timber buildings, which should increase their applicability to a diverse range of building typologies.

Abstract

The presented research describes the holistic development of a modular lightweight timber shell. So-called segmented timber shells approximate curved geometries with the use of planar plates, thus combining the excellent structural performance of double curved shells with the resource-efficient prefabrication of timber modules using only planar elements. Segmented timber shells constitute a novel building system that demands for innovative approaches on structural design and construction technologies. The geometric complexity of plate shells in conjunction with the particularities of the building material wood pose great challenges to the computational design and planning processes as structural requirements and fabrication constraints determine the shell design at early design phases. This paper discusses the design development and construction of the BUGA Wood Pavilion: A segmented timber shell structure made of hollow cassette components. Particular emphasis lies on the technical challenges of the employed building system, notably structural design and analysis, detailing solutions and the construction process. The authors further describe the integrative structural design and optimization methods developed for the timber shell in question. The BUGA Wood Pavilion demonstrates the possibilities of lightweight and sustainable wood architecture merging the merits of integrative design, structural engineering and high-tech robotic fabrication methods.

Abstract

Funicular shells are known to be an efficient design paradigm for self-weight-driven structural surfaces 1. Nevertheless, the rules that govern funicularity offer a fairly constrained design spectrum, limiting the scope of application for these structures 2. The principle of corrugation has proven to be an effective approach to enable efficient structural performance in non-funicular thin shells 3. The research presented in this paper explores the use of corrugation methods for shells in the context of a computational and structural design workflow. As an extension to existing methods, the authors introduce work on Dynamic Corrugation, a strategy for increasing bending and buckling performance on non-funicular global designs by modulating the undulation of their surfaces according to bending stress distribution. The bending-driven dynamic corrugation method was developed during the Form and Structure seminar of the ITECH programme at the University of Stuttgart and was evaluated through the design of a non-funicular funnel shell in textile concrete. The method consists of a two-step Shape Optimization workflow that integrates NURBS-based surface generation with FEA and a Multi-Objective Genetic Algorithm (MOGA). In a first step of the design workflow, the initial design surface is analyzed to give its bending energy vector field. This field then serves as the source to generate a modulation curve passing through the areas of peak bending stresses. This curve then regulates the frequency, amplitude, and influence of local bending on the corrugation. The MOGA is given control over these variables and attempts to minimize both bending moment and displacements, offering a wide spectrum of performances and expressions along the emerging Pareto front. Simultaneously, the introduction of local curvature is evaluated on its capacity to improve the buckling resistance and to allow reductions in material thickness. The presented iterative approach is incorporated in a computational design framework. A series of Dynamic Corrugation-optimized shell samples are then compared with the initial non-corrugated design showing great structural (improved bending and buckling resistance), as well as economical and ecological (material savings) potential. Further, the expressive value of dynamically corrugated shells is deemed as a contribution to the aesthetic value of a design proposal for a small infrastructural building.

Abstract

In the research field of segmented timber shells, two construction systems have lately received much attention, which both expose interesting structural and constructional characteristics: planar plate structures made of thin plywood and actively bent plywood structures. The research presented in this article combines elements of both approaches, resulting in a construction system for segmented shell structures with elastically bent elements. The increasing complexity of this approach requires a sophisticated design process, which integrates fabrication constraints as well as structural feedback. As a consequence, form-finding strategies of bending-active timber shells are discussed, with a special focus on the programming of the stiffness distribution in order to fulfil geometrical requirements. The authors also reflect on the specific structural challenges of joining thin sheets of plywood by transferring traditional textile connection methods to timber construction. Investigations of biological role models such as the sand dollar led to transfers of constructional principles on different levels. The resulting construction system was validated through the design and construction of a full-scale architectural prototype

Abstract

Recent developments in the field of segmented timber shells have shown promising structural and constructional characteristics. Advancements in computational design and digital fabrication enable architects and engineers to handle the increased geometric complexity necessary for this new construction type, integrating fabrication constraints and structural feedback in one design model. The research presented in this paper builds on new findings from biological role models for the constructional morphology, connection type, and material distribution of segmented shells. Based on the transfer of these principles, a robotic fabrication technique was developed that enables the production of elastically bent, double-layered segments made from custom-laminated beech plywood, by transferring traditional textile connection methods to timber construction. The construction system was evaluated through the design, production, and assembly of a large demonstrator.