Curved structural envelopes combine mechanical efficiency, architectural potential and a wide design space to fulfill functional and environment goals. The main barrier to their use is that curvature complicates manufacturing, assembly and design, such that cost and construction time are usually significantly higher than for parallelepipedic structures. Significant progress has been made recently in the field of architectural geometry to tackle this issue, but many challenges remain. In particular, the following problem is recurrent in a designer’s perspective: Given a constructive system, what are the possible curved shapes, and how to create them in an intuitive fashion? This thesis presents a panorama of morphogenesis (namely, shape creation) methods for architectural envelopes. It then introduces four new methods to generate the geometry of curved surfaces for which the manufacturing can be simplified in multiple ways. Most common structural typologies are considered: gridshells, plated shells, membranes and funicular vaults. A particular attention is devoted to how the shape is controlled, such that the methods can be used intuitively by architects and engineers. Two of the proposed methods also allow to design novel structural systems, while the two others combine fabrication properties with inherent mechanical efficiency. The feasibility of these new structural morphologies is demonstrated by the construction of two research pavilions. A video presentation giving an overview of this doctoral work can be found online at the following URL address: https://doi.org/10.5281/zenodo.3956351 or https://www.youtube.com/watch?v=iw4Hetw9lnY
The classical double layer space truss is revisited by replacing diagonals by curved thin-walled polyhedral modules. The expected improvements are both technological and mechanical. The complex 8-branch nodes are broken down into a connection of two overlapping continuous members and a line connection between bars and the polyhedron edges. Curvature in the faces and edges of the modules introduces shape resistance while stabilizing the members against buckling. The global optimization of the structure is performed by a form-finding process based on the individual parametrization of the modules. Finally, an experimental validation was carried out by fabricating and testing a full-scale prototype (approximately 6 x 6 m).
"Metal Euplectella Folie" is a prototype which explores an innovative design and manufacturing method for free-form architecture. Four 40m long by 0.4m wide by 1.5mm thick steel sheets, each cut to a unique pattern and then spiral-wrapped, form a sculptural tube assembled without the need for any adjustment, plans or jigs. This experimental construction is inspired both by the structural concept of the deep-sea sponge "Euplectella Aspergillum"-a thin-walled shell stiffened by helicoidal fins-and by the industrial process for fabricating helicoidal pipes-manufactured by wrapping a continuous strip of constant width. By adopting a strip of variable width, a new range of potential forms may be explored. This shaping process takes advantage of the property of developable surfaces that allows complex three-dimensional objects to be formed from flat cut shapes by simple bending.
The shape of a complex freeform architectural envelope is usually generated by methods such as NURBS that offer a great design freedom, but that do not take into account fabricability. This often leads to higher than expected building costs. In this article, we present how a forgotten family of surfaces-namely, surfaces with planar curvature lines-can be used for a rationalized design of gridshells. We propose a discrete model of these surfaces, that enjoys properties that simplify the fabrication of all the elements of a gridshell: beams, nodes, and cladding panels. We propose an intuitive generation method, that allows a real-time exploration of the entire family of surfaces with planar curvature lines. Finally, we show how this method can be used to design a great variety of envelope shapes. Figure 1: Surfaces with planar curvature lines. Left: The HippoHaus in Berlin , revisited as a junction of five patches with planar curvature lines. Right: A building roof, with mesh edges aligned with a façade.
In this paper, we propose a method to generate circular and conical meshes with planar lines in both directions. The method is based on the discretization of the Gauss map of surfaces with planar curvatures lines. It allows generation of meshes in real-time via two planar guide curves. The resulting meshes can be used as a geometric base to build gridshells with flat panels, torsion free-nodes, node offset and planar arches. A particular technological application is for gridshells built with curved members: those can be built with planar piecewise-circular beams, and identical nodes if beams have circular cross-section.
Designing freeform architectural envelopes is a challenging task, as it requires a balance be-tween structural efficiency, fabricability and architectural requirements. In this article, we present a novel numerical form-finding method based on the generation of the so-called Linear Weingarten surfaces. The method allows to build these surfaces on a target boundary curve. Surfaces are calculated by minimizing of a new functional. The method is well suited for con-ceptual design, as it generates shapes at membrane equilibrium under uniform pressure load, and gives a direct feedback on internal stresses. One notable application is for the design of steel-glass gridshells, for which mechanical performance and ease of fabrication can be com-bined.
The fabrication of a freeform structural envelope is usually a highly complex task. The costliest aspect is often the connections between the constitutive parts. X-Mesh is a pavilion that demonstrates a new rationalization strategy. Its structure, composed of a hexagonal grid of beams and cladding panels, is based on a geometry that rationalizes connections at two levels: firstly, nodes are repetitive, only two types of nodes are used throughout the structure. Secondly, panels can easily be connected to the support beams as they are orthogonal to each other. We prove that the proposed geometrical configuration can be asymptotically built on a smooth surface. We generate the meshes by numerical optimization from a smooth target surface, with an initialization derived from the asymptotic case. This pavilion shows another way of rationalizing a gridshell beyond the popular planar-quad meshes and circular/conical meshes. It also demonstrates a way to generate hexagonal gridshells which are not necessarily synclastic, this limitation being typically imposed to achieve planarity of cladding panels.
This paper presents a case study of environmental evaluation of innovative shell-nexorade hybrid timber construction system designed within fabrication-aware technic and fabricated using robotic construction technology. The life cycle assessment of construction phase of the system has been performed; a sensitivity study of the robotic system’s outlay has been effectuated. The results show that the contribution of robotic construction system to the overall result is fairly significant and, in some figures, can even exceed the material’s one.
This paper introduces topology finding of patterns for shell structures such as beam grids for gridshells or voussoir tessellations for vaults, among others. The authors refer to topology finding, by analogy and in complement to form finding, as the design of the connectivity of these patterns in order to follow architectural, structural and construction requirements. This paper presents a computational approach relying on a specific design space and data structures based on singularity meshes, which encode the information about the singularities in patterns. The designed patterns are structured, i.e. with a low number of singularities, can include high-valency pole points, and respect alignment to surfaces, curves and points. A feature- based exploration approach is introduced with a generation procedure for singularity meshes following the boundaries of a surface as well as point and curve features, using a topological skeleton or medial axis. These features can stem from statics heuristics, whose efficiency is assessed in a case study. A rule-based editing approach for singularity meshes supplements feature-based topology finding, using a grammar of strip rules as parameters to further explore the singularity design space. This conceptual design approach and its algorithms are an aid for topological exploration of patterns for shell-like structures by architects and engineers.
Elastic gridshells are structures made of flat two-way grids which are deformed elastically before they are braced and which afterwards mechanically behave like continuous shells. Gridshells present some advantages in terms of manufacturing, lightness and time of assembly. Their covering remains however a technical issue. The present article proposes hence an alternative method to cover them by planar quadrilateral facets, which could also be used as natural bracing if connected properly. It relies on the duality between a certain family of circular meshes with a unique radius and some Tchebycheff nets. The approach is versatile and allows for the design of a large variety of shapes from two curves in space. Real time numerical tools are developed for open and closed curves as well as a strategy for umbilical points. The relaxation of the Tchebycheff net shows finally that an equilibrium configuration can be found in the vicinity of the planar quadrilateral mesh (PQ-Mesh) which confirm the practical feasibility of elastic gridshells covered with planar facets.
added a research item
The aim of this paper is to introduce a bottom-up methodology for the modelling of free-form shapes in architecture that meet fabrication constraints. To this day, two frameworks are commonly used for surface modelling in architecture: NURBS modelling and mesh-based approaches. The authors propose an alternative framework callled generalised cyclidic nets that automatically yields optimal geometrical properties for the envelope and the structural layout, like the covering with planar quadrilaterals or hexagons. This framework uses a base circular mesh and Dupin cyclides, which are natural objects of the geometry of circles in space, also known as Möbius geometry. This paper illustrates how complex curved shapes can be generated from generalised cyclidic nets. It addresses the extension of cyclidic nets to arbitrary topologies with the implementation of a 'hole-filling' strategy and demonstrates also that this framework gives a simple method to generate corrugated shells.
This paper presents a methodology to generate structural patterns for masonry vault design. First, a quad- dominant block decomposition is proposed based on a medial axis pruning/rebranching method from an input that comprises outer and inner boundaries as well as point and curve features, representing a point load or a crease in the structure, for instance. The meshing and smoothing of the resulting set of patches is straightforward and the mesh densities can be controlled globally and locally. The resulting meshes can be processed for form finding and further optimisation. Second, fabrication-and construction-aware rules to convert these form-found patterns into a tessellation are proposed.
This work focuses on the design of ultra-light concrete walls for individual or collective housing, the normative context being constrained masonry. It is stated that current block work building is very inefficient in terms of quantity of concrete used for cinderblocks and mortar joints, and with regards to thermal insulation. Here is proposed a robotic manufacturing technique based on mortar extrusion that allows producing more efficient walls. First we present the fabrication concept, then design criteria for such objects. In the last section we show a comparative study on different geometries. We conclude with a discussion on the performances of this proposed building system.
This study focuses on deployable systems actuated by shape memory alloys in the perspective of designing adaptive sun shading devices for building facades. We first set the context of smart materials for adaptive facades and underline the remarkable characteristics of shape memory alloys for mechanical actuation purposes. After outlining the constraints on the integration of this material into deployable structures, we introduce three different prototypes actuated by shape memory alloy wires. They have been fabricated and tests have been carried out on two of them. Finally, we present some perspectives on the use of these actuators for solar shading systems in façade engineering.
Navier laboratory, a joint research unit between the Ecole des Ponts ParisTech, IFSTTAR, and CNRS, gathers about 50 permanent scientists, 120 Ph.D.’s and general skills in the mechanics and physics of materials and structures, in geotechnics, and their applications to, in particular, civil engineering and petroleum geophysics. For last 15 years, Navier has chosen to reinforce the links between mechanics of materials, structural engineering, and applied mathematics at a very high level to explore new paths and propose building innovations.
The simulation and construction of elastic gridshells in composite materials is nowadays a technique that one can consider mastered. The bracing of the grid in its final form remains however a time consuming step with a lot of manual work. The lack of alternatives to membrane covering is also an important limitation to the development of such technology. The proposed paper tries to tackle both issues through a novel concept of a hybrid structural skin made of an elastic gridshell braced with a concrete envelope. The idea is to use the gridshell as a formwork for the concrete and to guarantee a mechanical connection between the thin concrete skin and the main grid, so that the concrete ensures the bracing of the grid and that the thickness of the concrete is reduced to a minimum. To demonstrate the feasibility and interest of this structural concept, a 10 m² prototype has been built. The main aspects of the design and of the realization of the prototype are presented here (including detailing and mix design).