Sectioning is a method of profiling components in relation to a surface geometry. By taking a series of sectional cuts through a digital model, it offers a quick and effective way of gathering the necessary data to inform a CAD/CAM process. With the ongoing interest in and experimentation with complex, and often curvilinear, geometries, the ability to slice through the design to understand and communicate relationships of form, surface and space is highly beneficial. Digital modelling software commands typically provide instant sections through a three-dimensional form, and using a series of such sections in parallel it is immediately apparent how this will convert into a physical structure and surface. Whilst a relatively novel technique in the coupling of digital fabrication with architecture, it reflects a much longer tradition in shipbuilding and aeroplane construction. In these contexts, the form of the object is defined as a series of sections that are subsequently clad with a material or skin. Digital-fabrication techniques typically used in sectioning are cutters, particularly laser cutters and CNC routers, although, as with the process of folding, plasma and water-jet cutters expand the range of materials that may be worked in this manner. Sectioning was one of the primary tooling procedures that facilitated full-size prototyping, since the section profiles are essentially the same and may be scaled as required according to sheet material constraints.
Curvilinear geometry and methods of overlaying combine to form a complex structure in Zaha Hadid Architects’ design for the Burnham Pavilion, Chicago. The pavilion comprises intricate bent-aluminum structural sections, each shaped and welded to create its unique curvilinear form. Outer and inner fabric skins wrap tightly around the metal frame to create the fluid shape. These skins also serve as the screen for video installations. The project aimed to maximize the recycling and reuse of materials after its role in Millennium Park. It can be installed for future use at another site.
CAD drawings illustrating the complex geometry.
The pavilion during the day, mirroring the design data of the digital model.
The pavilion’s transformation after dark, as lighting effects and projections radically alter its appearance.
Case study Sectioning a roof structure
Barkow Leibinger – Campus Restaurant and Event Space, Ditzingen, 2008.
This pavilion provides a new central cafeteria and event space for Trumpf’s campus and headquarters in Stuttgart. The canopy roof was developed as a polygonal leaf-like structure with long spans over groups of columns. This remarkable structure combines a steel frame and columns with glue-laminated wood-cell infill. The columns are intentionally located away from the beam perimeters and intersections to enhance the roof’s cantilevered, hovering effect. While the steel allows large spans of up to 20m, the glulam infill was an attractive choice for its workability and sustainability. Hierarchically, the steel delineates a primary, vein-like structure while the glulam construction achieves a cellular web-like infill, completing the leaf analogy. The wood cells are functionally ‘coded’ and constructed as either skylights with solar-glass, perforated-wood acoustic planking (tying the roof diaphragm together); or as artificial lighting cells, modified by an aluminium honeycombed deflector. In order to economically achieve this highly complex structure, CNC routing and sawing was used to accommodate the more than 300 unique honeycomb joints. This is a particularly interesting development, as ‘mass customization’ is becoming essential, economically and time-wise, for an increasing number of the practice’s projects.
A, B, C, D, E AND F Initial freehand sketches outline the original concept of a leaf-like, polygonal roof structure, and are made into physical models early in the design-development process to explore different types of structural arrangements and patterns.
G The connections between each structural ‘cell’ are determined using three-dimensional digital-modelling software to ensure the integrity and performance both of elements and the composite whole.
H A full-size prototype of several structural cells allows the designers to inspect the aesthetic and structural characteristics of the roof.
I The finished project in situ, demonstrating its extensive spans on relatively minimal structure, and the skylights afforded by the innovative roof design.
Case study Sectioning as structural frame
Franken Architekten – Dynaform, Frankfurt am Main, 2001.
This exhibition pavilion for BMW aimed to express a dynamic sense of movement around the stationary cars inside. To achieve this the space was ‘accelerated’ using the Doppler effect, which was translated spatially along with the ‘forces’ of the surroundings to generate the parametric digital design for the building. This project uses a sectioning process to develop its design and fabrication data.
A, B, C AND D Form generation of the building, using forces derived from the immediate context.
E The bearing structure as a sequence of sections ‘moving’ through space to represent the fluidity of the design.
F AND G Sectioning is explicitly revealed during the process of assembly.
H Digital render, illustrating the dynamic design intention.
I AND J The completed building, echoing automotive geometry and notions of movement.
Case study Sectioning complex geometry
Rogers Stirk Harbour + Partners – Capodichino Metro Station, Naples, 2006–14.
Parametric design provided the key generative and design-development tool for this metrostation roof. Its form was determined through a series of sunpath and movement studies, following the route that passengers take to and from departures and arrivals at Naples Capodichino Airport. By varying the sun and route parameters in a digital model, the architects were able to calculate the optimum roof form, and the density and angle of fixed louvres to give the greatest average shading to passengers on the most direct routes throughout the year. The design process initially resulted in each rib being a unique form. Once the form had been applied to elliptical sections of a toroid, the whole structure was greatly simplified to only 21 repeated elements. Thus, a selfsupported structure was achieved through simple geometry that would have been inexpensive to build conventionally.
The roof is the central element of the station design, which utilizes complex geometry based on a toroid 3D shape with 46 main radial ribs. These ribs spring from the top of the station shaft, and each has a diameter of 33m across its inside faces. The maximum length of one rib is 39m and the area of the main canopy is 4,700m². The ribs are interconnected by diagonal struts, which stiffen the structure. These section sizes vary to suit their internal forces. The design has been parametrically optimized to minimize the number of elements needing to be fabricated. This, in turn, will simplify the construction process and, ultimately, ensure cost-effectiveness.
A AND B Digital renders of the proposed design.
C Digital model, showing roof in context.
D Early digital model, showing the roof as mapped from a toroid.
E AND F Physical model of the roof structure.
G Sectional model of the roof, illustrating the geometry.
H AND I Scale prototype of the roof structure, made for evaluative purposes.
