My interest in shell structures is part and parcel of a more general interest in advanced structural engineering and its capacity to handle, shape and exploit complex, differentiated geometries via relative optimization strategies. In Philippe Block’s and similar structural engineering researches – in the tradition pioneered by Frei Otto -  I find an exciting coincidence of pursuits that is congenial to my architectural striving for a richly differentiated and clearly articulated architectural order. The emerging style of parametricism1 that I try to contribute to and promote builds upon recent advances in engineering and needs the congenial contribution of sophisticated, creative engineers to achieve its global ambitions.

The premise of my contribution here is a double thesis that implies both the strictest demarcation and the closest collaboration between architecture and engineering as preconditions for the productive advancement of the built environment. The underlying division of labour might be posited as follows: Architecture is responsible for the built environment’s social performance. Engineering is responsible for the built environment’s technical performance. Technical performance is a basic precondition of social performance. In this sense engineering might be argued to be primary. Social performance is the goal. In this sense architecture might be argued to be primary, in the sense that means are selected according to ends. However, ends are also defind and selected in accordance with the means available. Thus the relation cannot be brought into a strict hierarchy. Rather it is a relation of mutual dependency and dialecical advancement. Architectural goals must be defined within a technically delimited space of possibilities. Enginering research and develpment thus expands the universe of possibilities that constraints architectural invention. However, it cannot be taken for granted that enginering research and develpment expands the universe of possibilities in relevant, desired directions without being prompted and inspired by architectural goals. In turn architectural goals and inventions might be prompted and inspired by recent engineering advances. The two disciplines co-evolve in mutual adaptation. Evidence of this can be found in the congeniality between the architectural avant-garde style of parametricism and structural engineering’s contemorary capacity to model and evolve optimizing, smoothly differentiated structures. Philippe Block’s work is paradigmatic here.

Above I distinguished the technical functioning of the built environment from its social functioning. While the technical functioning considers the physical integrity, constructability and physical performance of the building in relation to its users understood as physical-biological bodies, architecture must take into consideration that a building’s social function, i.e. its function as ordering and guiding communicative frames which succeed via their visual legibility. The core competency of architecture is thus the task of articulation. Legibility involves two aspects: the perceptual tractability/palpability and the semantic-informational charge. Accordingly I distinguish phenomenological articulation and semiological articulation2.
The relationship between the technical and the articulatory dimension of the build environment leads to the concept of tectonics, here understood as the architectural selection and utilization of technically motivated, engineered forms and details for the sake of a legible articulation that aims at an information rich, communicative spatial morphology.  There are plenty of examples in the history of architecture where architectural elements and features with technical functions become the object of articulatory (“ornamental”) endeavours. This is the domain of tectonics3.
My idea of tectonics is the utilization of structurally – or in general technically – indicated morphologies for the purposes of giving distinct characterization to the different social domains within a project. This implies the selection and systematization of these morphologies. This includes both the accentuation of certain features that can be used to give a specific character to a certain space and the supression of other features that would distract or obfuscate.
The engineering logic of adapting member sizes in proportion to stresses can be taken up within an architectural strategy of articulation. For instance, the skeleton of a tower might be expressed on the outside as exo-skeleton. It might be differentiated along the vertical axis describing a gradient transformation from massive to filigree. This structural logic might be correlated with an occupational logic and the structure’s articulation might in turn come to signify the occupational distribution.

The advantage of tectonic articulation is that what is required anyway, for technical reasons, is utilized as convenient means of articulation. The agenda of articulation selects the final solution from all technically viable solutions according to the phenomenological and semiological requirements.
The exposure of the primary structure can be very effective in giving an identifiable character and atmosphere to certain spaces. The socially different spaces acquire distinct character through their correspondibg distinct structural and technical requirements. The internal ordering of large spaces might be further facilitated by the lawful differentiation of the structural system: the different (longitudinal versus transversal) directions of the space might be indicated by the direction of the primary beams. The centre of a large space might be indicated by the greatest depth of the beams following the parabol-shaped moment profile etc. These features might serve as orienting clues within a large, otherwise visually partitioned space like a large market space.
This kind of tectonic articulation is more satisfying than “free” or „arbitrary“ articulation. The articulatory integration of the morphological consequences of technical requirements is always the more elegant solution than the attempt to cover them with arbitrary motifs. In order for architects to pursue tectonic articulation they need to guide and orchestrate the engineering investigations and then select the engineering options that most suit their primary task, namely to fulfil the social functions via ariculated framing communications. The adaptive differentiation of structures as well as the adaptive differentiation of volumes and envelopes according to the building’s environmental performance (with respect to its exposure to sun, wind, rain etc.) also afford many opportunities for differential tectonic articulation. A thus lawfully differentiated built environment would be much more legible and navigable than the modernist, isotropic order of repetition. With the development of sophisticated computational design tools  - both within architecture and within the engineering disciplines -  the scope for nuanced tectonic articulation  has much increased. The adaptation of structural morphologies to the force distribution within a structural system offers a fantastic opportunity for architectural articulation. In turn the more complex architectural orders proposed within contemporary architecture are reflected and potentially accentuated by sophisticated, adaptive structures. The realization of this potential requires an intensified collaboration between innovative architects and engineers. The contemporary avant-garde style of parametricism  is pushing in this direction. Although there can be no doubt that architecture remains a discourse that is distinct from engineering, a close collaboration with the engineering discipline’s as well as the architect’s acquisition of reliable intuitions about their respective logics are increasingly important conditions for the design of contemporary high performance built environments.

Shell structures  - especially clusters of merging shells like those explored by Zaha Hadid Architects -  are among my favorite devices to differentiate and articulate spatial compositions. The convex curvature of the shells makes spatial units easily recognizeable and traceable even if such spatial units proliferate and interpenetrate in complex arrangements. While intersecting rectangles soon produce an undecipherable cacophony of corners intersecting shells remain perceptually tractable. Their size is indicated by their height, and locally by the degree of curvature. While straight walls are mute with respect to whether one is inside or outside of a certain territory, in the case of shells the distinction of concave and convex clarifies one’s relation to the spatial unit in question. Thus shell configurations are in many ways conducive to the ordered, legible build up of organisational complexity. Shape-optimized shell configurations are inherently information-rich artefacts that give clues allowing for local to global inferences as well as for local to local inferences. This is a direct consequence of the the calculative information processing that has generated their final form.

Field of concrete shells, exterior views, 2012, by Zaha Hadid Architects

In my design work I am now more and more trying to move away from the free-form play with complex curvature towards the disciplining use of structural form-finding algorithms. The increased computational power to handle complex formations makes this possible. The lightness that can be achieved with structural optimization in general and with shells in particular is a much apprecated factor here. However, the fact that I prefer a structurally preconstrained seach-space to an unconstrained search space is not only motivated by technical efficiency considerations or by the achievement of relative lightness. What motivates me here as well is the morphological coherence that comes with rule-based or law-governed design logics. This allows me to give a unifying character to a the morphological world I choose for a paricular project or part of a project. These unifying rules give a character and identity that remains recogniseable despite the rich differentiation that remains available within these logics. I am not only talking about the overall spatial forms here but also include subarticulations like grids (grid-shells), ribs (ribbed vaults), perforations, and tessellations. All these subarticulations are driven by scripted rules that include structural logics, fabrication logics or environmental logics. Here the collaboration between engineering and design (tectonic articulation) takes the form of feeding data that come from engineering simulations into geometric responses that serve as articulating patterns that deliver further character enhancements and orienting information. The rule-based form-production that computes results from multi-variable inputs in turn allows  - at least in principle -  for inferences to be drawn in the inverse direction: from the resultant output variables to the input variables. An intuitive grasp of the embodied logic of such rulebased spatial formations gives users a sense of orientation and successful, intuitive navigation. It is this search for coincidences between technical and communicative morphologies is where my the key project of tectonic articulation resides.

Why is this important? The ability to navigate dense and complex urban environments is an important aspect of our overall productivity today. Post-Fordist network society demands that we keep continuously connected and informed. We cannot afford to beaver away in isolation when innovation accelerates all around. In order to remain relevant and productive we need to network all the time and coordinate our efforts with what everybody else is doing. Everything must communicate with everything. In terms of urban environments this implies that we should be able to see and participate in as many events as possible, always remaining exposed to many further choices to select our next move. This is facilitated best, if the visual field presents a rich, ordered scene of manifold offerings where the spatial/functinal units – the relevant units of interaction -  can be identified a within a complex field and their associative relations become conspicuous.

The speed and confidence with which one can make new experiences and meaningful connections is decisive. The design of environments that facilitate such hyper-connectivity must be very dense and complex and yet highly ordered and legible. As urban complexity and density increase, effective articulation becomes more important. The maturing style of Parametricism is geared up  - in terms of its computational techniques and attendant formal-spatial repertoire -  to build up and order unprecedented levels of spatio-morphological complexity.

Field of concrete shells interior views, 2012, by Zaha Hadid Architects

Field of concrete shells interior views, 2012, by Zaha Hadid Architects