Tectonic Articulation – Making Engineering Logics Speak
Patrik Schumacher, London 2014
Published in: AD 04/2014, Future Details of Architecture, Guest-edited by Mark Garcia, July/August 2014

The demarcation between architecture and engineering1 rests on the distinction of the built environment’s social functioning from its technical functioning. While the technical functioning considers the physical integrity, fabrication constraints, on site 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 frame, is functioning via its appearance and legibility. The core competency of architecture is thus the task of articulation. Legibility involves two aspects: the perceptual palpability and the semantic-informational charge.

Accordingly the general task of articulation bifurcates into the two specific tasks of phenomenological articulation and semiological articulation2. Both aspects need to guide the designer’s decision making process in the context of the proliferating options that emerge from the engineering discourse. Semiological articulation presupposes a successful phenomenological articulation. Phenomenological articulation pursues the visual decomposition of the (increasingly complex) urban scene by making the relevant functional units (units of interaction) conspicuous. This concern with the visual decomposition of a complex composition motivates us at Zaha Hadid Architects to work with shell structures. The perceptual identification of functional units and their interrelations is facilitated by the use of shells. The use of convex and concave surfaces with various degrees of curvature gives useful orienting information. The use of structural form-finding logics disciplines the spatial morphologies in ways that are advantageous for the task of articulation, i.e. the task of elaborating a systematic spatial language. Semiological articulation can then map significant programmatic distinctions onto conspicuous morphological distinctions so that differences make a difference. Tectonic articulation is here proposed as the concept for the strategic articulatory utilization of the morphological differentiations that emerge from engineering logics like structural engineering, environmental engineering and façade engineering.

Fig.1 Phenomenological articulation: The perceptual identification of functional units and their relations is facilitated by the use of structural shells. Convex bodies, concave spaces and curvelinearity in general is advantageous for the visual decomposition of a complex scene.
Zaha Hadid Architects, Qingdao Cultural Centre, China

Tectonic Articulation

The relationship between the technical and the articulatory dimension of the build environment leads to the general concept of tectonics, here understood as the architectural selection and utilization of technically motivated, engineered forms and details for the sake of an articulation that aims at legibility for the sake of social communication. The history of architecture abounds with examples where architectural elements and features with technical functions become the object of articulatory or “ornamental” endeavours. However, we need to understand the instrumentality of ornament, i.e. we need to grasp ornament not in contrast to performance but as a special type of performance: communicative performance. A technically efficient morphology thus assumes also an articulatory, communicative function. The articulatory integration of the morphological consequences of technical requirements is always the more elegant solution than the attempt to fight and deny them by hiding or obfuscating them. This latter stance would require the invention of additional communicative features because social distinctions desire and require expression. However, the utilization of the initially technically motivated morphological features for the characterization of spaces is not only more economical but leads to a higher level of credibility of the communication because the morphological signifier is already an index rather than a merely arbitrary symbol. Thus in the terminology of Peirce tectonic articulation thus transforms indexical signs into symbolic signs. This process too gives degrees of freedom to the designer in the selection of the indexical features that might be heightened and systematized to become elements of a semiological system of signification.3 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 posed social functions via framing spatio-morphological communications. The adaptive differentiation of load bearing 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.) as well as differentiations that stem from fabrication logics (e.g. tessellations) 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, within the engineering disciplines, and within the construction industry - 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, engineers and fabricators. Although there can be no doubt that architecture remains a discourse that is distinct from engineering and construction, a close collaboration with these discipline’s as well as the acquisition of reliable intuitions about their respective logics are increasingly important conditions for the design of contemporary high performance built environments. A clear understanding of the distinct agendas and core competencies of architects, engineers, and fabricators facilitates their effective collaboration.

Semiological Form to Function Correlations

The exposure of the primary structure can be very effective in giving an identifiable character and atmosphere to the different spaces within a building. The orchestration of the engineering and design agendas might succeed as follows: The design process might proceed in the following sequencing of concerns: spatial ordering, technical performance/materialization, articulation. (It is only the second concern – the technical performance/materialization - where engineering input must be integrated.) The materialized organization, materialized according to the concerns of technical efficiency, produces a certain morphology with a certain appearance. Before adding an additional material layer for the purposes of articulation, it thus makes sense to investigate whether this technically given material morphology is suited to serve required articulatory function. The recent ability of computationally based structural engineering techniques to offer parametric variation and nuanced parametric differentiations of structural systems is congenial with the rule-based approach and the general aesthetic principles of the contemporary style of parametricism. The structural engineering logic of adapting member sizes in proportion to stresses can be taken up within an architectural strategy of articulation. The internal ordering of large spaces might be 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 etc. These features might serve as orienting clues within a large, otherwise visually partitioned space like a large market space. Another example might be the case of a skeleton of a tower that is being 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 visually accentuated to become perceptually palpable and the systematically correlated with an occupational logic so that the structure’s articulation might in turn come to signify the occupational distribution. Thus a sequences of structural changes from massive to filigree might come to signify the programmatic stacking from retail (massive) via work spaces, to residential spaces (filigree). A more simple alignment of the structural differentiation of a tower exo-skeleton with its programmatic differentiation has been achieved in our design for a residential tower in Miami. Here the skeleton thins out from the three-bay structure at the lower part of the tower via a two-bay structure in the middle section to become a single-bay structure at the top of the tower. This structural transformation is correlated with the division of the floor-plates into three apartments in the lower part, two apartments per floor in the middle section and single pent-house style apartments at the top segment of the tower. Through this correspondence the exo-skeleton thus expresses the differentiation and distribution of the programme (apartment types) within the tower.

Fig.2 The structural differentiation of the exo-skeleton corresponds to the differentiation of apartment types. This differentiation is further accentuated by subtle difference in the articulation of the glazing line in relation to the slabs. Zaha Hadid Architects, 1000 Museum, Miami

Fig.3 The differentiated parametric articulation of the tower structure follows the principles of parametricism. The eloquence of parametric articulation stands out against the mute, monotonous seriality of the modernist context. Zaha Hadid Architects, 1000 Museum, Miami

Accentuation and Suppression

The task of articulation can be posed independently from engineering concerns as the task to orient users by means of expressive morphologies. The specific strategy of tectonic articulation as defined and proposed here is burdening the task of articulation with the constraints of engineering logics. This means that the designer’s repertoire and universe of possibilities has been respectively constrained. However, contemporary engineering possibilities have recently expanded to such an extent that there remain sufficient degrees of freedom for the designer to exercise his core competency under the constraint of tectonic articulation. In particular, as analytic and generative computational engineering tools (physics engines) become more and more readily available to architects, they are enabled to explore this more disciplined universe of possibility with the eyes and intuitions of a designer, while simultaneously keeping engineering constraints in play. The designer can explore various engineering logics and morphologies in his search for a medium of articulation that allows him to characterize and differentiate the social functions that need to be organized and articulated. This process always involves both the visual accentuation of the selected morphological features as means of expression on the one hand and the visual suppression of all other technical features on the other hand. The raw, unedited imposition of pragmatic engineering and fabrication priorities does not deliver legibility. In fact, an unsightly visual chaos is likely to ensue, especially as there are usually multiple engineering concerns that need to be negotiated. The designer must not allow these concerns to agglomerate without aesthetic control and orchestration. Visual order needs to be imposed via a ruthless formalism and aesthetic principles that guide the accentuation and suppression of features. Tectonic articulation implies that the selected formalism has been derived from a selected engineering logic. However, the transformation of the engineering logic into a formalism is necessary to constitute tectonic articulation as architectural strategy.

Both accentuation and suppression are at play in our façade design for the Dongdaemon Design Centre in Seoul. The tessellation of the aluminium façade follows a rule (script) that converts the (smooth) differentiation of degrees of curvature into the (stepped) differentiation of degrees of subdivision. Tighter curvature leads to smaller panels. This makes sense with respect to the material fabrication constraints of sheet metal. This makes sense even though a reprogrammable mould (pin-machine) was used to press the panels into a double-curvature shape. In the areas of tighter curvature the finer tessellation made more joints available to fit the panels to the overall curvature. However, beyond this technical rationality the rule-based tessellation strategy delivers a heightened visual plasticity and thus legibility of the buildings form. The turning points in the surface are being accentuated by the denser tessellation. The volume’s shape becomes perceptually more palpable, also from the distance and under less favourable lighting conditions. The second plasticity enhancing detailing strategy is the utilisation of iso-curves as tessellation lines. These curves follow and thus accentuate the flow of the surface rather than being arbitrarily imposed onto the surface.

Suppression is also at work here. The major spaces of the design centre do not need any day-light. Therefore an altogether solid façade is an appropriate response. However, there are various ancillary spaces that do require windows. Rather than allowing these windows to disrupt the fluidity of the overall form we decided to radically suppress the existence of these windows by letting the smooth envelope continue uninterrupted across these windows. The need for light was accommodated by perforating the metal sheets that hide the windows. Moreover, the location of the windows is being further dissimulated by avoiding any one-to-one correlations between windows and perforated panels. Instead the distribution of the perforated panels across the façade has been to some extent randomized and thus adding to the overall organic expression of the building. The windows would have disrupted the architectural figure and would have drawn more attention to themselves than their functions merits. Cuts within the envelope have been reserved for the entrances which are thus as conspicuously communicated as one could wish. Legibility in the service of quick, intuitive orientation and navigation  - prerequisites of the building’s social functionality -  are the accomplishments of these strategies of tectonic articulation.

Fig.4 The tessellation follows a rule that correlates curvature with subdivision. This makes sense in terms of fabrication. This also is a strategy of phenomenological articulation: it accentuates the plastic features of the form and thus enhances its perceptual palpability.
Zaha Hadid Architects, Dongdaemon Design Centre, Seoul

Fig.5 Accentuation and suppression: subdivisions and joints follow and accentuate the surface curvature. Perforations suppress the expression of windows and allow for the monolithic sculptural expression of the overall complex volume. Zaha Hadid Architects, Dongdaemon Design Centre, Seoul