A new approach to the concept of tectonics N.S.Yordanova UASG, University of Architecture, Civil Engineering and Geodesy, Sofia, Bulgaria. ABSTRACT: Tectonics in architecture or „poetics of construction“as Frampton defined it, has a multifarious nature and many manifestations. This paper explores a new approach to the concept of tectonics, which systemises the various tectonic expressions. The proposed approach reveals tectonics as an artistic expression of mechanical and spatial functions of building’s material elements. Construction technologies appear as a means for expressing these functions. This paper clarifies all mechanical and spatial functions and gives examples of their tectonic expressions. The review concludes that this functional approach to tectonics has a wide scope, encompassing most of tectonic manifestations and gives a basis for their systematisation. 1 INTRODUCTION In contemporary architectural theory the term tectonics refers to specific artistic expressions, which originates intrinsically from the materiality of the architectural form and a materialising process called construction. Tectonics is the inherent quality of buildings and according to some authors it is the tectonics which counters outer influences in architecture coming from different trends in figurative arts (Frampton 1995). The great works devoted to tectonics witness that it has a multifarious nature and many manifestations (Boetticher 1852; Semper 2004; Frampton 1995). To give a small overview, Bötticher called it “a system“, for Semper it is an art of „dressing“and Frampton define it merely as „poetics of construction“. All this ambiguity raises the question “Can tectonic expression be systematised and explained by using a new approach to the concept of tectonics? “ This paper demonstrates the soundness of such a theory. Although the theoretical deduction of the proposed approach is a subject of previous publication by the author, it is briefly explained here for reasons of clarity (Yordanova 2017). According to Kate Nesbitt the problem with “meaning” and consequently tectonics lies in the lack of consensus about the essence of architecture in contemporary postmodern theory (Nesbitt 1996). The three parts of Vitruvian triad – utiltas, fermitas, venustas are still struggling to take precedence of one above the other. Finding an appropriate theory for the theoretical point of departure for a new approach to tectonics means thoroughly reviewing the existing concepts and bringing out basic common touch points which should indicate what kind of architectural ideas are needed. The outcome of such analysis of the most influential works on tectonics leads to the conclusion that tectonics is closely connected to: the materiality or „thingness” of architecture; the materializing process called construction (constructional technologies); and the creative act of designing an architectural form. Also, some cultural and symbolic meanings have influence over the tectonics (Yordanova 2017). Moreover, tectonics deals with the ethics in construction and as Eduard Sekler has noticed it visualizes the reality of architectural form (Sekler 1965). Consequently, theoretical ideas are needed which concern the process of transformation of matter through technologies in an architectural form. Most information related to materials and construction techniques is contained in handbooks, textbooks and albums full of technical information, details and description of executions. However, there are not many theories that give theoretical base for such technological knowledge. The book „Technological Theory of Architecture “presents a concept for the transformation of matter into architectural form and the essence of that form”. According to Tilev, architectural spaces and all material components (architectural structures) embody the pith of buildings through the unifying role of composition, which for its part provides the functionality in architecture (Tilev 2013). Composition is the internal organization of architectural form and it gives functions to every space and material element. Tilev states also that tectonics is inherited property of buildings to have artistic expression through their internal structure (organization). Thus the artistic expression of internal organization is an artistic expression of functionality which composition conveys to the material components of architectural form. This in fact is the Seklerian visualization of reality. Hence the functional concept of tectonics gives grounds for the systematisation of tectonic expressions according to the spatial and mechanical functions of material elements. Figure 1 Structure of architectural form according to Tilev and a classification of mechanical and spatial functions which are bases for tectonic expressions. The taxonomy of mechanical functions is derived from Tilev’s classification of architectural components’ functions (Tilev 2013). That the aesthetics of the load-bearing structure is constituted through its mechanical and spatial functions is not new (Sandaker 2010). However, in considering tectonics, it is necessary to include all material elements of buildings: load-bearing and non-loadbearing. Architectural form can also be regarded as a system with different hierarchical levels: modules, elements and structures (Deplazes 2013). The artistic expressions of mechanical and spatial functions have their manifestations on a „micro-tectonic“or elemental level and on a „macro-tectonic“or structural level. This paper explores spatial and mechanical functions of material components and gives examples for their poetic expressions on the two defined levels and depending on the type of elements and structures (load-bearing and non-loadbearing). Construction and all technologies associated with it are closely related to architectural form. An example of the dependence of form on technology is Deplazes’ examination of concrete and its wooden “corset”- formwork (Deplazes 2013). Functions, on the other hand, are always accomplished in technologically grounded forms (Tilev 2013). Construction technologies are the means of artistic expression of spatial and mechanical functions of material elements, because they are conditions for form generation. Semper’s technological theory of tectonics also relays on that interconnection between form and technology (Semper 2004). In the functional approach to tectonics technologies are a means for expressing functions, which correspond to the general concept of technologies as a source of meaning and tectonic manifestation. The functional approach to the concept of tectonics should not remain abstract. All mechanical and spatial functions should be explained and some well-known examples from Frampton’s influential work on tectonics „Studies in Tectonic Cultures: The Poetic of Construction in the Ninetieth and Twentieth Century Architecture” may serve to illustrate the argument. 2 TECTONICS AS AN ARTISTIC EXPRESSION OF MECHANICAL FUNCTIONS 2.1 Load transfer and distribution The forces running through the main load-bearing structures of buildings have always been an object of artistic expression for architects. Two basic functions of structures and elements are the transfer and distribution of incoming loads. Concepts of even and uneven distribution and transfer of loads are basic for these functions and they are very often tectonically emphasized. Thinking holistically the even and uneven distribution of loads in a load-bearing structure or in an element means uniformed or respectively ununiformed organization of its constituent parts. That organization can be expressed artistically or even dominate tectonically. That is the case with buildings made from repetitive structural units. For example, the expressive potential of these spatial modules plays a significant role in buildings such as the Centraal Beheer by Herman Herzberger, the Kimbell Art Museum by Louis Kahn or the Municipal Orphanage by Aldo van Eyck in Amsterdam (Frampton 1995). The additive principle of successive constructive cells, whether or not they are framed or divided into compartments by walls, results in an artistic manifestation of the even distribution of loads. Perhaps the most convincing example on the micro-tectonic level is the poetics of fair faced brickwork. The repetition of a structural cell or a module such as the brick is a result of the implementation of certain construction technology. It is known that line supported and point supported structures define two basic types of load transfer: distributed and concentrated. The play of load and support has been tectonically exploited many times throughout the history of architecture. Each new construction material and technology challenges the artistic manifestation of that function. Looking at the trabeated ceilings of Auguste Perret’s Musee de Travaux Public and Robert Maillart’s point supported concrete slabs, one can see the poetic results of efforts to express distributed and concentrated transfer of loads between concrete horizontal (slabs, beams) and vertical loadbearing elements (columns). The concepts of distribution and concentration can be applied to the load transfer between the vertical elements only. The paths of the gravity loads can represent interrupted or uninterrupted straight or curved lines. Structures whose vertical loading paths undergo drastic change of direction demonstrate the concept of concentration, while straightforward transfer shows even distribution of loads in the vertical paths. As further examples, the high rise block “Zur Palme” in Zurich, the Unite d’Habitation in Marseille and the Shanghai Bank in Hong Kong – all these buildings count on the tectonic expression of loads transfer in vertical paths. The manifestation of the same function is applicable on the lower elemental level to the substructure of the building elements: forked and tree like columns for example. The mechanical functions are inherent not just for loadbearing structures and elements. All material components of buildings transfer and distribute loads and, as such, can be expressed tectonically. On the „macro-tectonic” level, the non-loadbearing components should be examined as a system that distributes and transfers loads to the system of the loadbearing elements. There are two basic models of organization of these complementary elements. They can repeat the pattern of structural elements (infill walls) or follow completely different schemes. The two approaches respectively define two concepts in regard to the mechanical function of distribution of loads from the system of non-loadbearing components: the concept of repetition and the concept of contrast. Both concepts of relations can be sources of artistic representation, particularly in the skeleton frames where the enclosing and partition walls play such a determinative role in the overall architectural form. In the apartment block on the Rue Franklin, Auguste Perret expresses artistically the traditional infill walls, which conveys the concept of repetition, while the German Pavilion in Barcelona may be one of the most demonstrative examples of the concept of contrast : “… in the opposition between the marble-faced pinwheeling planes and the symmetrical placement of the eight columns in relation to roof” (Frampton 1995). The microtectonic dimensions of load distribution in the system of elements and subcomponents can be found in the coincidence between an element and its envelope (cladding, rendering, stains). This tectonic aspect is part of the representational versus ontological discourse in architecture. Distributed and concentrated transfer of loads between the system of components and the loadbearing structure manifests itself again through the type of support that the latter system provides to the former. All built-in, enclosing and partition walls have linear support, while suspended and curtain walls contact the structure by point connections. The tectonic impact that both types of load transfer have are evident in the glass infill façade of the Garage Marboeuf by Perret and the suspended curtain wall of the Fagus Factory by W. Gropius. In fact, every curtain wall bears tectonic expression of concentrated transfer of loads to the main structure behind it. The type of load transfer could be found on the level of the elements as well. Point, surface and linear contact between finishing and core is frequently a subject of tectonic expression. Manifesting mortar in the gaps or the caps of bolts by which a revetment is held in place, as in the Otto Wagner’s Post Office in Vienna, expresses concepts of distributed or concentrated load transfer between subcomponents and elements on the „micro-tectonic“ level in architectural form. 2.2 Type and rate of deformation Excepting distribution and transfer of loads, every material object which is subject of external forces exhibits strain: “a change in the form of its structure measured as a fractional extension perpendicular to the cross-section” (Silver & McLean 2013). Strain is the material’s reaction to these forces. Deformations in the structures, elements and components are another realm of tectonic manifestations by which architects “make visible” the reality of architectural form. Generally changes in the cross-section of the building elements due to loading are not distinguishable enough for direct tectonic statements. However, what is visible is the dimension of the object’s cross-section. Through it, the material responds to forces. Consequently, the mechanical function rate of deformation can be expressed indirectly through the massiveness of elements’ and structures’ sections due to which they cannot undergo impermissible deformations. Here a distinction can be made between the tectonics of light and heavy construction, between “stereotomy” and “tectonics” as termed by Semper. There is another aspect of tectonic dimensions of mechanical function the rate of deformation. Looking at the structure on macro-tectonic level, it can be regarded as a single element with specific dimensions of its cross-sections. Most buildings have commensurable dimensions, but there are some groups of buildings in which one of the dimensions is significantly larger than the others. High-rise buildings, towers and bridges have special tectonics due to the specifics of one of their cross-section to exhibits higher strain than the others. Even some styles in architecture characterize itself with that particular feature, as with Gothic buildings, which have high steeples, columns and arches. Moreover the structurally rationalist approach of cross section diminishing as it rises, due to the reduction in compressive load, may be regarded as tectonic expression of the mechanical function rate of deformation. Schinkel applied this in his Neuer Packhof warehouse in Berlin, Mies in his Promontory apartments and Perret in his columns in the Musee de Travaux Public, although on a microtectonic level. The building components that do not belong to the main load-bearing structure can also contribute to the overall massiveness of the building by their own massive cross sections. Heavy or light enclosing elements such as panels and walls can respectively complement or reduce the heaviness of the load-bearing structure. Glass walls give the highest lightness to buildings, due to their transparency. This explains why they are a common feature of the high-rise construction: glass curtain walls simply complement the higher level of strain in the loadbearing structure. On the micro-tectonic level, massiveness of cladding, lining and revetment plays a significant role in expressing the nature of the “core form”. The concepts of complementation and reduction are both applicable on this level. Atectonic manifestations of mechanical function the rate of deformation also exist - a well-known example is Josef Hoffmann’s Stoclet Palace. Depending on the forces acting on an element or a structure, a distinction is made between several types of strain: compressive strain, tensile strain, bending strain and shear strain. Expressing type of strain means direct expression of deformations that occur in compression, tension or bending. In some types of constructions, that expression is intrinsic: tensile membranes, cables, air-supported structures, suspended bridges, cable-stayed beams etc. Frei Otto’s Olympic Park in Munich and the catenary roof of the Lowara Office Building by Renzo Piano both have, as tectonically dominant, the expression of the mechanical function type of deformation. It is interesting to find the National Nederlanden Building by Frank Gehry is an atectonic manifest of deformations on the macro-tectonic level, in a loadbearing structure coming from the action of unexisting forces. The system of nonloadbearing elements can suggest visual deformations that have tectonic statement. Sometimes components of buildings are used to convey the idea of nonexistent deformation in the load-bearing structure, which is the case with the enclosure of Calatrava’s the Turning Torso skyscraper. Similar atectonic use of a building’s skin for expression of deformation in structure is traceable in many of the neo-futurist buildings of Zaha Hadid as well. Artistic expressions of visualized deformations in elements are noticeable in elements and components on the micro-tectonic level. All textile enclosures or partitions demonstrate a perceivable strain in their fabric. Cables and thin plates demonstrate their tendency to exhibit deformations. In the Pavilion des Temps Nouveaux, Le Corbusier applies such tectonic expressions on both levels: once in the catenary curve of load-bearing cables and again in the fabric of the enclosure tent. Further expressions of deformations in surface treatments of elements, are encountered in the sculptural ornamentation of classical Greek columns. Details of the capitals, moldings of bases (torus and scotia) and even the entasis of the shaft all speak of compressive forces and the results of their action. 2.3 Structural integrity The last mechanical function that has tectonic articulation in architecture concerns the rigidity and stability of load-bearing structures, stiffness of their elements and the role of nonloadbearing building components to the overall integrity of buildings. Structural integrity encompasses methods for providing rigidity and stability for the structures. The form, the specialized elements in structure, the type of connections and the position of structural elements may provide the rigidity of buildings. These modes implement poetic expressions in architecture through different construction technologies. Every structure that owes its own integrity to the form it represents bears the artistic outcome of that fact. Domes, shells, and vaults are two and three dimensional surfaces and have inherent in their tectonics the manifestation of the mechanical function integrity. Other structures achieve their rigidity through specialized elements: bracing, buttresses and shear walls. One of the most convincing examples of the artistic articulation of these elements is the flourishing of the flying buttress during the Gothic period. While the rigid connections are a subject of articulation on micro tectonic level, the position of structural elements can have a higher tectonic expression. Including angling and raking columns in a structure may help to provide rigidity, which can simultaneously be a strong tectonic manifestation such as in the City Tower project of Louis Kahn. Three dimensional systems of interlocking plates form robust cellular structures. Many forms of solid construction with bearing walls contain that cellularity in their tectonics as an indication of their rigidity. Recent examples for bearers of similar tectonics are the contemporary multi-story timber buildings with CLT panels. Non-loadbearing components can also participate in assuring the rigidity of structures, generally as infills in frame construction. Some traditional self-containing constructive systems with wood show how the infill planks between posts can contribute to a specific tectonic image. On the elemental level, it is the properties of the material and the different forms of the sections that determine the stiffness of elements. Part of a material’s tectonic expression is the inherit knowledge that we have about their mechanical properties. The moment of inertia of an element’s section also determines its stiffness and, when appropriate, leads to natural lightness. This is one of the reasons behind Louis Kahn’s advocacy of construction with tubular steel (Frampton 1995). Folded plates also owe their stiffness to the form of their cross section. Stiffening elements of the main load-bearing structure may have many other tectonic manifestations in the use of additional elements: props, guys, knee braces, purlin frames etc. (Herzog 2004). Structural sheeting and planking can also have an artistic functional interpretation such as the “coursed” expression in Wright’s early wooden architecture (Frampton 1995). There are some other mechanical issues concerning the stability of structures and elements that are subject to tectonic articulation. Buildings should not move as a whole, which depends on their anchorage to the ground and the position of their centre of gravity. The indirect result of generally invisible foundations is the relation of buildings to surrounding terrain. The different topographical concepts, ranging from constructing entirely underground to elevated buildings are researched in detail by Alois Diethelm (Diethelm 2013a), (Diethelm 2013b). These concepts concern our judgment about the stability of the structures. Frampton also observed such tectonic expressions in some of the works of Alvar Aalto and Sverre Fehn (Frampton, 1995). The position of the centre of gravity to its base of support directly affects the stability of material bodies, which is used in architecture to express this mechanical function artistically. Inclined buildings, skyscrapers and elevated buildings convey a certain degree of instability due to the location of their centres of gravity. This expression has a strong tectonic impact, as opposed to the apparent stability of traditional vertical buildings. Non-loadbearing components also can influence the stability of buildings, most of all with their mass. Greater mass of components can be beneficial for overall stability in respect to wind overturning or providing clamping gravity force in rocking systems, such as the heavy cornices of Greek temples (Jamil et al. 2012). On the micro-tectonic level, the stability of elements manifests itself through the type of connections to the other elements. Moment resistant or hinge connections can be tectonically expressed and can even be a tectonic dominant, such as the rigid ovals in the frames of the Tamedia Office Building by Shigeru Ban, or the steel hinges in the Turbine Factory of Peter Behrens. The centre of gravity conceptualized on the elemental level leads to the conclusion that all inclined components of buildings manifest a certain degree of instability. The artistic treatment of fastenings in the substructures of elements is another group of tectonic manifestations in relation of stability. The works of Carlo Scarpa are a good example of such expressivity. 3 TECTONICS AS AN ARTISTIC EXPRESSION OF SPATIAL FUNCTIONS The spatial functions defined in this paper represent the attitude of material elements to the spaces they create. Space-separation and space-transformation can be interpreted as reversed material equivalents of Henri Focillon’s „border space” and “medium space”(Focillon 1996). Both functions signify the capacity of material objects to create and influence these two types of spaces depending on geometrical form of the elements, their size and their mutual position. All elements have both functions, but in some only one dominates. 3.1 Structural systems and elements with dominating space-separation function. The function of space-separation is intrinsic to the elements with planar form. The main attitude that walls, slabs and plates express to surrounding spaces is by acting as a boundary. Their mechanical functions may not be always expressed, but the separating role they perform is undeniable. One perspective on the development of boundaries is Gottfried Semper, who in his textile theory, claims that all walls come from the fabric screens ones existed in the primordial shelters. Regarding spatial functions, it is the space separation function that is ontological for walls. Structures which are made entirely from plates (slab and plate systems) or that contain predomi nantly planar elements (bearing wall constructive systems) express the space-separation function to a greater or lesser extent. The inside-out boundary is crucial in experiencing the spatial functions of structures on the macro-tectonic level. According to Bejder, slabs and plates can define three building configurations, ranging from “enclosed box” to “floating structure” (Bejder, 2012). In each of these configurations, walls have different contacts with the outer boundary of the building. Compartmentalization leads to a higher degree of space separation, while placement of planar elements perpendicular to the outer boundary, as in the “floating space” configuration, leads even to a manifestation of space-transformation function. This last is a result of the expression of the mechanical function rate of deformation through the width of walls. An example of an attempt for reducing the space-separation function of planar elements is Rietveld’s Schroder House. The supporters of Der Stijl movement experiment with the spatial functions of slabs and plates, trying to display their space-transformation function as well. Another means for manipulation of the difficult-to-master space-separating function of plates is light. Carlo Scarpa used it to create space over the walls behind the white gypsum casts in the Gipsoteca Canova. Space exists where there is light. The role of the secondary non-loadbearing elements in slabs and plates structures generally consists of reducing their dominating space-separation function. These elements are windows, doors and glass walls. Although most of the windows have plates in their structures, these plates are transparent and the light that passes through them makes them space-transforming elements. However, the potential of openings and windows to curb space-separation in slab and plates systems is not so great, because large windows in load-bearing walls lead to compromising struc- tural logic and complicated constructive solutions. An example of such an attempt is the country brick houses of Mies van der Rohe, particularly the Josef Easters House and the Herman Lange House (Frampton, 1995). On the micro-tectonic level architectural elements can have different substructures. They can be solid elements, elements made of plates (with cellular honeycomb structure) or lattice elements. Solid walls, columns, floors etc. have dominating space-separation function because they do not contain internal spaces. The form of their surfaces has a great impact on their spatial functions. It is known that freestanding solid columns have a better spatial effect when they are round. Therefore, the space-separating function of solid structure can be manipulated by curved surfaces of elements. Plastic decorations with curved surfaces also have the aim of enhancement of the spatial function of elements, and are even stylistic features of some architectural styles, such as Renaissance, Baroque and Rococo. Light is another means for spatial functions manipulation. Guiseppe Terragni’s “Dandeum” project is a brilliant example of how the space-separating function of solid elements can be almost eliminated. Some finishing has similar effect of spaceseparation mitigation: for example, the mirror effect of the Venetian “stucco luccido” or some wall-paintings. On the other hand, finishing such as casings and claddings, may significantly influence the spatial functions of elements by changing their dimensions and form. These spatial relations between form and content are described by Robert Venturi in his book Complexity and Contradiction in Architecture (Venturi, 1977). 3.2 Systems and elements with dominating space-transformation function Linear elements have special impact on Henri Focillon’s “medium space”: they have the capacity to transform it. Depending on their size and distances between them they can attach different characteristics to the spaces that surround them. This special effect have been noticed by Auguste Perret in his church Notre-Dame de Raincy where for the first time he have offset the enclosing walls out from the perimeter columns in sacral building. In his words “ this greater number of columns in sight tends greatly to increase the apparent size of the church with a sense of spaciousness and vastness” (Frampton, 1995). May be there is not a more precise explanation of the space-transformation function which dominates in linear elements. On the macro-tectonic level, expression of space-transforming function means an artistic exposure of the load-bearing structure’s lattice. A well known example of such manifestation is Joseph Paxton’s Cristal Palace, where inclusion of infill glass panels between steel frames allows an articulation of structure’s dominating spatial function. The distance between linear elements has significant impact on space-transformation. Large spans intensify it, while close mutual positions of posts have a reducing effect on it. The most extreme degree of the latter is “log construction”. Non load-bearing components in filigree construction can completely conceal all traces of linear elements and their spatial functions (solid walls) or complement them (glass panels). There is a third indirect manifestation of skeleton structure’s spatial function when these functions are only hinted, such as with Le Corbusier’s “fenetre en longeur”. Elements with lattice substructure also express the space-transformation function but on the micro-tectonic level. A good example is the Sendai Mediatheque by Toyo Ito, where exactly that expression is a tectonic dominant through the substructure of the columns. Very often the spatial functions on the elemental level are concealed under suspended ceilings, casings and claddings, owing to fire requirements or the passing-through of interstitial services. On the other hand, casings have the potential to amplify space-transformation function, as is the case with the chromium-planted sheet steel case covering of Mies van der Rohe’s Tugendhad House cruciform columns. 3.3 Systems and elements with balancing spatial functions Domes, vaults, shells and all single or double curved surfaces have special expressivity in relation to the spaces that they create. Due to this fact, structures with such forms are even called “spatial structures,” although spatiality is an intrinsic quality of every three-dimensional structure or elements. It is logical to think that this specific effect is a result of the spatial functions of curved surfaces. On one hand, they possess the space-separation function of planes, but on the other, they attach special characteristics to the “medium space”. It is similar to space in nature, and it evokes the same feelings of vastness and flowing as the space under the sky. That is one of the reasons why roofs with single or double curvature are widely spread in sacral architecture. Obviously, the space-transformation function is typical for such structures as well. The balance between the two spatial functions has a significant tectonic impact: structures with that characteristic are almost always tectonic dominants, even when they are combined with structural elements with other spatial functions. For example the expressivity of the shells in the Sydney Opera House is so strong that they entirely dominate over their podium (Frampton 1995). Non-load-bearing components similarly have limited repercussions over the spatiality of curved surfaces, but the position of windows and illuminating holes can significantly strengthen their space-transformation function through light. For example, sliding light coming from the slots in the apexes of Kimbell Art Museum’s vaults contributes to a similar amplification. 4 SUMMARY AND CONCLUSIONS This attempt for clarification of a functional approach to tectonics has encountered a very wide scope of associated themes with it and with the creation of architectural form. Most of them are not new to architectural theory. However the contribution of this approach is that all of these themes are systematised and have found their logical position in it. 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