On Shells, Structural Landscapes and Performative Geometry

On Shells, Structural Landscapes and Performative Geometry Oliver Tessmann1, Klaus Bollinger2, Manfred Grohmann3 1,2,3Bollinger + Grohmann Ingenieure, Germany http://www.bollinger-grohmann.de [email protected], [email protected], [email protected] Abstract: The paper exemplifies a collaborative design approach of architects and engineers by two projects that remotely resemble shell structures. Their geometry is rather driven by a complex network of manifold requirements. Parametric modeling and scripting is used to enhance collaboration and speed up the synthesis analysis loop. Keywords: Collaborative design; associative design; structural analysis. The structural notion of shells without incurring bending forces and thus can be constructed with minimal material thickness. When The overall performance of an architectural project forces can be reduced to pure tension and compres- results from balancing a complex network of mul- sion the entire cross section of a structural element tifaceted, interrelated requirements that originate is exploited whereas bending causes stress only in from multiple sources. In such a collaborative de- the outer areas and therefore disrates the remaining sign process the authors conceive of structure as an material to be useless ballast. The elegant shells of integral part of architecture. Geometry becomes an architects and engineers like Heinz Isler, Felix Can- important mediator for all people and disciplines in- dela and others exemplify the slenderness, which volved in the process. To enhance collaboration and can be achieved by finding forms free from bend- speed up feedback loops of synthesis and analysis ing forces. Surface structures like shells or domes an integrative representation including architectural resist forces through their double-curved form and and structural aspects at the same time is of great integrity. The bearing mechanism is achieved by a interest. membrane-like behaviour. Like a balloon that is not The paper will discuss two projects that seem- able to resist bending with its thin surface, shells ingly belong to category of shell structures. But on resist external loads through tension and compres- closer examination one can see that those forms sion. In case of symmetrical loads the form will be originate from design procedures, which consider kept in equilibrium by meridional forces and ring a broader set criteria then mere load bearing. The forces only. Structural shells are ideally defined by tools that enable seeing design as a dialogue in revolving catenary curves. Such geometry leads to which ideas are bounced off the different members mere membrane forces and is best supported by lin- of a design team are presented here. ear bearings. However, any incision in such an ideal From an engineering perspective, homogenous, shape leads to fundamental, problematic changes in idealized shells are elegant as they transfer forces the structural behavior. Session 01: Digital Aids to Design Creativity 1 - eCAADe 27 47 Figure1 EPFL Rolex Learning by SANAA, Visualization A structural landscape Classic form-finding is superseded by processes of The Rolex Learning Center at the EPFL Lausanne tracing performative capacities in the specific mor- by SANAA Kazuyo Sejima and Ryue Nishizawa is a phology. As the load-bearing characteristics vary single-storey building which hosts a central library, across the landscape-like articulation, no region lecture halls, study facilities and services, exhibition represents a pure structural typology. The analysis halls, conference halls, cafeteria and a restaurant also reveals problematic areas that would neces- (Figure 1). The building is supposed to be the centre sitate a disproportionate thickness of the concrete of campus life in the future. Instead of a planar floor shell. Wavy tensile force progression, high bending slab the Japanese architects designed an architec- movements and redirected forces combined with tural landscape generating a topographic separation the lack of support points in the patio areas were of different zones of use. The load bearing shell con- addressed by redirecting the force flow between the sists of two perforated free-span reinforced concrete Figure 2 Structural arches in relation shells, spanning up to 90 metres. to patios, on objective of SANAA’s undulating landscape building includes intensive negotiation between patios, openings and various spatial qualities de- architects and engineers fined by an artificial topography. Hence structural aspects were just one set of design criteria among many in the design process. The landscape inte- grates a wide range of design criteria far beyond just structural aspects, which prohibited the use of con- ventional structural form-finding strategies for shells and barrel vaults. The structural design rather focused on analyz- ing and identifying local areas of shell or arch behavior, which were subsequently further developed and modified in an ongoing dialogue with the architects. 48 eCAADe 27 - Session 01: Digital Aids to Design Creativity 1 Figure 3 EPFL Rolex Learning Centre concrete shell under construction shell perimeters through modification to geometry, model. The geometry could be represented by only size and location of the patios. Such an iterative pro- few surfaces with trimmed patio areas. The model’s cess of tracking performance in collaboration with complexity increased when the structural system the architects entails ongoing design and evaluation required a description of several arcs as primary cycles (Figure 2). structure and areas that span in-between. A multi- In the early design phase the architects predom- tude of surfaces were now necessary to represent inately used physical models to develop their design. the structural components. Furthermore their con- The obvious advantage of physical models is that nection became important because the NURBS sur- they offer a common base for more than one person faces were translated into meshes of a finite element to work on. The workforce could be directed towards model. Structural coherence could only be achieved the organization of a complex program within the when the vertices of neighboring elements meet in landscape. Details of the exact geometry were of the same point. With the progress of the project the minor interest at that stage of the process. Neverthe- workflow from architectural model to analysis model less the structural inquiry required a precise descrip- improved but at the same time became increasingly tion of surface curvature, symmetries and singulari- complex since all models gained detailed informa- ties like patio positions. Thus the contour model of tion (Figure 3). the architects was translated into a NURBS surface Figure 4 Section of the existing museum and the new roof Session 01: Digital Aids to Design Creativity 1 - eCAADe 27 49 Figure 5 Shell surface geometry with deflections for apertures/ Vertex manipulation con- trolled by fall-off curve A parametric shell structure The architectural notion of the roof shell The extension of the Staedelmuseum in Frankfurt The architectural approach of the museum roof shell am Main designed by Schneider + Schumacher Ar- is a continuous, quadratic surface with a central de- chitekten was represented as a digital model from flection. The roof dimension results from the shape early on. Thus communication, collaborative design of the existing courtyard. Apertures are placed ac- procedures and data exchange could be enhanced cording to a pattern defined in plan and subse- by a parametric 3d model and scripting procedures quently projected to the shell surface. In detail the which act as an interface between architects, engi- apertures form local deflections of the shell surface, neers and fabrication. self-similar to the overall form but smaller in scale. A spacious museum hall, submerged under an The result is a surface with a large central deflection existing garden, is covered by a concrete shell. The populated with a series of similar small-scale deflec- double curved roof is perforated by a pattern of tions (Figure 5). circular apertures, which subdivide the garden and The project is supposed to be built as a concrete bring light into the building. The spatial experience shell with glazed skylights. The continuous small- of the shell as a ceiling becomes a central feature scale deflections will be shown in the concrete shell of the building and its geometry is the objective of and then chopped and covered by planar glass pan- multiple requirements (Figure 4). els. The aperture size differentiation is limited to five Figure 6 Architectural and structural section curves 50 eCAADe 27 - Session 01: Digital Aids to Design Creativity 1 Figure 7 Dependency graph of the roof shell different sizes to provide a certain repetition in the becomes the revolve axis for the skylight profiles mould fabrication process. which than act as fall-off curves for the deflection of the reference surface by repositioning the affected Parametric representation of the shell control vertices. A dense uv-sample rate in the ref- The above described requirements are represented erence surface provides the necessary precision and negotiated in a single parametric surface model, for defining those local small-scale deflections. The which serves as an interface between the different result is an undulating reference surface that inte- parties of the design team. grates one large and many small-scale deflections. Due to the

Load more