Gestire strutture free-form: il computational design per una struttura in acciaio ed ETFE a Singapore

Questo articolo esplora l'approccio alla progettazione computazionale di una tettoia free-form in acciaio con cuscini in ETFE sull'isola di Sentosa, a Singapore. L'articolo evidenzia le sfide affrontate nella discretizzazione e nella produzione di documenti di fabbricazione per la struttura utilizzando metodi parametrici. L'obiettivo è ottimizzare la producibilità degli elementi strutturali partendo da un modello iniziale di gara che presentava numerosi clash e rappresentava più una visione architettonica che un modello di riferimento. L'articolo dimostra come l'approccio One Single Model, utilizzato dalla Maffeis Engineering, abbia gestito questa complessità, garantendo la continuità tra l'analisi FEM, la documentazione BIM e le attività di ottimizzazione all'interno di ambienti parametrici. L'obiettivo è mostrare come la progettazione computazionale enfatizzi le possibilità intrinseche delle strutture in acciaio, dimostrando che senza questi strumenti e approcci non solo l'efficienza strutturale sarebbe compromessa, ma anche l'estetica e l'eleganza dell'architettura coinvolta verrebbero sminuite.

Free form and ETFE as a structural celebration

Parametric modeling and computational design have revolutionized the architectural landscape, offering dynamic methodologies that transcend traditional approaches and unlock new possibilities in design, analysis, and fabrication. Within this paradigm, ETFE (ethylene tetrafluoroethylene) technology has emerged as a powerful complement to steel structures, allowing for a more pronounced and bold expression of the structural framework.

This synergy enables architects to make deliberate design choices that go beyond static necessities, fully embracing Vitruvius's triad of firmitas (strength), utilitas (utility), and venustas (beauty).

ETFE's lightweight and flexible nature, combined with its strength and transparency, enhances the aesthetic appeal and functional performance of steel structures. This material allows for the creation of airy, ethereal architectures that highlight and celebrate the underlying steel framework. As a result, steel structures are no longer just static necessities but become central design elements that drive the overall architectural vision.

By leveraging ETFE alongside advanced computational design, architects and engineers can push the boundaries of traditional architecture, creating iconic landmarks and sophisticated canopies that exemplify the harmonious integration of form and function.

The new Entrance Canopy for the Singapore Oceanarium on the island of Sentosa exemplifies this synergy between computational design and material innovation. The design features eight distinct bays, each hosting a free-form surface that defines the path of ETFE cushions.

The canopy reaches a height of 25 meters covering an area of about 1730 square meters covering the en- trace space of the Oceanarium. This project demonstrates an optimization experience that maintains the original architectural intent as intact as possible. Through the use of advanced parametric tools, the design team was able to address the challenges of discretizing steel elements and pro- ducing fabrication documents for the complex free-form structure, ensuring both structural efficiency and aesthetic elegance (Fig. 1).

In this article, we will introduce the One Single Model methodology adopted by Maffeis Engineering and its application in the design of the Sentosa canopy. We will examine the design criteria modeling phases of the main arches, taking into account topics such as fabrication, transportability, and the optimization of the number of ETFE cushion types (strictly correlated with the shapes of the primary steel structure).

Additionally, we will describe the treatment of the secondary steel, from the rationalization of curvature radii through machine learning to the definition and mode- ling of splices for installation.

Computational Design Approach for steel structures

Computational design proves to be widely used in engineering disciplines, and now more than ever its implementation in industry practices as a vehicle for innovation and control over even the most complex architectures, especially free-form structures, is crucial. This section will introduce the One Single Model approach adopted in Maffeis engineering and its declination in the canopy for the aquarium in Sentosa.

The One Single Model approach

Maffeis Engineering employs the One Single Model (OSM) approach, integrating a suite of inter- connected software and tools, many of which are internally developed or linked via API. This comprehensive methodology manages input data from geometric models to FEM analyses and BIM models, ensuring seamless integration and live-linking at the programming level.

The OSM framework coordinates technical reports, automatic verifications, IFC drawings, and BIM outputs, all within a visual programming interface designed to be intuitive for engineers, architects, and programmers. Although this approach requires significant upfront effort, it offers substantial advantages by maintaining control over subsequent project phases, including FEM analysis and BIM modeling.

The adaptable control panel, typically developed using software like Grasshopper and Dynamo, supports various design processes and phases, ensuring flexibility and adaptability in any kind of scenario (Fig. 2).

Sentosa’s ETFE canopy workflow

In the case of the work under discussion, the OSM scheme was applied as shown in Figure 3. Specifically, the main parametric model handled the three main apparatuses of the structure (main arches, secondary steel, and ETFE) in different portions of code. First, a script was developed in Grasshopper to handle the first bay. Once this prototype was defined and validated, the code was reapplied on the other bays which kept the same design rules but changing the boundary conditions described as input parameters in the code. The model wireframe is used within Rhino as a tool for design, optimization and verification of design choices.

At the same time, the same wire- frame, thanks to the interoperability provided by OSM and internally developed applications such as FeMM, allows structural verification in SAP. During all these steps, the Revit model is already populated with informationally enriched BIM objects to start producing the technical documentation required by the client. Any changes that arise through feedback received from outside are implemented by the main parametric model code that takes care of updating the other environ- ments involved (BIM and FEM) (Fig. 3).

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La presente relazione è stata presentata in occasione del XXIX Congresso CTA, svoltosi a Milano il 26 e 27 settembre 2024.