Researchers from ETH Zurich have built a prototype of an ultra-thin, curved concrete roof using innovative digital design and fabrication methods. The tested novel formwork system will be used in an actual construction project for the first time next year.
蘇黎世聯邦理工學院的研究人員，設計和建造了一個使用創新設計和製造方法的超薄混凝土屋面原型。該薄殼是一個屋頂單元的局部，將會於明年建構成一個名為 HiLO 的建築單元，隸屬於 NEST 大樓的一部分（the living lab building of Empa and Eawag in Dübendorf）。完工後下方的閣樓空間將成為 Empa 的客座教職員，未來生活與工作的空間。這群研究人員由 Architecture and Structures 的 Philippe Block 教授，以及 Architecture and Building Systems 的 Arno Schlüter 教授所領導，希望將嶄新的輕量化建築結構用於實際的測試，並將它與智慧和適應性建築系統結合起來。
A prototype for an ultra-thin, sinuous concrete roof using innovative design and fabrication methods has been designed and built by researchers from the ETH Zürich. The shell is part of a roof-top apartment unit called HiLo that is planned to be built next year on the NEST, the living lab building of Empa and Eawag in Dübendorf. The penthouse will provide living and work space for guest faculty of Empa. Researchers led by Philippe Block, Professor of Architecture and Structures, and Arno Schlüter, Professor of Architecture and Building Systems, want to put the new lightweight construction to the test and combine it with intelligent and adaptive building systems.
The self-supporting, doubly curved shell roof has multiple layers: the heating and cooling coils and the insulation are installed over the inner concrete layer. A second, exterior layer of the concrete sandwich structure encloses the roof, onto which thin-film photovoltaic cells are installed. Eventually, thanks to the technology and an adaptive solar façade, the residential unit is expected to generate more energy than it consumes.
嘗試與實際尺寸測試
屋頂的建築技術是由 Prof. Philippe Block 和高級研究員 Dr. Tom Van Mele 領導的 BRG（Block Research Group），與建築公司 supermanoeuvre 一同進行，一個真實尺度的原型測試。為了因應試做空間未來的使用需求，該原型目前已經拆除，這個原型的高度達到 7.5 米高，表面面積為 160 m²（投影面積為 120 m²）。混凝土的平均厚度為 5 cm，從屋頂邊緣最薄處的 3 cm 漸變到支撐部分的 12 cm 厚表面。
Tried and tested to scale The building technique for the roof was developed by the Block Research Group, led by Prof. Block and senior researcher Dr. Tom Van Mele, together with the architecture office supermanoeuvre, and tested out on a full-scale prototype. The prototype, which has already been dismantled to make space for future experiments, was 7.5 m high with a surface area of 160 m² (covering an area in plan of 120 m²). The thickness of the concrete has an average thickness of 5 cm varying between 3 cm along the edges of the roof to 12 cm at the support surfaces.
Instead of formwork using non-reusable custom-fabricated timber or milled foam, which would be needed to realise such sophisticated form, the researchers used a net of steel cables stretched into a reusable scaffolding structure. This cable net supported a polymer textile that together functioned as the formwork for the concrete. This not only enabled the researchers to save a great deal on material for construction, they were also able to provide a solution to efficiently realise completely new kinds of design. Another advantage of the flexible formwork solution is that during the concreting of the roof, the area underneath remains unobstructed and thus interior building work can take place at the same time.
Algorithms for controlling the shape The cable net is designed to take on the desired shape under the weight of the wet concrete, thanks to a calculation method developed by the Block Researcher Group and their collaborators in the Swiss National Centre of Competence (NCCR) in Digital Fabrication. The algorithms ensure that the forces are distributed correctly between the individual steel cables and the roof assumes the intended shape precisely. The cable net weighs just 500 kg and the textile 300 kg; thus, with a total of only 800 kg of material the 20 tons of wet concrete are supported.
如果沒有最先進的計算和製造技術，屋頂的建造將會難以想像的，但這個專案也很仰賴幾個工匠與專業技術。從 Bürgin Creations 和 Marti Group 的專家們開發了專為這個系統使用的噴灑混凝土技術，確保織品可以在任何時候承受住壓力。Holcim Schweiz 的科學家們調配了正確的混凝土配方，使其能有足夠的流動性被噴灑和振動，但又保有足夠的黏稠度，以不至於溢流出織物模具（甚至在垂直點的部分）。
The construction of the roof would be inconceivable without state-of-the-art computation and fabrication techniques, but the project also heavily relied on the expertise and experience of several craftspeople. Experts from Bürgin Creations and Marti sprayed the concrete using a method developed specifically for this purpose, ensuring that the textile could withstand the pressure at all times. Together with Holcim Schweiz, the scientists determined the correct concrete mix, which had to be fluid enough to be sprayed and vibrated yet viscous enough to not flow off the fabric shuttering, even in the vertical spots.
Proof that it works Block's team built the prototype over the course of six months in ETH Zurich's Robotic Fabrication Lab. It represents a major milestone for the NEST HiLo project: “We've shown that it's possible to build an exciting thin concrete shell structure using a lightweight, flexible formwork, thus demonstrating that complex concrete structures can be formed without wasting large amounts of material for their construction. Because we developed the system and built the prototype step by step with our partners from industry, we now know that our approach will work at the NEST construction site,” says Block.
The process to get to this point took almost four years, from the start of the project to the finished prototype, partly because Block wanted to involve several industry partners in development of the prototype. Next year, he plans to build the roof once again at the NEST building in eight to ten weeks. The individual components of the roof structure can be reused as often as needed. The cable net can be dismantled into a few parts that can be quickly reassembled and rehung.
（後記）為鄰房生產能源
HiLo 的發展之所以會令人印象深刻，不僅是因為其獨特的屋頂設計，也由於其創新的輕量化地板系統和建築技術，目標是達到能量的供需平衡。這些能量能在 NEST 大樓的各自單位之間被交換；HiLo 單元期許產生比它消耗更多的能量。作為補償, 它可以利用其他建築單位的廢熱，以及在 NEST 區域網路中的建築物。這也是為何 Arno Schlüter 教授參與計畫的原因：這位建築與建築系統的教授，正在開發一個新的建築系統，透過溫度感應器的使用，偵測出建築物低溫的區塊，使用這些熱能以營造宜人的室內環境。為此，他在結構體（包括屋頂）使用了這些熱能單件。
Energy production for the neighbours
The HiLo unit is impressive not only because of its unusual roof design, but also due to its innovative lightweight floor system and a building technology with a positive energy balance. Energy is exchanged between the individual units in the NEST building. The HiLo unit is required to produce more energy than it consumes. As compensation, it can use waste heat from the other building units, as well from buildings in NEST's district network. This is where ETH professor Arno Schlüter comes in: the professor of architecture and building systems is developing a building system with sensors that uses heat at low temperatures to create a pleasant interior climate. For this purpose, he uses components of the structure, including the roof, that are thermally activated.
