Nervi: The Master of Parametric Design and Construction
Today, advances in computer aided, parametric design have enabled practically limitless possibilities in the virtual design of structures and these tools are becoming more accessible than ever. Free to download and intuitive to learn, Rhino’s plug-in Grasshopper has inspired a whole online community of amateur designers who generate and share their awe-inspiring parametric creations. This kind of technology also makes it easier and quicker for architects and engineers to perform complex structural analysis, allowing them to create beautifully biomimetic and highly optimised structural designs.
One of the reasons we don’t regularly see these kinds of free-form structures in reality is because of their feasibility to construct. Whilst the fluidity of concrete makes it ideal for free-form structures, this relies on fluidly shaped, yet physically rigid formwork. Although traditional techniques, such as timber, are technically feasible they can be both time and labour intensive.
Research has begun to address this issue, focusing on new and innovative manufacturing techniques as well as the integration of computer aided design and automation. Yet engineers don’t routinely study precedent and, in the case of free-form parametric design, could learn something from the work of master builder Pier Luigi Nervi.
Nervi was one of the most prominent engineers of the 20th Century, and whilst formally trained as a Civil Engineer he also embodied the roles of architect and builder, combining the art and science of structure to create some of the most iconic pieces of contemporary architecture. Like the works of other master builders, from Gaudi to Frei Otto, he demonstrated a symbiotic relationship between design and construction, resulting in elegantly rational and materially efficient form.
Much of Nervi’s distinctive work draws from the field of Biomimetics. For example, the internal geometry of bone tissue which aligns according to the trajectories of maximum tensile and compressive stress. Here biological material is optimised to resist external forces creating a porous bone that efficiently maximises its strength to weight ratio. This inspiration can be seen in the former zoology lecture hall at the University of Freiburg below.
Nervi said that by drawing inspiration from these structural patterns “reinforced concrete beams lose the rigidity of wooden beams or of metal shapes and ask to be moulded according to the line of the bending moments”, stimulating both efficient and aesthetic structural design.
Nervi’s Parametric Approach to Design
Nervi could be seen as an early predecessor to modern parametric design and through this method he did not allow the reality of constructability to limit the visual sophistication of his geometry. Instead he harnessed it to maximise the complexity of his design by transforming and revolving simple forms that could be produced by equally simplistic construction methods. For example, forming parabolic columns using straight lines alone allowed custom formwork to be rapidly erected from thin timber boards simply twisted around metal jigs which could facilitate numerous geometrical permutations, as seen below. Nervi clearly understood the importance of the relationship between design and construction, and utilised this knowledge to drive his design.
Innovative Methods of Construction
In response to their 1935 invasion of Ethiopia, Italy was subject to international trade sanctions and the use of steel in construction was heavily rationed, until 1939 when reinforcing bars were completely banned. Post war construction in Italy continued to experience limited access to materials as well as a shortage of skilled labour due to exceptionally high levels of employment. Working throughout this period Nervi had to innovate out of necessity and pioneered methods of prefabrication which included the reinvention of ferrocement, a form of reinforced concrete which is produced by applying mortar to a thin but dense mesh of small diameter wires. Nervi successfully used this system in the construction of one of his most famous works, the Palazzetto dello Sport.
In order to avoid the need for costly continuous timber centring, the 60-meter diameter domed roof was divided into small repeatable elements — another example of Nervi’s symbiotic relationship between design and construction, geometrically limiting variation to 13 different shapes, which were sized to ensure that each unit could be lifted by two men to ease installation. 13 full scale templates were made for the wire mesh to be formed over before being sprayed with a cement mortar, creating a strong but relatively lightweight shell. These units were then assembled, like a large mosaic supported by a temporary frame, functioning as formwork for a cast in situ concrete slab. This created a structurally composite and seemingly monolithic shell, with the channels created between each unit forming what is seen from the underside of the roof as Nervi’s distinctive ribs.
Nervi’s method of construction was incredibly efficient, both in terms of time and overall cost, and remains economically competitive when compared to 21st century examples of similar structures.
Yet the ferrocement that Nervi pioneered has been relegated, with its most recent reincarnation in the 1960’s when the United Nations promoted its use for boat building projects in Asia, Africa, and Latin America. Nervi’s structural application of ferrocement is now predominantly used in developing countries due to its simple technology, readily available constituents and ease of construction, making it suitable for construction in even the most under-resourced and rural locations.
Today, ferrocement should not be considered as an inferior material, used only where cost is prioritised over quality, and instead as a sophisticated form of construction with the ability to compete against the more traditional reinforced and pre-stressed concretes.
Nervi showed that this reciprocal relationship between design and construction does not necessarily limit the creativity of structures and instead can be used to drive both architectural form and engineering efficiency. Whilst there has been increased interest in Nervi’s methods of parametric and biomimetic design there has not been a similarly parallel exploration of his construction methods, which in themselves were an integral part of Nervi’s overall approach. As such, revisiting Nervi’s use of ferrocement and his symbiotic philosophy to design could be the key to enabling the sustainable fabrication of highly engineered and visually complex free-form structures.
