What is concrete shell architecture?

Have you ever seen the amazing Opera House in Sydney or the Oceanogràfic at the City of Arts and Sciences of Valencia? Why is the form of the structure so strange? Is it only a decoration or is this shape structurally or otherwise functional? This type of architecture is called shell architecture. So, what is shell architecture?

A concrete shell, also called “thin shell” concrete structure, is composed of a thin shell of concrete formed in such a way as to be self-supporting, often with no interior columns or exterior buttresses. The shells are most commonly flat plates and domes. They can also take the form of ellipsoids or cylindrical sections. The first concrete shell dates back to the 2nd century.

These concrete shapes are usually strong structures, allowing clear spans without the use of internal supports, giving an open, unobstructed interior. The use of concrete as both the form and structure can reduce both material cost and construction cost over other approaches to design and construction, as concrete is relatively inexpensive and plastic to conform to compound curves. The resulting structure may be immensely strong and safe; modern monolithic dome houses, for example, have resisted hurricanes and fires, and are widely considered to be strong enough to withstand even F5 tornadoes.

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Today’s concrete shell architecture is an evolution of structural concepts and construction techniques used in Egyptian, Assyrian, and Roman civilizations, in which arched and vaulted structures were erected, using stone masonry and rudimentary types of concrete as primary building materials.

The Pantheon in Rome and the Hagia Sophia in Istanbul are the more ancient spectacular examples of Concrete Architecture.

The Pantheon, in particular, is the oldest known shell structure: completed in 125 C.E., is constructed of Roman Concrete which was typically at the time faced with stone or brick. Roman concrete was composed of cement, similar to modern concrete, and aggregate, typically far larger than in modern concrete, often amounting to rubble. As a result, Roman concrete was laid rather than poured.

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Modern thin concrete shells, which began to appear in Europe in the 1920s, are made from steel reinforced concrete of uniform thickness as thin as 2”-4” depending on the span. In many cases there were no supplementary ribs or additional structure, relying wholly on the thin slab or shell to perform the major structural tasks in the building. Modern shells were first introduced by architects and engineers such as Eugène Freyssinet (1879-1962), Bernardo Laffaielle (1900-1955), Pier Luigi Nervi (1891-1979), Eduardo Torroja (1899-1961), Félix Candela (1910-1997), among others. The strongest form of shell is the monolithic shell, which is cast as a single unit. The most common monolithic form is the dome, but ellipsoids and cylinders and variations thereof are also possible.

The design and construction of shell structure were a trend through the ‘60s. However, the approach to this type of structural and architectural design declined due to the high costs of labour, concrete, and cost of the complex project specific formwork. The shells also require a reasonably high level of maintenance to prevent leaks and other construction pathologies due to the exposed concrete also serving as the roof and primary moisture barrier. Since the 1980s, the preference for polygonal shapes and stretched structures occurred.

The Zarzuela Racehorse (MADRID) | Carlos Arniches Moltó and Martín Domínguez Esteban (architects), Eduardo Torroja Miret (engineer) | 1934-1941

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PalaTiziano (ROME) | Annibale Vitellozzi (architect), Pier Luigi Nervi (engineer) | 1956 – 1957

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Wyss Garden Center (SOLOTHURN – SWITZERLAND) | Heinz Isler (architect) | 1962

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El Oceanográfico (VALENCIA – SPAIN) | Félix Candela (architect), Alberto Domingo and Carlos Lázaro (engineers) | 2003

Credits: Commons Wikimedia

Do you know other impressive European shell constructions? Give us your suggestions!