ABSTRACT
This thematic session focuses on the construction of shells made of hyperbolic paraboloid (hypar) surfaces, which had their zenith in the 1950s and 1960s. The aim is to study in depth the various aspects that characterize and define this type of laminated reinforced concrete structure (which offered extreme efficiency given the advantageous structural characteristics of the hypar geometric form), and the conditions that determined its development and diffusion. Analysing and contrasting different points of view gives a panoramic view of one of the most surprising construction phenomena of the last century. Participants presented studies on hypar concrete shell structures that address the analysis of relevant aspects in their construction, under the following approaches:
Analysis methods employed: Everyone who builds must be able to guarantee the safety of the work done. This has been a permanent need in all types of construction. The introduction, development and diffusion of any construction technique must be linked to the knowledge of its behaviour, according to the means available at any given time, and to the capacity to demonstrate its safety. The study of the methods of analysis used in each place and at each time stems from these concerns.
Experimental studies: Reduced models. Analytical knowledge of the behaviour of shells usually led to inaccessible numerical solutions. As an alternative and support, some technicians developed tests on scale models to demonstrate the sufficient strength and rigidity of the structures, as well as the structural advantages offered by the hypar’s geometry.
Construction methods and materials used: Essentially, shells were made of reinforced concrete poured over continuous formworks. However, other materials and techniques were also explored, giving rise to local solutions that reached significant levels of development and resulted in remarkable works.
Relationship with the economic and social conditions: One of the fundamental aspects in understanding the emergence and success of a construction process is to understand the influence of the technical and economic conditions of the environment in which it takes place.
New materials and new techniques: The designers and builders of shells were faced with a new technique in which they were forced to reuse the techniques they had at their disposal and add their own contributions to simplify and improve the final result. These investigations gave rise to different procedures (formworks, scaffolding, prefabricated moulds, sprayed concrete) or materials (concrete of different qualities, pre-stressed sheets, concrete with fibres, plastics, etc.).
