History
Background
Lamellar structures first appeared in the Egyptian, Assyrian, and Roman civilizations, which built structures with arches and vaults using stone masonry and rudimentary types of concrete as material. At this time, structural calculation as we know it today did not exist; The buildings were built using the practical knowledge acquired by professionals through observation and repetition of procedures.[9].
The development of cylindrical surfaces has as its starting point the brick barrel vaults that were perfected by the Romans. The art of vaulting reappeared with the Romanesque and persisted during the Gothic period, evolving from the heavy brick vaults to the slender ribbed vaults of their cathedrals.[10].
Furthermore, domes have been used in architecture since early times. Its evolution has gone hand in hand with the development of materials. In ancient times they were built of stone or masonry, later moving on to brick and wood. The Romans frequently used domes to cover buildings such as basilicas, mausoleums or baths. The largest of all is that of the Pantheon in Rome (120-124 AD), 44 m in diameter, which also constitutes the oldest known laminar concrete structure.[5] Other important domes that marked the evolution of this typology are the domes of Santa Sofia in Istanbul (532-537), the cathedral of Santa María del Fiore in Florence (17th century), the Basilica of Saint Peter in Rome (1546-1590) and St. Paul's Cathedral in London (1705-1710).[10].
Vaults and domes evolved after the appearance of iron due to their greater speed of construction and their great resistance in relation to their weight; Later, the use of reinforced concrete was adopted. One of the first reinforced concrete domes is that of the Wroclaw Centennial Center (Poland), built according to the project of the architect Max Berg between 1911 and 1913.[10].
First modern lamellar structures
The first reinforced concrete laminar structure was built in Germany between 1924 and 1926, to cover a building destined for the Zeiss company factory, the current Jena Planetarium").[3]
Until the 1920s, the behavior of lamellar structures had been studied mathematically as if they were membranes. These studies concluded that if the forces existing in a thin, but sufficiently rigid shell, were exclusively tangential compression and traction and were contained in the thickness of the shell, without any bending stress, the thickness of the sheet could be very small, even just a few centimeters, provided that its shape and support conditions met certain requirements.[3].
In this way, the structure no longer solved the support problems due to its section, but did so through its pure form, thus managing to satisfy the principle of material economy so important to the engineers and builders of the time. The material that best suited these new structures was reinforced concrete, due to its great moldability; In addition, reinforcing armor could counteract shear and tensile stresses.[3].
After the First World War, reinforced concrete laminar structures were imposed as a structural typology capable of covering large spans "Light (engineering)") with minimal material expenditure. Thus, a new construction system emerged with an ideal geometry to cover large utilitarian spaces such as stations, airports, warehouses, warehouses, factories or hangars, which until then had been built primarily in steel.[3].
Development of the calculation of laminar structures
This new structural typology also required the development of a solid mathematical base that was capable of safely calculating these structures before their construction. In this context, the application of elastic theory was resorted to due to its more than proven validity in structural calculation. The application of elastic theory to the structural calculation of cylindrical laminar structures began to be developed in the 1930s in Germany.
However, the elastic theory turned out to be practically inapplicable to lamellar structures since it required solving complex eighth-order differential equations, formulated based on unrealistic hypotheses that assumed either idealizing a reality that was impossible to know a priori, or assuming an ideal, homogeneous and isotropic material, despite the fact that reinforced concrete does not have any of these properties. As a consequence, insurmountable discrepancies appeared between the results obtained using elastic calculation and what was observed in reality or through experiments.[3].
In this context, in 1944 the Danish engineer Knud Winstrup Johansen published a highly relevant article in which he carried out the structural calculation of a long cylindrical structure belonging to a real roof, using exclusively the approach of equilibrium equations, thus allowing a simple and safe calculation of these typologies. At the end of that decade, Johansen and H. Lundgren formulated a theory of practical, clear and simple application based on the equilibrium approach.[3].
In the 1950s, Heinz Isler developed a new approach to designing these surfaces, defining their geometry through experiments with physical models such as inflatable rubber membranes or hanging fabrics. These experiments generate balanced figures, since their shape distributes loads, such as the structure's own weight, through the membrane tensions. Also in the 1950s, researchers at the Frei Otto Institute of Light Construction at the University of Stuttgart experimented on the shapes of tensile structures, studying the minimal surfaces of soap bubbles, among others. Their physical models were later complemented and partially replaced by computational methods to determine structurally appropriate forms, applicable to both tensioned systems and laminar structures.[2].
Currently, modern computational models are used to calculate these structures, such as the finite element method.[9].
Later evolution
The success of laminar structures decreased from the seventies, due to fundamentally economic criteria, as a consequence of the high costs of labor, concrete and formwork methods that can hardly be reused in another work. Cable and stereometric presented equally efficient structural solutions for covering greater distances, but their construction problems could be more easily solved with the construction technology established for structural skeletons. The few lamellar structures built after the 1970s were mainly ribbed, the continuous surface being replaced by interconnected linear or curvilinear parts.[2].
However, at the beginning of the century there was a kind of "renaissance" of lamellar structures. Some of the most notable examples are L'Oceanogràfic by Félix Candela in Valencia (2003), the Casar de Cáceres bus station (2004), the Saijo crematorium in Kakamigahara (Japan) by Toyo Ito (2008); SANAA's Rolex Learning Center at the Federal Polytechnic School of Lausanne (2011) and the cover of the Grin Grin park in Fukuoka, also by Toyo Ito (2005).[10][12].