Croisée d'ogives | EPFL Graph Search

La croisée d'ogives est un facteur déterminant de l'essor de l'architecture gothique. Développée à partir de la fin du , en Normandie, elle constitue une structure d'arcs en plein-cintre puis brisés en voussoirs de pierre se rejoignant sur une clef au centre des diagonales d'une travée carrée, barlongue ou d'un hexagone puis couvert par un remplissage de voutains légers posés sur les nervures. Cette technique permet de reporter le poids et les poussées de la voûte aux pieds des arcs sur des sommiers contrebutés par des arcs-boutants. Sa mise en œuvre limite les travaux de coffrage aux arcs mais son équilibrage est plus complexe et sa fragilité impose une couverture. Cette innovation donne la liberté d'utiliser l'espace entre les arcs pour y installer de larges baies et créer une architecture de lumière et d'élan vers le ciel. Rappels historiques L'architecture romane, qui précède le gothique, se caractérise par des arcs en plein cintre et des voûtes. Ces voûtes romanes

German Concrete, 1819 - 1877

Salvatore Aprea

This dissertation originates from an investigation about the arising of the modern, German building expertise involving the use of concrete, which develops during the first three quarter of the 19th century against the backdrop of a general modernisation process, and moving from the observation of more advanced building techniques in France, Italy, Holland and the United Kingdom. Early uses of modern concrete in Germany essentially concern the construction of foundations underwater and in marshy soils. Between the end of the 18th and the begin of the 19th century, some traces are to be found in the mixtures of pebbles and mortar that are used as filling materials in the so-called well foundations, which consist of underground circular walls to be filled with rubble masonry work, and among the heads of the timber piles supporting the piers and the abutments of some bridges. From the end of the 1820s, we observe a more mature use of concrete to build underwater foundations, whose bearing capacity essentially depends on concrete itself. This trend further develops in the second half of the 1830s and during the 1840s, when concrete is recognized as an essential material to build underwater. The expertise in building concrete foundations develops along with an increasing interest for the nature and properties of hydraulic binders. This produces consequences on the scientific plan, giving rise to the development of essential chemical studies about lime and mortar, and in the domain of manufacturing, involving the foundation and the enlargement of several hydraulic lime and cement plants. The use of concrete to build above ground appears later than in the domain of the construction of foundations, and it is preceded by the development of a peculiar material, which is known as Kalksand. It is a very lean and lime-base conglomerate, the use of which spreads as of the mid-1840s, mainly in rural domains. Similar to concrete, it is poured in formworks to build walls and, in a few cases, onto centrings to build vaults. Between the mid-1850s and the mid-1860, Kalksand and concrete are recognized as similar materials, and the use of the second one gradually prevails. An important aspect of the use of concrete, or of similar cement-based compounds, concerns the production of moulded artificial stones, tiles, architectural decorations, pipes and other kinds of objects. After several attempts dating back to the first half of the century, this kind of production improves during the 1850s and the 1860s, giving rise to an independent branch of the young German manufacturing. From the second half of the 1860, a number of buildings are entirely built in plain concrete, from the foundations to the roofs, mainly following British examples. At the same time, techniques to build concrete foundations get more advanced and complex, especially for what concerns well foundations, while the study of cement is further developed through chemical analyses and strength tests.

EPFL2015

German Concrete, 1819 - 1877

Salvatore Aprea

EPFL2015