L’étude présentée ici a pour but d’analyser la manière d’utiliser l’arc outrepassé, en plan et en élévation, et l’arc en retrait sur ses piliers, dans une région et dans un temps pragmatiquement défini du monde méditerranéen particulièrement riche en éléments architecturaux de ce type. L’arc en retrait n’est pas inconnu dans la recherche mais, faute d’identification précise et donc de terminologie adaptée, il a été confondu avec l’arc outrepassé sous des dénominations différentes. Faisant l’objet de diverses théories dans l’historiographie, ces deux types d’arcs ont été utilisés comme arguments majeurs dans la datation et dans la filiation stylistique des édifices dans lesquels ils se trouvent. L’objectif de cette approche consiste à confronter ces courants historiographiques, inscrivant un monument donné comme relevant du monde wisigothique, mozarabe ou carolingienne, à l’analyse des monuments in situ dans les régions catalano-roussillonnaises et languedociennes où ces formes présentent une concentration considérable. Dans ces théories tenaces, souvent assimilables à des idées reçues sans discernement, l’abbaye de Saint-Michel de Cuxa a occupé une place particulière de sorte que son attribution s’est répercutée sur de nombreux édifices, surtout des chapelles rurales, gravitant dans son orbite. Les monuments situés sur les deux versants des Pyrénées possédant ces formes en élévation ou dans la planimétrie constituent un corpus de 98 édifices. Ils ne révèlent pas seulement une certaine uniformité pour l’ensemble du territoire mais, au-delà, permettent également de définir des microrégions homogènes. L’étude de ce territoire est intégrée dans une analyse historiographique plus vaste de ces deux types d’arcs qui cherche la réponse à leur origine, à leur propagation géographique au fil de temps et présente les différentes réflexions sur la raison d’être de leur emploi. A côté des théories pragmatiques qui considèrent ces formes comme des procédés techniques offrant des avantages constructifs et des mesures techniques qui cherchent à établir une typologie séparant les arcs de différentes époques et de différentes aires géographiques, une attention particulière est apportée aux dimensions idéologiques, liturgiques et symboliques liées à ces tracés. / This study focusses, in façade and in plan, on the horseshoe arch, the hallmark of architecture in the first flowering of the Middle Ages, and on the recessed arch on piers, its more or less unrecognised contemporary. The geographical extent of the occurrence of these two types of arch has been defined by the periodic enlargement of the area where they are really concentrated: Spanish Catalonia and French Languedoc-Roussillon. Applied often to dating a building, and becoming involved as a result in a stylistic epistemology, as well as being the targets of the entrenched dogmas of a vast historiography, these pieces of evidence are here studied on the ground in their architectural context so as to juxtapose fieldwork with the theories on their deployment developed a century ago. Given the spread of developed mediaeval arches, this work endeavours to place their corpus in a wider general study which clearly cannot depend on an exhaustive survey, but which is able to suggest, nevertheless, that the realm of the Moorish arch transcends the territorial and chronological limits of Visigothic, Mozarabic, Carolingian or Islamic culture. The origin of the recessed arch on its piers, for which we propose the term «mushroom shape» displays an undeniable origin in antiquity. Its diffusion in time and space coincides with the horse-shoe throughout the vast Mediterranean ambit. The corpus of the area studied brings together 98 buildings which preserve in their structure the Moorish arch and/or the recessed arch on piers. An analysis of arch assembly, incorporated in the overall study of a building’s construction, confirms that the Moorish design or that of the recessed arch on piers concerned not only arches but was inherent in a general building process observable in the raising of the vault, or of any transverse arches or in openings, doorways or windows. The endurance of these same building procedures for centuries, for minor works such as small country chapels, as for the great abbey church of Saint- Michel de Cuxa, testifies to a conservative art associated with basic techniques.

Topic of this dissertation thesis follows previous dissertations dealing with reconstructions of historical buildings that were successfully defended at Institute of Building Structures, Faculty of Civil Engineering, Brno University of Technology. The thesis deals with Romanesque and Pre-Romanesque round churches, called rotundas, that were built between 9th and 13th century in the historical territory of Great Moravia. Churches of similar shape can be also found in surrounding countries, but only scarcely. By the time of origin these rotundas were among the oldest masonry buildings built within borders of contemporary Czech Republic. Later some rotundas were destroyed and are known only thanks to the archaeological findings or written records. Some are still waiting to be discovered. Surviving rotundas are the oldest masonry buildings in Czech Republic, therefore it can be said that they belong to the most valuable historical buildings in the country. Preserved rotundas were often modified or rebuild in some way. Thanks to their age, origins of many of these buildings are shrouded in a mystery, which is one of the reasons why they attract attention of many researchers – archaeologists, historians and art historians. Many questions arise from their research. These questions have interdisciplinary character and finding the answers requires cooperation of specialists in different fields. One of these fields is building engineering. This dissertation thesis deals with proportional and structural analysis of Pre-Romanesque and Romanesque rotundas. For the proportional analysis author focused on verifying of some of the hypotheses of other researchers connected to the Romanesque rotundas. These include hypothesis dealing with use of historical units for the design of rotundas, hypothetical use of proportional canon, or some universal sets of proportional ratios of vertical and horizontal dimensions. The proportional analysis also helped with verification of some hypothe