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RESEARCH PRODUCT

La fractalité des structures urbaines

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Urban patterns show often an irregular morphology. The fact that this phenomenon appears often despite of the intensions of planers and that it is not related to a particular historical situation, incites to suppose the existence of self-organisation process, promoting such an evolution. To get more insight in these aspects of urban growth, it has been investigated, whether there exists appropriated quantitative measures to characterize the irregular structures. The analysis of the build-up area of a certain number of agglomerations of the scale of metropolitan areas has shown, that the urban patterns follow an interior order principle, and that they may be characterized by fractal dimensions. Thus the spatial organization of agglomerations follows a hierarchization principle, which appears on the scale of metropolitan areas as a radial dilution of the build-up area, according to a pareto-distribution. The fact that urban patterns follow such an order principle allowed to give an interpretation, based on sociological theories, of the socio-economic interactions giving rise to such an irregular growth. For some of these interactions it has been shown by use of a simulation model that these effects give really rise to a fractal urban pattern. The fractal analysis has been used too, to investigate the spatial organization of transportation networks. For town quarters, this method describes the hierarchical organization of the street pattern, and for metropolitan areas the accessibility, assured by the network, is measured.