the polycentric and multi-core model of city and metropolis: from theory to practice (a case of karaj)

the space structure that governs cities has depended on several corresponding relations and various factors which consist of: population, job and activities, transportation patterns, urban sub-structures, various services and etc that always were connected to each other and have formed its space structure. but since these relations are more complicated in big cities, the importance of paying attention to their space structure becomes more important. nowadays, civilization has turned to an important and complicated problem in various societies and is growing fast in recent period of ten days –especially in metropolitans it has caused several anatomic, economic and social problems. the fast spreading of cities have caused a number of problems such as emigration and slum, city order distribution, traffic and implication of environment, which must be carefully studied. small cities have just one center or one central core but nowadays big cities particularly metropolitans have several centers that according to economic, anatomic and connecting foundation factors centrals and different fireplace living have formed not so far from historical and central centers of the town. these cores have been created according to their position near the railway and transport direction, airports, industrials centers, universities and sporting (fun)center, etc. and follow that one centrality or a new urban center have developed and with spreading connection lines and completing that, the town has become polycentral. such space structure of cities depends on factors such as expanding industries, distributing economic institutions, expert and various activities, amount of rent, agent of cars, communication lines and the special earning of socio-economic, etc. the purpose of this research is to present polycentric space structure of urban and metropolitans and analyze and organize the space that was achieved by having a case study of karaj. in this research, using peter halls polycentric model and analyzing karaj city structure within this model, we achieved the space planning and appropriate strategies in this city.