Analysis the Process of the Sub-Cores Formation in the Spatial Structure with Emphasis on the Residence and Activity Pattern (case study: Kermanshah metropolis)

In the last few years, various concepts of urban-regional spatial structure have been developed and the spatial structure of big cities has exhibited multi-core characteristics. The phenomenon of polycentric is inherent in metropolises, and studies indicate more efficiency and the effect of quantitative methods in identifying functional nuclei. The time frame of this research was cross-sectional and sample data of Kermanshah metropolis, statistical block and land use of the existing situation and comprehensive plan zoning. The variables of this research included 8 major urban uses. Spatial analysis and measurement of the density of mixed uses in Kermanshah metropolis has shown the existence of new sub-centers in regions 1, 3 and 4. In addition to the historical and old core of the city, there are two dense cores of mixed activities in areas 3, 1 and 4 between areas 5 and 8. Of course, the types of services provided in the sub-centric of the metropolis have a regional scale compared to the central core of the city and have been created to meet some of the daily needs of citizens at this level of access. The spatial distribution of commercial and administrative activities shows the concentration of most of these activities in the central core of the city; However, sub-centric in areas 5 and 8 can also be considered as a core in the southeast. The development pattern of residential activity has differences with other activities and that is the formation of several cores other than area 1 as a physical core; In other words, other residential cores have been formed as competitors in areas 6, 5, 4 and 2, which can play an effective role in the formation of other sub-cores
Extended Abstract
Introduction
The increase in the population of cities has created various effects on the urban environment, and the spatial structure of cities has changed significantly, which has led to the emergence of multi-centric cities (cities with multiple urban centers). The urban spatial structure has two morphological and functional dimensions. The concept is a monocentric structure reflecting an urban system with a strong concentration of economic activities and jobs in the city center. The multi-centric spatial structure within the city also represents the clustering of population and occupation in a metropolitan area or urban area. A city's spatial structure significantly affects economic efficiency and the quality of the urban environment. In the growth and development of Kermanshah metropolis, it can be seen that this region, like other third-world metropolises, suffers from instability and spatial imbalance in terms of spatial morphological aspects, spatial division of labor, and political organization of space. The city of Kermanshah, in its expansion process in recent decades, has grown from the central core to the peripheral areas, and the sub-cores were able to play an effective role in the structure of the city. By playing a dominant role, the sub-cores were strengthened by using residential and commercial-service cores. Because of the density of construction and population, they are effective in the city's spatial structure. Identifying other areas with suitable space for creating a nucleus is necessary.
 
Methodology
In terms of purpose, the research is applied, carried out by descriptive-analytical method, and based on library studies, documents, and field investigations. Considering the nature of the data and the impossibility of controlling the behavior of the effective variables in the problem, this research was of a non-experimental type. It was carried out within the framework of the case-analytical model. The investigated time frame is the summer of 2021, and the investigated sample was the statistical block and all urban uses of Kermanshah metropolis. The main data, mainly using the data of Iran Statistics Center, including the comprehensive and detailed plan, have been obtained.
The spatial statistics method, Peter Hall method, mixed land use index, and Excel software were used for data analysis. Moreover, Arc GIS software and spatial analysis tools, including spatial statistics methods, were exploited for drawing and spatial analysis of layers. The variables of this research included eight major urban uses (distribution of industrial, commercial, tourism-recreational, cultural, administrative, medical, educational, and residential cores) and converting it into cross-sectional data. The generalized method of moments (GMM) has been used in the research process.
 
Results and discussion
The spatial autocorrelation coefficient (λ) results are significant at a high level, which confirms the existence of spatial dependence in the components of the residential core growth model and its significant relationship with other urban land uses. This means that the shock applied to one core has spread to other cores. Also, it shows to what extent the growth of the residential core in one area has been affected by the shock on the distance function and the accessibility of each core in other areas of the city. Therefore, the distance factor is considered one of the repulsion factors of each land use. According to the results, the degree of concentration of the administrative core has a negative and significant effect on the volatility of the residential core. This means that areas with a significant distribution of the administrative core have had less residential growth. Also, the career mixing index has a positive and significant effect on the growth model of each core; that is, the regions with a higher mixed land use index have functional cores and, as a result, have a denser distribution. This shows the centrality of body divisions in the growth and expansion of new cores.
 
 Conclusion
The explanation of the situation, planning and organization of the population, the function and the evolution of the spatial structure can be presented based on three important indicators of the spatial pattern of residence, the spatial morphological structure, the division of spatial work, and to some extent the organization of urban functions. Based on this, the current research sought a clear understanding of such concepts that the metropolis of Kermanshah has had a relationship with the spatial balance of population and function in the course of its developments. Suppose we accept that urban development plans improve the quality of life in urban areas through the creation of urban infrastructures, the establishment of equipment, and also the required public services. In that case, urban development plans create a positive perspective for developing and creating new cores. In other words, the development of urban areas directly increases the performance of the cores through the general plan of land, housing, and real estate prices. The population reacts to this price increase through the supply and demand market.