Document Type : Research Paper
PhD Student, Department of Architecture, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Assistant Professor, Department of Architecture, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Cities, especially in their modern forms, are constantly exposed to a wide variety of hazards, and this is one of the most important issues in large cities in recent years. Therefore, it can be said that the current era is an era of urban vulnerability, because as urban life becomes more complex, cities in various dimensions face natural hazards and technological crises on the one hand, and socio-security crises on the other. One of the main elements in the city that is very important in the discussion of passive defense management, especially in the post-crisis period, are urban public spaces. Tabriz city as one of the metropolises of the country has not been an exception to this rule. This city with its large population and complex urban structures and in some dilapidated areas, is the center of all political, administrative, economic and social structures in the northwest of the country. The development of Tabriz city during the last few decades and the location of this city on a zone with high risk in terms of earthquakes and floods according to the history of numerous historical earthquakes in this city, including 4.3 in 2007 and the occurrence of earthquakes. 2.6 and 3.6 magnitude in the region as well as the existence of northern faults in Tabriz and its activity over time and the threatening dangers resulting from it, approve the necessity and importance of discussing proper location in urban spaces and the issue of passive defense. According to the issues raised and the importance of passive defense in planning and location of urban public spaces, the present study was done with the approach of recognizing the problem and examining the causal model of locating urban public spaces in Tabriz in order to plan passive defense.
The present study is applied research in terms of purpose and descriptive-analytical one in terms of method. In this research, library studies and field methods have been used simultaneously to collect information. The statistical population of this study consisted of experts. Experts were selected by snowball method from among university professors and active researchers. The sample size intended to complete the questionnaire was determined by 25 university professors and research experts. In order to measure the reliability of the questionnaire, Cronbach's alpha test was exerted, and its value was 0.90. This rate indicates the appropriate reliability of the questionnaire. After collecting the questionnaires using FUZZY DEMATEL in Excel software environment, the causal relationships between the criteria were determined.
Results and discussion
Considering the DR values, the criteria of access to main thoroughfares, outdoor access, compatibility of land uses (observance of neighborhoods), population density, building density and physical characteristics of buildings, considering that the amount of values obtained for these criteria are positive in the cause group and in other words these criteria are more effective. Criteria for access to relief centers, distance from high-risk land uses, diversity of land uses, with regard to D-R values that are negative, have been identified as disabled or affected. Based on the values obtained for D + R, it can be stated that among the identified criteria, the building density criterion has the highest value of D + R, which indicates that this criterion is the most important one. It can be said that the building density factor increases the vulnerability due to the volume of mass in the space during crises and will disturb the peace, etc. Therefore, paying attention to this factor, especially in public spaces, is important. After that, the criterion of observing the access hierarchy is in the second place in terms of importance. This factor should also be considered in urban planning and planning for the time of crisis, especially in order to provide relief at the scene. Because ignoring this factor can increase the rate of accidents and risks.
This study was written to identify the spatial causal model of urban public spaces with a passive defense approach. Criteria such as access to main thoroughfares, access to relief and medical centers, observance of access hierarchy, access to open space, distance from high-risk land uses, diversity land uses, compatibility of land uses (observance of neighborhoods), population density, building density and physical characteristics of buildings were investigated using the FUZZY DEMATEL method. The results of the implementation of the FUZZY DEMATEL model showed that among the identified criteria, the criterion of access to the main thoroughfares is the most effective and important criterion for discussing location with a passive defense approach. Because access to the main thoroughfares is one of the most important factors in increasing or decreasing the vulnerability of a city in times of crisis. Also, how to access and the number of access routes by observing the hierarchy due to the facilitation of relief will have a significant impact on reducing the number of casualties. Therefore, this important principle should be considered when planning for location, as this criterion has been selected as the most important one in this research.
In the next step, the criteria of outdoor access, compatibility of land uses (observance of neighborhoods), population density, building density and physical characteristics of buildings are placed in the cause group due to the fact that the values obtained for these criteria are positive. Therefore, in a place where population density and construction are high, using access to main thoroughfares and open space and distance from high-risk cabins should also be a priority in planning. Therefore, citing these issues and results, the first step in passive defense planning is to identify critical arteries, sensitive and densely populated centers, and demographics and vulnerable textures. Therefore, in examining the location of urban passive defense planning, in addition to security considerations in camouflage, concealment and dispersion of fortifications, facilities and location, natural issues, topography and strategically sensitive location, other criteria such as access to passages and identification of dense areas should also be considered in planning.