Passive Defense
Hossein Mahdizadeh; Ghader Ahmadi; Mohammadreza Pakdelfard; Mahsa Framarzi
Abstract
Highlights
- The vulnerability of the semi-grid urban form is greater than that of the grid urban form with respect to the indicators of plot area, fabric pattern, building density, building age, building quality, distance from rescue centers, distance from hazardous centers, building facade, ...
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Highlights
- The vulnerability of the semi-grid urban form is greater than that of the grid urban form with respect to the indicators of plot area, fabric pattern, building density, building age, building quality, distance from rescue centers, distance from hazardous centers, building facade, population density, and building structure.
- The vulnerability of the grid urban form is greater than that of the semi-grid urban form with respect to the indicators of distance from open spaces, area of worn fabric, distance from faults, and distance from the main thoroughfares of the city.
- The grid urban form exhibits better performance than the semi-grid urban form in terms of vulnerability from the perspective of passive defense against earthquake.
Introduction
The present age is referred to as the age of urban vulnerability, because cities face natural hazards and technological crises from various aspects on the one hand and socio-security crises on the other as urban life becomes more complex. The issue of passive defense is no longer defined as a mere research topic but as a vital requirement for governing any country, both upon crisis and at other times, for maintenance of its material and spiritual values. Therefore, the theoretical and practical position of defense and defense against the crisis is very important in this area. On that basis, the application of passive defense and consideration of its principles in urban planning can greatly reduce the destructive effects of such crises. The checkered city of Salmas, Iran, a mid-sized city, according to Iranian Space Agency, with a population of 91239 people, is located in a region with high relative risk based on the relative earthquake risk zoning of Iran, from the study of the National Physical Plan of Iran. Due to its location on a fault, evidenced by the devastating 7.2-magnitude earthquake in 1930, it is very important in this city to observe the principles of passive defense in urban planning. Accordingly, this study was conducted with the aim of measuring and modeling the vulnerability of grid and semi-grid urban forms in Salmas against earthquakes from the perspective of passive defense.
Theoretical Framework
With respect to the type of fabric, there is less vulnerability and greater relief in case of earthquake in regular continuous fabrics over flat lands featuring roads with low or medium confinement and blocks with one or two regular rows of construction. The grid urban form of the roads is also effective in the provision of relief due to easy access. Regular and stepped discontinuous fabrics over foothill lands are moderate in terms of efficiency and vulnerability, and irregular continuous fabrics over flat areas are less effective against earthquakes. The indicators of urban fabric in the assessment of vulnerability against earthquake include the method of attachment of adjacent segments to the passage, adjacency of the open and constructed spaces of each section to the passage, extent of confinement of the fabric, pattern and size of the urban blocks, and pattern of combination of the roads and urban blocks.
Methodology
In this applied analytical research, data collection was carried out through library studies, existing articles, field studies, and 2016 census information from the Statistical Center of Iran. Thus, the effective indicators of vulnerability were extracted from the perspective of passive defense after the relevant documents and resources were studied, and fourteen indicators were then selected from among various influential factors according to their availability for specification of vulnerability in Salmas to obtain the research output. Given that each of the indicators effective in the specification of the vulnerability of the coefficient has a different importance, the opinions of the elite were used in this research to determine the weight (coefficient of importance) of each indicator. To weigh the indicators according to the BWM method, ten questionnaires with contents based on a pairwise comparison of the indicators were formulated given the preference of the best indicator over the others and the preference of the other indicators over the worst. In the next step, the data from the questionnaires were entered into the GAMS software and calculated and analyzed. The weight calculated with the value of λε obtained for the ten questionnaires was 0.097, which indicates the stability and consistency of the calculated weights due to its proximity to zero. For spatial analysis, the information layers of the indicators were first digitized and edited in the GIS software, and each of the indicators was multiplied by the significance coefficient calculated by the BWM method through conversion of the information layers into rasters and their standardization with large and small fuzzy functions and Boolean logic. Using the weighted sum of the indicators to measure vulnerability, the grid and semi-grid urban forms in Salmas were addressed separately.
Results and Discussion
Among the calculated weights of the indicators in GAMS, the highest concerned urban from pattern, with 0.164, and the lowest pertained to building façade, with a significance coefficient of 0.030. The average value of λε obtained for the ten questionnaires was 0.097, which indicates the stability and consistency of the calculated weights due to its proximity to zero. The results of combining the indicators in the grid urban form in Salmas demonstrated that there were 4866 parcels in the very low vulnerability zone in the grid urban form, 2719 parcels in low vulnerability, 2862 in medium vulnerability, 3435 in high vulnerability, and 430 parcels in the very high vulnerability zone. In the semi-grid urban form, there were 611 parcels in the very low vulnerability zone, 2598 in low vulnerability, 3669 in medium vulnerability, 5350 in high vulnerability, and 3057 parcels in the very high vulnerability zone.
Conclusion
In general, it can be stated that the level of vulnerability in the grid urban form is less than that in the semi-grid urban form. The semi-grid urban form was found to be more vulnerable than the grid urban form based on the indicators of area, parts pattern, building density, building age, building quality, distance from rescue centers, distance from hazardous centers, building facade, population density, and building structure. Moreover, the grid urban form was found more vulnerable than the semi-grid urban form based on the indicators of distance from open spaces, range of worn fabric, distance from faults, and distance from the main thoroughfares of the city.
Passive Defense
Mohammadreza Pourmohamadi; Rasoul Ghorbani; Ghafour Alizadeh
Abstract
The main objective of this research is to identify and provide a solution for the vulnerable infrastructure of Tabriz city from the perspective of passive defense. Therefore, this research is a type of applied-developmental study with a descriptive-analytical method. Data was collected using library ...
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The main objective of this research is to identify and provide a solution for the vulnerable infrastructure of Tabriz city from the perspective of passive defense. Therefore, this research is a type of applied-developmental study with a descriptive-analytical method. Data was collected using library sources and a supplementary questionnaire filled by 20 experts in the fields of architecture, urban planning and passive defense. The findings of the research indicate the desirable condition of passive defense safety considerations in providing suggestions. The research planning process is as follows: 1. The quantitative model for determining the levels of the centers of gravity of the Metropolis of Tabriz shows that, from the total 32 infrastructures, 17 infrastructures are classified as vital and critical infrastructures and 15 are classified as important and maintainable centers, representing the significant number of vital and critical centers. Creating a large number of vital and critical centers instead of a single critical center and increasing the distribution of important centers in the city to promote the security of the city against military attacks are regarded as key issues in the discussion of damages and threats in passive defense. 2. According to the quantitative threat model in Tabriz metropolitan area, the threat of missile and airborne strikes were selected as the base threat: 20 centers of gravity out of the total of 32 centers are at stake of this threat, indicating the predominance of this threat on the assets of the city. Therefore, missile and airborne strikes were considered as a major threat in the modeling, network analysis and layer standardization in the GIS environment. 3. The final map of the vulnerability of the metropolitan areas of Tabriz drawn using fuzzy overlapping functions in the ARC_GIS environment with 22 effective indexes in the form of five criteria (vital arteries, crisis management centers, military and police centers, urban facilities and support centers), the basic threat of airborne and missile attacks and coefficients of the criteria and indexes obtained from the Super Decision analysis software model show that the vulnerable zones of Tabriz are classified into five levels: The area with very low vulnerability is 13.7%, the low vulnerability area is 9.5%, average vulnerability area is 23.5%, high vulnerability area is 32.3%, and extreme vulnerability area is 21% of the total metropolitan area of Tabriz, which is in contradiction to the principles of passive defense and increases the spatial vulnerability of the city. It is therefore necessary to develop a strategy based on passive defense principles to reduce the vulnerability of the city. 4. According to the average model, the nearest neighbor, the average expected distance between infrastructures of Tabriz metropolitan area is 455 meters, but the average infrastructural gap is 264 meters. The ratio of the nearest neighbor is 58%, showing the cluster distribution of Tabriz city centers. This ratio is in contradiction to the principles of passive defense and exacerbates the spatial vulnerability of the city. It is thus necessary to apply the principle of dispersion of passive defense regarding centers of gravity in Tabriz. 5. According to the SWOT model, the results of evaluating the strengths and weaknesses of internal factors by studying and identifying critical centers in Tabriz metropolitan area indicate that the city’s weaknesses are more than its strengths. Therefore, drawing on the strengths, some strategies must be used to reduce vulnerabilities caused by the weaknesses and threats of the city.
Urban Planning
Manouchehr Tabibian; negin mozafari
Abstract
Geographical location and seismic records of many Iranian cities, including Tehran, draw attention to the vulnerability to earthquake hazards in various fields and specialties. Due to its nature, urban planning examines this issue in the urban fabrics. In line with this, the present study investigates ...
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Geographical location and seismic records of many Iranian cities, including Tehran, draw attention to the vulnerability to earthquake hazards in various fields and specialties. Due to its nature, urban planning examines this issue in the urban fabrics. In line with this, the present study investigates the texts and documents related to the earthquake and the role of urban planning in reducing its effects in terms of safety issues of settlements as well as crisis management. The residential fabric planning and its dimensions and features (including land use, plotting, texture formation, density, communication network, open space, service centers), as interfaces between the residential fabric and vulnerability, and thus the linkage between crisis management in these contexts and urban planning provides an operational model for earthquake vulnerability assessment of the residential areas in the 6th District of Tehran. This model is based on two important issues related to earthquake: the destruction rate and the number of human casualties, divided accordingly into two categories of factors and sub-factors. Based on this model, indicators were determined to study the vulnerability level. The physical resistance index of the fabric was extracted from the first category of the model sub-factors and the post-crisis fabric accountability index was extracted from the second one. Based on these 15 indicators, the vulnerability of the 6th District of Tehran was investigated separately for the residential neighborhoods. The vulnerability of residential neighborhoods was evaluated based on the values of evaluation factors extracted using the AHP method. Finally, the goals, strategies and policies needed to reduce the vulnerability according to the coefficient of significance were obtained separately for 7 neighborhoods using the same method. Based on the results, the following measures can be effective in promoting the safety of neighborhoods in the 6th district against earthquakes: setting objectives for increasing the physical strength of the fabric in order to reduce the destruction rate and increase the fabric efficiency in post-crisis response and relief efforts to reduce human mortality, and adopting strategies for increasing resistance in residential buildings and to strengthen the role and efficiency of open spaces, creating and strengthening an effective access network appropriate for the population, and controlling and guiding demographic indicators. In general, the proposed solutions are developed in five categories: the general form of residential fabric (segmentation, distribution, neighborhood...), green spaces and public open spaces, access networks, population density, and construction monitoring and supervision. Finally, the spatial priority of the implementation of proposed policies for neighborhoods, as well as the priority of policy implementation in each neighborhood is determined to look at the developed goals and strategies more efficiently.
