The Analysis of the Effective Elements on Vulnerability of the Facades by Passive Defense Approach and Using AHP & GIS, Case Study: Amiriyeh Neighborhood of Tehran

The formed buildings in the margins of streets, while being incompatible and unrelated to the cultural identity, cause a great deal of dangers to both passersby and residents in case of a crisis. Considering that Iran and specially Tehran somehow has been threatened by foreign enemies, the pathology of buildings in case of military attacks and discussing
the strength of buildings against explosions and the shots of attacks is very important and strategic. From the defense considerations perspective, facades are the weakest part of buildings against explosion. The facade of a building may be locally damaged and destroyed due to an explosion, so the facade pathology can reduce the number of casualties and can efficiently effect on the way people deal with a crisis while they are threatened. Architectural planning needs a pre-crisis pathology in order to be capable of dealing with incidents crisis and attacks with explosive waves properly. Vulnerability is a term used to indicate the magnitude and extent of the damages that may have occurred to communities, buildings, and geographical areas in result of natural disasters. The aim of this research is to provide an appropriate method for assessing the vulnerability of the building facade to explosion. Minor aims include:1. Achieving the effect of structural, non-structural, and the age of the building on vulnerability of the facades against blast wave
2. Identifying the effective elements on the resistance of the urban building facades against blast wave and the conversion of effective elements into measurable indicators
3. Characterizing the vulnerable facades in low, medium, and high vulnerability spectrums Amiriyeh neighborhood that is located in the 11th district of Tehran, is one the oldest
areas of this city. Due to the demographical compression and residential, commercial, and administrative land use in this area, it is rated as a highly populated area, which makes it seriously vulnerable in times of crisis. The 11th district of Tehran, which is the subject of this article, has an area of 1200 hectares while a population of 245,000 people and the concentration of crucial political land use makes it the most important region of Tehran. The over-compression of administrative and political land use and the way they are located in the area and beside each other, has increased the importance of this district. Such a characteristic has made it a permanent desirable target for military invasions of foreign enemies or terrorists. Accordingly, it is essential to adopt measures and methods that reduce the level of vulnerability of the area against conventional threats, which can result in severe damages to the buildings and people. In this research, four main indicators of architectural facades including compatibility of the building with demography, service life of the building, structural elements, and non-structural elements have been studied. The sub-indicators are as follows: construction age, building quality, block size, employment coefficient, form of the building and openings, balconies, materials, construction methods and roofing systems. The evaluation of the mentioned indicators has been done using Analytic Hierarchy Process (AHP). Weighing and prioritizing of the indicators was firstly done considering the views of seven specialists and then by Expert Choice software. After reaching the high priority indicators using the methods explained above, they were evaluated using GIS and multiplied by their weight coefficients and placed together to draw the plans of highly vulnerable areas and to be used as a hint for identifying the areas, which need to be secured. The results of this study show that the priority of defensive vulnerability factors of the district are mostly affected by those, which are related to the indicator of building compatibility with the urban demography and construction age as the first and second important indicators respectively. The occurrence of a crisis such as an explosion seems to involve the whole structure of a neighborhood depending on the blast distance and the amount of explosives used and this reflects the importance of a building in the overall urban space in neighborhood scale, which can have many parameters in vulnerability analysis. The high vulnerability of Amiriye neighborhood is due to demographic erosion for older buildings and low strength of materials used in the façades of newly built buildings in Amiriye neighborhood. Weak connections between the façade structure and the main structure are proved the most significant factor of their collapse against explosions. Considering the old and compressed demography of the following area, indicators such as the number of stories is the most vulnerable sub-indicator with a score of 1.753. The block size with a score of 0.568, building quality (considering old demography and the presence of restored and destructed buildings compared to the newly built ones) with 0.551, and the type of building frame in most of the buildings with 0.451, are the next priorities.