فرايند ايمن سازي لرزه اي بافت‌هاي تاريخي؛ مطالعه موردي: روستاي نايبند

Seisemic safety process of historical contexts; Case study: Nayband village

در كشور ما علي رغم وجود تعداد زياد بافت هاي تاريخي در معرض زلزله، تحقيق جامع و روشمندي در زمينه كاهش آسيب پذيري آنها صورت نگرفته و اسناد موجود عمدتاً به توصيف تجربه‌هاي پراكنده مقاوم سازي در مقياس تك بناها اكتفا كرده اند. نايبند در 200 كيلومتري طبس، روستايي با ارزش‌هاي تاريخي است كه در مجاورت گسل بزرگ نايبند قرار دارد. به دليل وجود بافت منحصر‌به‌فرد كالبدي و شكل گيري روابط اجتماعي، فرهنگي و اقتصادي و پيروي از الگوهاي بومي ساخت و ساز در تعامل با آن و همچنين اجراي طرح جابه‌جايي ساكنين و تخليه بافت، اين روستا گزينه خوبي جهت انجام مطالعات ايمن سازي لرزه اي است تا بتوان از فرايند تعريف شده براي آن به عنوان الگويي براي ديگر بافت‌هاي تاريخي استفاده كرد. فرايند معرفي شده در اين مقاله داراي دو بخش اصلي مي‌باشد. بخش اول به شناخت آسيب پذيري هاي كالبدي روستا در برابر زلزله اختصاص دارد كه طي آن با مطالعه تطبيقي 19 روش تحليل آسيب پذيري، در نهايت روش FAMIVE كه در سطح جهاني از اعتبار بالايي برخوردار است، انتخاب و انواع آسيب پذيري ها از طريق آن استخراج گرديد. در بخش دوم، نظر به تنوع خصوصيات بناهاي تاريخي و لزوم بهينه بودن سطح مداخله در آنها، سطوح هدف عملكردي به صورت روش مند پيشنهاد گرديد.

Iran has many historic cities and villages with economic, historic and cultural values facing with many seismic faults. There have been no comprehensive studies about reducing the vulnerability of the historic villages, and the available documents describe the retrofitting experiments only about the single buildings. Lack of a comprehensive look at the subject leads to the loss of the resources and carries out parallel and sometimes conflicting actions. Nayband, in the center of Iran, is a historic village near Nayband fault. Because of unique physical context, performing social, cultural and economic relations, follow up vernacular construction patterns and past earthquake evidences, this village is a proper case for conducting a seismic safety study to make use of defined process as a pattern to other historical contexts and villages that are exposed to earthquake. The first step in the seismic safety process is the identification of context structural vulnerabilities. seismic vulnerabilities can be achieved by different methods. Some of these methods have abilities such as large-scale covering and little time data processing. The appropriate method must be selected in according to evaluation objectives. In this research, a comparative study conducted for 19 vulnerability analysis methods, and finally based on data availability, large scale covering, low entry and data processing time and high reliability, FAMIVE method was chosen. This method which has high validity in the world can determine buildings vulnerabilities levels and major structural failure mechanisms in order to set them up later for retrofitting operations. Afterwards, based on factors include historical and artistic value of the building, usability of habitation after disaster, building type and structural evidence of past earthquakes, 39 facades belongs to 21 buildings were selected and their data were recorded to Excel forms. After processing forms using FAMIVE method, the following results were obtained: The anticipated failure mechanisms, The seismic vulnerability level of buildings and The Building resiliency in the face of different earthquakes. According to the results of the vulnerability analysis and a high level of risk faced by the village, the need for physical intervention and housing retrofit operation to protect the lives of residents and cultural heritage of the village was confirmed. Historical buildings in terms of structural systems, artistic value of its assets, and usability after disaster are differ. Also, newly constructed buildings or public buildings exist due to the presence of humans in them or having the potential to be service provider of post disaster, planners must consider them. By studying international experience and review their criteria, indicators recognized and given weight to identify priorities for retrofitting in this area were: kind of ownership, potential use after disaster, historical and artistic values, number of occupants, hours of occupancy, kind of building use and number of stories. Finally priorities identified through the GIS analysis in terms of four distinct building groups. Finally, considering the need to optimize the physical intervention level and output of previous steps, the anticipated seismic performance levels of buildings against earthquakes recommended.