چکیده:
کاربرد مصالح خشتی و گلی به عنوان مصالحی در دسترس، کم هزینه و با قابلیت اجرای آسان در مناطق گرم و خشک از دیرباز تا کنون در ساخت ابنیه رایج بوده است. با توجه به زلزله خیزی ایران و اهمیت بالای توجه به آسیب پذیری احتمالی کلیۀ ساختمان های بومی، تلاش برای شناسایی نقاط ضعف احتمالی ساختمان های خشتی روستایی در مقابل این رخداد به منظور حفظ جان انسان ها اهمیت می یابد. از طرفی سنت های ساخت و همچنین الگوهای زیستی مرتبط با ابنیۀ خشتی روستایی بخشی مهم از تاریخ معماری ایران در کاربرد مصالح بو مآورد است که نیاز به حفاظت دارند. یکی از مجموعه ساختمان های خشتی که در جریان زمین لرزه سال ۱۳۵۷ ش آسیب دیده و دچار تخریب های گوناگونی شده است، روستای اصفهک واقع در شهرستان طبس است که در فهرست آثار ملی ایران نیز به ثبت رسیده است. از نکات جالب توجه در ابنیۀ روستا، رخداد نرخ متفاوتی از آسیب های لرزه ای در ساختمان های مذکور، پس از زلزله است. به طوری که بعضی دچار خسارات جدی شده اند، اما برخی دیگر کم تر آسیب دیده و یا به کلی سالم مانده اند. وجود تفاوت های احتمالی در الگوی معماری و شیوۀ اجرای ساختمان، به عنوان عامل احتمالی مؤثر در تفاوت نرخ آسیب ها و عملکرد بهتر برخی از ساختمان ها در خلال زلزله قابل طرح است که این پژوهش به بررسی آن پرداخته است. این پژوهش توصیفی تحلیلی بوده و اطلاعات مورد نیاز نیز از طریق مطالعات کتابخانه ای و میدانی به دست آمده است. نتایج حاصل از پژوهش حاکی از آن است که عبور قنات از زیر برخی خانه ها باعث تشدید آسیب ها در آن ها شده و همچنین الگوی ساخت متفاوت ابنیۀ روستا (دست کند، چینهای، و خشت قالبی(، اثر مستقیمی بر تفاوت عملکرد لرزه ای آن ها داشته است. کیفیت پایین اجرا و عدم استفاده از تمهیداتِ ساختمانیِ مناسب با هدف ارتقای مقاومت لرزه ای ساختمان های مذکور توسط سازندگان، از دیگر علل رخداد آسیب های لرزه ای متفاوت در این بناهاست.
Earthen building materials have been in common use as cheap, available, and practical construction materials in hot and dry areas for a long time. Earthen buildings exist in Iran, especially in villages, because of the large and numerous areas that have the same climate. Given that Iran is highly earthquake prone and the importance of paying attention to the possible vulnerability of all the indigenous buildings, endeavours for identifying the possible weak points of the earthen village buildings in an earthquake situation become doubly important. Especially to save human life. On the other hand traditional building methods and life patterns related to village earthen buildings are an important part of the Iranian architectural history in using local building materials that need conservation. One of the collections of earthen buildings that has been damaged and has suffered various degradation during the Tabas earthquake of 1979 is the village of Esfahak located 38 kilometres south-east of the Tabas county, which has also been inscribed in the National Heritage List of Iran. After the aforementioned earthquake and the damage and destruction of the earthen houses in this region, the survivors left these buildings and started constructing buildings using new materials and building styles that clashed with their old architecture just a short distance away. But currently, with the focus on indigenous heritage and the development of the indigenous tourism sector, the residents in this area are asking for the repair and restoration of these buildings. In this respect and before any action is taken on strengthening the above-mentioned buildings, it is essential to study the earthquake damage in these buildings. A remarkable point related to the earthen buildings, is the different rates of damage in these buildings during the earthquake. Some of the buildings have suffered serious damage while other others have only minor damage or are completely unharmed. The existence of possible difference in the architectural template and the implementation method for these buildings is a possible factor in the variance in the rate of damage in the buildings and better performance of some of these structures during the earthquake. Examining the validity of this matter and a study on the existence of other factors influencing the difference in performance of some of these earthen structures have been done in this research. In this research, a field study of the different rates of damage in the earthen structures has been used as a basis to perform diagnostic studies in attaining the reasons for the structural failures of the earthen buildings in this village. Apart from endeavouring to reach a correct understanding of the seismic behaviour and the damage in these structures form the earthquake, such research is a precursor for any type of seismic improvement of these structures. This research is descriptive-analytical and the required information has been gathered using academic and field studies. The results of this research show that the passing of the Qanat underneath some of the homes has resulted in the increase in the damages. Also the different building patterns used for the structures (troglodytic, strata, moulded mud brick), has a direct impact on the seismic performance of these structures.
The low implementation quality, and not using the appropriate structural strengthening methods to increase the seismic resistance of these buildings by the builders is another reason for the different rates of damage in these buildings.