ارزيابي ايمني لرزه اي بناي تاريخي ارگ تبريز با استفاده از آناليز اجزاي محدود وآناليز حدي جنبشي ساده شده

Seismic Safety Evaluation of Tabriz Alisha Historical Citadel Using Finite Element and Simplified Kinematic Limit Analyses

امروزه براي آناليز سازه‌هاي مختلف اغلب، ابزارهاي قدرتمندي نظير نرم افزارهاي اجزاي محدود سه بعدي مورد استفاده قرار مي‌گيرد. اما بكارگيري اين نرم‌افزارها براي ارزيابي ايمني لرزه‌اي ، آناليز و ارايه طرح بهسازي سازه‌هاي تاريخي با مشكلاتي همراه است. هندسه پيچيده سازه، نبود اطلاعات دقيق از خصوصيات فيزيكي مصالح و عدم دسترسي به قسمت‌هاي داخلي احجام تشكيل دهنده بدنه سازه و آگاهي از خصوصيات مكانيكي آنها ، ممنوع بودن انجام آزمايش‌هاي مخرب روي اينگونه از سازه‌ها، توالي و تسلسل در ساخت و طولاني بودن زمان آناليز و هزينه بر بودن آن از جمله مشكلات پيش روي محققين و مهندساني است كه در زمينه مدلسازي و آناليز بناهاي تاريخي بصورت تخصصي فعاليت مي‌نمايند. آناليز حدي جنبشي ساده شده، روشي قدرتمند براي آناليز بناهاي تاريخي است كه در نشريه O.P.C.M.3431كشور ايتاليا استفاده از آن براي ارايه طرح بهسازي ساختمان هاي بنايي مجاز دانسته شده است. روابط مورد استفاده در اين روش بر مبناي اصل كار مجازي بدست آمده‌اند. اطلاعات مورد نياز در اين روش، جهت مدلسازي و ارزيابي ايمني لرزه‌اي سازه‌ها بسيار كمتر و قابل دسترس‌تر مي‌باشد. در اين مقاله تحقيقي در رابطه با قابليت‌هاي اين روش براي ارزيابي ايمني لرزه‌اي بناي تاريخي ارگ عليشاه تبريز صورت گرفته است و صحت ‌سنجي نتايج بدست آمده از اين روش با نتايج آناليز عددي نرم‌افزار ANSYS.V10 مقايسه شده است . نتايج نشان داد كه سازه در برابر بارهاي لرزه اي مستعد منطقه ايمني لازم را ندارد. شتاب مبناي طرح ساختگاه ارگ g 35/0 ( احتمال وقوع 10% در 50 سال) مي باشد.

Iran with more than 11000 historical monuments constructions is introduced one of the oldest civilizations in the word. Moreover, most of major earthquake in the world is referred to Iran , that is a serious threat for historical building that because during these constructions usually seismic loads are not considered, therefore it is necessary to identify these buildings behaviour in front of this natural hazard (earthquake), and doing necessary actions to strengthening the buildings and even reconstruct them in some cases. One of these splendid constructions is historical Tabriz citadel or Arge Alisha Tabriz.Remained Citadel Alisha is a U shape plan with average 33 meters height, 51.2 meters width, 21.1 meters length. Arge Tabriz is situated in a city that is a high earthquake prone area. Thus because of different faults in this area and Arge Alisha’s historical cultural significance, this safety assessment of this building is unavoidable.Historical masonry structures have complex geometry that because of erosion, humidity and their materials mechanical properties has changed a lot. Usually, there is not enough exact information about compose materials of internal parts of the walls. On the other hand, because these constructions are cultural monuments of a country doing destructive tests for recognizing materials mechanicals properties is against international laws. Therefore producing a numerical model for construction analysis seems difficult, and if applicable solving it by software using FEA programs is time consuming. Simplified Kinematic Limit Analyses (SKLA) is a powerful method for historical building safety assessment analysis and its usage for retrofitting purpose that is permissible by O.P.C.M. 3431 Italian ordinance in both of the linear and nonlinear. In this research linear analysis is used for SKLA analysis. Because of masonry buildings have a rigid box behaviour, often local collapse mechanism (part of structure) is more important than its global collapse mechanism .this method assume that is collapse local, and large part of the structures are collapsed during earthquake. To identify probable collapse mechanism, we can use collapse of similar structure in the past earthquakes events. In this paper a research has been about this method (SKLA) capabilities for Tabriz Alisha Citadel seismic safety analysis. The results show that it doesn’t have enough safety against earthquake prone loads in the site. The analysis of both methods is more or less similar. Non linear time history response analysis results includes: displacement, stresses, wall’s collapse time, while SKLA only used for seismic safety assessment in different mechanisms. This method advantages such as, no need to exact information about materials mechanical properties and any destructive and non destructive test cause this method to be a powerful tool for evaluating seismic safety of historical buildings especially for huge and complex geometry structures. If we choose behaviour factor of structure 2 based on Italian ordinance, 3 mechanisms will not be active, although capacity and demand of the structure in three mechanisms have close value that indicates getting close to mechanism formation threshold.