شبيه‌سازي اثر اندركنش ميان‌قاب آجري- قاب بتن مسلح بر پتانسيل فروريزش پيش‌رونده

Simulation of the Interaction Effect of Masonry Infill Panels - RC Frame on the Progressive Collapse Potential

چكيده- ساختمان‌هاي بتني در فرايند تحليل و طراحي به صورت قاب‌هايي كه از اعضاي اصلي سازه‌اي مانند تيرها، ستون‌ها و ديوارهاي برشي ساخته شده، در نظر گرفته مي‌شوند. اما در بيشتر مناطق شهري، قاب‌هاي ساختماني در نواحي مياني يا پيراموني ساختمان با ديوارهاي مصالح بنايي به عنوان جدا‌كننده‌ها‌ يا عايق‌هاي صوتي و حرارتي پر مي‌شوند كه رفتار آن‌ها با رفتار قاب خالي، يكسان نيست. در اين پژوهش پاسخ ميان‌قاب تحت تغييرشكل‌هاي ناشي از حذف ستون و اثر آن بر رفتار سازه، مطالعه عددي شده است. وجود ميان‌قاب با استفاده از مدل‌سازي اجزاي تشكيل‌دهنده (ريز مدل‌سازي) و در نظرگرفتن اندركنش آن با قاب، مدل شده است. بر اساس نتايج بررسي استاتيكي غيرخطي روي قاب داراي ميان‌قاب با هندسه و ويژگي‌هاي مصالح گوناگون و بررسي الگوي گسترش ترك‌ها و خرابي در ميان‌قاب، مدل ساده‌شده‌اي براي در نظر گرفتن ميان‌قاب در قاب‌هاي بتن مسلح با حذف ستون ارايه شده و با استفاده از نتايج مدل ريزمقياس، اعتبار سنجي شده است. براي نمايش كاربرد مدل و كنترل كارايي آن، پاسخ دو ساختمان بتن مسلح به حذف ستون با در نظر گرفتن ميان‌قاب و بدون در نظر گرفتن آن، با استفاده از آناليز استاتيكي غيرخطي بررسي و مقايسه شده است.

Abstract: Progressive collapse is a rare event during which all or a part of the structure is destroyed due to damage or failure of a small section of the structure. Progressive collapse due to abnormal loading or the design and construction errors can lead to great financial and human losses. Therefore, during the past decades many engineers have been interested in this type of failure. Although a great research effort has been done to investigate the effect of masonry infill panels on the seismic response of frame buildings, there is not so much work on evaluating progressive collapse potential of masonry infill frames. Reinforced concrete structures are considered as bare frames in analysis and design process, including the main structural members such as beams, columns and shear walls. However, in the urban areas, structural frames are filled with masonry walls as acoustic and thermal insulation in the middle or peripheral areas of the buildings therefore they have not the same behavior as the bare frames. This research aims at investigating the effect of unreinforced masonry infill panels on the response of RC frames against the progressive collapse. For this purpose a micro based modeling approach is adopted for numerical simulation of the masonry infill panels and through a parametric study, the effect of influencing parameters is numerically investigated. Also an equivalent compressive strut model is proposed for macro modeling of masonry infill panels. The comparison between numerical and available experimental results confirms the reliability of the developed model. Finally, the developed macro model is used to investigate the influence of masonry infill panels on the progressive collapse resistance of two reinforced concrete frames with different ductility capacity. It is shown that, under the progressive collapse phenomenon, the ductility of RC frame is the main effective parameter and masonry infill panel plays an important and non-ignorable role in structural response. In this paper also progressive collapse resistance is studied for two six-story reinforced concrete frame structures. The first structure has been designed according to Iranian concrete code (ABA) with high ductility and in the second building, seismic design load has not been considered and the structure was designed only against gravity load. The critical column has been removed from the models to numerically investigate the progressive collapse potential of the structures. Because of the lack of national regulations for evaluating the effect of progressive collapse, in this article nonlinear static analysis method of the U.S department of defense regulations (UFC) is used to evaluate the progressive collapse potential. The result of the analysis shows that the structure with high ductility is resistant under remove of column, but the structure designed without considering seismic effects needs to retrofit against progressive collapse.