بررسي تحليلي اثر پارامترهاي مختلف بر عملكرد لرزه‌اي ميان‌قاب‌هاي مصالح بنايي داراي بازشو در قاب‌هاي بتن مسلح با جزئيات لرزه‌اي و غير‌لرزه‌اي

Analytical study of the effect of different parameters on the seismic performance of masonry infill with opening in RC frames with seismic and non-seismic detailing

قابهاي داراي ميان‌قاب مصالح بنايي رايج‌ترين نوع سازه‌اي است كه براي ساخت سازه‌هاي چند طبقه در كشورهاي در حال توسعه استفاده مي‌شود. ميان‌قاب‌هاي مصالح بنايي عمدتاً براي افزايش سختي و استحكام اوليه ساختمان‌هاي بتن مسلح مورد استفاده قرار مي‌گيرد. از طرفي قرار گرفتن بازشوهاي درب و پنجره در ميان‌قاب مصالح بنايي سازها اجتناب نا‌پذير خواهد بود. در مطالعه حاضر، با مدل‌سازي عددي به روش اجزاي محدود غير خطي اثر وجود ميان‌قاب‌هاي مصالح بنايي داراي بازشو‌هاي مختلف درب و پنجره بر رفتار داخل صفحه قاب‌هاي بتني با جزئيات لرزه‌اي و غير لرزه‌اي در سطوح مختلف بار محوري و ضخامت‌هاي مختلف ميان‌قاب، در عملكرد لرزه‌اي قاب‌هاي بتني مورد بررسي قرار گرفته است. براي اين منظور ابتدا مدل‌هاي پيشنهادي با استفاده از نتايج آزمايشگاهي در نرم‌افزار اجزاي محدود ABAQUS اعتبار سنجي مي‌شود. نتايج حاصل از تحليل‌هاي صورت گرفته نشان مي‌دهد كه افزايش بار محوري باعث افزايش مقاومت نهايي، سختي مؤثر و كاهش شكل‌پذيري در نمونه‌هاي داراي ميان‌قاب مصالح بنايي با بازشو مختلف درب و پنجره و قاب‌ بتن مسلح با مشخصات لرزه‌اي مي‌شود. افزايش ضخامت ميان‌قاب بنايي باعث افزايش مقاومت نهايي و سختي مؤثر در نمونه‌ها با جزئيات لرزه‌اي و غير لرزه‌اي ‌گرديد. نتايج اين بررسي‌ها نشان مي‌دهد كه حالت‌هاي مختلف قرارگيري بازشوها در نحوه رفتار قابها اثرات قابل توجهي دارد.

Frames with masonry infill are the most common type of structures used in developing countries. Masonry infill affected the initial stiffness and strength of reinforced concrete buildings. The presence of opening in masonry infill is often used for placing doors and windows and it may reduce the seismic performance of the RC frame structure. Nowadays, the impact of the frame and infill on structure is one of the challenges in engineering researches. Engineers generally ignore infill in designing the building and consider it as non-structural part. When the masonry infill is placed in the concrete frame, significantly changes its mechanical properties, the stiffness and strength of the structure increase and ductility of the concrete frame reduce. There is interaction between masonry infill and itchr('39')s frame, so, the frames with infill behave differently than those frames without infill. Disregarding the effect of masonry infill, they can be safe and reliable in terms of resistance in design, since the increasing strength around frame has a positive effect on earthquake strength and overall structural stability, however, it should also be considered that masonry infill will increase the stiffness of the infill-frame and larger portion of the lateral load would attracted by frames. This can be a negative factor when ignore the infill masonry in the design. In the present study, by numerical modeling by nonlinear finite element method, the effect of the presence of masonry infill with different door and window openings on the behavior of concrete frames with seismic and non-seismic details at different axial load levels and different masonry infill thicknesses in seismic performance of frames concrete has been examined. For this purpose, the proposed models are first validated using laboratory results in ABAQUS finite element software. The results of the analysis show that increasing the axial load increases the final strength, effective stiffness and reduces ductility in specimens with masonry infill with different opening of doors and windows and reinforced concrete frame with seismic characteristics. The ultimate strength in specimens with reinforced concrete frame with seismic characteristics shows a slight increase compared to similar samples with reinforced concrete frame with non-seismic characteristics, which can be ignored. Increasing the thickness of the specimens increased the ultimate strength and effective stiffness of the specimens with seismic and non-seismic details. The results of these studies show that the different positions of the openings have significant effects on the behavior of the frames. If the opening is large or moves away from the center of the masonry infill, the final strength drop and stiffness effective reduction will be more.