بررسي عددي رفتار تير هاي عميق بتن مسلح دو سر ساده داراي بازشو

Numerical Study of Behavior of Simply Supported RC Deep Beams with Openings

به طور كلي تير‌هاي عميق به عنوان شاه‌تير‌هاي حمال و سرپوش شمع‌ها و همچنين در ديوار‌ها ي ساختمان هاي بلند كاربرد دارند. براي اجراي سرويس‌هاي اساسي مثل كانال‌هاي هوا، دسترسي به كابل‌هاي شبكه‌هاي الكتريكي و كامپيوتري، تاسيسات مكانيكي و يا رفت و آمد از اتاقي به اتاق ديگر، در جان تير‌هاي عميق بتن مسلح بازشو‌ طراحي مي‌كنند. در اين مقاله به بررسي رفتار تير‌هاي عميق بتن مسلح دو سر ساده داراي بازشو با استفاده از روش اجزا محدود پرداخته شده است. براي مدل‌سازي نمونه‌ها از نرم افزار Abaqus استفاده شده است. 24 تير عميق داراي بازشو مدل و پارامتر‌هاي اندازه‌ي بازشو، محل بازشو، چيدمان آرماتور جان بررسي شده است. در تمام اين تير‌ها ارتفاع و ضخامت ثابت و به ترتيب mm750 و mm100 است. بارگذاري تيرها به صورت بار متمركز دو نقطه اي و متقارن است. تيرهاي داراي بازشوي بزرگتر مقاومت كمتري نشان مي دهند و محل بازشو تاثير زيادي روي رفتار و مقاومت نهايي تير ها ندارد. بيشترين تاثير روي رفتار و بار نهايي با تغيير چيدمان آرماتور جان ايجاد مي‌شود كه به ترتيب چيدمان مورب، شبكه‌اي، قايم و افقي منجر به افزايش بيشتر بار نهايي مي‌شوند. به گونه‌اي كه مقاومت چيدمان مورب آرماتور به طور متوسط 67/1 برابر چيدمان افقي است. همچنين براي شبيه سازي تيرهاي عميق موجود در سازه هاي واقعي 12 تير عميق با ارتفاع mm2000 و دهانه ي خالص mm3500 و ضخامت mm220 مدل شدند. بازشو در اين تيرها داراي ابعاد mm200×350 است. نتايج تحليل نشان مي دهد كه براي تيرهاي عميق با اين ابعاد نيز به ترتيب چيدمان مورب، شبكه‌اي، قايم و افقي بيشترين تاثير را در افزايش بار نهايي دارند و محل بازشو در ارتفاع تير عميق تاثير زيادي روي مقاومت نهايي ندارد.

Generally reinforced concrete deep beams are used as transfer girders, pile caps, coupling beams and foundation walls. Openings are frequently provided in RC deep beams to facilitate essential services, such as ventilating ducts, water supply and drainage pipes, network access, or even movement from one room to another. Existence of opening leads to disturbance of compressive force path from the loading point to the support. Due to the lack of experiment on deep beam with opening, code provisions do not give any explicit guidance to designing these elements with opening. So this research studies the behavior of reinforced concrete deep beams with opening using finite element methods. To this end the commercial software ABAQUS/standard was used. The accuracy of model was verified with available experimental data. in two separate parts the behavior of these members was studied. First, 68 beams with opening were modeled to study the effect of size and position of opening, arrangement of web reinforcement, ratio of clear span to depth and ratio of shear span to depth. In all of these beams depth and thickness was 750 and 100 millimeter respectively. The most effective parameter on behavior and ultimate load capacity was arrangement of web reinforcement. Also the size effect on the behavior of these members was studied. So 8 beams were modeled and result indicates that by increasing size of the beams the normalized shear strength decreases. Generally reinforced concrete deep beams are used as transfer girders, pile caps, coupling beams and foundation walls. Openings are frequently provided in RC deep beams to facilitate essential services, such as ventilating ducts, water supply and drainage pipes, network access, or even movement from one room to another. Existence of opening leads to disturbance of compressive force path from the loading point to the support. Due to the lack of experiment on deep beam with opening, code provisions do not give any explicit guidance to designing these elements with opening. So this research studies the behavior of reinforced concrete deep beams with opening using finite element methods. To this end the commercial software ABAQUS/standard was used. The accuracy of model was verified with available experimental data. in two separate parts the behavior of these members was studied. First, 68 beams with opening were modeled to study the effect of size and position of opening, arrangement of web reinforcement, ratio of clear span to depth and ratio of shear span to depth. In all of these beams depth and thickness was 750 and 100 millimeter respectively. The most effective parameter on behavior and ultimate load capacity was arrangement of web reinforcement. Also the size effect on the behavior of these members was studied. So 8 beams were modeled and result indicates that by increasing size of the beams the normalized shear strength decreases.