بررسی آزمایشگاهی رفتار تیرهای عمیق بتن مسلح دو سرگیردار تحت بار چرخه ای و یکنوا

نوع مقاله: پژوهشی

نویسندگان

1 عضو هیئت علمی/دانشگاه تربیت مدرس

2 مهندسی عمران - سازه- دانشکده مهندسی عمران- دانشگاه تربیت مدرس

چکیده

تیرهای عمیق بتن مسلح بدلیل هندسه، شرایط مرزی و رفتاری که در مقایسه با تیرهای معمولی دارند، نوع خاصی از تیرها محسوب می شوند. به عنوان مثال، فرض توزیع تنش - کرنش خطی در مقطع عرضی تیر معتبر نیست. در چند دهه اخیر تحقیقات گسترده ای بر روی تیرهای عمیق دو سر ساده انجام شده است، اما مطالعات کمی بر روی تیرهای عمیق بتن مسلح دوسر گیردار و پیوسته اختصاص یافته است. در این مقاله رفتار دو عدد تیر عمیق بتن مسلح دو سر گیرداربا شرایطیکسان؛یکی تحت بار چرخه ای و دیگری تحت بار یکنوا آزمایش شده و رفتار آنها مورد بررسی قرار گرفته است. نتیجه این آزمایشات نشان داد که هر دو تیر بصورت برشی گسیخته شدند و همچنین ظرفیت نهایی این تیر تحت بار چرخه ایی کاهش چندانی نسبت به بارگذاری یکنوا نداشته است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of Experimental Behavior of Fixed-End Reinforced Concrete Deep Beams under Cyclic and Monotonic Load

نویسندگان [English]

  • Abolfazl Arabzade 1
  • Rouhollah Hizaji 2
1 Associate Professor / Tarbiat Modares University
2 Civil Engineering Department , Tarbiat Modares University
چکیده [English]

Reinforced Concrete (RC) deep beams are a special type of beams due to their geometry, boundary conditions, and behavior compared to ordinary shallow beams. For example, the assumption of a linear strain-stress distribution in the cross section is not valid. In the past decades, considerable research works have been made on simply supported concrete deep beams, but fixed-ended support conditions have scarcely been investigated. Two reasons may be given for this situation: first, fixed-ended conditions are extremely difficult to create in a laboratory; and second, fixed-ended conditions introduce additional parameters which add more complexity to the structural model of RC deep beams.

Following the recent tendency for the application of deep beams, the possibility of using fixed-ended deep beams in structures has been widely increased. Deep beams are likely to be used as support for upper level columns due to architectural requirements and also fixed-end connectivity condition will result in experiencing cyclic loads during an earthquake due to formation of plastic hinges. Therefore, it is necessary to investigate the behavior of this structural element in more details. In this paper, two fixed-ended reinforced concrete deep beams were tested and their behavior was investigated under monotonic and cyclic loads. The results of these experiments showed that both beams’ failures were in shear mode and also the final capacity of fixed-ended deep beam under cyclic load was not significantly reduced compared to “ the final capacity “ under monotonic loading. The Load-Displacement curvature of this beam under cyclic load showed a hysteretic behavior with small energy dissipation (narrow hysteretic loops), small cyclic degradation (a small increase in displacements under consecutive cycles with constant load amplitude), small residual displacements, and low ductility (the steep drop of resistance after peak load). The crack patterns for the cyclically loaded specimen at the last positive recorded load stage prior to failure was essentially the same as that for the companion monotonically loaded test.

کلیدواژه‌ها [English]

  • Deep beam
  • Reinforced concrete
  • fixed-ended
  • cyclic load
  • monotonic load