عنوان مقاله [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.