Behavior of Pre-stressed Concrete Deep Beams

Six simply supported deep beams were tested to show the influence of prestressing strand on the behavior of reinforced concrete deep beams. All tested beams have same gross sectional area (42000) mm², compressive strength (30) MPa, clear span length (1000) mm, longitudinal and vertical reinforcement and the strengthened beams are strengthening by one strand with (12.7mm) diameter. Tested beams were divided into two groups according to the existence of prestressing strand, the first group consist of one deep beam without prestressing strand and it is considered as a reference, while, the second group consist of five Pre-stressed concrete deep beams divided according to the magnitude of jacking stress (fpj) ranging from (250 to 450) bar. During the test, it was found that, the load deflection curves for Pre-stressed concrete deep beams are stiffer compared with the reference beam and the percentage of stiffness was increased with the increase in the magnitude of jacking stress (fpj), and the maximum applied load increased to 8.89%, 13.68%, 18.00%, 24.77% and 33.55% with increasing the jacking stress respectively, compared with the refer beam. on the other hand, the deflection values at mid span increase with decreasing rate to 46.34%, 31.71%, 19.51%,9.75% and 2.44% with increasing the jacking stress respectively, compared with reference beam and the maximum applied load at first crack was increased to 13.64%, 15.56%, 17.4%, 20.84% and 26.93% with increasing jacking stress respectively, compared with reference beam. Finally, the failure mode for deep beam changed from flexural-shear failure to diagonal splitting failure when prestressing strand has been added.