Mechanical Behaviors of Super High Strength Partially Prestressed Concrete Having a Vertical Construction Joint

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Reinforced concrete beams and partially prestressed concrete beams having a vertical construction joint were produced by using both ordinary strength concrete and super high strength concrete. The vertical construction joint was placed in a shear span of the beam. A flexural loading test was carried out to take cracking behaviors and stirrup's strains of the beam. Strengthening effect of placing steel plates and prestressing to the beam was also investigated. The test results are as follows.1) The reinforced concrete beam with ordinary strength concrete was cracked firstly in the vertical construction joint and the flexural crack was turned to a diagonal tension crack lastly the beam was failured by shearing compression failure mode.2) The degree of shearing strength reduction by the vertical construction joint is smaller in the case of the beam with super high strength concrete. However the strains of the stirrups in the beam were increased by the vertical construction joint.3) Increase of the strains of the stirrups was restrained by steel plate strengthening in the portion of the vertical construction joint.4) The strengthening effect of prestressing to the beam was also ascertained as the same degree of the steel plate strengthening.5) The defect of the vertical construction joint was clear even in the super high strength concrete beam if a good treatment was not performed at the construction joint.