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

采用普通强度混凝土和超高强度混凝土生产钢筋混凝土梁和带竖向施工缝的部分预应力混凝土梁。垂直施工缝放置在梁的剪切跨度内。进行了弯曲加载试验，测量了梁的开裂特性和箍筋应变。同时还研究了布置钢板和预应力对梁的加固效果。测试结果如下：1)普通强度混凝土配筋混凝土梁在竖向施工缝处先发生裂缝，由弯曲裂缝转变为斜向张拉裂缝，最后以剪压破坏模式破坏。2)在梁采用超高强度混凝土的情况下，竖向施工缝对抗剪强度的降低程度较小。竖向施工缝增加了梁内马镫的应变。3)竖向施工缝部分的钢板加固抑制了马镫应变的增加。4)预应力对梁的加固效果也确定为与钢板加固程度相同。5)即使在超高强度混凝土梁中，如果施工缝处理不好，竖向施工缝的缺陷也很明显。

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.