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Study on Fatigue Characteristics of Reinforced Concrete Structure under Various environment and its Application to Design

不同环境下钢筋混凝土结构的疲劳特性研究及其在设计中的应用

基本信息

批准号：
08650533
负责人：
INOUE Shoichi
金额：
$ 1.41万
依托单位：
Tottori University, Faculty of Engineering
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Fatigue characteristics of reinforced concrete beams were investigated under various corrosion environment including under fresh water and sea water and in air. Significant differences were observed in the fatigue strengths between the beams tested in water and those in air. That is, the fatigue strength at 2 * 10^6 cycles for the beams tested in water is smaller by 15 - 25% compared to that in air. This value in the region of shear span/ effective ratio, a/d=3.5 - 4.0 becomes smaller with increases in the value of a/d. The failure pattern of beams differs in air and in water and the failure pattern tends to occur as shear failure without the fatigue fracture of stirrup in water even though the same beam exhibits flexural failure in air. Shear failures may be separated into the shear compressive failure, the failure due to the fracture of tensile reinforcement at the point of intersection of the diagonal crack and the diagonal tensile failure (related to the value of a/d, the strength … More of concrete and the magnitude of the applied maximum load level). The fatigue test the beams which the bending span only was immersed in water was carried. According to the flexural fatigue failure observed from these test, the flexural failure in air was caused by the fracture of tensile reinforcement, but those in water was not only caused by the fracture of tensile reinforcement but by compressive fatigue failure of concrete in bending span.For the beams subjected to repetitive load under moisture condition the surface treatment and strengthening method using carbon fiber sheet has the effect of increasing in fatigue life. Static and fatigue tests were also conducted on strengthened reinforced concrete beams to investigate the type of failure, and deformation and strength characteristics of the beams, with the presence/absence of anchor bolts and the kind of strengthening materials (steel or CFRP (carbon fiber reinforced plastic) plate) used set as the factors. As a result, (1) the CRRP plate-bounded bemas, as compared with steel plate-bonded beams, were found to have 1) smaller crack widths and crack spacings under identical loadings, 2) smaller deflection and toughness at failure, and 3) larger fatigue strength, and (2) the type of fatigue failure differs depending on the kind of plate, presence of anchor bolts and the magnitude of the applied load. Lastly, from the point of the mechanism of shear fatigue failure tested in water, the shear force component carried by concrete decreases with increases in the number of repetitive loading. Though the shear force component carried by stirrups increases with increases in the number of repetitive loading, the stirrup strain was in pre-yield range. Less

研究了在淡水、海水和空气中不同腐蚀环境下钢筋混凝土梁的疲劳特性。在水中和空气中测试的梁之间的疲劳强度观察到显着差异。也就是说，在水中测试的梁在2 * 10^6次循环下的疲劳强度比在空气中测试的梁的疲劳强度小15 - 25%。该值在剪跨/有效比a/d=3.5 - 4.0区域内随着a/d值的增大而变小。梁在空气中和水中的破坏模式不同，即使同一梁在空气中表现出弯曲破坏，其破坏模式也倾向于发生剪切破坏而不发生水中的疲劳断裂。剪切破坏可分为剪压破坏、斜裂缝交点处受拉钢筋断裂破坏和斜拉破坏（与强度a/d值有关 ...更多信息混凝土的强度和施加的最大荷载水平的大小）。进行了仅受弯跨浸水梁的疲劳试验.根据试验中观察到的弯曲疲劳破坏，空气中的弯曲破坏是由受拉钢筋断裂引起的，而在水中，混凝土梁的疲劳破坏不仅是由于受拉钢筋的断裂，而且是由于混凝土在受弯跨内的压缩疲劳破坏所致，对于潮湿环境下反复荷载作用下的梁，碳纤维布表面处理加固方法具有明显的加固效果，提高疲劳寿命。对加固后的钢筋混凝土梁进行了静力和疲劳试验，以研究梁的破坏类型、变形和强度特性，试验中将有无锚栓和加固材料（钢板或CFRP（碳纤维增强塑料）板）作为影响因素。结果表明：（1）与钢板粘结梁相比，CRRP板粘结梁1）在相同载荷下的裂缝宽度和裂缝间距较小，2）破坏时的挠度和韧性较小，3）疲劳强度较大，（2）疲劳破坏的类型因板的种类、是否有锚栓和施加载荷的大小而异。最后，从水中剪切疲劳破坏机理来看，混凝土所承受的剪切力分量随重复加载次数的增加而减小。虽然箍筋所承载的剪力分量随重复荷载次数的增加而增加，但箍筋的应变仍处于屈服前的范围内。少