混合配筋混凝土梁抗弯疲劳试验

为了研究混合配筋(混合配置FRP筋和钢筋)混凝土梁的抗弯疲劳性能,设计了4根混合配筋混凝土梁(1根梁承受静力荷载,3根梁承受等幅疲劳荷载),进行了疲劳试验。结果表明:混合配筋混凝土梁抗弯疲劳破坏始于受拉钢筋的疲劳断裂,GFRP筋断裂或者基体开裂剥落,随后压区顶部混凝土压碎; 破坏时纯弯段出现1条或2条主裂缝,钢筋疲劳断口光滑,未出现静力拉断时的屈服和颈缩现象; GFRP筋疲劳破坏未出现静力受拉破坏时纤维“扫帚”型破坏模式; 疲劳加载后构件产生不可恢复的残余挠度,残余挠度随着疲劳次数和疲劳上限荷载的增加而增大; 疲劳过程中纯弯段基本不出现新裂缝,均是沿已有初始裂缝扩展; 基于有效惯性矩法的刚度计算值和基于刚度解析法的刚度计算值均大于试验值,偏于不安全; 基于EN 1992-1-1:2004提出的刚度预测模型相对偏差均在10%以内,且刚度计算值小于试验值,偏于安全。

Experiment on Fatigue Flexural Behaviors of Hybrid Reinforced Concrete Beams

In order to study the fatigue flexural behaviors of hybrid(combination of FRP bars and steel bars)reinforced concrete beam, four beams(one beam was subjected to static loading and three beams were subjected to fatigue loading)were designed, and the fatigue test was carried out. The results show that the fatigue failure of the specimen starts with fatigue fracture of one tension steel bar, followed by the broken or matrix stripping of GFRP bars, and ends with concrete crushing at the top. One or two major cracks occur when flexural fatigue failure occurs. The fatigue fracture surface of steel bars is smooth, and no yielding or necking occurs. The fatigue failure mode of GFRP bars is different with the broomlike failure mode in static tensile test. The irrecoverable residual deflection of component occurs after fatigue loading. The residual deflection increases with the upper limit of fatigue loading and fatigue cycles. Cracks propagate along the existing cracks, and no new crack occurs in the pure bending zone during fatigue process. The calculation values of flexural stiffness based on effective moment of inertia and the calculations values of flexural stiffness based on stiffness analytic method are both larger than the test results, which is unsafe. The relative deviation of proposed flexural stiffness based on EN 1992-1-1:2004 is less than 10%, and the calculation values of flexural stiffness are less than the test results and safer.