Utilization of fiber reinforced concrete to control crack width of reinforced concrete structures

1.通过抗弯试验，研究了不同类型纤维混凝土(普通钢纤维混凝土和两种高性能纤维水泥复合多细裂缝)对钢筋混凝土梁的抗裂性能。在梁的受拉区采用纤维混凝土，减小了裂缝宽度。即使在屈服荷载水平下，采用高性能混凝土的梁的裂缝宽度也小于0.1 mm。然而，梁的裂缝分布受HPFRCC.2材料性能的影响。为了解纤维混凝土对混凝土裂缝宽度和与钢筋粘结性能的影响，进行了单轴钢筋混凝土试件的拉伸试验。普通混凝土和纤维混凝土的粘结性能差别不大，纤维混凝土的减裂作用是由于纤维在裂缝表面的桥联作用所致。通过纤维增强混凝土的拉伸软化曲线来评价纤维的桥联效果。对钢筋混凝土单轴试件和拉拔试件进行了有限元分析，阐明了粘结性能的机理。混凝土材料特性的超细网格模型和压缩软化模型的结合导致了变形钢筋肋面前部的压应变局部化。由于应变局部化，无法模拟高应力水平下的粘结滑移。为了克服应变局部化问题，提出了宏观键模型。在该模型中，粘结滑移由钢筋周围粘结损伤层的剪切变形表示。

1. Crack behavior of reinforced concrete beams using various types of fiber reinforced concrete (ordinarily steel fiber reinforced concrete and two types of high performance fiber reinforced cement composites with multiple fine cracks (HPFRCC)) was investigated through the flexural loading tests. The crack width was decreased by using the fiber reinforced concrete in the tensile region of the beam. The crack width of the beams using HPFRCC was little than 0.1mm even at yield loading level. However, the crack distribution of the beams was influenced by material properties of HPFRCC.2. The tensile tests of uniaxial reinforded concrete specimens were carried out to clarify the influence of fiber reinforced concrete on the crack width and bond property between the concrete and the steel bar. There were little differences between bond property of the plain concrete and that of the fiber reinforced concrete.The reducing effect of crack width by using fiber reinforced concrete was caused by the bridging effect of the fiber at the crack surface. The bridging effect of the fiber was evaluated by the tension softening curve of the fiber reinforced concrete.3. The finite element analysis on the uniaxial reinforced concrete specimen and the pull out specimen were carried out to clarify the mechanism of the bond behavior. The combination of the very fine mesh model and the compression softening model for the concrete material property caused the compressive strain localization at the front of the rib surface of the deformed steel bar. The bond slip at the high stress level could not be simulated due to the strain localization. The macroscopic bond model was proposed to overcome the problem of the strain localization. The bond slip was represented by the shear deformation of the bond damaged layer around the steel bar in the proposed model.