Development of Hybrid Fiber Reinforced Cementitious Composites and their Structural Application

开发了一种新型的纤维增强水泥基复合材料，其中既有高性能的聚合物纤维，也有钢丝帘线。这就是混杂纤维增强水泥基复合材料。这些新材料实现了宽度如此之薄的多重裂纹，从而使复合材料具有高强度、应变硬化和高塑性。研究结果总结如下：1)。为制备高韧性复合材料，研究了高强碾压混凝土的配合比。考察的参数是纤维的长度和体积含量，以及纤维的结合。对其力学性能和工作性能进行了研究。2)对新型高强碾压混凝土中的变形筋进行了单轴拉伸试验。用一种独特的X射线技术对变形棒材周围的微裂纹进行了仔细观察。通过对宏观粘结性能的研究，发现了比素混凝土更明显的抗拉硬化效应。在钢筋屈服后，HFRCC仍能抵抗荷载，使其总强度远高于屈服强度。3)进行了一种剪力作用下的HFRCC梁的试验。还考察了纤维类型和箍筋的影响。4)对高强高强混凝土柱型构件进行了反复荷载试验，考察了其吸能性能，并采用非线性有限元方法对其进行了数值分析。从延性和破坏程度的角度来看，X型配筋变截面构件即使在大变形后也表现出了很好的效果。结果表明，采用X型配筋的变截面杆件作为耗能器是可行的。

New type of fiber reinforced cementitious composites were developed, in which not only high performance polymeric fibers but also steel cord were mixed together. That is Hybrid Fiber Reinforced Cementitious Composites (HFRCC). These new materials achieve multiple cracking of so thin width that the composites are possessed of high strength, strain hardening and high ductility. The summary of the results are as follows :1). Mix proportion of HFRCC was studied to produce the highly ductile composites. Examined parameters were the length and volume contents of fibers, and the combination. Not only the mechanical performance but also the workability was investigated.2) A series of a uniaxial tension test was carried out on a deformed bar embedded in the newly developed HFRCC. Microcracking around the deformed bar was carefully observed by means of a unique method of X-ray technique. Macroscopic bond behavior was also studied to find a much more obvious tension stiffening effect than that observed in plain concrete. Even after yielding of the steel bar, HFRCC still resisted the load so that the total strength capacity is much higher than the yield strength.3) HFRCC beams reinforced with deformed bars were tested under a type of shear loading. Influences of type of fibers and also stirrups ware examined. Cracking process was carefully observed by means of the X-ray technique to discuss the fracture mechanism.4) Column-type members made with reinforced HFRCC were tested under cyclic loading to examine the energy absorption capacity and also numerically analyzed by means of a nonlinear FEM. Tapered members with X-shaped reinforcement showed very good results from the view point of the ductility and the damage level of cracking even after a large deformation. It proved that the tapered members with X-shaped reinforcement can be practically applied as energy absorbers.