Size Effect in Concrete Structures Reinforced with New Materials

为建立CFRP、AFRP和GFRP等纤维增强塑料（FRP）加固混凝土结构的受力机理模型，采用虚拟裂缝模型，采用新开发的杆单元进行有限元分析。根据分析，可以预测，随着纵向钢筋刚度的降低，FRP筋混凝土梁的抗剪强度将降低。与钢筋混凝土梁一样，FRP筋混凝土梁的抗剪强度也表现出明显的尺寸效应。除了断裂力学方法外，非线性格点模型作为一种新的宏观力学模型也得到了发展。在该模型中，抗剪机制被认为是桁架机制和拱机制的总和。利用该模型，可以合理地预测由于纵向钢筋刚度的降低而引起的抗剪强度的降低以及抗剪强度中的显著尺寸效应。这些观测结果已发表在一些期刊上。最后，混凝土梁的抗弯强度的尺寸效应进行了检查。考虑收缩引起的初始应力分布和混凝土的断裂能等实际断裂参数，用断裂力学方法可以准确地预测混凝土梁的抗弯强度变化和尺寸效应。

The aim of this research is to make a model for the resisting mechanism of concrete structure reinforced with fiber reinforced plastics, such as CFRP,AFRP and GFRP.Using the fictitious crack model in which a newly developed rod element is incorporated, finite element analysis has been carried out. According to the analysis, it is predicted that the shear strength of concrete beams reinforced with FRP rods will be reduced with the decrease in the stiffness of longitudinal reinforcements. In addition, the shear strength of concrete beams reinforced with FRP rods shows the significant size effect as well as concrete beams reinforced with steel bars. These results have been summarized and published in several journals.In addition to the fracture mechanics approach, nonlinear lattice model, that is a kind of macroscopic mechanical model, has been newly developed. In this model, the shear resisting mechanism is considered as the summation of truss mechanism and arch mechanism. Using this model, the decrease in the shear strength due to the decrease in the stiffness of longitudinal reinforcements and also the significant size effect in the shear strength can be predicted reasonably. These observations have been published in several journals.Finally, the size effect in the flexural strength of concrete beams has been examined. Considering the initial stress distribution due to the shrinkage and also the actual fracture parameters, such as fracture energy of concrete, the change of the flexural strength of concrete beams and the size effect can be predicted accurately by the fracture mechanics approach.