Size Effect in Concrete Structures Reinforced with New Materials

本研究的目的是建立CFRP、AFRP和GFRP等纤维增强塑料加固混凝土结构的抗裂模型，并采用新发展的杆单元的虚拟裂缝模型进行有限元分析。根据分析预测，FRP筋加固混凝土梁的抗剪强度将随着纵向钢筋刚度的降低而降低。此外，FRP筋混凝土梁的抗剪强度与钢筋混凝土梁的抗剪强度一样具有显著的尺寸效应。除了断裂力学方法外，非线性晶格模型是一种新的宏观力学模型。在该模型中，抗剪机制被认为是桁架机制和拱机制的总和。利用该模型可以较好地预测由于纵向钢筋刚度降低而引起的抗剪强度下降，以及抗剪强度的显著尺寸效应。这些观察结果已经发表在几种杂志上。最后，对混凝土梁的抗弯强度的尺寸效应进行了研究。考虑到收缩引起的初始应力分布以及混凝土的断裂能等实际断裂参数，用断裂力学方法可以较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.