DISCUSSION AND DEFINITION ON YIELD POINTS OF MATERIALS, MEMBERS AND STRUCTURES

The yield point is a very critical characteristic of structural performance in design and research of engineering structures, which is the basis of evaluating properties such as ductility, yield-ultimate ratio and so on. However, there is no unified definition and expression for yield point of structures. With the development of new mechanical behavior of emerging structural materials, the existing graphic method, the equivalent energy method, and the residual plastic deformation method are not suitable for them. In this paper, a unified expression of yield point for the typical materials including steel, concrete and fiber reinforced polymer is given based on the original definition of metal yielding under uniaxial tension. Then, for structural members and structures, the definition of the yield point based on the application conditions and the physical reality is proposed, which provides the basis for design of emerging material structures. As examples, this definition is applicable for reinforced concrete beams and short columns. Furthermore, a simplified method named Farthest Point Method is given, which has a specific physical meaning and a wide applicability. This method is more suitable for the computer programming. Based on existing experimental results of members and structures, the rationality of the farthest point method is verified by comparing the yield points defined by farthest point method and the presented definition. Thus, an explicit and unified definition for yield points of materials, members and structures is given in terms of the fundamentals and determination approach.