材料、构件、结构的“屈服点”定义与讨论

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

"屈服点"是工程结构研究和设计中一个极为关键的性能点,是衡量延性、屈强比等性能的前提,但在当前结构设计中尚缺少统一的定义。随着新型结构材料的不断出现,新的构件行为也在不断出现,作图法、等能量法、残余塑性变形法等确定屈服点的方法不能适用。该文首先从材料层次基于金属单轴拉伸屈服点的定义,给出了金属、混凝土和纤维增强复合材料等典型材料的屈服点定义的统一表述;再从构件和结构层次,基于应用条件与物理本质,明确了屈服点的定义方法,为新型材料构件、结构设计提供了依据,并对钢筋混凝土梁和短柱使用此方法进行了讨论。此外,还建议采用"最远点法"确定构件和结构的屈服点,该方法具有明确的物理含义,且适用性广、适合于电算。通过分析构件和结构的试验结果表明建议的屈服定义和提出的最远点法具有一致性和合理性,从而从基本原理和定义方法上明确了材料、构件和结构屈服点。

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.