应变硬化对钢框架塑性区域长度的影响

Effect of Strain-Hardening on the Length of Plastic Zone of Steel Frames

目的在理论上研究了钢材应变硬化和钢框架塑性区域长度之间的关系,分析各国规范对屈强比规定上限值的原因,为研究高屈强比钢材的应用提供参考.方法根据平截面假设,对塑性区域长度进行了定义,并按照定义对不同钢材本构模型下塑性区域长度的表达式进行了推导,对影响其大小的参数进行了理论分析.结果针对钢材本构有无屈服平台两种情况,推导出悬臂梁塑性区域长度的计算公式,比较了钢材屈强比(屈服强度fy/抗拉强度fu)、屈服应变、屈服平台末端应变、极限应变对塑性区域长度的影响,其中屈强比在0.5～0.64、0.75～0.90变化,屈服应变在0.001 14～0.001 44、0.003 35～0.003 65变化,屈服平台末端应变在0.01～0.025变化,极限应变在0.15～0.30、0.08～0.14变化.结论随着屈强比的增加,无论钢材有屈服平台或无屈服平台,其塑性区域长度均变小,且塑性区域长度随屈强比线性变化;应变对塑性区域长度的影响都很小;在塑性设计和抗震设计中屈强比应该被限制.

In order to provide a reference for studying the high Y/T ratio steel,the relation between strain-hardening capacity and the length of plastic zone is studied and the reason of why yield-to-tensile strength（Y/T）ratio is limited in specifications of many countries is analyzed.Theoretical analysis was done to learn the influence of parameter on the length of plastic zone based on the assumption of strains changed by plane-section.This paper deduces the calculation formula for the length of plastic zone of cantilever beam for two kinds of steel material whether yielding plateau exists,and compares the influences of Y/T ratio,yield strain,yield plateau end strain and ultimate strain on the length of plastic zone,and the Y/T ratio is changed at a range of 0.5～0.64、0.75～0.90、yield strain is changed at a range of 0.00114～0.00144、0.00335～0.00365、yield plateau end strain is changed at a range of 0.01～0.025、ultimate strain is changed at a range of 0.15～0.30、0.08～0.14.The results demonstrate that the length of plastic zone decreases as the Y/T ratio increases whether steel has yield plateau or not,and the length of plastic zone decreases linearly with Y/T ratio;Strain has little influence upon it;Y/T ratio should be limited in the plastic design and seismic design.