混凝土疲劳性能影响因素综合分析

Analysis for factors affecting fatigue behavior of concrete

研究表明循环荷载下的应力水平S、应力比R、应力幅ΔS、温度T等每个因素都影响混凝土的疲劳寿命。但是对于以上各种因素对疲劳寿命产生综合影响的程度,尚缺乏系统研究。本文对此进行系统分析,从而为有关混凝土结构疲劳问题的理论计算及设计提供可靠依据。本文根据大量国内外文献资料中的实验数据,借助方差分析的手段,定量分析了以上四种因素对混凝土疲劳寿命影响的显著性程度。主要结论:应力水平S、应力比R和相对应力幅ΔS′对混凝土疲劳寿命的影响都可以认为是显著的,但应力水平S的影响比后两者大得多,应力比R和相对应力幅ΔS′的影响程度基本相同;环境温度T的影响显著与否不能一概而论,在本文所讨论的T的取值范围内,可以认为T的影响与S一样显著。因此建议规范中关于混凝土常温下的疲劳强度应重点考虑应力水平S,对应力比R和相对应力幅ΔS′在考虑时应予以同样程度的重视;在非常温条件下,对环境温度T应该与S同样加以考虑。

Fatigue life of concrete is affected by various factors,such as the stress level S,stress ratio R,stress amplitude ΔS and temperature T under cyclic loading.However,systematic study for the combined effects of all the above-mentioned factors on fatigue life of concrete was seldom reported.The purpose of this paper is to present a systematic analysis of the combined effects,and in this way to provide reliable basis for theoretical fatigue calculation and design of concrete structures.Based on groups of data of fatigue tests of concrete in literatures,the means of variance analysis is employed to conduct quantitative analysis of effects of all the above-mentioned four factors on fatigue life of concrete.It can be drawn that effects of stress level S,stress ratio R and relative stress amplitude ΔS on fatigue life of concrete are significant,but the effect of S is more significant than the latter two.Effects of R and ΔS′ are significant at almost the same level.The effect of T cannot be generalized,but within the framework of the value of T in this paper,the effects of T and S are significant at the same level.Therefore some suggestions for code are presented to take the above-mentioned conclusions into account.