摘要
为了给公路钢桥损伤等效系数λ的准确编制提供理论依据,引入等效疲劳细节强度和综合疲劳抗力系数(comprehensive fatigue resistance factor, CFRF)概念,构建三段式S-N曲线条件下λ系数的精确解,提出基于临界CFRF指标的安全寿命设计极限状态分析方法;在此基础上,通过开展实际交通流模拟,分别对等效内力幅简化计算方法精度、载荷谱疲劳设计极限状态分布以及规范λ_(max)系数合理性等问题进行分析讨论。研究结果表明,载荷谱等效应力幅Δσ_(E2)的理论解对应于等效疲劳细节强度,λ系数精确解具有疲劳抗力门槛属性;在λ系数近似标定方法中,二次等效法相比于单斜率法更适用于公路钢桥载荷谱,绝大部分工况下仅略高于精确解5%;λ_(max)<λ的疲劳设计极限状态主要出现在峰均比较小的短跨径桥梁载荷谱中,但此类载荷谱的等效疲劳细节CAFL在长周期模拟中有较大概率会被极值超越,采用超限损伤极限状态作为λ系数的限值策略表现出一定的不安全性;当前规范制定的λ_(max)对于大交通流、多车道均匀作用工况标定的λ系数存在一定低估情况;考虑到实际工程中载荷谱的复杂性,不建议取用统一λ_(max)值进行安全寿命设计极限状态限定。
In order to provide a theoretical basis for the accurate determination of damage equivalence factor λ of road bridges,the concepts of equivalent fatigue detail strength and comprehensive fatigue resistance factor(CFRF)are introduced,and a precise solution of λ factor under the trilinear S-N curve is constructed.Additionally,a load spectrum fatigue design limit state analysis method based on critical CFRF index is proposed.On this basis,the accuracy of the simplified calculation method of damage equivalent load range,the load spectrum fatigue design limit state distribution and the rationality of code λ_(max)are analyzed through the actual traffic simulation.The results show that the theoretical solution of the load spectrum equivalent stress range Δσ_(E2)is equivalent to the fatigue detail strength,and the exact solution of the λ factor is related to the structural fatigue resistance threshold.Among the simplified λ factor calibration methods,the two-step equivalent method(TSEM),which is only 5%higher than the exact solution under most calculation conditions,is more suitable for the road bridge load spectrums than the single slope method(SSM).The fatigue design limit state of λ_(max)<λ mainly appears in the short-span bridge load spectrums with small clipping ratios,but the equivalent fatigue detail CAFLs of these kinds of spectrums have a high probability that will be exceeded by the extreme values in the long-term simulation.As the restriction strategy of λ factor,the CAFL exceedance damage limit state shows a certain degree of insecurity.For the λ factors calibrated under large traffic volume and multi-lane even loading conditions,the current code λ_(max)is of obvious underestimation.Considering the practical complexity of load spectrums,it is not recommended to assign a unified λ_(max)to define the safe-life design limit states.
作者
郑祥隆
张鹤
沈明江
谢旭
Zheng Xianglong;Zhang He;Shen Mingjiang;Xie Xu(College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,China;Center for Balance Architecture,Zhejiang University,Hangzhou 310058,China;The Architectural Design&Research Institute of Zhejiang University Co.,Ltd.,Hangzhou 310027,China)
出处
《土木工程学报》
EI
CSCD
北大核心
2023年第10期32-42,共11页
China Civil Engineering Journal
基金
国家自然科学基金优秀青年科学基金及面上项目(52122801,51978609)
浙江省杰出青年基金(LR20E080003)。
关键词
公路钢桥
损伤等效系数
综合疲劳抗力系数
疲劳设计
极限状态
road steel bridges
damage equivalence factor
comprehensive fatigue resistance factor
fatigue design
limit state
