考虑钢材锈蚀的桥梁焊接节点概率疲劳寿命评估(英文)

Probabilistic fatigue life assessment of bridge welded joints considering steel corrosion

由于循环外荷载和腐蚀性环境的共同作用,近海桥梁结构易受疲劳破坏.本文提出了一种考虑钢材锈蚀的桥梁结构改进疲劳可靠度评估模型,并基于青马大桥长期结构健康监测数据对其典型焊接节点的概率疲劳寿命进行了评估.通过建立有效截面衰减模型和材料疲劳性能退化函数,利用Miner损伤累积准则的连续概率函数表达式,提出了考虑钢材锈蚀的疲劳可靠度解析模型.同时考虑交通载荷(包括汽车载荷和火车载荷)和台风影响,通过统计分析长期应变监测数据建立了标准日应力谱.采用有限混合分布方法及基于遗传算法的混合参数估计算法,得到了标准日应力谱多模态有限混合分布函数.比较分析了考虑和未考虑钢材锈蚀的焊接节点疲劳寿命失效概率和可靠度指标,研究结果表明钢材锈蚀因素对桥梁焊接节点的疲劳可靠度评估结果有较大影响.

The offshore bridge structures are vulnerable against fatigue failure due to the combined action of cyclic external loadings and corrosive environments.In this paper,an improved fatigue reliability model considering the effect of steel corrosion is proposed and applied for probabilistic fatigue life assessment of the typical welded joints of Tsing Ma Bridge based on the long-term structural health monitoring（SHM） data.By developing the reduction model of cross-sectional area and the deterioration equation of material fatigue behavior,an analytical fatigue reliability model is formulated in the framework of continuous probabilistic formulation of Miner ’ s damage cumulative rule.A standard daily stress spectrum accounting for highway traffic,railway traffic,and typhoon effects is derived by statistically analyzing the long-term strain monitoring data.A multi-modal probability density function（PDF） of the standard daily stress spectrum is obtained by use of the method of finite mixture distribution in conjunction with a genetic algorithm-based（GA-based） mixture parameter estimation approach.A comparative study is carried out to investigate the failure probability and reliability index versus the predicted fatigue life with and without considering the steel corrosion effect.The results indicate that the failure probability and reliability index of the bridge welded joints will be significantly affected by the effect of steel corrosion.