变幅荷载下钢桥疲劳裂纹扩展规律及长度预测方法研究  

Investigation on fatigue crack propagation law and its length prediction method for steel bridge under variable amplitude load

作　　者：袁周致远 吉伯海[1] 杜彦良 徐赵东[3] Yuanzhou Zhiyuan;Ji Bohai;Du Yanliang;Xu Zhaodong(Hohai University,Nanjing 210098,China;Shijiazhuang Tiedao University,Shijiazhuang 050013,China;Southeast University,Nanjing 210096,China)

机构地区：[1]河海大学,江苏南京210098 [2]石家庄铁道大学,河北石家庄050013 [3]东南大学,江苏南京210096

出　　处：《土木工程学报》2023年第10期43-51,共9页China Civil Engineering Journal

基　　金：国家重点研发计划(2017YFE0128700);江苏省自然科学基金青年项目(BK20200511);江苏省博士后科学基金(2021K564C)。

摘　　要：为探明变幅荷载对钢桥疲劳裂纹扩展的影响,该文以钢桥面板顶板-竖向加劲肋为构造细节,开展了9组常/变幅疲劳试验,对比分析常/变幅荷载下疲劳裂纹扩展行为,探讨载荷次序、过载比、高/低载循环次数对疲劳扩展行为的影响。在此基础上,采用Kujawski扩展模型对常/变幅疲劳扩展规律进行预测分析,并建议复杂变幅荷载下疲劳裂纹扩展的预测方法。结果表明,变幅荷载下的裂纹扩展存在迟滞和加速行为,其中由高应力幅变为低应力幅时会产生明显的扩展迟滞现象,并且过载比越大、高载循环次数越多,所产生的迟滞现象越明显。变幅荷载下各应力幅加载阶段的扩展速率与对应常幅扩展速率较为接近,可以将复杂变幅荷载下的疲劳裂纹扩展近似等效为多段常幅裂纹扩展,并利用Kujawski扩展模型实现对实际疲劳裂纹扩展长度的初步预测。现场测试及跟踪结果也验证了该文所提出裂纹长度预测方法的合理性。In order to study the influence of variable amplitude load on fatigue crack growth of steel bridge,constant/variable amplitude fatigue test of deck-to-vertical stiffener weld was carried out On 9 groups of specimens.The fatigue crack propagation behavior under constant/variable amplitude load was analyzed and the influence laws of load sequence,overload ratio and high/low load cycles were discussed.Then,the law of fatigue propagation was analyzed using the Kujawski Extended Model,and a prediction method of fatigue crack propagation under complex variable amplitude loading was proposed.The results show that hysteresis and acceleration behaviors exist in crack propagation under variable amplitude load.The spreading hysteresis occurs obviously when the high stress changes to the low stress.The larger the overload ratio and the number of high load cycles are,the more obvious the hysteresis is.The expansion rate of each stress amplitude loading stage is close to the corresponding constant amplitude expansion rate under variable amplitude loading.Fatigue crack propagation under complex variable-amplitude loads could be approximated as multi-stage constant amplitude crack propagation.The Kujawski Extension Model was used to predict the actual fatigue crack propagation length,and the rationality of the predicted values were verified by the field test results.

关 键 词：变幅疲劳 裂纹 过载迟滞 扩展模型 预测 

分 类 号：U443.35[建筑科学—桥梁与隧道工程]