矩形渡槽槽身结构时变可靠度分析

Time-varying reliability analysis of a rectangular aqueduct body structure

为分析服役期内渡槽安全度变化,将时间离散法引入渡槽结构时变可靠度计算中。基于工程实例,建立矩形渡槽槽身纵向和横向两个方向3个部位的承载力和抗裂极限状态方程以计算时变可靠度,用蒙特卡罗法的计算结果验证其精度,并与动态可靠度法计算结果进行比较。结果表明:渡槽结构纵向承载力可靠度随服役年限下降,尤其在服役后期降幅远大于横向承载力,纵向承载力极限状态为渡槽寿命的控制状态;纵向和横向抗裂可靠度较承载力可靠度下降均较慢;由于初始值不高,底板抗裂可靠度在服役后期略低于目标值;时间离散法计算结果整体误差相对较小,尤其对服役后期的结构安全性评价更精确,其计算精度比动态可靠度法更高,因此,应用时间离散法进行渡槽可靠度计算和安全性评价更为合理。

In order to analyze the safety change of an aqueduct in service,the time-discretization method was introduced into the time-varying reliability calculation of the aqueduct structure.Based on a project case,the bearing capacity and crack resistance limit state equation of the rectangular adueduct body were established for three parts in the transverse and longitudinal direction,and the time-varying reliability was calculated.Its accuracy was verified by comparing the calculation results of Monte Carlo method,and compared with the calculation results of dynamic reliability method.The results show that the reliability of the longitudinal bearing capacity of the aqueduct structure decreases with the service life,especially in the later stage of service the decline is much greater than the transverse bearing capacity,indicating that the limit state of the longitudinal bearing capacity is the control state of the aqueduct life.Both the longitudinal and transverse crack resistance reliability decline is slower compared with the bearing capacity reliability.The crack resistance reliability of the bottom plate is slightly lower than the target value in the later stage of service due to the low initial value.The overall calculation error of the time-discretization method is relatively small,especially for the safety evaluation of the structure in the later stage of service.Compared with the dynamic reliability method,the calculation result of the time-discretization method is more accurate.It is more reasonable to use the time-discretization method for the reliability calculation and safety evaluation for aqueducts.