基于断裂力学的老龄钢桥剩余寿命与使用安全评估

提出了基于断裂力学评估老龄铆接钢桥剩余寿命与使用安全的基本方法。根据铆接构件的疲劳破坏特征,建立了铆接钢桥简化断裂分析模型。鉴于简化断裂分析模型的不足,建立了铆接构件断裂分析模型,该模型可合理计入铆接构造、钉载等对疲劳裂纹扩展的影响。运用板壳断裂力学有限元程序,经计算回归得到了铆接构件断裂分析模型的几何修正因子公式。按铆接构件简化断裂力学模型和构件断裂力学模型,计算了浙江路桥主要杆件的剩余寿命,结果表明:按后者计算的剩余寿命均比前者降低约35%,可见钉载、钉孔应力集中等的影响是显著的。为保证正常使用功能,简化断裂分析模型和构件断裂分析模型的超声波探测间隔分别为4、2 a;若按保证主桁结构承载安全,则探测间隔已超过100 a,这样的探测间隔在一般情况下已无须考虑。

Assessment of Remaining Fatigue Life and Service Safety for Old Steel Bridges Based on Fracture Mechanics

A fracture mechanics method to evaluate the remaining fatigue life and service safety og old riveted steel bridges was proposed.According to the fatigue failure character of riveted members,a simplified fracture mechanics model(SFMM) was developed.Since SFMM could not incorporate the influence of the riveted details and pin load upon fatigue crack growth,an alternative riveted member fracture mechanics model(RMFMM) was proposed in this paper.Furthermore,a fracture finite element program was developed to calculate the geometry function of RMFMM.With the SFMM and RMFMM,the remaining fatigue life of all the vital members in Zhejiang Road Bridge was calculated through the simulation of crack growth.The calculation results show that the fatigue life of RMFMM is shorter 35% than SFMM,which indicates that the influence of the riveted details and pin load upon fatigue life is remarkable.In order to assure the normal service safety,the ultrasonic inspection intervals of SFMM and RMFMM are 4 years and 2 years respectively.The ultrasonic inspection interval is beyond 100 years for assuring the limit load capacity safety,which do not need to be considered in the bridge normal service life span.