腐蚀影响下服役钢箱梁抗弯可靠性分析

Flexural Reliability Analysis of In-Service Steel Box Girders under Corrosion Effects

摘要: 本文针对腐蚀环境下Q370qD高强钢箱梁的抗弯性能退化及结构安全性评估问题，开展了基于概率统计理论的时变可靠度研究。首先，深入分析了腐蚀对钢结构截面几何参数减损与材料力学性能劣化的耦合机理，构建了考虑材料–几何双重损伤耦合抗力衰减模型，并确定了材料性能、几何参数及计算模式的不确定性统计特征。其次，依托道滘河大桥工程实例，采用JC法(验算点法)计算了钢箱梁在100年设计基准期内的抗弯时变可靠指标。研究结果表明：钢箱梁的可靠指标随腐蚀年限增加呈非线性下降趋势，从初始状态的6.854降至100年后的4.892，但始终高于公路桥梁一级安全等级的目标可靠指标，表明该结构在服役期内具备足够的安全性。最后，参数敏感性分析指出，计算模式的不确定性对可靠度影响最大，荷载效应影响略低，而材料与几何参数的变异性影响相对较小。本研究结论可为既有高强钢桥梁的维护决策与寿命预测提供理论依据。

Abstract: To address the flexural performance degradation and structural safety assessment of Q370qD high-strength steel box girders under corrosive environments, this paper presents a time-dependent reliability study based on probabilistic statistics. First, the coupling mechanism of corrosion-induced cross-sectional geometric loss and deterioration of material mechanical properties is thoroughly analyzed. A resistance degradation model considering the time-varying elastic modulus is established, and the statistical characteristics of uncertainties in material properties, geometric parameters, and calculation models are determined. Then, using the Daojiaohe Bridge as a case study, the JC method (checking point method) is employed to calculate the time-dependent flexural reliability index of the steel box girder over a 100-year design service life. The results show that the reliability index of the steel box girder decreases nonlinearly with increasing corrosion time, from an initial value of 6.854 to 4.892 after 100 years, but remains above the target reliability index for the first-class safety level of highway bridges, indicating sufficient safety throughout the service life. Finally, parametric sensitivity analysis reveals that the uncertainty in the calculation model has the greatest impact on reliability, followed by load effects, while variabilities in material and geometric parameters have relatively minor effects. The findings provide a theoretical basis for maintenance decision-making and life prediction of existing high-strength steel bridges.