超宽混凝土自锚式悬索桥健康监测及不同预测模型下的时变效应对比分析

摘要

The structural health status of Hunan Road Bridge during its two-year service period from April 2015 to April 2017 was studied based on monitored data. The Hunan Road Bridge is the widest concrete self-anchored suspension bridge in China at present. Its structural changes and safety were evaluated using the health monitoring data, which included deformations, detailed stresses, and vibration characteristics. The influences of the single and dual effects comprising the ambient temperature changes and concrete shrinkage and creep (S&C) were analyzed based on the measured data. The ANSYS beam finite element model was established and validated by the measured bridge completion state. The comparative analyses of the prediction results of long-term concrete S&C effects were conducted using CEB-FIP 90 and B3 prediction models. The age-adjusted effective modulus method was adopted to simulate the aging behavior of concrete. Prestress relaxation was considered in the stepwise calculation. The results show that the transverse deviations of the towers are noteworthy. The spatial effect of the extra-wide girder is significant, as the compressive stress variations at the girder were uneven along the transverse direction. General increase and decrease in the girder compressive stresses were caused by seasonal ambient warming and cooling, respectively. The temperature gradient effects in the main girder were significant. Comparisons with the measured data showed that more accurate prediction results were obtained with the B3 prediction model, which can consider the concrete material parameters, than with the CEB-FIP 90 model. Significant deflection of the midspan girder in the middle region will be caused by the deviations of the cable anchoring positions at the girder ends and tower tops toward the midspan due to concrete S&C. The increase in the compressive stresses at the top plate and decrease in the stresses at the bottom plate at the middle midspan will be significant. The pre-deviations of the towers toward the sidespan and pre-lift of the midspan girder can reduce the adverse influences of concrete S&C on the structural health of the self-anchored suspension bridge with extra-wide concrete girder.%本文研究了目前中国最宽的混凝土自锚式悬索桥—湖南路大桥的结构健康状态.利用2015年4月至2017年4月两年运营期内的结构变形、内力及振动特性监测数据进行了结构变化及安全性评价,并进行了环境温度变化及混凝土收缩徐变效应影响分析.基于ANSYS有限元模型,采用CEB-FIP 90预测模型及B3预测模型及对混凝土收缩徐变效应进行了预测及对比分析.采用按龄期调整的有效模量法模拟混凝土材料的老化特性,通过有限元逐步计算法考虑预应力损失.实测数据表明主塔横桥向偏位较纵桥向明显,超宽主梁空间效应明显,主梁纵向应力的变化沿横桥向不均匀分布.季节环境升温引起主梁压应力增大,季节环境降温引起主梁压应力减小,主梁内温度梯度效应明显.与CEB-FIP 90预测模型相比,可以考虑混凝土材料参数的B3模型得到的混凝土收缩徐变效应预测结果与实测数据更为接近.梁端及塔顶的主缆锚固点在混凝土收缩徐变效应影响下向中跨偏移.中跨跨中主梁下挠明显,主梁顶板压应力增大,底板压应力减小明显.主塔向边跨方向的预偏及中跨主梁的预抬有利于超宽混凝土自锚式悬索桥的结构安全状态.