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首页> 外文期刊>Journal of bridge engineering >Time-Dependent Monitoring and Modeling of I-35W St. Anthony Falls Bridge. II: Finite-Element Modeling
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Time-Dependent Monitoring and Modeling of I-35W St. Anthony Falls Bridge. II: Finite-Element Modeling

机译：I-35W圣安东尼瀑布桥的时变监视和建模。 II：有限元建模

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Data collected from the monitoring system installed in the St. Anthony Falls Bridge, a posttensioned concrete box girder bridge in Minneapolis, Minnesota, represented a combination of temperature-dependent effects due to daily and seasonal temperature changes and time-dependent effects related to creep and shrinkage of the concrete. In the companion paper of this study, the time-dependent creep and shrinkage effects were isolated from the data, and the rates of the creep and shrinkage were adjusted according to the Arrhenius equation. In this paper, results from finite-element models incorporating a variety of time-dependent provisions were compared with the measured time-dependent behavior. The modeling methodology is discussed extensively, including the procedures for incorporating the segmental construction staging sequence and midspan closure pour. Each of the models provided different predictions, and none were found to provide reliable estimates of the measured results throughout the entire 5-year period of investigation, although this was not unexpected due to the uncertainty inherent in the long-term predictions of the time-dependent behavior of concrete structures. Provisions from several standards with asymptotic creep models underestimated the longitudinal deformations and were found to approach asymptotic creep and shrinkage values before any indication of asymptotic behavior was observed in the measured data, although early-age behavior was accurately captured by these provisions. The shape of available logarithmic creep models appeared to be consistent with the measured data, although these models overestimated the longitudinal deformations of the bridge. The best predictions of the measured data were given by the provisions of a previous model code with an asymptotic creep model that properly accounted for the large volume-to-surface ratio of the bridge. Investigation of the computed vertical deflections showed that for all models the direction of the deflections reversed after completion of the structure, and that this bridge was not in danger of failure from excessive deflections. This was believed to be due to how continuity of the structure was achieved and the balance between the posttensioning forces and the gravity loading. Finally, Bayesian regression was proposed to update the finite-element model predictions to better match measured data. This technique could be used in structural monitoring applications to detect when time-dependent deformations fall outside expected bounds. (C) 2017 American Society of Civil Engineers.
机译：从安装在明尼苏达州明尼阿波利斯市的后张拉混凝土箱梁桥圣安东尼瀑布桥的监视系统中收集的数据代表了由于每日和季节性温度变化而产生的温度相关影响以及与蠕变和温度相关的时效影响的组合。混凝土的收缩。在本研究的伴随论文中，从数据中分离出了随时间变化的蠕变和收缩效应，并根据Arrhenius方程调整了蠕变和收缩率。在本文中，将包含多种时变规定的有限元模型的结果与测得的时变行为进行了比较。广泛讨论了建模方法，包括合并分段施工阶段顺序和中跨封闭浇筑的程序。每个模型都提供了不同的预测，但在整个调查的5年中，没有一个模型可以对测量结果提供可靠的估计，尽管由于时间的长期预测固有的不确定性，这并不意外。混凝土结构的依赖行为。尽管在这些标准中可以准确地观察到早期行为，但在一些标准中，渐近蠕变模型的规定低估了纵向变形，并在接近任何渐近行为迹象之前，已接近渐近蠕变和收缩值。尽管这些模型高估了桥梁的纵向变形，但可用的对数蠕变模型的形状似乎与实测数据一致。对测量数据的最佳预测是通过使用具有渐近蠕变模型的先前模型代码来提供的，该模型正确地说明了桥梁的大体积与表面比率。对计算出的竖向挠度的研究表明，对于所有模型，挠曲的方向在结构完成后都将反转，并且该桥不存在因过度挠度而失效的危险。据信这是由于如何实现结构的连续性以及后张力和重力载荷之间的平衡。最后，提出了贝叶斯回归来更新有限元模型的预测，以更好地匹配测量数据。该技术可用于结构监测应用中，以检测与时间有关的变形何时超出预期范围。 （C）2017年美国土木工程师学会。

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