Abstract

Scour has been recognized as one of the leading causes of bridge collapse in the United States. Therefore, it is essential to be able to build models that accurately capture the response of bridges vulnerable to scour, including those located in layered rather than homogeneous soil deposits. Simple removal of soil springs due to scour ignores the effect of stress history for layered soils, which can lead to unconservative designs of foundations. This article proposes a methodology called the equivalent stress history and layered effects (ESHaLE) approach to capture the impact of soil stress history of layered soils on vulnerability assessment of scoured bridges. It utilises conservation of strength and mass to derive corresponding soil and depth parameters. Results show that neglecting to include stress history impacts in layered soils can lead to an underestimation of the single pile axial displacements by up to 35% in static analysis, and underestimation of the probability of exceeding bridge deck deflection thresholds by up to 25% in seismic fragility assessment. The study presents a method to include both soil stress history and layered effects in soil modeling and shows the importance of including these soil effects in the assessment of bridges vulnerable to scour.

摘要

冲刷被认为是美国桥梁倒塌的主要原因之一。因此，必须能够建立模型来准确捕捉易受冲刷影响的桥梁的响应，包括位于分层而非均质土壤沉积物中的桥梁。由于冲刷而简单地去除土壤弹簧忽略了层状土壤的应力历史影响，这可能导致基础设计不保守。本文提出了一种称为等效应力历史和分层效应 (ESHaLE) 方法的方法，用于捕捉分层土壤的土壤应力历史对冲刷桥梁脆弱性评估的影响。它利用强度和质量守恒推导出相应的土壤和深度参数。结果表明，忽略分层土壤中的应力历史影响可能会导致在静力分析中低估单桩轴向位移高达 35%，并在地震分析中低估超过桥面挠度阈值的概率高达 25%脆弱性评估。该研究提出了一种在土壤建模中包括土壤应力历史和分层效应的方法，并显示了将这些土壤效应纳入评估易受冲刷的桥梁的重要性。