Settlements severely affect historic masonry arch bridges worldwide. There are countless examples of structural dislocations and ruins in recent years due to severe settlements at the base of pier foundations, often caused by shipworm infestation of wooden foundations or scouring and riverbed erosion phenomena. The present paper proposes an original way to approach the failure analysis of settled masonry arch bridges. The proposed method combines two different 2D numerical models for the prediction of masonry arch bridge capacity against settlements and for safety assessment. The first one is the Piecewise Rigid Displacement method, i.e. a block-based limit analysis approach using the well known Heyman's hypotheses; the second one is a continuous Finite Element approach. The case study of the four-span Deba Bridge (Spain, 2018) failure is presented with the aim to illustrate how the methods work. The failure analysis produced satisfactory results by applying both methods separately, in confirmation of their reliability. Their combination also allowed to obtain a significantly reduction in computational cost and an improvement of prediction accuracy. A sensitivity and a path-following analysis were also performed with the aim to demonstrate the robustness of the presented method. The obtained simulations highlighted that the results do not depend on the friction angle and that a proper prediction of the evolution of the structural behavior can be obtained only taking into account geometric nonlinearities. Such results demonstrate once again that in settled masonry arches geometry prevails over the mechanical parameters. The current study paves the way for the fruitful use of the proposed approaches for a wider range of applications, as, for example, the mechanism identification or the displacement capacity assessment of masonry structures under overloading as seismic loads.

定居点严重影响了世界范围内历史悠久的砖石拱桥。近年来，由于码头基础严重沉降造成的结构错位和废墟的例子不胜枚举，通常是由于木基础的船虫侵扰或冲刷和河床侵蚀现象造成的。本文提出了一种解决沉降砌体拱桥破坏分析的原始方法。所提出的方法结合了两种不同的二维数值模型，用于预测砌体拱桥抗沉降能力和安全评估。第一个是分段刚性位移方法，即使用众所周知的海曼假设的基于块的极限分析方法；第二个是连续有限元方法。四跨德巴大桥的案例研究（西班牙，2018）失败的目的是说明这些方法是如何工作的。通过分别应用这两种方法，故障分析产生了令人满意的结果，证实了它们的可靠性。它们的组合还可以显着降低计算成本并提高预测精度。还进行了灵敏度和路径跟踪分析，目的是证明所提出方法的稳健性。获得的模拟强调了结果不依赖于摩擦角，并且仅在考虑几何非线性的情况下才能获得对结构行为演变的正确预测。这样的结果再次表明，在稳定的砌体拱门中，几何形状优于机械参数。