Risk Assessment of Masonry Bridges Under Flood Conditions: Hydrodynamic Effects of Debris Blockage and Scour

最近发生的洪灾事件，例如2013/14年冬季在英国西南部发生的洪灾事件，突显了我们的交通基础设施具有更强的弹性的重要性。洪灾期间和洪灾后桥梁的损坏，甚至服务的减少，可能会给经济和社会造成巨大的直接和间接损失，并阻碍救援和恢复工作。例如，29座桥梁在2009年坎布里亚洪水期间倒塌或严重损坏，导致近3400万英镑的维修和更换费用，以及明显更大的经济和社会成本。这项研究旨在通过使从业者能够评估水道中堆积的碎片对桥梁造成的风险，从而增强我们的交通基础设施的弹性。水道中的碎片是英国和世界各地洪水期间桥梁故障或损坏的主要原因。它将满足一项重要的行业需要，因为目前没有指导意见可供从业人员评估桥梁，特别是最容易受到碎片堵塞的砖石桥梁处的碎片堵塞的水动力影响。漂浮在桥下或桥上游的碎片会显著增加下游的水流速度，这可能会加剧桥墩和桥台周围的冲刷。它还会增加桥梁上的水位，从而造成很大的侧向压力和扬压力，这对砖石桥梁来说尤其成问题，因为它们依赖于砖石和填充物的自重来传递荷载。该项目的目的是通过水槽实验室实验和计算流体动力学(CFD)模拟相结合的方法，了解和描述碎片堵塞的水动力效应。然后，它将制定一种基于风险的方法，以评估个别桥梁在洪水条件下因碎片堵塞而产生的冲刷、上浮和侧向力，并将这种方法纳入现有的水力作用下桥梁评估指南。该项目将由一个多学科研究团队实施，该团队在产生影响方面有着良好的记录，并由参与英国桥梁管理的主要利益相关者组成的行业联盟提供协助。

Recent flooding events such as those of winter 2013/14 in the South West of UK have highlighted the importance of having greater resilience in our transport infrastructure. The failure of bridges or even a reduction in service during and in the aftermath of floods can lead to significant direct and indirect costs to the economy and society, and hamper rescue and recovery efforts. For example, 29 bridges collapsed or were severely damaged during the 2009 floods in Cumbria leading to nearly £34m in repair and replacement costs, and significantly larger economic and societal costs. This research aims to enhance the resilience of our transport infrastructure by enabling practitioners to assess the risks to bridges from debris accumulation in the watercourse, a leading cause of bridge failure or damage during floods both in the UK and world-wide. It will address an important industry need as there is currently no guidance available for practitioners to evaluate the hydrodynamic effects of debris blockage at bridges and in particular, at masonry bridges, which are most susceptible to debris blockage. Floating debris underneath or upstream of a bridge can significantly increase downstream flow velocities, which can worsen scour around piers and abutments. It can also increase water levels on the bridge and thereby cause large lateral and uplift pressures, which are especially problematic for masonry bridges since they rely on self-weight of masonry and fill to transfer load. This project will aim to understand and characterize the hydrodynamic effects of debris blockage through a combination of laboratory experiments in flumes and computational fluid dynamics (CFD) modelling. It will then develop a risk-based approach for assessing the scour, and uplift and lateral forces at individual bridges due to debris blockage during flood conditions, and incorporate this approach within existing guidance for the assessment of bridges under hydraulic action. The project will be carried out by a multi-disciplinary research team with a strong track record of generating impact, and assisted by an industry consortium composed of major stakeholders involved in UK bridge management.