Assessing the Performance of Masonry Railway Viaducts in the UK by Detecting Hidden Defects and Geometric Features =Structural Engineering

英国的砖石铁路高架桥总体上已经超过了现代设计寿命120年，而它们的设计并不是为了这个目的。更重要的是，必须强调的是，砖石拱门(主要)是根据经验方法设计的，例如莫尔斯沃斯公式(小拱门)和Perronet为多跨结构开发的18世纪革命性方法(Robinson和Kapoor，2009)。因此，现代使用的结构能力的验证是一项重大的挑战，特别是考虑到这些结构的竣工信息缺乏、荷载变化、维护维修记录不佳以及评估各种缺陷对结构性能的影响的挑战。评估砌石铁路高架桥结构能力和剩余寿命的关键是从验证几何特征和缺陷开始，包括隐藏的缺陷。这种数据的收集可能是一个及时的过程，有许多访问限制。铁路高架桥内拱门的占用更是加剧了这种情况，这种拱门被称为“租赁拱门”。Network Rail目前在其投资组合中有10425个租赁拱门，其中许多包括覆层面板，防止了拱顶和桥墩的直接可见性。为了查看这些缺陷，检验员必须安排与租户接触，移除覆层面板(通常用锚固定)，然后将面板重新固定。重要的是要注意，拱门不是为这些覆层设备和荷载以及从拱脚底板悬挂的照明设备和其他服务而设计的。其中许多拱门包括竖井，竖井已被混凝土封顶或堵塞，这增加了结构的整体行为的复杂性。为了减少对运营铁路和这些结构内的租户的风险，有必要改进获得资产状况数据的方法，并根据收集的数据更准确地模拟结构行为。无损检测(NDT)方法可以帮助这一过程，并通过使用无人机系统(UAS)上的无损检测工具，避免拆卸覆层面板和在轨道层面验证几何特征的需要。这将带来额外的好处，例如节省维修费用、更好地遵守安全标准、改善与租户的关系以及更准确地了解建筑物的剩余使用寿命。Network Rail向公众发布了一份挑战声明，以应对他们目前面临的挑战，这突显了这一问题的重要性。这项研究的主要目的是确定在英国的砖石铁路高架桥上使用无损检测/无损检测技术的可行性，并利用采集的数据来改进高架桥的能力评估。研究的重点将是捕捉租赁拱门内的隐藏缺陷，其中拱脚底板覆盖着覆层面板，以及几何特征(扭曲、空洞、不连续、环分离等)。在轨道一级，部署配备各种无损检测/无损检测设备的无人机。Mohammed Al-Sharif目前代表Network Rail担任CIRIA项目的指导小组成员，以制定土木结构无损检测的最佳实践指导文件。CIRIA项目的成果将支持博士研究，并促进学术界和产业界之间的知识转移。

Masonry railway viaducts in the UK have at large exceeded the modern-day design life of 120 years, for which they were not designed for. More importantly, it must be highlighted that masonry arches were designed (largely) from empirical methods such as Molesworth's formula (small arches) and the 18th century revolutionary method developed by Perronet for multi-span structures (Robinson and Kapoor, 2009). As such, the verification of structural capability for modern day use is a major challenge, particularly considering the lack of as-built information for these structures, changes in loading, poor records of maintenance repairs and challenges with assessing the impact of various defects on structural performance.The key to assessing the structural capability and residual life of masonry railway viaducts begins with verification of the geometric features and defects, including hidden defects. The collection of such data can be a timely process, with numerous access restrictions. This is exacerbated by the occupancy of arches within railway viaducts, which are known as 'tenanted arches'. Network Rail currently have 10425 tenanted arches across their portfolio, many of which include cladding panels, preventing direct visibility of the soffit and piers of arches. In order to view these defects, examiners must arrange access with tenants, remove cladding panels (usually fixed with anchors) then fix the panels back on. It is important to note that the arches were not designed for these cladding fixtures and loads, as well as lighting fixtures and other services suspended from the arch soffit. Many of these arches include shafts, which have been capped or plugged with concrete, which adds another complexity to the global behaviour of the structure.In order to reduce the risk to the operational railway and to the tenants within these structures, there is a need to improve the methods to obtain asset condition data and model the structural behaviour more accurately with the data collected. Non-Destructive Testing (NDT) methods can aid this process and prevent the need to remove cladding panels and also to verify geometric features at track level, via the use of NDT tools on Unmanned Aerial Systems (UAS). This will provide additional benefits such as cost savings for maintenance, improved compliance with safety standards, better relationships with tenants and a more accurate understanding of the residual service life of the structures. The significance of this issue was highlighted when Network Rail released a challenge statement to the public to address the challenges they currently face. The main aim of this study is to determine the viability of using NDT/NDE techniques on Masonry Railway Viaducts in the UK, and to utilise the data captured to improve the capability assessment of the viaducts. The focus of the study will be to capture hidden defects within tenanted arches, where the arch soffit is covered with cladding panels, as well as geometric features (distortions, voids, discontinuities, ring separation etc.) at track level, by deploying UAS equipped with various NDT/NDE equipment. Mohammed Al-SHarif am currently sitting on the Steering Panel for a CIRIA project, on behalf of Network Rail, to develop a best practice guidance document for NDE of Civil Structures. The outcome of this CIRIA project will support the PhD study and enable knowledge transfer between academia and industry.