监视the structural health of 80-year-old Royal Canadian Air Force Warren Truss hangars

作者：TFD

监视the Structural Health of 80-year-old Royal Canadian Air Force Warren Truss Hangars

Meant to be temporary, many of the hastily constructed aircraft hangars built during WWII are still in use across Canada. For example, the Canadian Armed Forces still maintain approximately 70 Warren truss hangars across the country. The Canadian Forces Base (CFB) in St-Jean in Québec has several Warren truss hangars that it takes care of to meet current operational requirements. Although still functional, the hangars do pose some structural integrity and serviceability concerns. Safety limits placed on the buildings have an impact on CFB St-Jean’s day-to-day operations, so the Canadian Department of National Defence (DND) asked a research team (The RMC Green Team) from the Royal Military College of Canada (RMC) to investigate. The team devised a remote, continuous, real-time structural health monitoring (SHM) programme that includes the use of Leica Geosystems instruments. The SHM is both an alert system and a tool for in-depth structural analysis.

Developing a research-based, data-driven approach to building safety

The heritage timber hangers, constructed using 34m long double-span Warren trusses, were part of the Royal Canadian Air Force’s contribution to the British Commonwealth Air Training Plan in 1942. Material shortages during wartime, material degradation, environmental stresses, and significant repairs have weakened or altered the stress distribution within the buildings. To define whether they are still safe to use, DND approached Dr Nicholas Vlachopoulos, Full Professor, Civil Engineering Department, from RMC to design and install a monitoring program. Lt Henry Helmer-Smith, a PhD student, is the lead researcher on the project, supervised by both, Dr Nicholas Vlachopoulos and Dr Marc-André Dagenais from the Civil Engineering Department at RMC.

Hangar 1 – now serving as a supply depot at CFB St Jean – was the structure selected to be monitored. This hangar must be evacuated when snow on the roof exceeds 10 cm (4 inches), something that’s certainly not out of the ordinary in Québec during the winter months. Among other questions, the team wanted to find out if this snow accumulation limit warranted evacuations.

Long-term, continuous and remote monitoring with real-time alerts

The RMC Green Team built a monitoring system including solutions such as theLeica Nova TM50automatic total station with reflectorless EDM (R1000) andLeica Geomos软件套件。Vlachopoulos博士说：“首次与国防部内部的沃伦·桁架结构进行性能，自然，自然的总站，尤其是Leica Geosystems产品时，沃伦·桁架结构的性能是在初始清单上，亚博5分钟快三亚搏彩票手机版下载可能的解决方案。”

The key requirements were for the total stations to be continuously operable, remotely accessible, employable long-term, and most importantly, capable of transmitting alert messages. Deflection monitoring was included in the program, with the instruments able to send the users or the hangar occupants an alarm to evacuate based on absolute, short-term, and long-term displacements of the trusses and other structural members within the hangar. The comprehensive and flexible GeoMoS Monitor system includes several other alert options includingsensor connection loss, power failures, target loss (line-of-sight issues), among many others. The alarm system was programmed to communicate directly with users via email (built into GeoMoS Monitor) or SMS text by means of ASPSMS.com,an SMS monitoring solution与Geomos Suite兼容。选择Leica TM50是因为它满足了要求，并且因为兼容的Leica软件可以实时通过电子邮件和文本传输警报以供紧急情况传输。此功能通常用于监视建筑物的离散点。

“Extremely effective instrument for emergency monitoring”

Leica TM50自动总站于2018年春季安装在机库1中，今天仍在运行。它是使用Geomos Monitor编程的，以两个小时的间隔测量整个建筑物的20多个目标。然后，Geomos Analyzer用于远程和实时读取和显示所有处理的数据。根据指定的限制，可以增加读数的频率并在需要时变得连续。如果达到限制，则发出警报。Helmer-Smith说：“ TM50的可远程可操作功能以及实时传输和显示数据的功能使其成为紧急监控的极为有效的工具。”由于总站提供了准确和实时的反馈，因此基地能够减少机库1的撤离数量。

“比其他设备更加用户友好”

Before the monitoring equipment was installed, the research team built a quarter-size scale model of a single-span truss to test in the Structures Laboratory at RMC. The laboratory phase aimed to test the monitoring system and problem solve any limitations. Dr Vlachopoulos says: “The total station itself was very user-friendly and only took a few hours to learn. The software and messaging configuration took a few days to optimise and fully understand. Notably, this instrument was significantly more user-friendly than other equipment we tested.”

在全国范围内扩大具有成本效益的监控计划

除了成功的紧急监控外，Leica Geosystems Total Station还用于对Warren Truss机库的深入结构分析。这种深入的分析提供了有关桁架结构的真实行为的重要信息。该解决方案具有成本效益，因为它可以减少必要的现场访问。该团队通过Geomos Monitor远程访问总站，并从他们在金斯敦的办公室进行离散测量，距离超过300公里。在审判之后，将对监视计划进行优化，以期在全国范围内扩展该项目。如果安全，机库将继续他们的漫长而模范的服务。

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