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

Author:TFD

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

本来是暂时的，在第二次世界大战期间建造的许多匆忙建造的飞机机库仍在加拿大各地使用。例如，加拿大武装部队在全国各地仍然拥有大约70个沃伦·桁架机库。魁北克St-Jean的加拿大部队基地（CFB）有几个沃伦·桁架机库，可以满足当前的运营要求。尽管仍然有效，但这些机库确实构成了一些结构完整性和可维修性的问题。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.

开发一种基于研究的，数据驱动的方法来建立安全性

传统木衣架,构造使用34米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.

机库1 - 现在是CFB St Jean的供应台 - 是被选为监视的结构。当屋顶上的积雪超过10厘米（4英寸）时，必须撤离该机库ébec during the winter months. Among other questions, the team wanted to find out if this snow accumulation limit warranted evacuations.

长期的、连续的nd 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 software suite. Dr. Vlachopoulos says: “When first approached to come up with a structural health monitoring solution for the performance of Warren truss structures within the Department of National Defence, naturally, automatic total stations and in particular, Leica Geosystems products, were on the initial list of possible solutions.”

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。The Leica TM50 was chosen because it met the requirements and because compatible Leica software can transmit alerts via email and text in real-time for emergencies. This feature is often used for monitoring discrete points of buildings.

“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.”

Expanding the cost-effective monitoring program nationwide

Besides the successful emergency monitoring, the Leica Geosystems total station is also used for an in-depth structural analysis of Warren Truss hangars. This in-depth analysis has provided important information regarding the true behaviour of the truss structure. The solution has been cost-effective because it cuts down on necessary site visits. The team accesses the total station remotely via GeoMoS Monitor and carries out discrete surveying from their office in Kingston, more than 300 km away. Following the trial, the monitoring program will be optimised with a view to expand the project nationwide. If safe, the hangars will continue their long and exemplary service.

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