Beuth Hochschule für Technik Berlin

BE-SAFE: Web-Service und Frühwarnsystem für Schneelasten
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BE-SAFE: Real-time Snow Load Monitoring for Flat Roofed Buildings

Accumulation of snow and ice on top of flat-roofed buildings can lead to severe structural problems, including the loss of structural integrity and building collapse. A tragic example of such a scenario was the collapse of Bad Reichenhall’s ice-rink on 2 January 2006, which left 15 dead and many more seriously injured. This kind of hazard can be mitigated by putting in place an early warning system to monitor the snow load on buildings at risk. Then action can be taken before this kind of hazard occurs; this is the goal of BE-SAFE.

The project focuses on Steglitz-Zehlendorf which is one of the twelve districts of Germany’s capital city of Berlin. There, the monitoring of snow loads on a number of public buildings is laid out by regional experts in a non-automated, but well-proved way: an Excel spreadsheet, showing data from the cadastral land register for every building at risk, is used for updating the estimated snow load continually. In the event that the snow load hits a building’s maximum bearing capacity, the persons responsible can undertake appropriate action, from clearing the roof to evacuating the building. This duty is undertaken by the Berlin-based engineer office Dipl-Ing. Laschinski, in cooperation with the district’s building authorities (Bauamt Steglitz-Zehlendorf). This reliable method has two decisive disadvantages: first, communication between partners is time-consuming, and can sometimes hardly be maintained due to its time-consuming character. Second, the currently used system vaguely estimates the snow load, which can lead to under- and overestimations. The former implies unnecessary costs for clearing a roof or evacuation of a building; the latter can produce a “negative false” and represents a security risk.

BE-SAFE will attempt to enhance the very sensitive process of monitoring snow load and risk mitigation through early warning by establishing an internet-based Geographic Information System (WebGIS). A map-based, user-friendly web interface serves as the system’s central portal and front end. The real-time snow load data is visualized on the map in a self-explanatory way by using an extended traffic light scheme. On the one hand, this WebGIS functions as an information platform, which can be used to check the current snow load situation throughout the district; on the other hand, it serves administrators as a management tool, enabling them to access the system back end’s geo-database at any time. The implementation process will follow the paradigm of Service Oriented Architecture (SOA), achieving transferability, scalability and interoperability. These goals are reached by deploying only components which are based on the Open Geospatial Consortium (OGC) specifications. Handling dynamic data, which is changing over time, demands a specialized kind of software and information processing structure. This can be achieved using software belonging to OGC’s Sensor Web Enablement (SWE) Initiative.

Since the modeling approach should be adjusted to different groups of roof types, roof-specific parameters need to be collected. An empirical study provides this basic data to identify roof-specific driving factors affecting snow load and snow metamorphosis, including exposition, declination and quality of insulation. 

BE-SAFE will develop a system, capable of estimating and visualizing the snow load of every observed building in real time. It is put together from OGC-standards compliant geo-services, which are combined together to form an effective map-based early warning system. Monitoring and prediction of such a “rapid/sudden ongoing hydro-meteorological threat of minor temporal dimension” (UNEP) will be supported. Subsequent development plans are to invite additional user groups to the system, such as security officers who implement the emergency plans. At this level, BE-SAFE will offer an early warning system which can automatically initiate mitigation actions like the clearing of a roof, in order to prevent snow load-related hazards.

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