WHFF Project: 2019.04
Authors: Leo Bont, Laura Ramstein, Fritz Frutig and Janine Schweier.
The most important facts in brief
The project investigated how scientific knowledge of rope mechanics, developments in remote sensing, and mathematical optimization algorithms can be integrated into a modern, efficient tool for rope line planning.
The calculated sags and forces using the catenary approach (Zweifel's method) provided significantly more precise values than the results of the widely used Pestal's calculation method.
Different single tree detection methods were compared for identifying potential support trees for forested areas in cable crane terrain.
For practical application, either the methods need to be refined for different types of forests or better baseline data need to be available.
The biggest challenge from a forest practice perspective is the availability of geospatial data, which varies by canton. Especially in the case of cross-cantonal operations of forest contractors, data acquisition is time-consuming and sometimes cost-intensive
Project description
Regardless of the type of cable crane, planning a cable line is a demanding and time-consuming task. It essentially involves determining the start and end points of a line as well as the intermediate supports. It must be ensured that the permissible forces, in particular the rope tensile forces in the supporting rope, are not exceeded, that there is a sufficient distance between the load path curve and the ground, that suitable anchor trees are found and, at the same time, that the number of intermediate supports is minimized.
The present project investigates how scientific knowledge of rope mechanics can be combined with remote sensing data and mathematical optimization algorithms. It is hoped that this will significantly simplify the planning of rope lines, lead to solutions with an optimal number of supports, and increase work safety for forestry personnel.
The findings will be tested using a rope line planning tool based on new rope mechanics research results and integrated into a GIS system. The calculation of forces and sags is done using a catenary approach, all code is freely viewable and geodata can be directly consulted in QGIS for the planning process. Finally, recommendations for future rope line planning tools are derived from the experience with Seilaplan.
Conclusions
The two calculation methods according to Zweifel and Pestal were compared on the basis of measured data of two rope lines. Compared to Pestal, the calculation method according to Zweifel provides significantly more precise values with which a reasonable rope line layout can be calculated even for heavy loads and long span fields. For forestry, fixed rope cranes anchored on both sides, the use of Zweifel's method or similar methods based on the catenary is recommended, since these represent both sag and rope tensile forces more accurately than Pestal's approximation method.
The consolidation of the new scientific knowledge into a rope line planning tool was highly welcomed by forest practitioners. The test operations appreciated the implemented more precise calculation method according to Zweifel and the more realistic information it provided for the construction and operation of a rope line. They also used various remote sensing data and GIS layers for manual situational adjustment of the rope line, which was made possible by the integration of the tool into QGIS. According to the forestry practitioners involved, the output of the most important information about the rope line in graphical form and as a short report could be used well for the documentation of the rope line project according to the new EKAS guidelines (Swiss Federal Coordination Commission for Occupational Safety) and as a construction manual.
The biggest challenge from the forestry practitioner's point of view is the availability of geodata, which varies from canton to canton. Especially in the case of cross-cantonal operations of forestry contractors, data acquisition is time-consuming and sometimes cost-intensive. A nationwide free access to the digital elevation model and other remote sensing data would significantly simplify the entire planning process.
Finally, it can be stated that further research on static and dynamic forces in the rope system and on the determination of information on potential support trees is necessary and demanded by the forestry practice. In this context, Seilaplan as a practicable, freely available and expandable planning tool should also be used and further developed in the future for scientific investigations and practical tests.
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More information about the project can be found on ARAMIS.
The project was supported by the Swiss Forest and Wood Research Funding Switzerland (FOWO-CH) of the Federal Office for the Environment (FOEN) and the Conference for Forests, Wildlife and Landscape of the cantons.