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Abstract
Cable-based technologies are the backbone for logistics of timber or construction material on impassable terrain. In Central Europe, the use of standing skylines with pre-stressed, both-sided fixed-anchor cables and multi-span configurations with internal intermediate supports is common. To ensure a safe and cost-effective set-up for cable road operations, it is essential to identify and compute the properties of the skyline (e.g. load path, tensile forces). This task is challenging because it requires dealing with the non‐linear behaviour of the cable structure under the load and has to include all significant physical effects. Several approaches have previously been proposed as practical solutions, however not all physical effects were covered by those approaches, such as the inclination-dependent elastic prolongation of the cable or the longitudinal deflection of the sagging carriage. With our new proposed approach, we aim to close this gap of knowledge, and consider all relevant physical effects. We present a non-linear approach that is able to compute the properties of a wide range of standing skyline configurations, including those with additional cables. This approach offers an extensive solution and a flexible framework for considering individual configurations or particularities by adding equations to the equation system.
Highlights
Cable-based technologies are the backbone for timber harvesting as for logistics of construction material on steep slopes as on impassable lowlands
The aim of this paper is to introduce a procedure to calculate the properties of standing skyline cable yarding systems with a system of non-linear equations. We propose that this approach will make it possible to: 1. adapt to variations in the setting by using a modular system; 2. calculate the catenary or the parabola for any location in any number of carriages in any multi-span configuration; 3. ignore or consider essential physical effects or influences such as temperature, slide over intermediate supports, longitudinal deflection, friction, additional cables, elastic guy lines, and inclination-dependent cable elasticity; 4. find an equilibrium to solve all unknown variables in a twostep procedure; 5. design a skyline configuration where the result of a change in one assumption or situation can be displayed ; 6. describe an alternative to the current standard in Central Europe of computing cable yarder properties in the field
We showed that our results are very near to the most exact solution, but it can–in contrast with the other competing solutions—deal with the Central European cable yarder configurations or wider range of cases
Summary
Cable-based technologies are the backbone for timber harvesting as for logistics of construction material on steep slopes as on impassable lowlands. [21] presented simplified formulae to compute the properties of a cableway by using a parabola He analysed an unloaded span tensioned only by self-weight and loaded with a single or multiple load. The Pestal formulae are commonly used for approximate calculations of both-sided fixed-span cable yarders. The use of these formulae is acceptable for the calculation of the sag of an unloaded span, for which the variables relative weight per metre and mounting tension are known. The Pestal formulae produce inaccurate calculations for the loaded skyline Under such conditions only the weight of the load is known; the tension and the sag of the loaded cable, resulting from the loaded equilibrium, are unknown.
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