Intermediate Support Cable Logging Systems

by James W. Charland, Oregon State Univ, Corvallis, United States,
Alan G. Hernried, Oregon State Univ, Corvallis, United States,
Marvin R. Pyles, Oregon State Univ, Corvallis, United States,



Document Type: Proceeding Paper

Part of: Spatial, Lattice and Tension Structures

Abstract:

Cable systems for the transportation of fresh cut logs often employ existing trees as intermediate supports for the main support cable. Failure of these support trees is life threatening and catastrophic to the logging operation. To improve safety and reliability, the maximum loads on the support trees must be predicted before logging operations commence. A model of a general cable logging system employing one set of intermediate support trees is developed. The cables are assumed to be massless. The pulleys are assumed to be massless and frictionless. The support trees are represented as linear springs. The model is described by simultaneous equations of static equilibrium and compatibility for the pulleys and cables, respectively. These equations are highly coupled and non-linear. An iterative approach is used to solve these equations, specifically a modification of Newton's algorithm which utilizes a finite difference approximation to the Jacobian. Determining the static equilibrium configuration of the cable logging system yields the cable tensions and the loads on the support trees directly. An example system is presented to illustrate the methodology.



Subject Headings: Trees | Cables | Load factors | Approximation methods | Finite difference method | Structural reliability | Equilibrium | Suspended structures

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