Three-dimensional finite element model to predict pole strength
Date
1992
Authors
Franco, Nilson, author
Pellicane, Patrick A., advisor
Bodig, Jozsef, committee member
Criswell, Marvin E., committee member
Shuler, Craig E., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
A three-dimensional finite element model was used to predict the strength and location of failure of nine wood transmission poles. The poles were made from three commonly used species (western red cedar, Douglas-fir and southern pine) in North America. All poles were tested to failure as a cantilever beam with a concentrated load applied to the tip. The methodology involved was to select several eighteen inches long segments, located along the poles, which contained the most severe defects such as cluster of knots, spiral grain, including material inhomogeneity in the highly stressed region. Each segment was analyzed using the finite element technique with appropriate boundary conditions. Material properties for each segment were determined by measuring clear-wood elastic and strength parameters in boles taken from broken poles. The information about knots and spiral grain, obtained by visual inspection of the pole surface, was used to identify the worst knot clusters and grain deviation in any segment. Knots were modeled in the finite element mesh and the localized grain deviation around the knots were determined through the use of the flow-grain analogy model. Finite element computer analysis were performed through the use of the program GTSTRUDL. The model resulted in a total of 288 three-dimensional, isoparametric, linear strain, 20-node parallelopiped and 15-node wedge shaped elements. For the nine poles studied, the results showed good agreement between predicted and experimental strength. The predicted values for strength differed from the actual ones with an average deviation of 7% (below the actual). Concerning failure location, in six of the poles, failure was verified in the same places as those predicted by the model. In the three other cases the failure with the maximum error of three feet, except for one pole where the deviation was twelve feet. The study revealed that the three-dimensional finite element approach to model growth characteristics applied to the more critical segments along the pole length proved to be very useful tool for strength and failure location prediction of poles.
Description
Covers not scanned.
Print version deaccessioned 2020.
Print version deaccessioned 2020.
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Subject
Wood -- Testing
Wood poles
Strength of materials
Electric lines -- Poles and towers