Random Field of the Modulus of Elasticity Considering Knots: Application to Wood Utility Poles

Abstract

Wood utility poles are simple structures used in power networks and their failure can produce a significant impact on their reliability as well as economic consequences. The presence of knots is known to be the main source of the lengthwise variability and reduction in bending strength and stiffness in wood elements. Other authors have studied this variability and developed Modulus of Elasticity (MOE) distribution models for sawed wood elements, like beams. The aim of this work is to determine whether the aforementioned models, originally developed for sawn wood beams, can be applied to a wood structure without sawing such as wood utility poles. Load-displacement curves and natural frequencies of the poles were obtained from static and dynamic test, respectively. A visual survey is also carried out to record geometry data, the knot dimensions and location in the poles. Numerical models considering the surveyed geometry and the presence of knots are used. With this approach, the MOE random field is simulated through a weak zone model that accounts knots. The governing equations are discretized through the Finite Element Method (FEM). The stochastic analysis is performed by means of Monte Carlo Simulations (MCS). Then, experimental data (displacements and natural frequencies) are compared with numerical results in order to determine whether the models developed for sawn beams can be applied to wood utility poles.