Fragility Curves of Wood Utility Poles under Stochastic Wind Load with Material Uncertain Properties

Abstract

Wood utility poles are simple structures used in power networks. Wind loads are one of the main loads and can cause damage. Also, due to the construction procedure and the natural origin of the material, the geometrical dimensions and the material properties usually exhibit variability. The fragility curves are a useful tool to evaluate the failure probability of the poles for a defined failure mode. In this study, displacements are evaluated such that a percentage of damage is found for each wind velocity, and the dynamic behavior of Argentinean Eucalyptus grandis wood poles with uncertain material properties is analyzed, giving place to the fragility curves. The stochastic wind velocity field is derived using the Spectral Representation Method (SRM), considering temporal and spatial correlations. Then, the wind load is obtained under the considerations of the Argentinean standard CIRSOC 102. Furthermore, the lengthwise variability of the modulus of Elasticity is simulated through two probabilistic material models: as a random variable and as a random field through the Non Gaussian Karhunen-Loève Expansion . Results are numerically approximated by the Finite Element Method (FEM). Statistics of the response are obtained by means of Monte Carlo Simulations (MCS) with a previous convergence study to determine the acceptable number of realizations. Fragility curves for the probabilistic material models under stochastic wind loads are obtained and compared to assess the uncertainty of the material properties in the structural response.