Probabilistic Strength of Steel Poles Used for Power Production and Transmissions

Abstract

The profound changes in engineering over the last few decades were reflected by ideas of uncertainty recognized in engineering today. Civil engineering structures like steel transmission poles are to be designed for loads created by environmental actions such as wind, snow and earthquake, but these actions are exceptionally uncertain in their manifestations as one is required to quantify the risks and benefits involved. The subject of structural reliability offers a rational framework to quantify uncertainties mathematically. This study presents a probabilistic assessment of the strength of steel poles in service, the resistance of the steel poles, ultimate strength of steel, section modulus, cross sectional dimensions of the poles, distance at which the load acts on the pole and the magnitude of the load acting on the pole are treated as random variables, which can be significantly influenced by time and location. The study has been carried out to determine the structural safety levels of electric distribution steel poles under uncertain loadings using First Order Reliability Method (FORM) in MATLAB with FERUM Version 4.0. The reliability analyses in MATLAB gave lower values of reliability index, (1.4802E+00) and probability of failure (6.9407E-02) for moment failure mode, while higher values of (2.339E+01 and 5.1245E+01) were obtained respectively for deflection and shear failures, with negligible values of 0.100E-10. The effect of variation of parameters like thickness, diameters and length of steel poles were also studied, which indicates that the thickness, diameters and length significantly affects the strength of steel poles.