Overhead power lines are essential infrastructure in our modern societies and are ageing. In addition, transmission networks will be called upon to increase their transit capacity over the coming decades in the context of the electrification of transport. Thus, grid operators face several challenges in fulfilling their mandate to deliver electricity reliably and at the lowest possible cost. It is therefore essential for these companies to make use of advanced analysis tools to better understand the current and future condition of their overhead transmission line structures. The overall objective of this research project is to develop and apply advanced numerical analysis methods to optimise the design and service life of overhead transmission line structures. This research work concerns in particular advanced analysis methods which are separated into five parts: the analysis of lattice towers for the evaluation of their strength and mode of failure; the evaluation of the tensile strength of bolted connections of lattice towers; the evaluation of the effect of corrosion on the residual life of conductors; the evaluation of wind vibration amplitudes of conductors equipped with anti-vibration braces; and the evaluation of wind loads on lattices with a local approach. The methods developed will allow network managers to better evaluate the impacts of their decisions for the design of new lines and for the extension of the life of existing lines. Keywords: Power transmission, power system reliability, steel structure design, lattice structures, wind loads, cable mechanics, finite elements, cable corrosion.