The behaviour of transmission lines under severe winds is examined.;Firstly, the effect of scale of turbulence on the response of a line-like structure (cable model) is investigated through wind tunnel tests, and the experimental results are successfully compared with theoretical predictions made through the statistical method using influence lines. Consistency with theory allows for the development of a new modelling approach to conductor systems using a distorted horizontal (spanwise) scale to accommodate these systems in the wind tunnel. Cables with different characteristics are simulated and tested at transverse and oblique wind incidences.;The model cables are successful in reproducing full-scale behaviour of transmission lines. The results obtained demonstrate the effect of turbulence in the dynamic response. Resonant response can be important in the total response depending on the characteristics of the structure and of the wind flow. Aerodynamic damping plays an important role in the dynamic behaviour of the cables. Correlation and coherence between cable forces were found to diminish with increasing separation between cables.;Secondly, using a theoretical approach, the design procedure for the establishment of wind loading on transmission towers is reviewed and current procedures, such as Davenport's Gust Response Factor (GRF), are compared with the statistical method using influence lines (SIL), which is considered more realistic.;Peak loads calculated using SIL were larger than peak loads given by the GRF and by a typical Utility Company method by about 20% to 30%. It is found that the dynamic response of transmission structures is strongly dependent on the turbulence intensity level and is sensitive to the structures' design parameters. For members in which there is reversal in the member forces depending on the load position, the resonant response in the second mode of vibration was bigger, even by four to five times, than the corresponding one in the first mode. This may lead to fatigue problems.
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