Info Effects of bolt joint loosening on the dynamic characteristics of electric angle steel transmission tower

Abstract

Transmission towers, serving as the support structure of transmission lines, are significant for the functionality of an electric transmission system. Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers. In this study, the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern. First, the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation, based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints. Taking a 220-kV angle steel transmission tower as the object, the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed. The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower. In addition, the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases. In the case of double joints loosening simultaneously, the loosening of nondominant joints has nonnegligible effects on the tower as well.