Modeling and Analysis of Slope-Dependent Response Properties of Gas-Insulated Transmission Line System Under Vehicle-Induced Loads

Abstract

When a gas-insulated transmission line (GIL) is suspended beneath a bridge with a slope, moving vehicle loads generate both normal and tangential components acting on the supporting system, inducing coupled vibrations among the enclosure, conductors, and insulators. This paper establishes a slope-dependent dynamic model of the bridge-suspended GIL system, in which the vehicle-induced bridge vibrations are equivalently represented as dynamic forces acting on the support nodes of the GIL enclosure. The conductors are discretized using spatial Timoshenko beam elements, the enclosure is modeled with Reissner–Mindlin shell elements, and the insulators are simplified as three-dimensional elastic springs. The core structural components of the model are verified against harmonic force data, and the applicability of the model to vehicle-induced loads is discussed. Modal analysis reveals that the lower-order modes are dominated by bending deformation, while higher-order modes exhibit coupled bending–torsional patterns. Parametric studies systematically examine the effects of vehicle speed, vehicle load, insulator stiffness, and slope ratio on the displacement responses of the three-phase conductors. The results show that the vertical displacement response increases with vehicle load and speed. The axial displacement, which is negligible on horizontal bridges, becomes significant on sloped sections and poses a risk to connector integrity. The radial stiffness of insulators exhibits an adjustment effect on conductor displacement, while the axial stiffness monotonically reduces axial stress with negligible influence on flexural stress. This study provides a theoretical basis and technical guidance for the dynamic design, insulator selection, and safety assessment of bridge-suspended GIL systems, particularly for projects involving sloped bridge sections.