Effect of Soil–Structure Interaction on Free Vibration Characteristics of Antenna Structure

Abstract

The influence of soil-structure interaction in the Natural Frequency of a parabolic reflector antenna is investigated. The main free vibration characteristic of an antenna is natural frequency. The analysis model simulated with fixed base condition and soil structure interaction. A parametric study is conducted to understand the antenna structure soil behavior (soil structure interaction (SSI)) by changing the antenna orientation, soil properties with impedance functions (spring constants) as per ASCE 4-16 and 3D (three dimensional modeling of founding medium) model methods. To address this problem, Finite Element Method is used to model soil structure interaction analysis of antenna structure with foundation by MSC PATRAN & NASTRAN using direct method and impedance method. The soil considered as homogeneous and analyzed for shear wave velocity (Vs) 100 m/s, 180 m/s, 250 m/s, 450 m/s, 760 m/s for antenna with 90° elevation. To study the embedment effect, soil around the footing and pedestal is considered. The frequency results are compared for antenna with four orientations with Vs 100 m/s soil properties. Considerable reduction in frequency observed with soil structure interaction in higher modes. Soil structure interaction study in antennas helps in finding what extent the natural frequency falls when the soil interaction is incorporated in the model.