Modal analysis of a large-scale antenna under shock base excitation

The shock response of a large-scale antenna is investigated in this study. The antenna height is about 12 m and its material is mainly aluminium 6061. The analysis is conducted by two approaches i.e. shock response spectrum (SRS) and modal analysis. The ratio of the maximum response of the antenna under the shock excitation to its steady-state counterpart is obtained by SRS based on the pulse duration and the system’s natural characteristics. Moreover, the analysis is also performed by modal analysis in ABAQUS finite element software extracting the stress and displacement contour of the antenna structure. The results from SRS and modal analysis are in acceptable agreement. Based on the MIL-STD-810H standard, the shock distribution is considered as half-sine with 25g peak acceleration and 11 ms pulse duration. Moreover, the system’s overall critical damping is considered as 5%. Regarding the maximum stress, the antenna cannot tolerate a half-sine shock pulse with 25g peak base acceleration which is a standard value for launching systems. However, applying a lower standard value i.e. 16g, is in the safe region with a safety factor of 2.3.