DYNAMIC ANALYSIS OF GUYED MASTS USING THE STIFFNESS METHOD

Abstract

The Global System of Mobile Communication GSM revolution in Nigeria has resulted in an increased usage of communication towers and masts. However, observation has shown that most of the towers being used in the industry presently are the free-standing type. It will be necessary to investigate the suitability of guyed masts in the mounting of antennae for the GSM services in Nigeria.

This paper presents an investigation into the dynamic analysis of multi-level guyed masts using the stiffness method. The displacements and reactions of the masts are obtained from a linear dynamic analysis of the structure based on the stiffness method. The mast shaft and guy rope problems solved separately, forcing compatibility of displacements at the points of guy attachment. The model is then used to analyse a 60m two-level guyed mast at wind speeds of are 80km/h, 160km/h and 240km/h in the positive X-direction.

Results show that the bending moment values for the mast shaft at the third node points decrease gradually between zero and 3 seconds elapsed time, thereafter increase sharply.

The axial forces on the shaft also decrease gradually from a peak value at about 0.2 seconds elapsed time to a minimum value at about 3.0 seconds, increasing sharply thereafter.