Damping estimation using free decays response in short telecom structures

Abstract

The constant changes to which telecommunications have accustomed us in recent decades oblige a similar adaptation in other branches of engineering. Structures such as monopoles and short lattice towers are becoming increasingly wind-sensitive and dynamically active with the introduction of 5G technology, which will require new larger and heavier antenna equipment. Expert consultants agree the need to revise the current accounting for structural damping that has not changed in design codes after more than 30 years. A complete set of full-scale field tests is presented to obtain reliable structural damping values in short communications structures. The described methodology analyses free-decaying responses obtained after excitation of the main analysed cantilevered modes in the time domain. A standardized acquisition system based on local accelerometers and an external innovative system using the Video GaugeTM system are required to obtain the desired responses, which use curve-fitting and the eigensystem realization algorithm to estimate modal properties such as the corresponding modal structural damping. The results obtained using the presented methodology agree on higher values of structural damping for both damping estimators and perfectly converge with consultant feedback, which suggested over-conservative (i.e. low) values of structural damping as compared to the conventional values used in civil engineering.