Damping estimation using free decays response in short telecom structures

Jose A Jimenez Capilla,Ying Wang,James Mark William Brownjohn

doi:10.1177/13694332211042780

Jose A Jimenez Capilla, Ying Wang + Show 1 more

Open Access

https://doi.org/10.1177/13694332211042780

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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.

Highlights

In the progressive research areas of structural dynamic engineering, such as deterioration diagnosis from fatigue, monitoring of vibration in terms of response and loading identification, and response prediction to build adequate structural assessments, numerically modelled vibration modes must agree with real behaviour of structures in terms of stiffness and damping
Since the development of the current standards of communications structures in 70–80s, more and more structural assessments have been refusing coming technologies due to a lack of structural capacity of present structures according to longstanding knowledge, and the sub-optimal approaches frequently taken to the evaluation of dynamics
This paper provides damping evaluation using full-scale data on short telecom structures in the UK

Summary

Introduction

In the progressive research areas of structural dynamic engineering, such as deterioration diagnosis from fatigue, monitoring of vibration in terms of response and loading identification, and response prediction to build adequate structural assessments, numerically modelled vibration modes must agree with real behaviour of structures in terms of stiffness and damping. Unlike natural frequencies and mode shapes, where the accuracy is high enough to be accepted, structural damping requires further research on each structure typology to provide essential knowledge for increasing the precision of predictions. Three antenna panels are installed, with a small plate antenna at 14.3 m and all necessary cables run internally. This structure is joined to the foundation through a flange plate and 12 grade 8.8 M24 bolts, without grouting.

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