Abstract
A structural health monitoring (SHM) system was developed to study the ambient response of monopole communication structures in the UK operated by Arqiva Ltd. The exercise had several purposes that included the evaluation of the SHM system itself and the system identification procedures applied to the data, followed by analysis of the evaluated modal properties to validate the current analytical models, structural assessments and standardised design procedures advising on dynamics actions. This paper describes the instrumentation and procedures used during monitoring of a lightweight flexible 14.5 m tubular tapered monopole supporting an array of mobile telecoms antennas. A Bayesian OMA (BAYOMA) approach is implemented to identify structural modal properties under different time windows as comparison for further assessments. Results from stochastic subspace identification are also obtained and compared. The correlation between modal properties and monitoring wind-response data reveals specific tendencies such as nonlinear stiffness behaviour, the existence of aerodynamic damping and typical directionality of the mode shapes with future implications for reformulation of current methods of assessing dynamics on monopole.
Highlights
Due to requirements for new fifth generation of mobile telecoms (5G), structures for mounting antenna equipment at height need to be optimised to sustain the increased loads
For this purpose and to improve current approaches, the present paper introduces modal identification procedures to identify and explain dynamic load/response mechanisms
In the case of the monopole studies, Bayesian operational modal analysis (OMA) (BAYOMA) applied to Tfr = 10 min time frames is shown to be advantageous because it provides means and variances of all modal parameters (MPs), including mode shapes and the power spectral density matrix of modal forces along the whole range of amplitudes found during the monitoring
Summary
Due to requirements for new fifth generation of mobile telecoms (5G), structures for mounting antenna equipment at height need to be optimised to sustain the increased loads. New acquisition methodologies [9] based on economically viable equipment coupled with data delivery and analysis would better support decisions on structural management For this purpose and to improve current approaches, the present paper introduces modal identification procedures to identify and explain dynamic load/response mechanisms. In the case of the monopole studies, BAYOMA applied to Tfr = 10 min time frames is shown to be advantageous because it provides means and variances of all MPs, including mode shapes and the power spectral density matrix of modal forces along the whole range of amplitudes found during the monitoring This is the background to a project to install SHM system for structural diagnosis of several types of telecom structures in the existing portfolio
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