In situ measurement of resonant frequencies of a large cylindrical pier of a major telescope

This study addresses the critical need for cost-effective in-situ dynamic validation of large telescope piers, which must exhibit high stiffness to protect astronomical imaging from disruptive vibrations. The DAG Telescope pier was tested using a minimal protocol: impact hammer excitation and response monitoring with only two accelerometers. Operational modal analysis (OMA) of the data, consistent across multiple tests, identified all resonant frequencies to be well above the design threshold, with the fundamental mode at 76 Hz-an order of magnitude higher than the required 8 Hz. This confirms the pier's exceptional rigidity and compliance with performance criteria. Furthermore, discrepancies with finite element model predictions highlighted the influence of foundation flexibility, an often-overlooked factor. The core novelty of this work is multifaceted: it presents, to the authors' knowledge, the first published study to directly measure the resonant properties of a major telescope pier prior to telescope integration, providing a crucial baseline for future monitoring and model updating, and it validates a rigorous, low-cost methodology that offers a practical framework for assessing critical infrastructure in resource-constrained settings.

Journal

JOURNAL OF CIVIL STRUCTURAL HEALTH MONITORING

Year

2026

Volume

16

Issue

2

ISSN

2190-5452

eISSN

2190-5479

DOI

10.1007/s13349-025-01046-1

WoS UID

WOS:001688900300010