The Analysis of Long‐Term Frequency and Damping Wandering in Buildings Using the Random Decrement Technique

Abstract

The characterization and monitoring of buildings is an issue that has attracted the interest of many sectors over the last two decades. With the increasing use of permanent, continuous and real-time networks, ambient vibrations can provide a simple tool for the identification of dynamic building parameters. This study is focused on the long-term variation of frequency and damping in several buildings, using the Random Decrement Technique (RDT). RDT provides a fast, robust and accurate long-term analysis and improves the reliability of frequency and damping measurements for structural health monitoring. This reveals particularly useful information in finding out precisely how far changes in modal parameters can be related to changes in physical properties. This paper highlights the reversible changes of the structure's dynamic parameters, correlated with external forces, such as temperature and exposure to the sun. Contrasting behaviors are observed, including correlation and anti-correlation with temperature variations.

Experimental and Numerical Evidence of the Clustering Effect of Structures on Their Response during an Earthquake: A Case Study of Three Identical Towers in the City of Grenoble, France

“…In particular, ambient vibration-based methods have been applied to the towers to evaluate their modal response (Mikael et al, 2013;Valla et al, 2014). Two approaches have been applied, the first consisting in computing the Fourier spectrum of ambient vibrations recorded at the top of the building in the transverse (T) and longitudinal (L) directions; the second by applying frequency domain decomposition (FDD, Brincker et al, 2001) with ambient vibrations recorded on 15 different floors in MB to identify the modal shapes linked to each modal frequency.…”

“…The first two modes for the north-south direction, numerically calculated, are 0.75 and 2.65 Hz, whereas for east-west, they are 0.5 and 2.1 Hz. Building damping (Mikael et al, 2013;Valla et al, 2014) translates into a quality factor Q 10 corresponding to an equivalent critical damping equal to 5%.…”

Effect of Environmental Conditions on the Modal Response of a 10‐Story Reinforced Concrete Tower

“…Faravelli et al [33] analysed the daily fluctuations of frequencies of the Guangzhou New TV Tower (600 m high) in China observing that also ambient temperature variations of few degree Celsius may induce variations in the structural frequencies, up to 0.5%. Mikael et al [34] focused on the long-term variation of frequency and damping ratios in several buildings and reported contrasting behaviours, including direct and inverse correlation with temperature variations. More recently, Wu et al [35] presented results of the continuous dynamic monitoring of an office building using ambient vibration measurements in conjunction with a recently developed stochastic subspace identification methodology.…”

System Identification of Tunnel Response to Ground Motion Considering a Simplified Model

“…In the first case, the fundamental behavior is evaluated by involving solely collected data (Celebi, 2007;Mikael et al, 2013;Saaed Alqado et al, 2015;Loh and Chen, 2017). This can be seen as a "black-box" approach, where the supporting framework does not allow clear explanation of the observed results.…”