Non-parametric analysis of a single seismometric recording to obtain building dynamic parameters

Abstract

We propose a simple time-domain, non-parametric method to estimate the damping at the fundamental frequency of a building. The method aims at obtaining quick-and-dirty data on large sets of buildings, at the expenses of the accuracy provided by other, more complex and resource-demanding techniques. The analysis of a 10 min recording of ambient vibration with a single high-resolution seismometer atop the building can provide a good estimate of the required parameters for the first flexural modes on orthogonal components. The proposed methodology does not require complex filtering and assumptions on signal structure, nor multiple measurement points or clear single transients induced by shakers, shocks or release tests. We checked the stability of the proposed method in terms of duration and characteristics of the signal, and compared the results obtained by others with standard techniques. Then, we tested the ability of the proposed technique to identify damping and frequency variations due to large displacements, damage or changes in the structural characteristics. The proposed methodology provides a satisfactory agreement when compared with other techniques. Even if it is not always possible to obtain higher modes, the advantage is that it is possible to study with limited resources the fundamental parameters for a large number of buildings. This is useful to include experimental data on building behaviour in microzonation studies.

Keywords

• damping
• fundamental mode
• singledegree-of-freedom
• ambient vibration