Seismic vulnerability assessment to slight damage based on experimental modal parameters

Abstract

International audienceThe aim of this paper is to adjust behaviour models for each class of structure for vulnerability assessment by using ambient vibration. A simple model based on frequencies, mode shapes and damping, taken from ambient vibrations, allows computation of the response of the structures and comparison of inter-storey drifts with the limits found in the literature for the slight damage grade, considered here as the limit of elastic behaviour. Two complete methodologies for building fragility curves are proposed: (1) using a multi-degree of freedom system including higher modes and full seismic ground motion, (2) using a single-degree of freedom model considering the fundamental mode f0 of the structure and ground motion displacement response spectra SD(f0). These two methods were applied to the city of Grenoble, where 60 buildings were studied. Fragility curves for slight damage were derived for the various masonry and reinforced concrete classes of buildings. A site-specific earthquake scenario, taking into account local site conditions, was considered, corresponding to an ML=5.5 earthquake at a distance of 15km. The results show the benefits of using experimental models to reduce variability of the slight damage fragility curve. Moreover, by introducing the experimental modal model of the buildings, it is possible to improve seismic risk assessment at an overall scale (the city) or a local scale (the building) for the first damage grade (slight damage). This level of damage, of great interest for moderate seismic prone regions, may contribute to the seismic loss assessment

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

“…Overtones of bending modes close to 3Hz and 5Hz were also observed, as well as a torsion mode close to 1Hz. All these values were also observed by Michel et al (2011) using extensive modal analysis, with multi-channels recordings. Herein, only the fundamental mode was used to test the RDT.…”

“…In order to confirm the relevancy of RDT for long-term monitoring, two other buildings were tested ( The city hall building (CHB), fully described in Michel et al ( , 2011, is a 13-storey RC building (Fig. 2b), built in 1967 (LxTxH=44x13x52m).…”

“…Frequency and damping are then key parameters for earthquake design and seismic vulnerability assessment since, as mentioned by Spence et al (2003), the adjustment of structural models must assume a large set of unknown parameters influencing the response of existing buildings. Knowing frequency and damping can reduce the range of errors and epistemic uncertainties for representing the vulnerability as fragility curves (Michel et al, 2011).…”

Evaluating seismic retrofitting efficiency through ambient vibration tests and analytical models

“…Ambient vibration measurements have been found to carry valuable information on the linear elastic range of dynamic response [1]. Therefore, ambient vibrations constitute an effective source of structural data to assess the efficiency of seismic retrofitting of buildings [2].…”

Seismic response of an 8-story RC-building from ambient vibration analysis

“…Operational Modal Analysis (OMA) is generally preferred to forced vibration measurements due to the fact that the same modal parameters can be obtained from vibration data in operational rather than laboratory conditions (Reynders, 2012). There are several studies that have used ambient vibration testing for the identification of the dynamic behavior of civil engineering structures (Brownjohn, 2003;Ventura et al, 2003), finite element calibration and updating (Teughels, 2003;Jaishi and Ren, 2005), vulnerability assessment (Guéguen et al, 2007;Michel et al, 2008;Michel et al, 2012) and damage detection (Peeters, 2000).…”