Time‐wave velocity analysis for early earthquake damage detection in buildings: application to a damaged full‐scale RC building

Abstract

Summary An algorithm for time velocity analysis of building response is presented, which identifies the wave velocity of vertically propagating waves through the building and detects their changes. The algorithm is intended for use in SHM systems for rapid assessment of the structural health and integrity following an earthquake. The velocities are identified by an interferometric algorithm, which involves least squares fit of pulses in impulse response functions. An important feature of this method is that it is not sensitive to the effects of soil–structure interaction. The algorithm is applied to a 12‐story RC building in Los Angeles, lightly damaged by the San Fernando 1971 earthquake. The results of the time velocity analysis are critically compared with results of analysis of input power, interstory drift, and instantaneous frequency. The identified average vertical wave velocity was initially ~140 m/s for the NS and ~110 m/s for the EW response and reduced by ~26% and 32%, respectively. The detected reduction of the fundamental frequency of vibration was larger (~44% for the NS and 48% for the EW response). The difference is interpreted to be due to softening of the soil–foundation system, to which the identified frequency of vibration is sensitive. The change was larger in the lower half of the building (~31% for the NS and ~37% for the EW response) as compared with the upper half (~24% for the NS and ~27% for the EW response), consistent with the observed damage. Copyright © 2015 John Wiley & Sons, Ltd.

Detection thresholds in structural health monitoring

“…Those estimates appear to be robust and are realistic for all buildings for which such 1-D modeling is possible, and where earthquake damage has been documented and can be used to verify the modeling assumptions. However, more-detailed building models can and do provide more accurate estimates of changes in f 1 [90,94,75,76,[77][78][79]28,29]. Buildings with large plan dimensions relative to their height will require two-and occasionally threedimensional models, preferably with anisotropic properties.…”

A new full‐scale testbed for structural health monitoring and soil–structure interaction studies: Kunming 48‐story office building in Yunnan province, China

“…After small or distant earthquakes, the loss of stiffness due to structural degradation with time can be determined . Finally, in case of damage, the observed changes in damage‐sensitive parameters can be related to levels of observed damage . The dense sensor deployment in the basement and the borehole sensors will enable testing the validity of various assumptions made in the prediction of the seismic behavior of building foundations and soil–structure systems, in general.…”

“…For example, one can study how basements and foundations deform during the passage of seismic waves and how pile foundations respond during earthquakes . Equipment considered to be added are two dynamic global navigation satellite system receivers (base and rover), which would enable measuring residual deformation in the structure and rotational sensors …”

Structural damage detection using Bayesian inference and seismic interferometry

“…As the changes in the wave travel time between two observation locations only depend on the changes in the physical properties of the connecting medium, wave methods are considered to be more sensitive to local changes . However, wave‐based monitoring methods generally assume 1D wave propagation within the building and have its own limitations and challenges . For more in‐depth damage diagnosis, these macroscale dynamical features can be further coupled with computational models through successful implementation of finite element model (FEM) updating schemes when design information about the structure is available (e.g., materials, topology, and connection types) .…”