1 Structural Health Monitoring by Detection of Abrupt Changes in Response Using Wavelets : Application to a 6-story RC Building Damaged by an Earthquake by

A signal processing method for structural health monitoring is applied to detect damage in the former Imperial County Services (ICS) Building, caused by the 1979 Imperial Valley earthquake in southern California. The building response was recorded by a 13-chanel array of accelerometers, and a description of the distribution of the damage throughout the structure is available. The method is based on detecting abrupt changes in the seismic vibration response by analysis of the finest detail coefficients of a wavelet basis expansion of the recorded response. This method has been previously proven to work for numerically simulated response of simple models with postulated damage, but not for real earthquake data. The analysis in this paper critically examines the capabilities of this method to detect damage in real data. The analysis shows that most of the detected prominent abrupt changes are consistent with the spatial distribution and severity of the reported damage. Other less prominent abrupt changes can be explained by high frequency energy pulses of the input motion that propagated through the building. There are also few prominent abrupt changes that remain unexplained at this time. It is concluded that this method could provide useful information for structural health monitoring and for understanding the seismic response of structures and the occurrence of damage. Further investigations are needed of the “noise” of the method, how to distinguish those abrupt changes not caused by damage, and how to relate the magnitude of the detected abrupt changes to the level of damage.

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