HR: 1340h
AN: S53B-1265    [Abstracts]
TI: A Time-Reversed Reciprocal Method for Detecting High-frequency events in Civil Structures
AU: * Kohler, M D
EM: kohler@ess.ucla.edu
AF: Center for Embedded Networked Sensing, University of California, Los Angeles, Los Angeles, CA 90095, United States
AU: Heaton, T H
EM: heaton@caltech.edu
AF: Department of Civil Engineering, California Institute of Technology, Pasadena, CA 91125, United States
AB: A new method that uses the properties of wave propagation reciprocity and time-reversed reciprocal Green's functions is presented for identifying high-frequency events that occur within engineered structures. Wave propagation properties of a seismic source in an elastic medium are directly applicable to structural waveform data. The number of structures with dense seismic networks embedded in them is increasing, making it possible to develop new approaches to identifying failure events such as fracturing welds that take advantage of the large number of recordings. The event identification method is based on the hypothesis that a database can be compiled of pre-event, source-receiver Green's functions using experimental sources. For buildings it is assumed that the source-time excitation is a delta function, proportional to the displacement produced at the receiver site. In theory, if all the Green's functions for a structure are known for a complete set of potential failure event locations, forward modeling can be used to compute a range of displacements to identify the correct Green's functions, locations, and source times from the suite of displacements that recorded actual events. The method is applied to a 17-story, steel, moment-frame building using experimentally applied impulse-force hammer sources. The building has an embedded, 72-channel, accelerometer array that is continuously recorded by 24-bit data loggers at 100 and 500 sps. The focus of this particular application is the identification of brittle- fractured welds of beam-column connections.
DE: 7203 Body waves
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7260 Theory
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting