Wave propagation in a seven-story reinforced concrete building: III. Damage detection via changes in wavenumbers

Abstract This paper presents low frequency wavenumbers in a seven-storey reinforced concrete building estimated from its recorded response to eleven earthquakes, one of which (1994 Northridge) caused visible structural damage, and two of which are its aftershocks. The wavenumbers, Ki,j(f), are estimated from pairs (i,j) of records at neighboring recording sites in the building, distributed vertically or horizontally. Changes in Ki,j(f) from one event to another are compared in the undamaged (lower) and in the damaged (upper) part of the building, with the aim to find whether trends in Ki,j(f) can indicate damage. The results suggest significant and permanent increase of the wavenumbers in the damaged parts for the 1994 Northridge earthquake and its aftershocks, which is not the case for the other events in the damaged parts, and for all eleven events in the undamaged parts of the building. This increase in wavenumbers in the damaged parts can be explained by reduced wave velocities through the damaged structural members, and by scattering of waves from the discontinuities created by the damage. It is concluded from this qualitative analysis that wavenumbers estimated from strong motion recordings in a building can indicate location of damage, and that it would be useful to refine further this method (extend it to higher frequencies, and add the capability to quantify the damage). However, this would require more dense strong motion instrumentation in buildings than currently available. Deployment of dense arrays in selected buildings would provide data for further work on this subject.

[1]  Rune Brincker,et al.  Vibration Based Inspection of Civil Engineering Structures , 1993 .

[2]  Mihailo D. Trifunac,et al.  On identification of Damage in Structures Via Wave Travel Times , 2001 .

[3]  Mihailo D. Trifunac,et al.  A three dimensional dislocation model for the San Fernando, California, earthquake of February 9, 1971 10F, 3T, 42R Bull. Seism. Soc. Am. V64, N1, Feb. 1974, P149–172 , 1974 .

[4]  Mihailo D. Trifunac,et al.  Wave propagation in a seven-story reinforced concrete building: II. Observed wavenumbers , 2001 .

[5]  Mihailo D. Trifunac,et al.  Wave propagation in a seven-story reinforced concrete building: I. Theoretical models , 2001 .

[6]  Mihailo D. Trifunac,et al.  Experimental evidence for flexibility of a building foundation supported by concrete friction piles , 1999 .

[7]  S. S. Ivanović,et al.  Apparent Periods of a Building. I: Fourier Analysis , 2001 .

[8]  Mihailo D. Trifunac,et al.  A note on the useable dynamic range of accelerographs recording translation 1 We dedicate this paper , 2001 .

[9]  Mihailo D. Trifunac,et al.  Evolution of accelerographs, data processing, strong motion arrays and amplitude and spatial resolution in recording strong earthquake motion ☆ , 2001 .

[10]  Thomas H. Heaton,et al.  The slip history of the 1994 Northridge, California, earthquake determined from strong-motion, teleseismic, GPS, and leveling data , 1996, Bulletin of the Seismological Society of America.

[11]  Darryll J. Pines,et al.  Detection of utility pole rot damage by measuring the reflection coefficient , 1997 .

[12]  Maria I. Todorovska,et al.  Ambient vibration tests of a seven-story reinforced concrete building in Van Nuys, California, damaged by the 1994 Northridge earthquake , 2000 .

[13]  L. Murphy,et al.  San Fernando, California, earthquake of February 9, 1971 , 1973 .

[14]  Charles R. Farrar,et al.  Damage identification and health monitoring of structural and mechanical systems from changes in their vibration characteristics: A literature review , 1996 .

[15]  Mihailo D. Trifunac,et al.  Apparent Periods of a Building. II: Time-Frequency Analysis , 2001 .

[16]  M Richardson.  DETECTION OF DAMAGE IN STRUCTURES FROM CHANGES IN THEIR DYNAMIC (MODAL) PROPERTIES - A SURVEY , 1980 .