Abstract
In this paper, remote and in situ techniques to estimate the dynamic response of a building to ambient vibration are reported: data acquired through a real-aperture radar (RAR) interferometer and conventional accelerometers are analyzed. A five-story reinforced concrete housing building, which was damaged during the May 11th 2011 Lorca (Spain) earthquake, is used as a case study. The building was monitored using both types of instruments. The dynamic properties of the building are estimated first taking acceleration measurements using a set of 10 high-precision accelerometers installed on the roof of the building. Further, the displacement–time histories, recorded with the RAR device pointing to a corner of the building, are analyzed. Then, the ability and shortcomings of RAR measurements to deal with the fundamental frequencies of vibration of the structure are investigated. The advantages and limitations of from-inside (accelerometric) and from-outside (RAR) measurements are highlighted and discussed. A relevant conclusion is that, after strong earthquakes, RAR may be an interesting and useful tool, as it allows surveying the structural response of mid-rise buildings remotely, without the need to enter the structures, which may be dangerous for inspectors or technicians in cases of severely damaged buildings. Given that the instrumented building suffered significant damage, the ability of these kinds of measurements to detect damage is also discussed.
Highlights
Most guidelines for post-earthquake damage evaluation and traditional damage assessment methodologies rely essentially on expert-conducted on-site visual inspections
In this paper, remote and in situ techniques to estimate the dynamic response of a building to ambient vibration are reported: data acquired through a real-aperture radar (RAR) interferometer and conventional accelerometers are analyzed
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Summary
Most guidelines for post-earthquake damage evaluation and traditional damage assessment methodologies rely essentially on expert-conducted on-site visual inspections. The structural response clearly enhances the modal frequencies of the building, making their identification and isolation easy in the RAR recorded signals using advanced methods for signal analysis—narrow band pass Butterworth filtering, in our case This issue would be relevant if measurements were taken during strong ground motion due to great earthquakes, since the device’s base is not fixed, and the ground motion would be important. The use of RAR for the identification of fundamental frequencies in a building that suffered severe damage during the May 11th 2011 earthquake is analyzed and discussed To this end, first, the dynamic response to ambient vibrations of this building has been evaluated through a network of ten high-precision axial accelerometers. TThhee aarrrraannggeemmeenntt aanndd llooccaattiioonn ooff tthhee sseennssoorrss aarree sshhoowwnn iinn FFiigguurree 44. AA tthhiirrdd ppeeaakk,, mmiinnoorr iinn mmoosstt ooff tthhee cchhaannnneellss,, iiss ffoouunndd aatt aa ffrreeqquueennccyy ooff 33..9985. The line of sight (LOS), indicated with a red arrow, is in the T direction
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