Detection of Building Damage Using Helmholtz Tomography
High‐rise buildings with dense permanent installations of continuously recording accelerometers offer a unique opportunity to observe temporal and spatial variations in the propagation properties of seismic waves. When precise, floor‐by‐floor measurements of frequency‐dependent travel times can be made, accurate models of material properties (e.g., stiffness or rigidity) can be determined using seismic tomographic imaging techniques. By measuring changes in the material properties, damage to the structure can be detected and localized after shaking events such as earthquakes. Here, seismic Helmholtz tomography is applied to simulated waveform data from a high‐rise building, and its feasibility is demonstrated. A 52‐story dual system building—braced‐frame core surrounded by an outrigger steel moment frame—in downtown Los Angeles is used for the computational basis. It is part of the Community Seismic Network and has a three‐component accelerometer installed on every floor. A finite‐element model of the building based on structural drawings is used for the computation of synthetic seismograms for 60 damage scenarios in which the stiffness of the building is perturbed in different locations across both adjacent and distributed floors and to varying degrees. The dynamic analysis loading function is a Gaussian pulse applied to the lowest level fixed boundary condition, producing a broadband response on all floors. After narrowband filtering the synthetic seismograms and measuring the maximum amplitude, the frequency‐dependent travel times and differential travel times are computed. The travel‐time and amplitude measurements are converted to shear‐wave velocity at each floor via the Helmholtz wave equation whose solutions can be used to track perturbations to wavefronts through densely sampled wavefields. These results provide validation of the method's application to recorded data from real buildings to detect and locate structural damage using earthquake, explosion, or ambient seismic noise data in near‐real time.
Additional Information© 2018 Seismological Society of America. Manuscript received 25 October 2017; Published Online 7 August 2018. Data and Resources: The dynamic analysis ETABS output data are available upon request by emailing firstname.lastname@example.org. ETABS software is distributed by Structural and Earthquake Engineering Software, Computers and Structures, Inc., Berkeley, California (http://www.csiberkeley.com; http://docs.csiamerica.com/manuals/etabs/Analysis%20Reference.pdf, last accessed July 2018). Center for Engineering Strong Motion Data, available at http://www.strongmotioncenter.org (last accessed January 2018). The authors thank the Terrestrial Hazard Observation and Reporting (THOR) Center at Caltech and the Divisions of Geological and Planetary Science, and Engineering and Applied Science at Caltech for funding research connected with the Community Seismic Network. A. A. and F. L. were supported by National Science Foundation (NSF) Grant CyberSEES‐1442665 and the King Abdullah University of Science and Technology (KAUST) under Award OCRF‐2014‐CRG3‐2300. The authors are grateful to Nori Nakata and German Prieto for their thoughtful and careful reviews of this article.
Accepted Version - BSSA-2017322.pdf
Supplemental Material - 2017306_esupp.zip