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Design Ground Motion Library (DGML) – Tool for Selecting Time History Records for Specific Engineering Applications (Abstract)

by Robert Youngs, M. Power, G. Wang, F. Makdisi and C.-C. Chin

Youngs, Robert, M. Power, G. Wang, F. Makdisi, C.-C. Chin (2007). Design Ground Motion Library (DGML) – Tool for Selecting Time History Records for Specific Engineering Applications (Abstract).SMIP07 Seminar on Utilization of Strong-Motion Data, p. 109 - 110.

Abstract

The Design Ground Motion Library (DGML) is a software package for searching for ground motion time histories suitable for use by engineering practitioners for the time history dynamic analysis of various facility types in California and other parts of the western United States. The DGML was developed in a project funded jointly by the California Geological Survey-Strong Motion Instrumentation Program (CGS-SMIP) and the Pacific Earthquake Engineering Research Center-Lifelines Program (PEER-LL). The project was carried out by a multidisciplinary project team of practitioners and researchers in structural engineering, geotechnical engineering, and seismology. Currently, the DGML is limited to recorded time histories from shallow crustal earthquakes of the type that occur in California and other parts of the western United States. The software package includes a database of ground motion records and a software tool for selecting, scaling, and evaluating time histories for applications. The DGML is currently on a DVD, and consideration is being given to converting the DGML to internet web-based usage. The ground motion database used in the DGML consists of the PEER-NGA data base created for the Next Generation of Attenuation (NGA) relationships project. The database includes time histories from CGS-SMIP, U.S. Geological Survey (USGS), and other reliable sources including selected record sets from international sources. The DGML is documented and supported by a Users Manual and a report.

The DGML has the broad capability to search for ground motion time history records on the basis of (1) the response spectral shape of the records in comparison to design or target response spectra and (2) other characteristics of the records. Ground motion response spectral shape over a period range significant to structural response has been found to be closely correlated to inelastic structural response in a number of research studies. The period range of significance may include periods shorter than the fundamental structure period because of higher mode effects and periods longer than the fundamental structure period because of structure softening during inelastic response. Accordingly, a key capability of the DGML software tool is searching for and ranking time history records on the basis of the degree of match of the response spectral shapes of the time histories with design or target spectra over a user-specified period range. To support this capability, the software tool can construct design or target spectra using different approaches.

Other criteria are also specified by the user in constraining searches for ground motion time history records. These search criteria include: parameters for earthquakes that produced the ground motion records (ranges of earthquake magnitude, type of faulting); ranges of earthquake source-to-site distance for records; recording station site conditions (characterized by ranges of site shear wave velocity in the upper 30 meters, Vs30); ranges of significant duration for records; presence of pulses in near-fault records; direction of horizontal component of records (fault-strike-normal (FN) direction, fault-strike-parallel (FP) direction, either FN or FP direction, or two-component pairs in FN and FP directions); maximum number of records to search for; and ranges of acceptable scaling factors for scaling records to the level of the target spectrum.

The software tool includes a graphic interface for data input, processing, and plotting of target response spectra, spectra of individual or multiple time histories, and average spectra for selected time histories. In addition, acceleration, velocity, and displacement time histories can be plotted for the selected time histories.