1 / 13

BSSC Annual Meeting/Workshop – January 20, 2010

Potential Topics for Issues Team Study: Ground Motion Selection and Scaling for Response History Analysis Curt B. Haselton, PhD, PE California State University, Chico Presented on Behalf of the PEER Ground Motion Selection and Modification Program (PEER GMSM).

powa
Download Presentation

BSSC Annual Meeting/Workshop – January 20, 2010

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Potential Topics for Issues Team Study: Ground Motion Selection and Scaling for Response History Analysis Curt B. Haselton, PhD, PECalifornia State University, ChicoPresented on Behalf of the PEER Ground Motion Selection and Modification Program (PEER GMSM) BSSC Annual Meeting/Workshop – January 20, 2010

  2. Acknowledgments • The following PEER GMSM members contributed directly to the concepts of this presentation: • Jack Baker, Stanford University • Jon Stewart, University of California, Los Angeles • Christine Goulet, URS • Farzin Zareian, University of California, Irvine

  3. Some Issues with Using Current ASCE7 Method • Target Spectrum: Selection/scaling based on the Uniform Hazard Spectrum (UHS) can be very conservative in some cases. • Near-fault: For a near-fault site, NEHRP/ASCE7 gives little guidance for how to address directivity and pulse-like motions. • Maximum Direction Motion: Methods for selection/scaling based on the maximum direction motion could use more study. • Consistency: Two sets of ground motions selected by two different people will often not result in the same structural responses. • Non-recorded motions: Little validation/study has been done on: • Defining an “appropriate simulated ground motion.” • Guidelines for spectrum matched ground motions. NEHRP/ASCE7 Research and Guidance Documents (e.g. ATC)

  4. 1. Target Spectrum • Ground motions are currently scaled based on a uniform hazard spectrum. • Let’s quickly review what this means….

  5. 1. Target Spectrum Source: PEER GMSM (2009)

  6. 1. Target Spectrum UHS Source: PEER GMSM (2009)

  7. 1. Target Spectrum UHS Scenario Spectrum Source: PEER GMSM (2009)

  8. 1. Target Spectrum Source: PEER GMSM (2009)

  9. 1. Target Spectrum • Possible target spectra: • UHS: Envelopes the MCE Sa values at all periods simultaneously. • Scenario spectrum: Expected spectrum for an MCE at a single period. • Recent research has shown than in extreme cases, the drifts responses can be 30-40% different depending on which target is used. • Before including any changes in the NEHRP Provisions, the use of scenario spectra needs to be more fully vetted. • Recent research has shown that using a single scenario spectrum (anchored at the first mode period of the building) works well for: • Frames and walls from 4 to 20 stories • Prediction of the maximum interstory drift ratio

  10. 1. Target Spectrum • Further vetting/study is needed for: • Taller and more complex buildings (with more higher mode effects). • A more complete set of structural responses (element forces, element deformation demands, etc.). • Implementation questions to be answered: • Best manner to include this in NEHRP/ASCE7: • Fully codified scenario spectra (e.g. implemented on USGS website). • Not fully codified, but modify language to allow use of scenario spectra (perhaps better). • Specific guidelines needed for use of scenario spectra: • When should we use more than one scenario spectrum? • Which period(s) should we anchor the spectrum at? • Etc.

  11. 2. Near-Fault Ground Motions Observations from previous earthquakes: 1979 Imperial Valley 1992 Landers Source: Baker and Shahi, 2009 PEER Annual Meeting

  12. 2. Near-Fault Ground Motions • Issues: • The current ASCE7 approach does not explicitly address pulse-type motions (though 2009 NEHRP has new language for orientation of motions). • Pulse-type motions are observed in the near-fault region, but not always. • The treatment of pulse-type motions in the record set could have large impacts on the predicted structural responses. • Question: Should directivity be explicitly addressed in NEHRP/ASCE7, or should like be left to research and guidance documents? • If this is to be addressed in NEHRP/ASCE7: • Under what circumstances should pulse-type motions be included in the record set? • How should the target spectrum be modified to consider pulse-type motions? • What percentage of the motions should have pulses? • Should there be a requirement on the periods of the pulses?

  13. Summary and Closing • Possible topics for in-depth issue team study: • How to allow the use of a scenario spectrum instead of the uniform hazard spectrum. • How to provide more guidance on selection/scaling for near-fault sites (if this should be done directly in NEHRP/ASCE7). • Closing: • Thank you for your attention. • Questions/comments? • chaselton@csuchico.edu

More Related