A comparison of intensity‐based demand distributions and the seismic demand hazard for seismic performance assessment

SUMMARY This paper compares the seismic demands obtained from an intensity-based assessment, as conventionally considered in seismic design guidelines, with the seismic demand hazard. Intensity-based assessments utilize the distribution of seismic demand from ground motions that have a specific value of some conditioning intensity measure, and the mean of this distribution is conventionally used in design verification. The seismic demand hazard provides the rate of exceedance of various seismic demand values and is obtained by integrating the distribution of seismic demand at multiple intensity levels with the seismic hazard curve. The seismic demand hazard is a more robust metric for quantifying seismic performance, because seismic demands from an intensity-based assessment: (i) are not unique, with different values obtained using different conditioning intensity measures; and (ii) do not consider the possibility that demand values could be exceeded from different intensity ground motions. Empirical results, for a bridge-foundation-soil system, illustrate that the mean seismic demand from an intensity-based assessment almost always underestimates the demand hazard value for the exceedance rate considered, on average by 17% and with a large variability. Furthermore, modification factors based on approximate theory are found to be unreliable. Adopting the maximum of the mean values from multiple intensity-based assessments, with different conditional intensity measures, provides a less biased prediction of the seismic demand hazard value, but with still a large variability, and a proportional increase the required number of analyses. For an equivalent number of analyses, direct computation of the seismic demand hazard is a more logical choice and provides additional performance insight. Copyright © 2013 John Wiley & Sons, Ltd.

[1]  B. Bradley,et al.  Error estimation of closed‐form solution for annual rate of structural collapse , 2008 .

[2]  Julian J. Bommer,et al.  Hazard-consistent earthquake scenarios , 2000 .

[3]  Brendon A. Bradley,et al.  Improved seismic hazard model with application to probabilistic seismic demand analysis , 2007 .

[4]  J. Baker,et al.  Spectral shape, epsilon and record selection , 2006 .

[5]  Eduardo Miranda,et al.  FRAGILITY ASSESSMENT OF SLAB-COLUMN CONNECTIONS IN EXISTING NON-DUCTILE REINFORCED CONCRETE BUILDINGS , 2005 .

[6]  Robin K. McGuire,et al.  Probabilistic seismic hazard analysis: Early history , 2008 .

[7]  William T. Holmes,et al.  The 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures , 2000 .

[8]  Gokhan Saygili,et al.  Probabilistic Seismic Hazard Analysis for the Sliding Displacement of Slopes: Scalar and Vector Approaches , 2008 .

[9]  Misko Cubrinovski,et al.  EFFECTIVE STRESS ANALYSIS OF PILES IN LIQUEFIABLE SOIL: A CASE STUDY OF A BRIDGE FOUNDATION , 2008 .

[10]  Nicolas Luco,et al.  Probabilistic seismic demand analysis using advanced ground motion intensity measures , 2007 .

[11]  Jack W. Baker,et al.  Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses | NIST , 2011 .

[12]  Carlos Marcelo Ramirez.  Building-specific loss estimation methods & tools for simplified performance-based earthquake engineering , 2009 .

[13]  Brendon A. Bradley,et al.  Probabilistic seismic performance and loss assessment of a bridge-foundation-soil system , 2010 .

[14]  Brendon A. Bradley,et al.  Prediction of spatially distributed seismic demands in specific structures: Ground motion and structural response , 2009 .

[15]  Steven L. Kramer,et al.  Ground Motion Intensity Measures for Liquefaction Hazard Evaluation , 2006 .

[16]  B. Bradley.  A generalized conditional intensity measure approach and holistic ground‐motion selection , 2010 .

[17]  Brendon A. Bradley.  The seismic demand hazard and importance of the conditioning intensity measure , 2012 .

[18]  B. Bradley.  Design Seismic Demands from Seismic Response Analyses: A Probability-Based Approach , 2011 .

[19]  Jack W. Baker,et al.  Conditional Mean Spectrum: Tool for Ground-Motion Selection , 2011 .

[20]  B. Bradley.  A ground motion selection algorithm based on the generalized conditional intensity measure approach , 2012 .

[21]  Brendon A. Bradley,et al.  Prediction of spatially distributed seismic demands in specific structures: Structural response to loss estimation , 2009 .

[22]  R. Mcguire.  Probabilistic seismic hazard analysis and design earthquakes: Closing the loop , 1995, Bulletin of the Seismological Society of America.

[23]  Eduardo Miranda,et al.  Probability-based seismic response analysis , 2005 .

[24]  Brendon A. Bradley,et al.  Practice‐oriented estimation of the seismic demand hazard using ground motions at few intensity levels , 2013 .