Significance of accurate seismic site class determination in structural design

Ali Nasseri-Moghaddam

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Earthquake Engineering & Geophysics

ABSTRACT: Three cases are presented in which the seismic site class is determined using shear wave velocities and the data obtained from a deep borehole. The results show that depending on the methodology used different site classes may be obtained for the site. The significance of this discrepancy is investigated through a parametric study that comprises evaluation of seismic loads on typical steel and concrete frames with different configurations using the spectral values for major Canadian metropolitans. It is observed that a small change in the geotechnical measurements or a change in the geotechnical investigation methodology may result in a step change in the estimated seismic loads on the structure. It is shown that the accuracy of the geotechnical measurements are not sufficient to warrant such sharp changes in the structural loadings. Therefore, it is recommended that the spectral site coefficients be defined based on smooth functions of subsurface shear wave velocity. This approach will avoid sharp changes in the seismic loads, which is more consistent with the level of accuracy associated with geotechnical measurements and has a better physical justification.

RÉSUMÉ: Trois études de cas sont présentées dans lesquelles la catégorie d™emplacement est déterminée sur la base de la vitesse des ondes de cisaillement Vs, et des données provenant d™un forage profond. Les résultats montrent que différentes catégories d™emplacement peuvent être obtenues selon la méthodologie utilisée. La conséquence de cet écart est étudiée à l™aide d™une analyse paramétrique qui comprend une évaluation des charges sismiques sur des cadres typiques en acier et béton, de différentes configurations, en utilisant les valeurs spectrales de villes canadiennes d™importance.

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Cite this article:
Ali Nasseri-Moghaddam (2011) Significance of accurate seismic site class determination in structural design in GEO2011. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GEO11Paper905,author = Ali Nasseri-Moghaddam ,title = Significance of accurate seismic site class determination in structural design,year = 2011}