Directional Components of a Seismic Design Accelerogram

ABSTRACT

For the tridirectional time histories for seismic analysis, current codes and standards cannot guarantee isotropy in the horizontal directions, the code formula for statistical independence between components is not rigorous, and the bounds are arbitrary. In this paper, three conditions are defined for the horizontal inputs to be isotropic. Orthogonality is proposed to replace the statistical independence for the tridirectional components. Furthermore, the importance of a proper rate of mobilization of the excitation energy of a generated time history is discussed and emphasized, and an acceptance region is proposed for practical applications.

KEYWORDS:

• Tridirectional components
• seismic time history analysis
• synthesized accelerogram
• statistical independence
• Husid plot

Additional information

Funding

The research for this paper was financially supported, by the NationalNatural Science Foundation of China (Grant number: 51939004), Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University [No. 2020003] and the Natural Sciences and Engineering Research Council of Canada [NSERC]. A scholarship under the State Scholarship Fund from the China Scholarship Council is gratefully acknowledged.