Enveloped Seismic Excitation for Similar Buildings in Different Soil and Seismic Environments: from Six Analyses to Two Analyses. Part II. Internal Forces in the Structure

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Rubric:     Theoretical and experimental studies   
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One often has to analyze similar structures in different soil and seismic environments. Some time ago the author suggested enveloping seismic responses at the rigid basement in order to analyze the upper structure only once using «enveloped» excitation. However, it turned out that correlation between different components of base motion is lost during the synthesis of «enveloped» components matching «enveloped» spectra. This effect forced to move from the simultaneous application of all six «enveloped» components to the application of these components one by one. Thus, one has to perform six analyses instead of a single one – substantial loss of resources. Here the author suggests performing only two analyses instead of six ones, with simultaneous application of those components which can be considered statistically independent: three translational components and separately three rotational components. The results should be added to each other, which mean the full correlation. In the first part of this paper the author proved the suggested approach for in-structure response spectra. In the second part the author applies the same approach to the analysis of the internal forces in the structure.