Some Comments on the New Generation of Standards in Earthquake Engineering. Part I: General Requirements and Seismic Input. Part II: Seismic Forces in Linear-spectral Method.
Some Comments on the New Generation of Standards in Earthquake Engineering. Part I: General Requirements and Seismic Input. Part II: Seismic Forces in Linear-spectral Method.

Some Comments on the New Generation of Standards in Earthquake Engineering. Part I: General Requirements and Seismic Input. Part II: Seismic Forces in Linear-spectral Method.

Authors:  

Тяпин Александр Георгиевич Tyapin A.G.
Dr.Sci.Tech., JSC Atomenergoproject. Moscow, Russian Federation


Rubric:     Theoretical and experimental studies   
Key words: seismic input, linear spectral method, Standards in earthquake engineering, dangerous directions of the seismic excitation
Annotation:
The author gives his comments on the already started process of the revision of Russian Standards in earthquake engineering. He submits certain recommendations on the process and some recommendations of the general format of the new generation of Standards. Then the author in details discusses the seismic input in the Standards. The goal of the present text is not to give answers, but rather to stress main questions and to list the points where the authors of the future Standard will have to make a certain choice between alternatives. The author describes the alternative solutions for these choices. Some of such issues follow. The multi-level seismic input; the format of the seismic input required from seismologists, the non-exceedance level for seismic input; the location of the control point where seismic input is given. Besides, the issues of the intensity degrees and peak accelerations, the shape of the normalized response spectra, the composition of the wave fild (i.e. non-vertical seismic waves) are also discussed. Finally, the authors comments on the «dangerous directions of the seismic excitation» concept.
The author submits certain recommendations on the description of the linear-spectral analysis. Principal text is accompanied by the Comments. The author suggests the following changes. Matrix equations are introduced, as matrix calculations correspond to the current level of analysis. Mass matrix is populated (and not diagonal, as previously used). Residual mode is introduced as an alternative to the achievement of 95% total mass by the accumulation of modal masses. Seismic excitation is three-component without non-physical “dangerous directions” concept. Normalized spectra, responsibility coeffient, modifid damping coeffient are explained explicitly. Coeffient of non-linear response is applied to certain parts, and not to the whole structure. In the combination of modal responses the inter-correlation of the low-frequency modal responses is explicitly accounted for. If the suggested terms are fulfiled, the linear-spectral analysis should give the results like the time-domain analysis (provided response spectra are calculated from the actual components used in the time domain analysis). At the same time there is a certain smooth transition from the previous codes.

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