Antonov N.A.
Antonov N.A.

Antonov N.A.
канд. техн. наук, АО «Атомэнергопроект» (г. Москва)


Publications

Site Response Analysis for “Side” Soil Profiles
Issue: №1 2020
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The authors suggest a new procedure of Site Response Analysis (SRA) for the so-called “side” (or additional) soil profiles – Low Boundary (LB) and Upper Boundary (UB). Standards require the analyses of these profiles in addition to the Best Estimate profile (BE) to account for the uncertainty in the input data about soil properties. The authors suggest stopping using the same input time history for all three profiles as a control motion at the surface, because it corresponds to the different physical seismic excitations coming form the depth. This is not in line with the ideology of Standards. Instead the authors suggest using the same time history as a control motion at the outcropped surface of the underlying half-space. This is also not completely correct, because for these three profiles (BE, UB and LB) the underlying half-spaces are also different. However, due to the physical considerations if all half-spaces are stiff enough, the error should not be so important. The effect of the 
proposed change is demonstrated on a particular site. The changes in the velocity and damping profiles have proved to be negligible, but the difference in the resulting response spectra at the outcropped surface of the foundation mat has proved to be significant. Generally, the response spectra for the “side” profiles came closer to spectrum for the BE profile. This result reflects the real world logic.

Modal Damping Considering Soil Foundation
Issue:
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The simplest soil-structure platform model is considered in the paper. Soil foundation is modeled by six pairs of springs and viscous dampers. Impact of these soil dampers on the modal damping values is calculated by various methods and compared. First modal damping is calculated by direct approach, adding the contribution of the soil dampers to the modal damping value calculated for stand-alone structure model. Then alternative calculation is carried out using the substitution of the viscous damping by certain material damping — this approach makes it easy to obtain total modal composite damping for the further dynamic analysis. However it is demonstrated that for the first natural modes the alternative approach means the underestimation of modal damping, leading to the non-conservative results.