Effect of Seismic Wave Incoherence on Ssi Response of Us Epr Epgb (original) (raw)
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2007
The paper illustrates the effects of ground motion incoherency on seismic SSI responses of a typical axisymmetric nuclear reactor building and two industrial buildings with significant mass eccentricities. To incorporate the motion incoherency effects on SSI response we used both stochastic and deterministic approaches (Ghiocel, 2005, 2006, Ostadan, 2005, 2006, Ostadan and Ghiocel, 2007). In this study two the plane-wave coherency models are used: i) the Luco-Wong coherency model (Luco and Wong, 1986) and, ii) the Abrahamson incoherency model (Abrahamson, 2005). The motion incoherency approaches are comparatively applied for coherent and incoherent seismic input motions to illustrate the effects of motion incoherency on SSI response. The SSI coupling responses of structures are primarily examined to illustrate the additional rocking and torsional motion effects due to the motion incoherency. The SSI results in terms of transfer functions, acceleration response spectra and structural...
2020
The paper illustrates the effects of ground motion incoherency on seismic SSI responses of a typical axisymmetric nuclear reactor building and two industrial buildings with significant mass eccentricities. To incorporate the motion incoherency effects on SSI response we used both stochastic and deterministic approaches SEISMIC MOTION INCOHERENCY MODELING Assuming that the seismic wave field, U, can be modeled by a plane wave motion, the cross-spectral density of motion stochastic field for two points i and k, can be expressed by where is the cross-spectral density function for point motions Ui and Uk, and , j = i,k is the auto-spectral density for location point j. Inversely, from equation (1), the coherence between the two arbitrary motions can be derived as a complex function of frequency: The coherence is a measure of the similarity of the two point motions, including both the amplitude spatial variation and the wave passage effects. There are several ways of describing motion in...
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This paper presents a case study that illustrates the soil-structure interaction (SSI) effects on the seismic response of reactor building (RB) structures at a rock site in the Eastern US with input ground motion that is characterized with high frequency content and high peak ground acceleration (PGA). The study includes the site-specific SSI effects of 40 ft thick embedment backfill soil and the effects of seismic motion incoherency on the structural response at high frequencies. The responses obtained from these site-specific analyses are compared with results of a set of site-independent analyses that envelope the response of the R/B structures at a wide range of sites characterized with seismic ground motion with frequency content similar to the US NRC RG 1.60 and PGA of 0.3 g and serve as basis for standard design of these structures. The focus of the study is on the results of the SSI analyses that define the sitespecific demands for seismic design of the building structural m...
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This paper presents a case study of the soil-structure interaction (SSI) effects on the seismic response of reactor containment and reactor building (RB Complex) structures at a rock site in the Eastern US with input ground motion that is characterized with high frequency content and high peak ground acceleration (PGA). The study includes the effects of 40 ft thick embedment backfill soil on the SSI response and the effects of seismic motion incoherency on the structural response at high frequencies. The responses obtained from these site-specific SSI analyses are compared with results of a set of site-independent SSI analyses that envelope the response of the R/B Complex structures at a wide range of sites characterized with seismic ground motion with frequency content similar to the US NRC RG 1.60 and PGA of 0.3 g. The focus of the study is on the responses obtained from the SSI analyses that serve as basis for defining the demands for seismic design of the building structural mem...
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The paper discusses the effects of the 3D seismic random wave propagation (incoherent motion) vs. the 1D seismic deterministic wave propagation (coherent motion) on SSI response. Both theoretical and practical aspects are presented. The presented incoherent SSI analyses were performed using deterministic and stochastic incoherent SSI approaches with and without complex response phase adjustment as implemented in the ACS SASSI code (Ghiocel, 2013). The incoherent SSI approaches with phase adjustment were validated by EPRI (Short, Hardy, Merz and Johnson, 2007) and accepted by US NRC (2008) for their application to the seismic SSI analysis of the new nuclear power plant structures in United States. The paper investigates the effects of complex response phasing on the incoherent instructure response spectra (ISRS) for different nuclear island SSI models. It is shown that EPRI validated incoherent SSI approaches are always conservative, but sometimes they could be overly conservative fo...
Advances in Structural Engineering, 2014
Spatial variation of seismic ground motions is caused by incoherence effect, wave passage, and local site conditions. This study focuses on the effects of spatial variation of earthquake ground motion on the responses of adjacent reinforced concrete (RC) frame structures. The adjacent buildings are modeled considering soil-structure interaction (SSI) so that the buildings can be interacted with each other under uniform and non-uniform ground motions. Three different site classes are used to model the soil layers of SSI system. Based on fast Fourier transformation (FFT), spatially correlated non-uniform ground motions are generated compatible with known power spectrum density function (PSDF) at different locations. Numerical analyses are carried out to investigate the displacement responses and the absolute maximum base shear forces of adjacent structures subjected to spatially varying ground motions. The results are presented in terms of related parameters affecting the structural r...