Book Description

This study investigates the seismic response and dynamic cross-interaction effects on two closely located nuclear power plants (NPP) to a range of seismic inputs with varying frequency content. A comprehensive study is undertaken to examine the effects of the location of the seismic source as well as the soil characteristics beneath the NPP on dynamic structure-soil-structure interaction (SSSI) between the adjacent structures. The effect of proximity of the NPP is also studied by varying the distance between the power plants. In the preliminary phase of the study, the significance of using three dimensional seismic waves in response evaluation of nuclear power plant buildings is demonstrated. First, the responses of a single power plant subjected to one-dimensional and three-dimensional waves are compared. This is followed by a similar series of analyses on closely located adjacent power plants. It is shown that using one-dimensional waves can lead to misrepresentation of the seismic response of the NPP and non-conservative estimates of seismic demands. In general, the variation in response between 1D and 3D waves was more significant for the containment building than the auxiliary structure. Findings from the preliminary phase of the study formed the basis for the next set of comprehensive simulations to investigate the dynamic cross-interaction between adjacent nuclear power plant buildings for three earthquake scenarios and three different soil conditions. Each scenario represents a different form of seismic wave caused by a near source earthquake. For each scenario, to evaluate the influence of site conditions, simulations are performed on soft, medium, and hard soil sites. In addition, the free distance between the adjacent buildings is varied to study the influence of the proximity of the structures to the SSSI effects. The primary findings from the study can be summarized as follows: (i) increasing the shear wave velocity of the site which increases the minimum wave length, reduces the dynamic cross interaction between the buildings; (ii) unlike the response of the auxiliary building which is influenced the most on hard soil sites, the response of the containment building is influenced mostly on softer soils; (iii) high frequencies are introduced in the response due to presence of the adjacent building which influences the dynamic SSSI effects; (iv) dynamic cross-interaction effects are different depending on whether the buildings are located upstream or downstream of the propagating seismic waves and response in the downstream building is generally (not necessarily) higher than the upstream one; (v) for deep near-source events, dynamic cross-interaction is observed in all components of the response whereas for shallow earthquakes, the response is mostly influenced in the direction of the wave propagation; and (vi) generally, but not necessarily, increasing the distance between the power plants decreases the dynamic cross interaction.