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This article presents the findings of a study on the directionality effect observed in strong motion records. We set out to establish ratios between several seismic intensity measures that depend on sensor orientation (e.g., GMar, Larger) and others that are orientation-independent (e.g., RotDpp, GMRotDpp, and GMRotIpp), with the intention of proposing multiplicative correction factors. The analysis included an evaluation of the impact of site conditions, ground motion intensity, earthquake magnitude, and hypocentral distance on these ratios. Following a concise overview of the directionality effects and the associated intensity measures, the Costa Rican Strong Motion Database, comprising a total of 4199 horizontal accelerograms (two components), was employed to determine the correction factors. The analysis was carried out for 5% damped response spectra within the 0.01–5 s period range. The study focuses on orientation-independent intensity measures that are derived by combining the maximum values from the recorded motions. In the comprehensive analysis of the complete database, a trend was observed between these intensity measures and the magnitude of the earthquake along with the hypocentral distance. Specifically, records from earthquakes with greater magnitudes exhibited a lower maximum spectral response to the geometric mean of the response spectra of the as-recorded (ar) components ratio (RotD100/GMar), similar to records from earthquakes with larger hypocentral distances. Based on these findings, a proposal was put forth to estimate RotD100 values using GMar values. This ratio can prove useful in transforming data from previous seismic hazard studies, including those applied in many seismic codes, and in defining the maximum anticipated seismic intensity for design purposes in a more straightforward manner. [ABSTRACT FROM AUTHOR]

Soil-structure interaction is a key aspect when calculating the dynamic response of nuclear structures in front of ground motions induced by earthquakes. However, modelling the seismic response in the time-domain using FEM-based models to represent the soil volume is computationally expensive because of the large number of elements involved. For this reason, it is a common practice to employ 1-D models, which allows an explicit solution of the dynamic response of the system in a fraction of time. Yet, due to the importance of nuclear structures, sometimes it is mandatory to employ 3D FEM-based models. In addition, based on probabilistic estimations of the seismic hazard at a site, it is generally necessary that the seismic response of the model comply with the spectral ordinates of the input action at the surface level. In doing so, specific accelerograms acting at the bedrock should be developed. If these signals are obtained by deconvolution using the 1D model, and then applied to the 3D one, the response calculated at the surface level will always be somewhat different from the target free field motion (the one considered in the deconvolution process at the surface level). There are several sources, like the Poisson effect in the 3D model, explaining this difference. Therefore, it is necessary to modify the input signal so that the dynamic response obtained with the FEM model fit the target spectrum. This article presents an innovative approach to achieve this goal, developing an enhanced transfer function stemming from the 1D and 3D models. Two seismic scenarios and a specific soil profile have been used as benchmark. Results show that this approach provides an adequate solution for the studied problem. • Soil-structure interaction is a key aspect when calculating the seismic response of nuclear structures. • Modelling this response in the time-domain using FEM models to represent the soil volume is computationally expensive. • The seismic response of the model must comply with specific spectral ordinates related to the hazard of the site. • This article presents an innovative approach to achieve this goal, using an enhanced transfer function from 1D and 3D models. • Two seismic scenarios and a specific soil profile have been used as benchmark. • Results show that this approach provides an adequate solution for the studied problem. [ABSTRACT FROM AUTHOR]