## 3 Description of the Case-Study Hospital Building
### As-Built State of the Hospital Building
A probabilistic seismic hazard assessment (PSHA) was performed for the location of interest based on the Croatian Earthquake Catalogue (CEC) and available data on the seismotectonic characteristics \begin{table}
\begin{tabular}{c c} \hline \hline
**Eigenvalue \(\pm\) Standard Deviation (Hz)** & **Damping Ratio \(\pm\) Standard Deviation (\%)** \\ \hline
3.25 \(\pm\) 0.01 & 1.77 \(\pm\) 0.59 \\
3.81 \(\pm\) 0.02 & 1.72 \(\pm\) 0.63 \\
4.50 \(\pm\) 0.05 & 2.04 \(\pm\) 0.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Eigenvalues and damping ratios obtained by testing. Figure 7: Spectrogram of the transversal component of the velocity spectra measured on the sixth floor in the hospital building in the frequency range of 2–5 Hz. (**a**) Time period of the entire working time of the installed instrumentation (98 days); (**b**) time period of one week. Similar observations are also clearly present in the longitudinal component of the spectra. of the broader area. The hazard is generally described by the statistical probability of exceedance (frequency of exceedance) of the selected parameter in the given time interval. At the investigated location, it was expressed as the peak ground acceleration (PGA) on soil type A according to Eurocode 8 for the return periods of 95, 225, 475 and 2475 years. The seismic hazard for the return periods of 95 and 475 years is defined by the seismic hazard map of the Republic of Croatia compiled in 2011 [33]. For the return periods of 225 and 2475 years, the seismic hazard was estimated using the same procedure (with the same seismicity models--smoothed seismicity--and attenuation relations) and the same Croatian Earthquake Catalogue as used for the compilation of the seismic hazard map of the Republic of Croatia. This kind of procedure for seismic hazard estimation was applied, for example, in the works of [34; 35; 36; 37]. The peak ground accelerations for soil type A at the location of the building are determined as: 0.16 g, 0.21 g, 0.30 g and 0.51 g for the return periods of 95, 225, 475 and 2475 years. In accordance with the assessed hazard, artificial and simulated accelerograms were generated for the location. Unfortunately, accelerograms of a strong earthquake have never been recorded on the bedrock in the greater area of the hospital. Artificial accelerograms were generated using the artificial accelerogram generation method [38] with the SeismoArtifi tool [39]. This method defines each artificial ground motion modifying the starting random process through the use of a selected envelope shape and a power spectral density function (PSDF) calculated from the velocity target spectrum which is selected before the execution. With both the target spectrum and the envelope type defined, an artificial accelerogram is generated and a comparison between its response spectrum and the target spectrum is given, including the mean error in percentage, coefficient of variation, and PGA of the accelerogram. The target spectrum for the generated artificial accelerograms was the Eurocode 8 elastic response spectrum of type 1 (which is in use in Croatia) for the ground type A and for 5% viscous damping. Four levels of seismic action corresponding to four different return periods of interest were taken into consideration. The minimum duration of the stationary part of the accelerograms was equal to 10 s. Finally, 12 three-component (comprising of two horizontal orthogonal components and one vertical) artificial accelerograms were generated, three for each level of seismic action. Simulated accelerograms for the investigated location were calculated for the bedrock level using the following assumptions:  
1. The representative shape of the Fourier's amplitude spectrum (\(S_{0}\)) of the accelerogram on the bedrock level can be described as a function of an earthquake magnitude and the distance between its hypocenter and the studied location, as proposed by [40; 41];
2. Phase spectrum is a random function of frequency;
3.