## 4 Seismic Analysis  
### Structural Finite Element Model  
Different finite element software was used to conduct the three-dimensional models, simulating the actual behaviour of structures when subjected to ground motions. For modelling purposes in the current analysis, OpenSees 3.7.0 [25] was selected because this software offers greater flexibility through built-in advanced features, enabling modelling and analysis at both linear and nonlinear stages for structures under static and/or dynamic loads. SeismoStruct 2024 [23] was preferred for the efficiency of the numerical model calibration and for the linear elastic modal analysis. However, further into the study, moving \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Bare Frame** & \multicolumn{4}{c}{**Full Model (RC Frames + RC Walls + Infilled Masonry Walls)**} \\
**Mode** & **Period (s)** & **Frequency** & **Mode** & **Period (s)** & **Frequency** \\  & & **(Hz)** & **Mode** & **Period (Hz)** \\ \hline
1 & 0.244 & 4.10 & 1 & 0.214 & 4.66 \\
2 & 0.242 & 4.13 & 2 & 0.175 & 5.71 \\
3 & 0.226 & 4.42 & 3 & 0.151 & 6.59 \\
4 & 0.086 & 11.64 & 4 & 0.074 & 13.50 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Modal periods and frequencies for the bare frame model and the full model. Figure 7: First three identified mode shapes of the hospital Vega de Baja (block 14), (a) first mode T = 0.214 (s), (b) second mode T = 0.175 (s), and (c) third mode T = 0.151 (s). to nonlinear pushover and time-history analyses with bidirectional ground motions, it became necessary to switch to OpenSees. This software provided more freedom in scripting and allowed the incorporation of user custom code for modelling advanced material properties and cyclic degradation effects critical for capturing the nonlinear seismic response of the structure. Beams and columns were modelled using the lumped plasticity approach through elastic beam-column elements while accounting for nonlinear behaviour by introducing rotational springs at the two ends of each element [26; 27; 28; 29]. The peak-oriented hysteretic model developed by [PERSON] et al. (2005) [30], also known as the Ibarra-Medina-Krawinkler model, was used to model the beam flexural hinges. Material ModIMKPEakOriented was adopted for the simulation of the backbone and hysteretic behaviour of beams and columns, which were implemented according to formulations proposed by [PERSON] et al. (2008) [27]. This response model also includes hysteretic rules to simulate cyclic degradation as a function of the normalised energy dissipation capacity, which was calculated considering the axial load on members and the stirrup spacing to effective depth ratio. In addition, the columns were subjected to the corotational transformation in order to take into account P-Delta effects. In beams and columns, concrete core fibres were assumed to be provided with the constitutive relationships that include the confining effect due to transverse reinforcement, while the reinforcement steel rebars inside the concrete cross-section were replaced by equivalent straight layers of given thickness. The material models Concrete02 and Steel02 were used to represent the concrete and reinforcement of beams and columns, respectively. The Concrete02 uniaxial material model, based on the formulation by [PERSON] et al. (1982) [31], features a parabolic curve up to the maximum concrete stress followed by a linear descending branch. The model also incorporates linear tension stiffening. The parameters of Concrete02 vary depending on the concrete strength class and differ for concrete core and cover fibres to account for confinement effects due to longitudinal and transverse reinforcement.