## 2 Experimental Development
### Characteristics of the Isolated Building  
The residential building presented by [PERSON] [15] was used as the reference structure for the natural and recycled rubber isolators (Figure 7a). Based on the mechanical test results of small-scale prototypes, the horizontal stiffness, vertical stiffness, and damping properties of the modeled isolators were adjusted to reflect the effects of environmental exposure. The seismic response of the building with unexposed isolators was then compared to that of isolators subjected to environmental conditions, analyzing the maximum total displacement (D\({}_{\text{TM}}\)). It should be emphasized that, currently, there is no regulation in Colombia specifying the design of seismic isolators. Therefore, the recommendations established by [PERSON] [15] for the design of elastomeric fiber-reinforced isolators disconnected from the structure (UFREIs) were followed for the calculation of vertical stiffness. These recommendations include considerations from NSR-10 [53], FEMA 450 [54], and other authors referenced therein. Figure 7 and Table 1 show the typical characteristics of this structure without considering the modification factors of properties caused by environmental conditions (\(\lambda_{\text{ae,max}}\) and \(\lambda_{\text{ae,min}}\)). This isolated building was used to model the effect of changes in the properties of the UN-FREI and UR-FREI isolators to compare the building's response. Figure 6: Loading protocols: (**a**) shear compression test, and (**b**) cyclic compression test. Figure 7: Characteristics of the analyzed type of structure, (**a**) 3D and (**b**) the pseudo-acceleration spectra of the ground motion for a damping coefficient of 5%. ASCE 7-16 [55] allows a response spectrum analysis to be performed, provided that certain conditions are met: the isolated structure must be located on a Site Class of type A, B, C, or D; the effective period at maximum displacement must not exceed 5.0 s to prevent excessive flexibility and high displacements; the height from the base level must be less than 19.8 m; the damping associated with the maximum displacement must be less than or equal to 30%; and the structure must not exhibit irregularities in plan or height. Since the analyzed structure meets these criteria, the response spectrum corresponding to Zone 2 of the seismic microzonation of the city of Cali, which is similar to Site Class D, was selected (Figure 7b). The accelerations were multiplied by a factor of 1.5 to account for a return period of 2475 years (Figure 7b). The structural analysis was carried out using ETABS v20.0.0 software. For the calculation of seismic forces, a mass source composed of 100% dead load and 50% live load was defined. Table 2 presents a summary of the geometry of the UN-FREI and UR-FREI isolators and the final properties for D\({}_{\text{TM}}\) introduced in ETABS to model the building with rubber base isolators. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Concrete (MPa) (f\({}^{\prime}\)c) & 24 \\ Steel (MPa) (fy) & 420 \\ Columns & 45 \(\times\) 45 cm \\ Beams & 35 \(\times\) 40 cm, 40 \(\times\) 50 cm \\ Number of stories & 5 \\ Story height (m) & 3 \\ Number of isolators & 20 \\ Dead load (kN/m\({}^{2}\)) & 5.0 \\ Live load (kN/m\({}^{2}\)) & 1.8 \\ Weight of structure (kN) & 19,760 \\ Design period & 2.5 s \\ Horizontal damping (\(\gamma\) = 160\%) & 6.10\% \\ \hline \end{tabular}
\end{table} 
Table 1: Typical characteristics of the type structure analyzed.