## 3 Shake-Table Tests of Model with Innovative Infill Connection (Model IW-SB)
### Selected Results Based on Measurements from Transducers  
After the mounting of the model on the shake table, a random excitation test was applied in longitudinal direction of the model. This testing method is based on the concept of white noise input excitation when multi-frequency components uniformly participate in the Fourier amplitude spectrum of the input motion within the selected frequency range. Consequently, the model response contains natural frequencies as dominant in the Fourier amplitude spectra. In the presented case, a frequency range from 0.5 to 35 Hz was selected and was simulated by the shake table. Definition of dynamic properties of Model IW-SB was the first step of the experimental testing, which enabled acquiring of important information about the stiffness (natural frequencies) of the model. Natural frequency was defined in longitudinal direction of the model by applying resonant frequency search tests. Frequencies obtained in test 01 (before the start of the seismic response tests) and in test 14 (after the finishing of the last seismic response test with PGA = 1.6 g) are presented in Figure 19.  
The analysis results indicate a significant reduction in the fundamental frequency of the structure over the course of the seismic testing. Initially, the natural frequency was measured at 9.276 Hz, which decreased to 1.888 Hz following completion of all twelve seismic response test series. Correspondingly, the fundamental period T increased from 0.108 s to 0.530 s, representing an approximate 4.91-fold increase relative to the initial period. This marked shift reflects a substantial degradation of the initial stiffness, primarily attributed to damage accumulation in the masonry infill panels. Acceleration and displacement data, recorded via transducers (Figures 20 and 21) and complemented by strain gauge measurements, are presented for four selected peak ground  
Figure 19: Obtained frequencies of Model IW-SB, before and at the end of the seismic response tests. accelerations (PGAs): 0.1 g (low amplitude), 0.6 g (moderate amplitude), and 1.2 g and 1.6 g (high amplitudes). Raw data were processed using a double band-pass filter with cutoff frequencies set at 0.3 Hz (low) and 44 Hz (high) to remove noise and drift effects. Prior to detailed analysis, displacement time histories from the linear potentiometers (LP1-LP4) were cross-validated against displacement curves derived from double integration of acceleration records. The close correspondence between these datasets confirmed the reliability of the potentiometer measurements, which were subsequently utilized for all further analyses. Table 2 summarizes the maximum top displacements and inter-story drifts measured at the selected excitation levels. The maximum displacement at the roof level was approx  
Figure 21: Displacement time histories at each floor level in test No03_HN10 (0.1 g left and 0.6 g right). Figure 20: Acceleration time histories at each floor level in test No03_HN10 (0.1 g—left, 0.6 g, right). imately 2 mm for 0.1 g, 7 mm for 0.6 g, 38 mm for 1.2 g, and 52 mm for 1.6 g, indicating progressive nonlinear deformation with increasing seismic intensity. Additionally, base shear versus top displacement hysteresis loops were developed (Figure 22) to characterize the global structural response. The displacement time history recorded by transducer LP-01, located at the foundation level, served as the reference point for calculating relative floor displacements using measurements from other channels (LP-02 through LP-04).