## 3 Shake Table Study
### Instrumentation and Loading System  
The behaviors demonstrated by the test specimens under seismic influence were systematically analyzed, focusing on critical parameters such as acceleration, displacement, and strain. This analysis was facilitated by the use of advanced measurement tools. The experimental setup incorporated accelerometers and linear voltage displacement transducers (LVDTs), depicted in Figure 6, highlighting the complexity of the employed methods. Designed for precision, the LVDTs could measure high frequency displacements, achieving an exceptional range of up to 200 Hz, thus ensuring accurate capture of dynamic responses. These instruments were strategically mounted on sturdy frames firmly anchored to the ground rather than directly on the shaking table, enhancing the precision of displacement measurements in relation to a stable ground reference. LVDT#1 mounted on the slab level was to measure lateral story displacement and the drift response, accordingly, as shown in Figure 6. In addition to the LVDT positioned at the slab level (LVDT#1), two more LVDTs were placed at each end of the TnT brace (LVDT#2 and LVDT#3) to effectively record axial displacement demands on the load-bearing tube during seismic activities, as illustrated in Figure 6. These two LVDTs (LVDT#2 and 3) were installed to record the relative movement of the outer tube with respect to the end plates connected to the gusset plates at each end. Therefore, the axial displacement demand on the load-bearing tube can be computed as the summation of the relative displacements measured from LVDT#2 and 3.  
Furthermore, accelerations were meticulously monitored at various strategic locations, including the foundation, slab of the test frames, and the shake table surface, through four accelerometers securely attached to both the foundation and the shake table.  
All accelerometers were mounted on rigid aluminum brackets that were chemically anchored either to the shake table platen or to the foundation beam, thereby eliminating relative slip and ensuring that each device registered the true input or response acceleration of its host mass. Two sensors on the platen recorded the exact base input; two additional sensors on the foundation cross-checked that the anchorage transmitted the input without phase lag. At the superstructure level, twin accelerometers were positioned symmetrically at the beam-column joints to capture torsional tendencies as well as planar response, with their sensing axes aligned to the principal directions of motion. This arrangement allowed direct calculation of story accelerations and modal participation without numerical differentiation of displacement data.  
It is essential to underline that both acceleration and displacement data were collected in real-time using a sophisticated computer-based data acquisition system, ensuring thorough data capture throughout the experimental process. Additionally, twelve strain gauges were integrated into the reinforced concrete frame to monitor strain responses from various carefully chosen points, thus providing a comprehensive understanding of the structural performance under seismic loading conditions.