# Shaking Table Tests of Suspended Structures Equipped with Viscous Dampers
## 3 Experimental Observations  
The two test models responded with a weak tremor. For the conventional suspended structure, the primary structure has a hardly observable tremor, and the suspended floors have slightly visible relative displacement. For the damping suspended structure, the suspended floors have a slightly larger relative displacement. As the peak acceleration of the seismic wave was increased step by step, the vibration of the primary structure and suspended floors became gradually more intense. Compared with the vibration of suspended floors, the primary structure's vibration was significantly less. For the suspended structure with the rigid-bar links, i.e., the conventional suspended structure, some fastening bolts at the ends of the rigid-bar joints loosed, a few of them even showed bending, and a slight relative vibration occurred between suspended floors and the primary structure under the rare earthquake condition. The findings showed that the swing of suspended floors and the deformation of the bolts absorbed the seismic energy input. For the damping suspended structure, the relative vibration between suspended floors and the primary structure was very obvious, and the vibration of the suspended floors lagged behind the primary structure. The bolts connected to the viscous dampers showed no obvious deformation and were only slightly loosened. The finding of the above test phenomenon showed that the swing of the suspended floors and viscous dampers dissipated the seismic energy input. However, under all working cases (Table 4), the whole structure, including the primary structure and suspended floors, had no cracks from the test beginning to end, and the hang booms also had no traces of shear damage, even in the case of rare earthquake excitation. Moreover, the slight, visible deformation produced during the vibration process was quickly restored, which indicates that the test models were in the elastic working phase. These results suggest that the seismic-resistant performance of the test models was superior, and the structure system, especially the damping suspended structure system, can satisfy or even surpass the requirement for \"no damage under frequent earthquake, repairable damage after an occasional earthquake, and no collapse when subjected to a rare earthquake,\" as described in the code for seismic design of buildings [24]. In order to explore the failure mode of the structures, after the above various conditions, an additional condition under 9 rare earthquakes was carried out. For the conventional suspended structure, a few rigid joints were broken, and some of the bolts connecting the rigid bar had large bending deformation at one end and were pulled out at the other end. At this time, the suspended floors still had no obvious cracks, and the primary structure had only minute fine lines at the intersection of the hanging beam and the giant columns. It can be inferred that after the rigid joints between the primary structure and the suspended floors were destroyed, the entire suspended section was equivalent to a mass pendulum, which was used to dissipate energy, thereby protecting the primary structure from damage. For the damping suspended structure, most of the bolts used to connect the dampers had moderate bending deformation, but none had been pulled out. In addition, there were no obvious cracks in the primary structure and suspended floors. It can be foreseen that as the seismic energy input is further increased, the dampers between the primary and secondary structures will be destroyed and cease to function. At this time, the primary and secondary structures will be connected only by the booms, and the suspended section will use its own free swing to dissipate energy. It can be seen from the experimental observations of the above two model structures that the damping suspended structure has multiple seismic fortification lines.