## 3 Results and Analysis of Prefabricated Lightweight CFST Framework-Composite Slab Structure  
### Hysteretic Performance  
Figure 16 showed the load (\(F\))-displacement (\(\Delta\)) curves of the tested specimens.  
Figure 16 showed that the hysteresis curve of specimen FM was clearly different from the hysteresis curves of the specimens with sandwich panels. The hysteresis curve of specimen FM did not exhibit a turning point as the load increased, which indicates smaller load-bearing and a smaller-energy dissipation capacity. The curve was shuttle-shaped and did not exhibit a clear centralization trend.  
Regarding specimens FM-S, FM-SW, and FM-SD, the slopes of the hysteresis curves increased with an increase in displacement and load, which exhibits a turning point right before the displacement reached the target value. It then decreased with an increase in displacement. The curves under the same direction of loading show that the slope under a later loading increment was clearly smaller than that under an earlier increment. Additionally, after repeated loading increments, the hysteresis curves of the specimens gradually became more full-rounded, which changes from a reverse-'S' shape to a 'Z' shape.  
Figure 15: Demonstration of occurrence of damage to beam–column joints.  
When the sandwich slabs and framework underwent synergistic deformation, the slabs continuously squeezed the framework, serving as a support structure. Consequently, the slope of the hysteresis curve increased with the load. When the slabs cracked, and plastic deformation occurred in the framework, the slope of the curve decreased with the load increase. The phenomenon where the slope of the hysteresis curve decreased with an increase in the number of load increment indicates increasing damage to the framework and the slabs. As the load increased, greater sliding between the sandwich panels occurred, and the friction between the sandwich panels and the plastic deformation of the steel tubes of the framework resulted in energy dissipation. Consequently, the hysteresis curve became more fully rounded.  
The hysteresis curves of specimen FM-SS was the reverse-'S' shape, which has a smaller enveloped area and indicates smaller energy-dissipation capacity of the structure. However, the specimen exhibited a higher load-bearing capacity at displacement angles smaller than 1.8%. A comparison of the curves under the same direction of loading revealed greater slopes and smaller reductions of the hysteresis curves prior to the point of the ultimate displacement angle (i.e., the displacement angle corresponding to the ultimate load), and a drastic decrease of the slopes of the hysteresis curves beyond the point of the ultimate displacement angle.  
Figure 16: Hysteresis curves of the tested specimens.  
Additionally, the authors had carried out a shaking table test on a full-scale and two-story prefabricated lightweight concrete-filled steel tubular (CFST) framework composite slab structure, with a building height of 5400 mm, and plane size dimensions of 4400 \(\times\) 4400 mm. The experimental results showed that the structure was subjected to an earthquake of 8\({}^{\circ}\). The inter-story displacement angle was approximately equal to 1/500. There was no clear damage to the structure. This showed that the structure had good seismic performance. Accordingly, the structure exhibited functional recoverability at large earthquake intensities. Although the shape of the hysteretic curve was not full, the functionality could be recovered after the earthquake.