## 4 Technological Advancements
### Manual to Automatic Non-Detachable Inter-Modular Connections  
For manually operating PFISBs, inter-modular connections (IMCs) that are welded, bolted, and prestressed are frequently used, as shown in Figure 2a-f. While all of these IMCs have been demonstrated to have an adequate seismic resistance in pertinent investigations, they do have challenges. Due to the extensive onsite work of the welded IMCs, there is not enough room for MEP services, a secure weld quality, and full welding [54]. Welded connections were the most common type of IMC studied by [PERSON] et al. [10, 54, 55, 56] that exhibited a satisfactory performance; nevertheless, they are costly, of a poor quality, and require functional space for internal connection welding [57]. As depicted in Figure 2a, welding connections are avoided due to the aforementioned difficulties; hence, bolted connections are chosen on the construction site [38, 54]. Bolted IMCs have strict operational space requirements and a lower production efficiency [58]. [PERSON] et al. [59] discovered that bolted bracket connections were susceptible to prying failure, exhibiting a brittle behavior and are suited for low-rise structures. Thus, [PERSON] et al. [60, 61] developed rotary connectors that protect the columns; access holes are used for large bolt tightening, as displayed in Figure 2b [62]. The experiments demonstrated an outstanding bearing capacity and ductility in high-rise PFISB extreme dynamic situations [63]. Plug-in supported joints are developed which can fully assemble interior IMUs, and their seismic performance has been studied, such as the beam and column bolted IMC in Figure 2d [64]; fully bolted IMC in Figure 2e [65]; and beam bolted IMC in Figure 2c [66, 67]. They demonstrated a superior ductility, energy dissipation, plastic deformation, and bearing capacity, whereas the weld of the intra-modular joint fractured; nonetheless, the failure was transmitted to the column. The building regulations for the prestressed IMC are stricter and more complicated. Prestressed rebars can join columns vertically, but their limited moment-resistance capability makes them unsuitable for high-rise buildings because superimposed forces can cause elevating and joint failure [40]. In order to achieve the composite prestressed joint shown in Figure 2f, the columns are filled with concrete. This joint effectively transfers medium-level lateral forces in a ductile manner due to the contact bond between the concrete, plug-in, strands, and shear bloc; however, a significant bond reduction can cause concrete crushing, a gap formation, strength, and stiffness degradation [68, 69]. Workers may also bolt or weld the corners and exterior interface from the outside. The IMUs' wall panels and slabs, particularly the installation, do not have the necessary construction clearance for the internal IMC. Some IMCs do not make the final IMU tighter. Others, on the other hand, prefer to make holes in order to assemble them, which may compromise the IMUs' sectional integrity and interior design. In order to address the problems above, various automatic IMCs that require no functioning space have recently been developed, as shown in Figure 3a-g. The researchers designed a sliding bloc IMC that joins the IMU via a self-locking setup, as shown in Figure 3a [57]. The joining method resembles the lock-tongue joint in Figure 3f in appearance [70]. Another investigation also created the self-locking slider joint displayed in Figure 3e which works similarly with the joins in Figure 3a,f [71]. The top movable panel and springs are attached to the side of the bottom IMU column, and the plug is attached to the base of the upper IMU column. As a result, the connector is fixed, the slider panels move laterally during the mounting of the IMU, and a slip forms between the top and bottom segments of the plug. Self-locking connections' hysteresis behavior featured plumper hysteretic rings and worked well in seismic tests.