## 8 Technical Challenges and Potential Solutions
### Inter-Modular Joints Damage Issues  
The IMU-to-IMU, IMU-to-frame, IMU-to-core, and IMU-to-foundation connections are the four types of IMC. IMU-to-IMU connections are semi-rigid since they are installed onsite and cannot be welded. They stack IMUs in horizontal and vertical directions to offer a lateral and vertical way to distribute the loads between the PFISBs, core, and frame. IMU-to-frame and IMU-to-core connections are rigid through onsite casting or welding plates as they are believed to resist lateral loads. The IMU-to-foundation connection is deemed rigid by anchoring or welding to resist the high sliding and overturning caused by lateral loads. These connections' mechanical properties considerably impact the structural strength, safety, stability, serviceability, and robustness.  
According to the seismic provisions provided by the A1 SC, the SMF requires a 4% story drift, while the IMF requires only 2% [176]. This doubts the appropriateness of various IMCs for use in high-rise PFISB structures and earthquake zones. Prestressed composite IMCs are fragile and susceptible to concrete crushing [68; 69]. Most IMCs demand to be open access with a limited workspace, fastening the structural members for the fourth IMU [58]. So, a detachable, self-aligning, easy-to-install connection is advised. This must consider the constructional tolerances, be adaptable to varying IMUs, and meet the seismic design criteria. The authors recommend that the requirements be met by combining the automated and damping joints capable of recentering. Because the study showed that the damper joint dissipates energy more efficiently than rigid joints [94], automated joints can fulfill the architectural and structural requirements.  
Additionally, the only work which has studied the IMU-to-foundation IMC has examined the column in an infilled frame, neglecting the column's discontinuity [107]. However, the PFISB IMUs actual design in the IMCs' region includes discontinuous columns, which significantly impact the connection and structural behavior of the grouped columns in the base region. In order to solve the problems, further innovations and follow-up research is recommended. The authors suggest that using a mechanical connection or the proposed top-down approach can be helpful on the ground floor to deal with the foundation connection issues because it is based on the construction of a structure from the top floor [95]. The authors also suggest applying a base-isolation system [90] or FREEDAMAGE dampers [177] to reduce the structural damage while fitting the group columns' IMC.  
IMU-to-frame/core connections are made by directly welding a connecting plate suited only for a lateral load transfer. However, the tensile fracture can fail a tie connection if the plate is subjected to overturning or twisting due to the IMUs' rolling, rocking, and axial deformations. However, no comprehensive research has been conducted on these design concerns involving principal lateral stabilizing systems in high-rise PFISBs. Moreover, no practically applicable possible connection has been researched dealing with this issue. The authors suggest using FREEDAMAGE dampers the joints. One can use them to safeguard the nonstructural components, minimize the fragility, and enhance the energy absorption efficacy for multiple modes. Additionally, the authors indicate that INNO3 DJOINTS [178] can be adapted because they are demountable and reusable in the event of a seismic disaster. Further studies are therefore needed in this direction to develop a high-rise PFISB.