Constructability and Structural Evaluation of Foldable Modular Building Systems

The growing demand for sustainable and adaptable construction has increased interest in modular building systems; however, conventional modular solutions often face limitations in transport efficiency and reusability. Foldable modular buildings (FMBs) provide a compact, deployable alternative that enhances delivery efficiency and on-site constructability. This study classifies four FMB types based on their deployment mechanisms, namely midcolumn fold, Z-fold, expandable fold, and 2D panelized systems. It evaluates their constructability using a weighted decision matrix derived from established modular construction decision-making criteria. The results indicate that vertically deployed systems (Z-fold and midcolumn fold) achieve the highest constructability scores due to reduced assembly complexity and lower labor demands. In contrast, 2D panelized systems offer greater design flexibility. A sensitivity analysis demonstrates that constructability preferences depend on application context, with panelized systems favored for residential use and foldable modular systems better suited to emergency and temporary buildings. Finite-element modeling of glass fiber–reinforced polymer (GFRP)-framed modules shows adequate global structural performance, although midcolumn joints reduce lateral stiffness and midbeam joints increase gravity-induced deflections. A fatigue-based serviceability assessment incorporating stiffness degradation of GFRP bolted joints indicates that fatigue effects under wind loading do not govern performance within the design life. Overall, FMBs exhibit high constructability and sufficient structural reliability, highlighting their potential for efficient, adaptable modular construction.