Evaluation Framework for Inter-Module Connections in Steel–Concrete Composite Modular Structures

This study presents a structured evaluation framework for inter-module connections in the context of steel–concrete composite modular structures, addressing a gap in existing reviews that have focused almost exclusively on steel modular systems. The paper examines tie-rod (TR), locking mechanism (LM), and bolted inter-module connections, while introducing a new sub-classification of bolted connections into direct bolted (DB) and plug-assisted bolted (PB) types based on assembly methods. A novel four-metric, five-point rating framework is introduced to assess the Composite Compatibility Score (CCS), proposed as a new metric to evaluate the applicability of steel-oriented connections to composite modules; the Validation Evidence Score (VES), which reflects the extent of experimental and numerical validation; the Demountability and Reusability Score (DRS), which measures the ease of assembly and disassembly; and the newly developed Normalised Capacity Index (NCI), which standardises structural capacity assessment across studies reporting different load capacity types. When applied to nearly 50 inter-module connections, the framework reveals that PB connections provide the most well-rounded performance across all evaluation metrics. Overall, the framework establishes a conceptual benchmark for composite modular connection technologies, providing a basis for future research and design practice.