Experimental investigation on bolted inter-module connections and subassemblies of steel modular frames

Modular construction, which involves prefabricating free-standing modules in a factory and assembling them on site to form a building, is gaining popularity worldwide. However, the existing inter-module connections generally require additional operation space and present difficulties in aligning adjacent modules quickly. Additionally, the global behavior of modular frames with inter-module connections under lateral loading is not well understood. To address these issues, this study investigates two types of inter-module connections (referred to as Type A and Type B), with high buildability and self-aligning features. Five pull-out tests were conducted to study the tensile behavior of the two types of inter-module connections, and five subassemblies of modular frames with these two types of inter-module connections were tested to study their global behavior under lateral loading. Based on the test results, the yielding distribution and development, strength, ductility, and failure modes were discussed for both types of inter-module connections under tensile loading and for the modular frames under lateral loading. Yielding of the steel plate (the end plate or anchoring plate), as anticipated, is found to be preferable to bolt failure for both types of inter-module connections to achieve greater ductility under tensile loading. Premature fracture of the beam-to-column weld was identified as the main failure mode for all tested subassemblies of modular frames. As this early weld fracture prevented further development of both strength and deformation of the modular frame, it is recommended to avoid this failure mode in the design of modular frames.