Experimental Research on the Seismic Performance of a Novel Interior Column Joint for Integrated Modular Steel Structures

The critical technical bottleneck confronting current modular steel structure systems stems from the lack of universality in their connection joints， which fails to accommodate the structural adaptation requirements under diverse boundary conditions （e.g.， interior columns， exterior columns， and corner columns） within a unified design framework. To effectively address this intractable issue， this study adopts a novel approach and proposes a prefabricated “eight-column and sixteen-beam” joint characterized by central symmetry and axial symmetry. This joint achieves the connection between modular units using a special connector， which consists of a bearing plate， positioning steel plates， T-shaped limiting steel plates， and screw rods， thus enabling a rapid and precise butt joint of modular units. A quasi-static loading test was conducted on a full-scale specimen to evaluate its seismic performance. The failure mechanism， hysteretic behavior， ductility， stiffness degradation， and energy dissipation capacity of the joint were systematically investigated using digital image correlation （DIC） technology. A series of important results were obtained from these experiments. The hysteretic curves of the novel joint presented a full spindle shape without any obvious pinching effect. The equivalent viscous damping coefficient reached 0.417， which strongly demonstrated the excellent energy dissipation capacity of the joint. Furthermore， the ductility coefficient was 3.689， which far exceeded the specified limit for conventional steel structural members. According to the Eurocode （EN） criteria， this joint is classified as a rigid joint. Its failure mode is fully consistent with the scientific seismic design concept of a “strong column-weak beam，” with plastic hinges forming at the beam ends.