Experimental study on seismic cyclic behavior of an innovative blind bolted connection joint between modules in modular steel frame

Three full-scale cruciform specimens are created and subjected to low-cycle reciprocal loading to examine the novel blind bolted connection joint. The mechanical properties of the specimens, such as failure mode, hysteretic behavior, moment rotation curves, and member deformation characteristics, are studied and compared with finite element models. The study's findings demonstrate that the specimens' hysteretic curves are generally full, and the maximum equivalent viscous damping coefficients of the three joints are 0.411, 0.232, and 0.355 respectively, indicating that the joints have strong energy dissipation capacity; the ductility coefficients of the three specimens are higher than 3.00, and the inter-story drift angle is greater than 7%, meeting the requirements of the Chinese code for the seismic design of multistory steel frames; the failure mode of the specimens with joint zone diaphragms is that the beam ends produce plastic hinges; the energy dissipation performance, bearing capacity, and stiffness of the specimens without diaphragms are significantly lower than those with diaphragms; the cover plates on beam end flanges can move the plastic hinges at the beam-column connection welds outward to the end of the cover plates, and compared with specimens without cover plates, their bearing capacity and stiffness are significantly improved; according to Eurocode 3, the specimens with joint zone diaphragms can be classified as rigid joints and full-strength joints and the specimens without diaphragms in joint zones can be classified as semi-rigid joints and partial-strength joints; when the thickness of the connecting plate increases, the initial stiffness of the joints increases, but the effect is not significant.