Research on seismic behavior of tapered-head bolted inter-module connection of modular steel buildings

Modular steel buildings (MSBs), which comprise prefabricated modular units, are a new type of assembled buildings. The inter-module connection of MSBs plays an important role in the connection between modular units and structural safety. At present, several types of inter-module connections are in use, such as welded, bolted, prestressed, or self-locking. However, they present problems such as poor welding quality, low construction efficiency and no operation space for the internal connection. To solve these problems, this study proposes an innovative tapered-head bolted inter-module connection. Cyclic tests were conducted considering three different parameters: the modular beam section form, axial compression ratio, and thickness of the modular floor beam. Seismic behavior indicators such as stiffness degradation and energy dissipation of the specimens were investigated. Subsequently, a refined finite element model (FEM) was established to verify the corresponding test results. Finally, based on test fitting and nonlinear regression analysis, a restoring force model of the tapered-head bolted connection was established. The results indicated that the calculated ratios of the restoring force model to test results were within 0.07 on the yield, maximum, and failure points and the coefficient of variation (COV) was 0.03, with high accuracy and application. This research provides a reference to some extent for designing MSBs.