Cross-sectional and bidirectional connection design methods for volumetric steel modules

Modular steel constructions (MSCs) are becoming increasingly popular because of their advantages such as rapid construction speed, less demand for on-site labor, quick demolition, and recycling after demolition. An architecturally pleasing all bolted joint called modular bidirectional load-bearing and energy-dissipating joint (MBJ) with innovative modular bidirectional load-bearing and energy-dissipating connectors (MBC) was proposed in this study to achieve vertical and horizontal connection of adjacent modules simultaneously. Design methods that involve cross-sectional design of modules, as well as bidirectional connection design among modules were proposed to establish a relationship between the design of modules and MSCs by “equal initial stiffness” principles of MBJs and traditional bidirectional joints (TBJ). The initial stiffness of MBJs is based on a deep analysis of the force transfer mechanism and deformation characteristics of MBJ panel zones. The FEM of the MBJs was set according to the verified modeling approach, in contrast to the experimental results. Finite element models were set to verify the proposed design method, and theoretical studies were conducted. Our findings show that the ratio of the total cross-sectional moment of inertia of adjacent columns to that of the traditional column ranged from 0.600 to 1.228, the “equal initial stiffness” of MBJs to that of TBJs can be achieved, and the lateral strength of MBJs is consistently greater than that of the corresponding TSJs. In addition, the proposed design method can easily achieve standardization of modules because the ratio of the total cross-sectional moment of inertia of the MBC, ceiling beam, and floor beam to that of traditional beams is in a large range. The maximum error of the initial stiffness of the MBJs between the FEM results and theoretical values was 13.89 %, which meets the engineering accuracy requirements. The research results provide a theoretical basis for the design of MSCs for seismic regions.