Stability study on sway modular steel structures with semi-rigid connections

Sway modular steel structures with semi-rigid connections (SMSS-SRCs) have special configurations of connections and columns. Hence, current design requirements regarding effective length factors are unsuitable. Therefore, the displacement method was used to derive expressions for single-module lateral stiffness in the first, middle, and top stories, thereby obtaining the overall lateral stiffness of SMSS-SRCs. The negative lateral stiffness of the modular column was obtained by modifying the rotational constraints at both of its ends. Subsequently, the overall negative lateral stiffness of SMSS-SRCs was obtained as well. The story support factor was used to quantify the degree of mutual support between stories. Finally, formulas for calculating for the critical buckling load and effective length factors of columns in SMSS-SRCs were obtained. Finite element models were established to verify the proposed formulas. The results showed that the proposed method has good accuracy. Hence, this study could provide a reference for calculating the critical buckling load and effective length factor of columns in SMSS-SRCs.