Behavior of HCR semi-rigid joints under complex loads and its effect on stability of steel cooling towers

Abstract A single-layer reticulated steel (SRS) cooling tower consists of members and joints. Joint stiffness is an important component of SRS cooling towers, as it significantly influences the overall behavior of the structure. A new semi-rigid joint system consisting of H-shaped and C-shaped rolled steel, known as an HCR joint, has been developed for application in SRS cooling towers. In this study, a finite element (FE) model of an HCR joint under bending conditions is established and verified by joint tests. Then, HCR joints subjected to different loading combinations, including bending and shear forces, bending and certain axial forces, and eccentric forces, are numerically analyzed. The bending moment-rotation (M-Φ) curves and change rules for the stiffness and ultimate bending capacity are obtained. Next, the stability of SRS cooling towers with semi-rigid HCR joints is analyzed based on the M-Φ curves of the HCR joints under various eccentric forces. Two FE models of the structures are established. In FE Model-1, the stiffness of the HCR joints under a bending load is used for all of the joints in the structure. In FE Model-2, the stiffness of the HCR joints under different eccentric forces are used based on the different ratios of bending force to axial force in the joints at different locations in the structure. During the analysis, the structural height, grid size, and joint stiffness are considered, and the effect of the parameters on the critical load and buckling mode of the structure is determined.