Load-carrying capacity of semi-rigid double-layer grid structures with initial crookedness of member

•Load-carrying capacity of grid structure is remarkably affected by joint bending stiffness.•The effect of initial crookedness of member on load-carrying capacity is closely related to member slenderness ratio.•The distribution of initial crookedness of member distinctly affects the limit load of grid structure.•The failure mode of grid structure is affected by distribution of initial crookedness of member and joint bending stiffness.•The existence of initial crookedness of member leads to lose its stability prematurely. The main aim of the present study is to investigate the effect of joint bending stiffness and initial crookedness of member on load-carrying capacity of double-layer grid with different member slenderness ratios. Firstly, a mechanical model of semi-rigidly jointed double-layer grid with initial crookedness of member is developed, followed by verification of two simple grid structures. Then, the influence of joint bending stiffness and random initial crookedness of member on load-carrying capacity of double-layer grid is systematically investigated. Finally, failure mechanism and destructive process of the double-layer grid are discussed. The results indicate that the load-carrying capacity of double-layer grid with initial crookedness of member is remarkably affected by joint bending stiffness, especially for double-layer grid with slender member. The limit load of double-layer grid markedly decreases when κ less than 1.5–2. The effect of initial crookedness of member on load-carrying capacity of double-layer grid has a close relationship with member slenderness ratio. With the increase of member slenderness ratio, the limit load reduction gradually increases. The distribution of random initial crookedness of member distinctly affects the limit load of double-layer grid, and some of them can observably reduce the limit load, especially for double-layer grid with large member slenderness ratio. The failure mode of imperfect double-layer grid is affected by distribution of initial crookedness of member and joint bending stiffness. The existence of random initial crookedness of member can aggravate P-Δ effect, and some compression members of double-layer grid lose their stability prematurely, which further leads to the instability of whole double-layer grid.