Punching the chord member due to axial force according to EN 1993-1-8, Table 7.2, row 4

N_{i, Rd} = \frac{f_{y 0}}{\sqrt{3}} \cdot t_{0} \cdot π \cdot d_{i} \cdot \frac{1 + \sin (θ_{i})}{2 \cdot \sin^{2} (θ_{i})} / γ_{M 5}

N_i,Rd	Design value of axial force resistance of connection for structural component i
f_y0	Yield strength of material of a chord member
t₀	Wall thickness of chord cross-section
π	Circle number
d_i	Total diameter for CHS components i
θ_i	Enclosed angle between strut i and chord member
γ_M5	Partial safety factor

Do you have any questions?