The elastic section modulus W el is calculated by dividing the second moment of the area I with the corresponding distance from the centroid to the most distant edge: The plastic section modulus W pl is calculated by adding the contribution of the external boundary and then subtracting the contribution of the internal void.

For the case of circular hollow sections (tubular sections) that cannot be classified as Class 3 their strength and stability verifications should be based on EN 1993-1-6: Strength and Stability of Shell Structures. The design plastic bending moment resistance of the cross-section is specified in EN1993-1-1 §6.2.5(2). In general the overall element resistance is smaller and must be verified according to the relevant clauses of EN1993-1-1 Section 6. The design resistance of the cross-section for axial force, shear force, and bending moment are calculated in accordance with EN1993-1-1 §6.2.Due to symmetry the centroid of the cross-section (center of mass) as well as the shear center are located at the center.

Design properties of hot finished Circular Hollow Section (CHS) for S235 steel class ( γ M0 = 1.00, units = mm)Baglietto SRL have started providing bulb flats since 70s, remarking the significant request, initially from the ship-repairing field, so then specializing more and more in the shipbuilding sector also. The shear area A v for the case of circular hollow sections is specified in EN1993-1-1 §6.2.6(3) as: