(1) The geometrical characteristics of the straight seam steel pipe
section are good, the pipe wall is generally thin, the section material is distributed around the centroid, the section has a large radius of gyration, and has strong torsional rigidity; as a compression, bending and bidirectional bending member, The bearing capacity is high, and the straightness and cross-sectional dimension of the cold-formed pipe are more accurate than the cross-section of the hot-rolled opening.
(2) In terms of anti-hydrodynamic characteristics, the cross section of the round pipe is the best, and the effect of wind and water flow is greatly reduced. The cross section of the rectangular tube is similar to this in this respect.
(3) The steel pipe is a closed section; in the case of the same average thickness and cross-sectional area, the exposed surface area is about 50% to 60% of the opening section, which is advantageous for corrosion prevention and can save the coating material.
(4) The connection of the nodes is suitable for direct welding, and it can save labor and materials without passing through the gusset plate or other connecting parts.
(5) The appearance is relatively beautiful, especially the pipe truss composed of steel pipe members, without redundant node connection, and has a strong modern feeling.
(6) If necessary, concrete may be poured in the pipe to form a composite member.
Due to the above advantages, the steel pipe structure can save about 20% of the steel in the industrial building and 50% in the structure of the tower compared with the structure made with the open section. The structure of the steel pipe may be a round pipe structure or a rectangular pipe structure according to the force condition, supply condition, production and processing conditions and cost of the component, or a mixture of two steel pipes. When used in combination, the general chord adopts a rectangular tube and the web is a round tube; sometimes, the chord can also be made of I-beam or H-shaped steel, and the rib is a rectangular tube or a round tube.
When the mechanical properties are stable, the local buckling is easy to occur when the pressure is applied, but the post-buckling strength and the anti-hydrodynamic characteristics are most favorable. The minimum force is the same, the surface area is the smallest, and the surface area is slightly larger. There are school corners, anti-corrosion and fire-resistant, corrosion-resistant and fire-proof without corners; fire-resistant and anti-corrosion materials use a little more material.