Steel pipe structures currently used in engineering can be classified according to cross-sectional shape, structural form and manufacturing method.
According to the cross-sectional shape of the component, the steel pipe structure can be divided into three categories: the circular tube structure (CHS), the square (rectangular) tube structure (RHS) and other shapes. Due to the superiority in appearance and mechanical performance, the round tube structure and the square tube structure are the most common. According to the structural form, the tube structure can be divided into four types: grid (reticulated shell), truss, frame and steel tube concrete structure. In the usual sense, the tube structure refers to a structure in which a round tube and a square tube are used as components, and the tubes are connected by intersecting welding. According to the production method, the pipe structure can be divided into hot-rolled seamless steel pipe structure, cold-rolled seamless steel pipe structure and welded steel pipe structure. The wall thickness of hot-rolled seamless steel pipe is large and the production cost is high, while the wall thickness of cold-rolled seamless steel pipe is relatively thin.
Characteristics of round pipe and square (rectangular) steel pipe structure
The characteristics of the steel pipe structure can be roughly summarized as follows:
(1) Both the circular tube and the square (rectangular) section
have the characteristics of biaxial symmetry, the centroid of the section and the shear center coincide; the moment of inertia of the section of the circular tube and the square tube is the same for each axis, as the bending and compression members advantages are prominent.
(2) The section is closed, the torsional rigidity is large, and the local stability of the plate is good. Especially the round tube section is particularly effective in resisting torsion.
(3) The appearance is simple and smooth, the rods can be directly welded at the same point, and the gusset plate can be omitted to save steel.
(4) Compared with the open section, the round pipe and the square (rectangular) section have the characteristics of smooth surface, no dead angle and small external surface area, which is conducive to saving anti-corrosion and fireproof coatings, and is also convenient for dust removal.
(5) The wind resistance coefficient of the steel pipe section is small, which has significant advantages when exposed to fluids (such as wind and water flow).
(6) The inner space of the steel pipe structure is available. Filling concrete in the steel tube (concrete-filled steel tube structure) can not only improve the bearing capacity of the component, but also prolong the fire resistance limit of the component (up to 2h on average). Rainwater pipes, etc.; prestressing cables can also be placed in the pipes to apply prestressing in the body.
(7) The unit price of the material of the steel pipe structure is higher than that of the section steel in the form of ordinary open section.