Square steel pipe has obvious advantages over round steel pipe for three reasons:
Firstly, the bearing capacity and seismic performance of alloy steel tubes are better than those of square and circular tubes with the same side length and diameter. According to the test of three-story two-span alloy steel tube and circular tube concrete column frame carried out by a university in Tianjin, the side length of alloy steel tube column is 150 mm and the diameter of circular tube is 150 mm. The yield capacity and ultimate bearing capacity of the former are 80% higher than those of the latter, and the seismic performance index of the former is about two of the latter. Times;
Second, alloy steel pipe construction is more convenient. In general, the circular concrete column of steel structure residence needs further construction, and the circular section should be changed into square section.
Thirdly, the connection between circular concrete column and beam is difficult to deal with. In the future steel structure market of our country, the cold-formed square rectangular tube will occupy an important share.
In practical application, these two basic methods should be allocated to a reasonable technological position according to the product requirements in the forming of alloy steel pipes. Attention should be paid to the effect of the stretching/thinning effect of solid bending and the compression/thickening effect of empty bending on product quality. Otherwise, it will lead to concave side and longitudinal warping of finished pipe during alloy steel tube forming, and it is difficult to straighten.