3.1　Steel

3.1.1　The steel tube used in CFST arch ribs should be carbon or low alloy high strength structural steel of Grade B or above.The steel quality shall comply with the provisions in current national standards GB/T 700 Carbon Structural Steels or GB/T 1591 High Strength Low Alloy Structural Steels.

3.1.2　Steel tubes may use rolled welded tubes or seamless steel tubes.Whenever the requirement of rolling is satisfied，straight seam welded tubes should be used.

3.1.3　Main mechanical properties of steel shall be in accordance with those specified in Table 3.1.3.

3.1.4　The physical properties of steel specified in Table 3.1.4 may be used.