Standard Specification for Structural Steel for Bridges
This specification covers carbon and high-strength low alloy steel structural shapes, plates and bars and quenched and tempered alloy steel for structural plates intended for use in bridges. Heat analysis shall be used to determine the percentage of carbon, manganese, phosphorus, sulfur, silicon, and copper for the required chemical composition. Tension test shall be used to determine the required tensile properties such as tensile strength, yield strength, and elongation. Materials shall undergo: (1) impact test for non-fracture critical and fracture critical members; and (2) Brinell hardness test for Grades 100 and 100W. Atmospheric corrosion resistance shall also be determined.
1.1 This specification covers carbon and high-strength low-alloy steel structural shapes, plates, and bars and quenched and tempered alloy steel for structural plates intended for use in bridges. Seven grades are available in four yield strength levels as follows:
1.1.1 Grades 36 , 50 , 50S [345S], and 50W [345W] are also included in Specifications A 36/A 36M, A 572/A 572M, A 992/A 992M, and A 588/A 588M, respectively. When the supplementary requirements of this specification are specified, they exceed the requirements of Specifications A 36/A 36M, A 572/A 572M, A 992/A 992M, and A 588/A 588M.
1.1.2 Grades 50W [345W], HPS 50W [HPS 345W], HPS 70W [HPS 485W], and HPS 100W [HPS 690W] have enhanced atmospheric corrosion resistance (see 13.1.2). Product availability is shown in Table 1.
1.2 Grade HPS 70W [HPS 485W] or HPS 100W [HPS 690W] shall not be substituted for Grades 36 , 50 , 50S [345S], 50W [345W], or HPS 50W [HPS 345W]. Grade 50W [345W], or HPS 50W [HPS 345W] shall not be substituted for Grades 36 , 50  or 50S [345S] without agreement between the purchaser and the supplier.
1.3 When the steel is to be welded, it is presupposed that a welding procedure suitable for the grade of steel and intended use or service will be utilized. See Appendix X3 of Specification A 6/A 6M for information on weldability.
1.4 For structural products to be used as tension components requiring notch toughness testing, standardized requirements are provided in this standard, and they are based upon American Association of State Highway and Transportation Officials (AASHTO) requirements for both fracture critical and non-fracture critical members.
1.5 Supplementary requirements are available but shall apply only if specified in the purchase order.
1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.7 For structural products produced from coil and furnished without heat treatment or with stress relieving only, the additional requirements, including additional testing requirements and the reporting of additional test results, of Specification A 6/A 6M apply.
TABLE 1 Tensile and Hardness RequirementsA
Note—Where “. . .” appears in this table, there is no requirement.
A See specimen orientation and preparation subsection in the Tension Tests section of Specification A 6/A 6M.
B Measured at 0.2 % offset or 0.5 % extension under load as described in Section 13 of Test Methods A 370.
C Elongation and reduction of area not required to be determined for floor plates.
D For plates wider than 24 in. [600 mm], the reduction of area requirement, where applicable, is reduced by five percentage points.
E For plates wider than 24 in. [600 mm], the elongation requirement is reduced by two percentage points. See elongation requirement adjustments in the Tension Tests section of Specification A 6/A 6M.
F Elongation in 2 in. or 50 mm: 19 % for shapes with flange thickness over 3 in. [75 mm].
G Not applicable.
H The yield to tensile ratio shall be 0.87 or less for shapes that are tested from the web location; for all other shapes, the requirement is 0.85.
I A maximum yield strength of 70 ksi [480 MPa] is permitted for structural shapes that are required to be tested from the web location.
J For wide flange shapes with flange thickness over 3 in. [75 mm], elongation in 2 in. or 50 mm of 18 % minimum applies.
K If measured on the Fig. 3 (Test Methods A 370) 1½-in. [40–mm] wide specimen, the elongation is determined in a 2-in. or 50-mm gage length that includes the fracture and shows the greatest elongation.
L 40 % minimum applies if measured on the Fig 3 (Test Methods A 370) 1 ½-in. [40-mm] wide specimen; 50 % minimum applies if measured on the Fig. 4 (Test Methods A 370) ½-in. [12.5-mm] round specimen.
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