Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO M 270M/M 270:2020
• Năm ban hành / Publication date: 2020
• Tình trạng / Status: A - Còn hiệu lực
• Tên tiếng Anh / Title in English: Standard Specification for Structural Steel for Bridges
• Thay thế cho / Replace: AASHTO M 270M/M 270:2019
• Số trang / Page: 17

Phạm vi áp dụng / Scope of standard

This specification covers carbon and high-strength low-alloy steel structural shapes, plates, and bars and quenched and tempered alloy steel, and stainless steel for structural plates intended for use in bridges. Twelve grades are available in five yield strength levels as follows:

Grades 250 [36], 345 [50], 345S [50S], 345W [50W], and 345CR [50CR], QST 345 [QST 50], QST 345S [QST 50S], QST 450 [QST 65] and QST 485 [QST 70] are also included in ASTM A36/A36M, A572/A572M, A992/A992M, A588/A588M, A514/A514M, and A1010/A1010. When the supplementary requirements of this specification are specified, they exceed the requirements of A36/A36M, A572/A572M, A992/A992M, A588/A588M, A514/A514M, and A1010/A1010M.

Grades 345W [50W], 345CR [50CR], HPS 345W [HPS 50W], HPS 485W [HPS 70W], and HPS 690W [HPS 100W] have enhanced atmospheric corrosion resistance (Section 13.1.2). Product availability is shown in Table 2.

Grade HPS 485W [HPS 70W] or HPS 690W [HPS 100W] shall not be substituted for Grade 250 [36], 345 [50], 345S [50S], 345W [50W], 345CR [50CR], or HPS 345W [HPS 50W]. Grade 345W [50W], 345CR [50CR], or HPS 345W [HPS 50W] shall not be substituted for Grade 250 [36], 345 [50], or 345S [50S] without agreement between the purchaser and supplier.

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 ASTM A6/A6M for information on weldability.

For structural products to be used as tension components requiring notch toughness testing, standardized requirements are provided in this standard. These requirements are based on American Association of State Highway and Transportation Officials (AASHTO) requirements for both fracture-critical and non-fracture-critical members.

Supplementary requirements are available but shall apply only if specified in the purchase order.

The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system is to be used independently of the other, without combining values in any way.

For structural products cut from coiled product and furnished without heat treatment or with stress relieving only, the additional requirements of ASTM A6/A6M, including additional testing requirements and the reporting of additional tests, apply.