H-20 loading, also known as HS-20 loading, is the design criteria of the American Association of State Highway Transportation Officials, or AASHTO. It “means” a truck axle loading of 32,000 pounds or wheel loading of 16,000 pounds. Standards as published by AASHTO are categorized into classes. The classifications, load rating classifications and other AASHTO terms are as follows:
- Light Duty or “Non-Traffic”- No roadway traffic. Pedestrian or hand truck traffic only.
- H15 or “Medium duty”- Light duty traffic rating. 12,000 lb. wheel load or 75% of H20.
- H20 or “Traffic-Rated”- Heavy duty traffic rating. Commonly known as H-20, HS-20, traffic rated or heavy duty (HD). Designed for a 16,000 lb. wheel load (32,000 lb. dual spaced wheel load)
- Extra HD or “Airport-Rated”- Meets the design loading associated with the FAA wheel loading. Castings can accept loading from 200,000 lbs. and up and may include an additional safety factor beyond FAA design loading where noted and required.
Total wheel load and tire contact area must be provided by purchaser or final destination end user. Heavy concentration loads such as H-20 or airport traffic must be noted where required.
Bass & Hays traffic load or “traffic rated” service castings have a first article proof load test conducted and results are available on request. Proof load shall be conducted in accordance with the method and procedure outlined in AASHTO M306, Section 7.0 “Proof Load Testing”. The casting is tested on a suitable and calibrated load testing machine and the casting will hold a 40,000 pound proof load for one minute without experiencing any cracks or detrimental permanent deformation.
Castings shall have contact (bearing) surfaces machined and certified as non-rocking, shall be of uniform quality free from sand holes, shrinkage, cracks and other surface defects and shall be ground smooth and well cleaned by shot blasting. Casting dimensions may vary within accepted foundry tolerances as outlined in the Iron Castings Handbook published by the American Foundry Society. Castings are manufactured from iron conforming to ASTM A48, Class 35B or better, and Ductile Iron Castings conform to ASTM A536 or better. Castings shall be unpainted, unless specified otherwise. A non-polluting coating may be applied on request.
Gray iron castings shall conform to ASTM A48, Class 35B, as noted in section 7.1.1 and 7.1.3 of AASHTO M306, ductile Iron castings shall conform to ASTM A536, and steel grates shall be hot rolled steel in accordance with ASTM A36, and shall be galvanized when conforming to ASTM 123.
Castings used for any purpose must be properly installed in accordance with current and accepted government, engineering and industry standards, and under the guidance of a qualified inspector, engineer, architect, contractor, or job superintendent. All improper installation or use voids the original manufacturers warranty.
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