，要么你拿到这个题目，你要查阅大量的资料，认真详细的写出来。
Hot-rolled ribbed bars for reinforced concrete (GB1499-1998)
This standard is applicable to hot-rolled ribbed bars for reinforced concrete with nominal diameter of 6-50 mm. The standard stipulates the appearance, shape and sizes, technical requirements, test methods, inspection rules, packaging, marking and quality of hot-rolled ribbed bars for reinforced concrete.
The nominal diameter of hot-rolled ribbed bar (steel bar) is expressed in mm and written in the form of a number with the unit symbol mm. The nominal diameter is not a measure of the actual diameter, but a number used to divide different diameters of ribbed bars.
The appearance and shape requirements of hot-rolled ribbed bars require the surface of ribbed bars to be smooth, without laminar defects and seriously exceeded roll marks, and the ribs should be evenly distributed and consistent, with appropriate torsion angle, steepness and height. In general, the torsion angle of the rib should be 50-70 degrees. The greater the torsion angle, the smaller the rib rotation distance and the smaller the variability of the rib spacing.
Unless otherwise agreed by the supplier and the purchaser, the permissible out-of-straight deviation of ribbed bars does not exceed 0.5% of the total length of the ribbed bar. The permissible value of the winding of ribbed bars is 0.3m/m. The severity of the winding may not exceed 30%, and the distance from the bottom of the rib to the centre of the spiral should be uniform.
The range of sizes available is 6-50 mm, but sizes in coefficients of 1, 2, 3 and 4 such as 12, 24, 36, etc. It is suitable for reinforcement of concrete structures such as bridges, tunnels, wharves, chimneys, etc.
The chemical composition requirements of hot-rolled ribbed bars require steel to be composed of C≤0.17%, Si≤0.35%, Mn ≤ 1.40%, P ≤ 0.060%, S ≤ 0.050%. The mechanical properties of steel ribbed bars should meet the requirements of tensile strength 1450-1980MPa, yield strength 1250-1710MPa, ductility 13%-20%, and the tensile and yield strength decrease with the decrease of nominal diameter.
The test method for the performance of ribbed bars includes the determination of the tensile properties, the determination of the bending properties, the determination of the chemical properties, the determination of the optical properties and the determination of the surface quality. The most commonly used performance test for ribbed bars is the tensile test.
The determination of the tensile properties includes the determination of the tensile strength and the determination of the yield strength. The determination of the tensile strength is achieved through a tensile test and the determination of the yield strength is achieved through a tensile test or a bending test.
Inspection involves sampling inspection, foreign matter inspection and physical and chemical properties inspection. Sampling inspection is carried out according to the specified minimum sample size and the inspection should include, as far as possible, the inspection requirements that are likely to lead to non-conformance.
The foreign matter inspection of ribbed bars should visually examine the surface of the ribbed bar for foreign matter, and should include any foreign matter that adheres to the ribbed bar, as well as any foreign matter embedded in the ribbed bar.
The physical and chemical properties inspection should include the determination of the tensile properties, the determination of the bending properties, the determination of the chemical properties and the determination of the optical properties.
The inspection rules state that the head of the ribbed bar should be flat, straight and free from burrs, and the weight of the ribbed bar should meet the requirements of the relevant standards. The packaging, marking and quality of ribbed bars should also meet the specified requirements.
In summary, Hot-rolled ribbed bars for reinforced concrete (GB1499-1998) is a standard applicable to hot-rolled ribbed bars for reinforced concrete with nominal diameter of 6-50 mm. The standard stipulates the appearance, shape and sizes, technical requirements, test methods, inspection rules, packaging, marking and quality of hot-rolled ribbed bars for reinforced concrete. It stipulates the permitted deviation of out-of-straight and winding of ribbed bars, and it states the requirements of the chemical composition, mechanical properties and surface quality of ribbed bars. The standard also states the requirements of the inspection rules, packaging, marking and quality of ribbed bars. It is an important standard concerning the quality of ribbed bars for reinforced concrete.
