1. Indicate the quantity, diameter and grade of reinforcement: 3 Ф 20.
3: Indicates the number of steel bars.
Ф: diameter symbol.
20: Indicates the rebar diameter.
2. Indicate the grade and diameter of reinforcement and the center distance between adjacent reinforcement: Ф 8 @ 200.
Ф: symbol indicating the diameter of steel bar.
8: Indicates the diameter of reinforcement.
@: Equal center distance symbol 200: Center distance between adjacent reinforcing bars (≤200mm).
Extended data:
Reinforcement refers to the working process of setting reinforcement in concrete, and designing, processing and configuring it to enhance the bearing capacity of concrete.
(1) The shrinkage and creep of reinforced high-strength and high-performance concrete in natural environment are characterized by rapid development in the early stage and slow development in the later stage, which accords with the development law of concrete shrinkage and creep. ?
(2) The shrinkage and creep of reinforced concrete are less than that of plain concrete. When the reinforcement ratio is low, it has little influence on shrinkage and creep, so it can be treated as plain concrete in engineering application. When the reinforcement ratio is high, the effect of reducing shrinkage and creep needs specific experimental study; ?
(3) Through the finite element analysis of reinforced concrete and the comparison with the experimental results, it can be concluded that the influence of creep should be considered in the shrinkage strain analysis of reinforced concrete, and ignoring the influence of creep will cause great errors in the shrinkage strain; ? The influence of reinforcement ratio on creep is also different. The higher the reinforcement ratio, the smaller the creep. Under the same reinforcement condition, the creep of concrete with different loading ages is similar.
Beam reinforcement
(1) When the span-height ratio of continuous beam is less than 9, the reinforcement is basically controlled by the minimum reinforcement ratio, and the crack width and combustion degree are small because the beam bears a small bending moment.
(2) When the span-height ratio is ≥ 10, the calculated reinforcement ratio of longitudinal reinforcement decreases obviously with the increase of reinforcement strength;
(3) When the span height ratio is large and the load is large, the reinforcement may be limited by the crack width and deflection. Compared with HRB400 steel bar, the strength advantage of HRB 500 steel bar cannot be reflected, so HRB500 steel bar should be selected.
(4) When the span-height ratio is between 10 ~ 14, HRB500 steel bar is more effective than HRB400 steel bar, so HRB500 steel bar should be adopted.
Steel bars for reinforced concrete refer to straight steel bars or rolled steel bars used to strengthen reinforced concrete. Its shape can be divided into smooth circular reinforcement and deformed reinforcement, and the delivery state is straight and coiled.
Smooth round steel is actually a small round steel and coil of ordinary low carbon steel. Deformed steel bars are steel bars with ribs on the surface, usually with two longitudinal ribs and transverse ribs evenly distributed along the length. The shapes of transverse ribs are spiral, herringbone and crescent. Expressed in millimeters of nominal diameter. The nominal diameter of deformed steel bar is equivalent to the nominal diameter of smooth round steel with equal cross section.
The nominal diameter of reinforcement is 8-50mm, and the recommended diameters are 8, 12, 16, 20, 25, 32 and 40 mm.. Steel grade: 20MnSi, 20MnV, 25MnSi, BS20MnSi.
Steel bars mainly bear tensile stress in concrete. Deformed steel bars have great bonding ability with concrete due to the action of ribs, so they can better withstand the action of external forces. Steel bars are widely used in various building structures. Especially for large, heavy and light thin-walled and high-rise building structures.
Waste heat treatment of reinforced concrete Waste heat treatment of steel bar: water is introduced immediately after hot rolling to control surface cooling, and then the finished steel bar is tempered by the waste heat of the core itself.
Ribbed steel bar: steel bar with two longitudinal ribs and transverse ribs evenly distributed along the length direction.
Crescent rib: the longitudinal section of the transverse rib is crescent-shaped and does not intersect with the longitudinal rib.
Longitudinal rib: a uniform and continuous rib parallel to the axis of steel bar.
Transverse rib: Other ribs that are not parallel to longitudinal ribs.
Nominal diameter of ribbed steel bar: the diameter of a circle equal to the nominal cross-sectional area of steel bar.
Relative rib area of ribbed steel bars: the ratio of the projected area of transverse ribs on the plane perpendicular to the axis of steel bars to the product of the nominal circumference of steel bars and the spacing of transverse ribs.
References:
Baidu Encyclopedia-Strengthening