Determining the required cross section of reinforcement in the spans and on the supports and bent the valves, move for the appointment of the number and diameter of rods. At the same time are guided by the following provisions:
The number of rods must be assigned so that the valve would fit in one row (but not less than 3 rods). Diameter of working cores should be appointed from 12 mm to 25 mm.
The number of bars in the span should be coordinated with the required section of the bent rebar by calculation and with the number of bent bars that are required to overlap the section of the envelope of the transverse forces diagrams.
All bent armature should be received by means of a bend of the bottom longitudinal cores and, as a last resort if they are not enough, to put "ducks". The number of planes of bends and the area of the bent cores in each plane shall be not less than required on calculation. The angle of inclination of bends to the beam axis (at h < 800 mm) is accepted 45°.
It is necessary to aspire to smaller quantity of different diameters of working fittings. The difference in diameters of working fittings shall not be less than 2 mm.
From the cores lying on the beam visa not less than two cores shall be brought to the support on a beam bottom (at b > 150 mm).
Selection of the number of rods and their dimeters should be carried out in such a way that the difference between the calculated cross-sectional area of the reinforcement and the total area of the rods laid in the spans is minimal (up to ±5%).
At placement in cross-section of cores it is necessary to watch observance of a backlash between them, proceeding from the accepted width of a beam. Above the support, the gaps between the rods in the row are increased for the convenience of concreting.At the arrangement of the bottom armature more than in two numbers on section height the distance between the cores located in the third and following numbers shall be accepted not less than 50 mm.
On supports required for the calculation of the moment of longitudinal working reinforcement must be obtained through the span of rebar that you can bend, and fixtures adopted at the negative moment in the adjacent spans and stacked in the far empty seats so they were ' at the same time, and mounting rods.
In the reference section, the rod that has a straight section of at least ho / 2 before the reference section operates on the perception of the bending moment.
In some cases, it is possible to obtain support for the required cross-sectional area of rebar to install additional straight bars that are placed in the extreme available.
It is recommended to place bending bars at least 2d from the side faces of the element, where d is the diameter of the bending bar
Based on these requirements, we will select the diameter and number of rods.