Requirements for steel bar binding
Usually, the binding of reinforcing bars should be carried out according to the following requirements:
(1) Reinforcement mesh binding. The crossing point of reinforcing bar should be tied with wire No. 20-22. For the reinforcing steel mesh of slab and wall, besides the intersection point of two rows of steel bars close to the periphery, the intersection point of the middle part can be secured alternately, but it is necessary to ensure that the stressed reinforcing steel bars do not suffer from azimuth deviation; the intersection point of two rows of steel bars close to the periphery should be bound by cross-stitching; the direction of the binding should be changed interlacingly according to the specific situation, so as to avoid the distorted mesh in one direction. For large meshes, reinforcement with steel bars can be properly used as oblique tension reinforcement. All intersecting points shall be firmly secured by two-way loaded steel bars.
(2) stirrups of beams and columns. The stirrups of beams and columns should be straight with the stressed steel bars, and the bending hooks of the stirrups should be staggered along the direction of the stressed steel bars. The hoop hook of the beam should be placed in the compression zone. In some cases, such as the support of the connecting beam, the compression zone is at the lower part of the section. If the hoop hook is located below, it may be "opened" by the steel bar. At this time, the hoop hook has to be placed in the tension zone (the upper part of the section, that is, the side of the stressed steel bar), but it should be tied up specially and welded with arc welding points when necessary.
(3) The bending hook of column longitudinal reinforcement is oriented. When binding the steel bar of rectangular column, the hook plane of the corner steel bar should be 45 (the hook plane of the polygonal column corner steel bar should be located on the bisector of the inner corner of the template; the hook plane of the circular column steel bar should be straight with the tangent plane of the template, that is, the hook should be oriented towards the center of the template); the hook plane of the middle steel bar of the rectangular column and the polygonal column (that is, the steel bar not at the corner) should be straight with the template plane. The angle between the bending hook plane and the plate surface shall not be less than 15 degrees when a column with a small cross section is poured by a piercing vibrator.
(4) Reinforcement treatment at the intersection of members. At the intersection points of members, such as the intersection points of columns and beams, beams and beams, and structural and truss joints, steel bars are interwoven vertically and horizontally. Most of them collide in the same direction and cannot be installed. This situation needs to be dealt with in the process of drawing examination before construction. In general, the treatment method is to set the reinforcement in one direction in the prescribed direction (the thickness of the protective layer is taken according to the prescribed), while the reinforcement in the other direction avoids it (usually by adjusting the thickness of the protective layer).
(5) fixing the orientation of reinforcement. The installation has accurate orientation of reinforcing bars. The reinforcing bars should not be displaced during construction. If necessary, corresponding brackets, cushion blocks or cushion bars should be set in advance to fix them.
(6) Reinforcement protective layer. The minimum thickness of the protective layer (calculated from the outer skin of the stressed steel bars) shall be in accordance with the regulations and shall not be less than the diameter of the stressed steel bars. The traditional method is to use cement mortar to make pads of certain thickness on site.