Once abnormal or missing signs are found, they shall be strictly inspected.
(4) Except for welded closed loop stirrups, hooks shall be made at the ends of stirrups, and the form of hooks shall meet the design requirements; Generally, the hook shall be 1350, and the length of the straight part of the stirrup after bending shall not be less than 6D (d-stirrup diameter) and 50mm for general structures; For structures with seismic requirements, it shall not be less than 10d and 75 (as shown in Figure 4).
The labels on each bundle of reinforcement are made of steel, which are important quality information to prove the manufacturer, heat number, specification, model, batch number and production date of the reinforcement.
(3) Surface quality: the wire rod has cracks, folds, scabs, ears, delaminations and inclusions, bumps, pits, scratches and other surface defects, which fail to meet the national standards.
(6) Hook direction of reinforcement mesh: the hook of foundation reinforcement shall be upward; For the hook of slab reinforcement, the hook shall be upward when the reinforcement is at the lower part of the slab; When the rebar is on the upper part of the slab, the hook is downward.
Figure 2 bending diameter of 900 or 1350 bent D-bar at the end of reinforcement; D- reinforcement diameter Figure 3 reinforcement bending processing d- bending diameter of reinforcement; D- rebar diameter Figure 4 Schematic diagram of beam and column stirrup hook 3 Hot rolled steel bars are not used for steel bars.
The length of the straight part of the hook after bending shall not be less than 3 times the diameter of the reinforcement (as shown in Figure 1).
There are several cases of unqualified appearance: (1) abnormal or missing labels.
(4) The shape difference is mainly the ribbed reinforcement, some longitudinal and horizontal ribs are not high enough, and some crescent ribs are too wide at the top.
For the reinforced concrete structural members in civil air defense engineering, the cracking state after yielding is still a normal working state, which is very different from the state of structural members under static action.
The intersection points of the long-term reinforcement and the short-term reinforcement must be firmly tied, and the binding directions of the adjacent binding points shall be staggered to avoid The mesh is skewed and deformed.
Fixing Socket Cross Pin Nail Plate
2.
the hook or bending of the reinforcement does not meet the requirements of the specification.
The reinforcement such as frame beam, bracket and column cap shall be placed inside the longitudinal reinforcement of the column.
The commonly used hot-rolled steel bars for reinforced concrete structures of civil air defense projects are hpb300, HRB335, HRB400 and rrb400.
(5) The beam stirrup shall be perpendicular to the main reinforcement, the joint of stirrup shall be staggered on the four corner longitudinal reinforcement, and the intersection of stirrup corner and longitudinal reinforcement shall be firmly tied.
Figure 1 1800 hook d-bending diameter of reinforcement at the end of reinforcement; D- rebar diameter (2) when the ends of HRB335, HRB400 and rrb400 rebar need to be bent by 900 or 1350, the inner diameter D of the bending arc of HRB335 rebar shall not be less than 4 times of the rebar diameter; HRB400 and rrb440 rebar should not be less than 5 times of the rebar diameter; The length of the straight part of the hook after bending shall be determined according to the design requirements (as shown in Figure 2).
Cold drawn ribbed steel bars, cold drawn steel bars and other cold processed steel bars have low elongation, poor plastic deformation capacity and poor ductility, and are not allowed to be used in civil air defense projects.
During the mobilization of rolled steel bars, spot check 1 ~ 3 bundles of steel bars to make statistics on the nominal weight and compare it with the actual weight.
(3) When the longitudinal stressed reinforcement of beam and slab is arranged in double layers, short reinforcement with a diameter of 25mm or more shall be placed between the two rows of reinforcement to maintain the correct design distance.
The allowable deviation shall not be greater than the national standard.
At the same time, it shall be noted that the clear distance between the main reinforcements on the top of the beam shall be 30mm to facilitate the pouring of concrete.
The hook or bending of the reinforcement shall meet the following requirements: (1) 1800 hooks shall be made at the end of hpb300 reinforcement, and the inner diameter D of the bending arc shall not be less than 2.5 times the diameter of the reinforcement.
The intersection points of the long direction reinforcement and the short direction reinforcement must be firmly tied, and the binding directions of the adjacent binding points shall be staggered.
For example, the binding of inner and outer vertical reinforcement is reversed when binding the reinforcement of the free wall; In some projects, the reinforcement binding of the bottom slab inverted beam does not meet the requirements of the drawing.
The correct practice of the bottom slab inverted beam is shown in the following figure: precautions for the binding of structural reinforcement of the bottom slab inverted beam reinforcement: (1) when binding the foundation reinforcement mesh, the position line of the short-term reinforcement shall be drawn on the base, the short-term reinforcement shall be placed according to the line, and then the long-term reinforcement shall be placed on the short-term reinforcement according to the spacing of the long-term reinforcement.
(4) At the intersection of slab, secondary beam and main beam, the reinforcement of slab is at the top, the reinforcement of secondary beam is in the middle, and the reinforcement of main beam is at the bottom.
(7) During rebar binding, drawings and design changes must be carefully checked to avoid errors such as wrong rebar diameter and spacing or reversed binding of internal and external rebar.
The straight part of the stirrup and the longitudinal intersection can be fastened at intervals to prevent the skeleton from skewing.
Advertising space: common problems and solutions in civil air defense engineering construction (I) common problems and solutions in civil engineering 1 Common problems of rebar appearance inspection appearance inspection is a necessary procedure for rebar acceptance.
Hot rolled steel bars must be used for civil air defense engineering copper reinforced concrete structures.
The reinforcement shall be straight without damage, and the surface shall be free of crack, oil stain, granular or flake old rust.
The design values of reinforcement strength are as follows: strength unit: n/mm2 reinforcement type (or brand) design strength dynamic design strength hpb300 270405hrb335 300405hrb400 rrb400 3604324 The binding of reinforcement is inconsistent with the drawings and design changes or does not meet the requirements of construction specifications and inspection and evaluation standards.
(2) Weight difference – generally, the weight difference caused by the size difference of reinforcement in production.
(2) When binding the silver reinforcement net of the orientation plate, the position line of the short direction reinforcement shall be drawn on the formwork first, the short direction reinforcement shall be placed according to the line, and then the long direction reinforcement shall be placed on the short direction reinforcement according to the spacing of the long direction reinforcement.
(3) The bending internal diameter D at the bending position in the middle of the bent reinforcement shall not be less than 5 times of the reinforcement diameter (as shown in Figure 3).
Cold rolled ribbed steel bars, cold drawn steel bars and other cold processed steel bars shall not be used.
At the same time, the allowable deviation of rebar position must meet the requirements of inspection and evaluation standards (see Table 1)..
