Steel bars can be divided into various types such as force bars, stirrups, frame bars, and distribution bars, and they play the role of "skeleton" in buildings. The quality of their construction is crucial. Today we have summarized the common steel bar problems at construction sites.
(I) Common foundation errors
1. The joint position of the foundation beam is incorrect. It is set according to the joint position of the floor frame beam, and there is no stagger (the forces of the foundation beam and the frame beam are exactly opposite, and the joints are the same).
2. The reserved length of the raft slab steel bar joint at the construction joint is not enough, and the joint is not staggered.
3. The foundation horse stool is placed incorrectly. If you change the direction, each row of horse stools can save a fixed full-length steel bar. Or, the full-length steel bar on the horse stool uses the longitudinal bars in the same direction on the upper part of the raft slab.
4. The raft slab has a large area, but it is still connected at a 50% joint percentage, not at a 25% joint percentage, resulting in a waste of steel bar joints.
5. The length of the bottom plate longitudinal reinforcement joint is too long, exceeding one lap length, and some are too short and cannot meet the length required by the specification. The full-length reinforcement of the bottom plate is not tied into parallel straight lines, resulting in different numbers of steel bars with the same cross-section.
6. The abutment is not reduced according to the specifications, but the design "optimization" is reduced according to the independent foundation structure, which is a design of cutting corners.
7. The edge sealing structure of the raft slab is not in accordance with the specifications and design, and the bending length of the upper and lower longitudinal reinforcement of the raft slab is set without authorization.
8. The longitudinal reinforcement joint of the raft slab is set in the post-casting strip (the longitudinal reinforcement joint should not be set in the post-casting strip position).
9. The reinforcement of the pile connection is put together.
(II) Common errors in columns
1. The top-level side columns are not set with bending. 11G101-1 "Drawing rules and structural details of the overall representation method of the concrete structure construction drawing (cast-in-place concrete frame, shear wall, beam, slab)" stipulates that when the outer lap joint of the column is adopted, the outer side of the column can be unbent, but the inner side of the column is required to be bent when the beam height is less than the anchor.
2. The middle column of the top layer is bent. If the longitudinal reinforcement of the middle column of the top layer meets the straight anchor in the beam, it does not need to be bent.
3. The stirrups at the column-beam node are not set or the spacing is too large. The column-beam node is the core node and the key node for earthquake resistance. It is better to put less longitudinal reinforcement in the beam than to save the stirrups in the beam-column node.
4. The longitudinal reinforcement of the column is not staggered in length. This is a problem of steel bar turning. When the number of upper and lower steel bars of the column changes, the length of the vertical steel bars is not adjusted in the lower layer, resulting in the failure to stagger the joints.
5. The column protective layer does not meet the minimum protective layer thickness.
6. Some hidden columns are very long, and the hidden stirrups are arranged in a U shape, which will increase the steel bar joints. They should be closed stirrups to save steel bars.
7. The hidden column stirrups have an inner angle, which is not allowed. The angle formed by the intersection or anchoring of two stirrups does not belong to the inner angle.
(III) Common mistakes in walls
1. The horizontal reinforcement of the wall (outer and inner guillotine) is overlapped at the same position, and the joints are not staggered according to the joint percentage.
2. The joints of the horizontal reinforcement of the wall are not set at the minimum stress. The horizontal reinforcement on the outside of the exterior wall should be located at 1/3 of the span or 1/4 of the wall height, and the inside of the exterior wall should be located at the support and near the support.
3. The position of the vertical reinforcement joint of the basement exterior wall is wrong. According to the specification, the vertical reinforcement on the outside of the exterior wall should be located in the 1/3 area between the wall height, and the vertical longitudinal reinforcement on the inside of the exterior wall should be located in the 1/4 area at the root of the wall height.
4. The top formwork of the reinforcement on the outside of the exterior wall has no protective layer. The consequences of the exposed reinforcement on the outside of the exterior wall are very serious, and the entire exterior wall will eventually be destroyed. The outside of the exterior wall is in direct contact with soil and water, and the protective layer is not less than 40mm.
5. The general structural description does not indicate whether the top plate is a simple support or an elastic embedded support of the exterior wall, and the construction is not carried out according to it. The bending of the longitudinal reinforcement of the exterior wall is based on the wall thickness minus the protective layer. I don't know what the construction is based on, or it is taken for granted.
6. The lap length of the longitudinal reinforcement of the wall is too long, directly based on the wall height. When the wall is capped, the vertical reinforcement of the wall should be subtracted from the reserved length below and then added to the lap length.
7. The wall reinforcement is not tied in a standard way, either the spacing is wrong or the method is wrong, such as not pulling the horizontal wall reinforcement or the reinforcement length is wrong, and it is not pulled vertically but diagonally during construction.
(IV) Common mistakes in beams
1. Additional stirrups are added on both sides of the main beam at the junction of the main and secondary beams. The main beam is not equipped with normal stirrups at the secondary beam position, and three additional stirrups are directly laid.
2. The bottom reinforcement of the beam is generally not tied. The workers' excuse is that they can't tie it, but in fact it can be tied. First, raise the beam and fix it with a steel pipe bracket. After all the upper and lower reinforcements of the beam, including the waist reinforcement, are tied, the beam is dropped. This is a simple construction process.
3. The beam hook is constructed with 90° at one end and 135° at the other end. It should be 135°. Of course, it is not easy to place the hook at both ends at 135°. You can first process one end to 90° and then bend it to 135° with a wrench after the binding is completed.
4. No reinforcement is arranged around the beam opening. The specification strictly prohibits opening holes in beams, but it is inevitable to open holes in beams. The remedial measure is to strengthen the openings.
5. The beam joints are not set at the place with less stress (the upper longitudinal reinforcement is the 1/3 area of the span), but at the place with the greatest stress. Some places the upper reinforcement of the beam at or near the beam support.
6. The hanger is constructed according to the height of the secondary beam, which should be constructed according to the height of the main beam.
7. The beam pad is not made correctly. The pad is not strong enough and is crushed, resulting in direct contact between the beam and the formwork, which will cause exposed reinforcement; some use transverse reinforcement to support the board directly.
8. The beam tension reinforcement is omitted or placed obliquely, and some are not tied, which cannot play the role of tension reinforcement.
9. The position of the second row of beam reinforcement is wrong, and the distance from the top of the beam is too large, so it cannot play a force-bearing role.
10. The upper reinforcement of the beam adopts a tied joint but does not increase the stirrups at the joint position. According to the specification, transverse stirrups are set at the joint position with a spacing of min (5d, 100). It is actually very difficult to do. If it is done according to the specification, it will almost become fully encrypted. It is best to use mechanical connection or welding (non-electroslag pressure welding) for the longitudinal reinforcement of the beam, so that there is no need to increase the number of stirrups at the joints.
11. The spacing of the upper reinforcement of the beam is too close, making it difficult to pour concrete.
12. The beams in several directions intersect and overlap, and the upper reinforcement of the beam has no protective layer or even exceeds the height of the beam. In this case, the upper longitudinal reinforcement of the secondary beam can be placed under the upper longitudinal reinforcement of the main beam.
