What is the function of construction joint

2022-07-22
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Many people will ask what construction joints are. The construction joint mainly refers to the concrete pouring in modern building construction. Because of the construction requirements and other conditions, the concrete needs to be poured in sections, so this kind of joint will be formed between the concrete

as we all know, construction joints are actually when we use concrete and reinforcement to pour, and often not all the work is completed at one time. What we need to consider is the design requirements and the need for convenient construction, which makes it impossible to complete the concrete pouring at one time, but by sections. In the process of the last and next pouring, because the time of the two pouring is different, a small joint will be produced. Then, let's introduce what construction joints are and their functions

what is the construction joint

the joint reserved between the partitions of each construction unit due to the needs of construction organization. Construction joints are not real “ Sewing ”, It is only because the later poured concrete exceeds the initial setting time, and there is a joint surface with the first poured concrete, which is called construction joint. Because the joint surface formed by concrete pouring is prone to various hidden dangers and quality problems, different structural projects need to be cautious in the treatment of construction joints

the role of construction joints

everyone knows a word, “ Rome was not built in a day;. In fact, the construction of any building cannot be achieved overnight, and it has to be built several times in sections. However, if the subsection construction is right, there will be many follow-up problems. For example, when building the foundation, because the area of the foundation is too large, it needs to be carried out in sections. If the specific implementation of the subsection construction cannot be reasonably calculated, then the foundation of the house cannot be solid, and the house cannot stand

therefore, we can also see the role of construction joints. Reserving construction joints can accurately grasp the specific implementation of sub construction (or subsection construction), and can effectively ensure the construction quality of buildings. Generally speaking, construction joints need to be reserved before the building. If you plan in advance where to reserve construction joints, you can make the building not be unstable and have problems because of the sub construction. When reserving construction joints, we need to calculate how long it takes for each section to set the concrete, and then determine a reasonable time difference, so that each part can be constructed in sections and firmly combined. This is the role of construction joints and the significance of their existence

retaining position of construction joint

1. The construction joint should be retained on the top surface of the foundation, below the bracket of the beam or crane beam, above the crane beam, and below the column cap of the beamless floor

2. For the large section beam connected with the floor slab, the construction joint should be left 20 ~ 30mm below the bottom of the slab. When there is a beam bracket under the plate, it shall be left at the lower part of the beam bracket

3. For one-way slabs with a length width ratio greater than 2, the construction joint should be left at any position parallel to the short side of the slab, and the construction joint should be left vertically, and cannot be made into an inclined tenon

4. The floor slab with primary and secondary beams should be poured along the direction of the secondary beam, and the construction joint should be left within the middle 1/3 of the span of the secondary beam

5. The construction joint on the wall should be left within 1/3 of the lintel span of the door opening, or at the junction of vertical and horizontal walls

6. The construction joint on the stairs should be left at 1/3 of the step board. The concrete of stairs should be poured continuously. If it is a multi-storey staircase, and the upper floor is a cast-in-place floor slab but not poured, the construction joint can be left; It should be left in the middle 1/3 of the stair section, but it should be noted that the joint surface should be inclined and perpendicular to the axis of the stair. (the reason for the dispute in the construction is that the old specification stipulates that the stair construction joint must be left in the middle 1/3 section, while the traditional construction is left in the upper and lower steps. When it is left in the middle of the ladder, the shear force is theoretically small, but the quality of the construction joint is not easy to control during the construction, and it is easy to form a short “ overhang ” at the poured part during the secondary formwork erection, which is not conducive to the quality control of the components.)

7. The construction joint of the pool wall should be left on the vertical wall 200 ~ 500 mm higher than the surface of the bottom plate

8. For two-way stressed floor slab, mass concrete, arch, shell, warehouse, equipment foundation, multi-storey rigid frame and other complex structures, the location of construction joints shall be reserved according to the design requirements

editor's summary: that's all for what construction joints are and what they do. I hope it will help you. If you want to know more about it, you can pay attention to the information

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