In Construction, What is a Concrete Slab?

The building formwork is a temporary supporting structure. It is produced according to design requirements, so that the concrete structure and components are shaped according to the specified position and geometric size, maintain its correct position, and bear the self-weight of the building formwork and external loads acting on it. The purpose of the formwork project is to ensure the quality and safety of the concrete project, speed up the construction progress and reduce the cost of the project.

The formwork structure for the construction of cast-in-situ concrete structures is mainly composed of three parts: panel, support structure and connector. The face plate is a bearing plate that directly contacts the freshly poured concrete; the supporting structure is a temporary structure that supports the face plate, concrete and construction load, ensuring that the building formwork structure is firmly combined to prevent deformation and damage; the connecting piece is to connect the face plate and support The structure is connected as a whole.

Building formwork is a formwork for concrete pouring and

Wooden building template is a kind of artificial board. The slabs which are formed by using the glued veneer crisscross according to the direction of the wood grain are pressed under the condition of heating or not heating. The number of layers is generally odd, and a few have even numbers. The physical and mechanical properties of the vertical and horizontal directions are small. Commonly used

1. Formwork and support (arch) structural parts shall be inspected and accepted after entering the site, and they may be used only after meeting relevant standards.

2. The formwork and its embedded parts and reserved holes shall meet the design and process requirements.

3. When design requirements or construction requirements, triangle ribs can be added at the corners of the formwork.

4. The façade or plane of the support (arch) frame structure shall be installed firmly, capable of resisting vibration or accidental impact, and the support (arch) frame columns shall be fixed in two mutually perpendicular directions.

5. The use of wood for supporting (arch) frames should meet the following requirements:

(1) Members that are subjected to bending moment or lateral pressure should not be made of wood, and the number of connections between members should be reduced.

(2) Reduce the number of joints for long members.

(3) The longitudinal connection of pressure rods shall use butt joint method, and be clasped with hardwood or steel plywood. Lap method can only be used for the connection of secondary members.

(4) The connection joints of two adjacent columns should be located on different horizontal planes.

6. The joints of wooden members can be jointed and meet the following requirements:

(1) Steel plywood should be used at the support (arch) nodes and clamped with bolts.

(2) When the cross section of the member has been determined according to the bearing area at the joint, it should be clamped with a supporting plate made of steel or hardwood.

(3) Tooth connection should not be set where the wood is subjected to shearing force. When toothed connection is required, the joint length must not be less than 30cm, and the possibility of cracking when the wood is dried should be considered.

(4) The hacksaw nail can only be used as a temporary connection or a reinforced connection without calculating the force.

7. The supporting part of the support (arch) shall be installed on a reliable foundation and foundation, and shall meet the following requirements:

(1) When installing support (arch) directly on the foundation (especially collapsible loess), measures shall be taken to prevent and drain water.

(2) On the foundation of frost heaving soil, it shall be ensured that the structure can maintain the design position when the soil is subjected to the freeze-thaw cycle during construction.

8. The following factors should be considered when the arch of support (arch) is reserved for construction:

(1) Elastic deformation of the support (arch) frame under full load.

(2) Elastic deformation due to static live and impact loads.

(3) Inelastic deformation due to the compression of the component joints after loading.

(4) Inelastic deformation due to foundation settlement.

9. The support (arch) frame should be provided with jacks, wooden wedges, sand cylinders or other support pads that are easy to loosen the supporting members, and should meet the following requirements:

(1) Planked hardwood should be used for wood wedges, and the inclination should not be greater than 1: 2; the pressure at the contact surface of the two wedges should not be greater than 2MPa.

(2) The structure of the sand cylinder shall be determined by design. The pressure placed on the sand should not be greater than 10 MPa; the sand should have a hard, clean and screened dry sand, and its particle size should be 0.315mm to 0.630mm; the design load should be added to the sand tube before use (necessary) The safety margin can be increased by 20% to 50% when pre-pressing; the gap on the sand cylinder should be filled with putty that is not easily cracked and has high elasticity.

(3) The jack used for the support pad must have a self-locking device.

(4) Arches with a span of 10m or more or beams with a span of 24m or more shall not use wood wedge support pads.

10. Post-tensioned prestressed concrete simply-supported beam bottom formwork and side formwork shall be preset inverse arch and reserved compression amount according to design requirements and actual tensile force, concrete elastic modulus and upper arch data.

11. In order to eliminate the inelastic deformation of the support (arch) frame, determine the elevation of the formwork formwork. The support (arch) frame of the cast-in-situ concrete structure should be preloaded before it is officially used.

12. The formwork and support (arch) frame should be inspected regularly during use. ^[3]

Full hall scaffolding main keel secondary keel stigma template keel stigma template, roof template assembly slab template keel inside and outside the ceiling template adjustment acceptance carry out the next process.

Reasons : 1. The small steel molds were assembled and not set as required, resulting in poor overall performance of the building.

2. The foundation on which the formwork is placed is not solid, and the slab is not placed, and the foundation sinks due to poor waterproof measures.

3. Use wooden building formwork or plywood for construction. After passing the experience, the concrete is not poured in time, and the sun-drenched surface will be deformed for a long time.

4. The support distance is too large, and the rigidity of the steel plate is poor.

5. The speed of pouring wall and column concrete is too fast, the height of one pouring is too high, and the vibration is excessive.

Solution :

1. When assembling small steel molds, the connecting parts should be placed in accordance with regulations, and the spacing and specifications of the enclosures and tension bolts should be set according to the design requirements.

2. The support distance of the bottom of the beam should be able to ensure that no deformation occurs under the effect of concrete weight and construction load. If the bottom of the support is mud foundation, it should be compacted carefully, a drainage ditch is set up, and long wooden blocks or sections are laid to ensure support Don't sink.

3. When using wooden construction formwork and plywood construction formwork, concrete should be poured in time after passing the experience to prevent the wooden construction formwork from being exposed to rain and rain for a long time.

4. When designing the building formwork and supporting system, full consideration should be given to its own weight, construction load, and self-containment of the concrete and the lateral pressure generated during pouring to ensure that the building formwork and support have sufficient bearing capacity, stiffness and stability.

5. For cast-in-situ reinforced concrete beams and slabs with a span of not less than 4m, the building formwork should be arched according to the design requirements; when the design has no specific requirements, the arching height should be 1 / 1000-3 / 1000 of the span.

1. Make sure his position is correct, and the shape and size fully meet the requirements of the design drawing.

2. With sufficient bearing capacity and stability, it can bear various loads in various situations during construction.

3. Simple structure, easy to install and disassemble, flexible to use. It can meet the requirements of banding steel bars, suitable for centralized manufacturing, saving raw materials, improving efficiency, speeding up work, and meeting the requirements of subsequent processes.

In the construction industry, every small nuance may lead to the failure of the entire engineering project. The building formwork is also an important part. The correct method for selecting the building formwork is as follows:

1. The construction of beam-column structures should adopt medium-sized composite building templates. Because beams and columns have many changes in section, it is not suitable to cut with multi-layer boards, so it is suitable.

2. The wall formwork can be used as a medium-sized composite building template. Due to the uniform requirements of high-rise building groups of the same type, the medium-sized composite building template helps ensure a high turnover rate.

3. The core tube of super high-rise or high-rise building should adopt "hydraulic climbing formwork". The climbing formwork technology combines the advantages of large formwork and sliding formwork. It can rise layer by layer with the construction of the structure, the construction speed is faster, and the site Tower cranes are safe for high-altitude operations without external scaffolding. In terms of construction, they are especially suitable for the construction of concrete inner cylinders of steel structures.

4. The floor slab building template is recommended to use a whole multi-layer board, and as far as possible, a 15 to 18 MM thick multi-layer building template with phenolic covering is used. After this kind of building formwork has been used for many times, the edges are damaged. It is necessary to cut in time to ensure that the edges of the multilayer boards are flat.