What does formwork arching mean during the concrete pouring process

When building long-span floors, roof beams, and slabs, measures to increase the height of the mid-span in advance to improve the illusion of viewing angles and to correct the settlement of self-weight.

For example, let's say a ceiling, which has not been arched. There are two consequences, one is that if there is no settlement, after the completion of the roof, although the roof is very flat, but due to the existence of optical illusion, at a glance, it seems that there is a feeling of falling downward in the middle of the ceiling, and the second is that when the roof is in the formwork, if the template is very flat, due to the natural gravity settlement;

When the formwork is removed, the center of the roof will also drop a few centimeters downward, so in order to avoid the above two consequences, all structures with a larger span should be arched during construction. The so-called arching is actually an advance amount, or a means of prevention. That is, increase the height size of the middle part of the span to an appropriate proportion.

Construction Code Requirements:

For cast-in-place reinforced concrete beams and slabs with a span of not less than 4m, the formwork should be arched according to the design requirements; When there are no specific requirements for the design, the arch height should be 1 1000 3 1000 of the span.

This is to reduce the visual deflection of the beam plate due to its own weight and upper load, and of course it also considers certain construction formwork factors.

If the beam with an excessively large span does not consider the deflection on the premise of satisfying the bearing capacity.

, the deflection of the beam will be great, concrete specification.

A certain deflection value is required, which is required for the serviceability limit state.

The arching is to prevent the beam from sagging too much (too much deflection) of the formwork during the pouring process, and it is the role of the beam to reach the level!

Explanation of the provisions For cast-in-place concrete beams and slabs with large spans, considering the influence of self-weight, moderate arching is conducive to ensuring the shape and size of the components. It should be noted that the arching height of this article does not include the design arching value, but only considers the sagging of the template itself under the load, so the steel formwork can take a small value, and the wood formwork can take a large value.

For beams with large spans, the formwork should be arched in advance to offset the deformation under gravity loads.

GB50204 Reinforced Concrete Structure Code Provisions; Considering the self-weight of the concrete structure, proper arching is conducive to maintaining the cross-sectional size and shape of the component

For cast-in-situ reinforced concrete beams and slabs with a span of not less than 4m, the formwork should be arched according to the design requirements; When there are no specific requirements for the design, the arch height should be span!

Construction specification requirements: for cast-in-place reinforced concrete beams and slabs with a span of not less than 4m, the formwork should be arched according to the design requirements; When there are no specific requirements for the design, the arch height should be 1 1000 3 1000 of the span. This is to reduce the downward deflection of the visual beam plate due to its own weight and upper load, and of course also consider certain construction template factors.

Provisions for formwork arching:

1. For cast-in-place steel reinforced concrete beams and slabs with a span of not less than 4m, the formwork should be arched according to the design requirements.

2. The construction of more than 4m must be in accordance with the design requirements.

3. When the design is not required, the arch is 1 1000 of the total length of the beam span, that is to say, the height of the middle of the beam is 1 1000 higher than the end of the beam.

Arching refers to the measures taken to increase the height of the mid-span in advance in order to improve the illusion of viewing angle and to correct the settlement of self-weight when building large-span floors or roof beams and slabs.

For cast-in-situ reinforced concrete beams and slabs with a span of not less than 4m, the old baffle plate should be arched according to the design requirements; When there are no specific requirements for the design, the high arch should be the span of the liquid Hu!

Construction specification requirements: for cast-in-place reinforced concrete beams and slabs with a span of not less than 4m, the formwork should be arched according to the design requirements; When there are no specific requirements for the design, the arch height should be 1 1000 3 1000 of the span.

This is in order to reduce the downward deflection of the visual beam plate due to its own weight and upper load, and of course, it also considers a certain amount of pure cherry pigment caused by the construction formwork.

If the beam with an excessively large span does not consider the deflection on the premise of satisfying the bearing capacity.

, the deflection of the beam will be great, concrete specification.

A certain deflection value is required, which is required for the serviceability limit state.

GB50204-2002 project construction.

The Quality Acceptance Code and the design requirements stipulate that the construction of more than 4m must be arched in accordance with the design requirements; When the design is not required, the arch is 1 1000 of the total length of the beam span, that is to say, the height of the middle of the beam is 1 1000 higher than the end of the beam, for example, the beam is 8m, then the elevation of the middle of the beam is 8mm higher than the end of the beam.

If the design requires the arching to be carried out according to the requirements of the design, for example, the design requirement is 3 1000 arching, then the beam is 8m, then the elevation of the middle of the beam is 24mm higher than the elevation of the end of the beam. The main purpose of arching is to support the formwork for the beam.

Provide space for downward deflection under the action of the self-weight of concrete and formwork, and avoid downward bending and deflection of the wheel plexus after the concrete pouring is completed.

For example, the allowable deflection of a 12m beam is 40mm, and the arch is 24mm during construction, and the final lower deflection value becomes 16mm (this is the theoretical value), which is difficult to feel visually. If the deflection of the beam or slab is too large to give people a feeling of insecurity, in fact, under the premise of satisfying the bearing capacity, the deflection of the beam is also safe.