Formwork - Designing Buildings
May. 06, 2024
Formwork - Designing Buildings
Formwork
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What is formwork? The term 'formwork' referst to a temporary mould into which concrete is poured and formed so that it can set to the required shape. Traditional formwork is fabricated using timber shuttering, but it can also be constructed from steel, glass fibre reinforced plastics, plywood and other materials.
Shuttering is most common type of formwork, constructed on site using timber and plywood. A special grade of plywood is necessary for shuttering, as it must be water-resistant. Shuttering is relatively easy to produce, although it can be time consuming for large structures or complex shapes. This type of temporary formwork is used when the labour costs are lower than the cost of producing re-usable formwork from materials such as steel or plastic.
Both shuttering and other types of formwork need to be supported by falsework. Falsework refers to poles, stabilisers, and other supports that keep the shuttering or formwork in place as the concrete dries. For more information, see Falsework.
Once the concrete has gained sufficient strength the formwork can be struck (removed). A minimum value of 5 N/mm2 is recommended in all cases when striking vertical formwork as so not to damage the concrete in the process.
High quality workmanship and inspection are necessary to ensure a high standard and appearance of the resulting concrete structure, particularly where the concrete will remain visible in the completed structure.
When selecting formwork, the type of concrete and temperature of the pour are important considerations as they both effect the pressure exerted. The formwork sides must be capable of resisting the hydrostatic pressure of the wet concrete which will diminish to zero within several hours depending on the rate of setting and curing. The formwork base or soffit must be capable of resisting the initial dead load of the wet concrete and the dead load of the dry set concrete.
Formwork should be:
Types of formwork A range of different types of formwork are described below.
Formwork for beams takes the form of a three-sided box which is supported and propped in the correct position and to the desired level. The removal time for the formwork will vary with air temperature, humidity and consequent curing rate. Typical striking times are as follows (using air temperature of 7-16 ºC):
This consists of a vertical mould of the desired shape and size for the column to be poured. As a means of keeping the formwork material thickness to a minimum, horizontal steel or timber clamps (or yokes) are used at equal centres for batch filling and at varying centres for filling that is completed in one pour.
If you want to learn more, please visit our website Zolo. The head of the column formwork can be used to provide support for the beam formwork, but while this gives good top lateral restraint it can make the formwork complex. Alternatively, the column can be cast to the underside of the beams. Later on, a collar of formwork can be clamped around the cast column to complete the casting and support the incoming beam formwork.
Plastic formwork
Re-usable plastic formwork is generally used for quick pours of concrete. The formwork is assembled either from interlocking panels or from a modular system and is used for relatively simple concrete structures. It is not as versatile as timber formwork due to the prefabrication requirements and is best suited to lost-cost, repetitive structures such as mass housing schemes.
Stay-in-place structural formwork is generally assembled on site using prefabricated fibre-reinforced plastic. It is used for concrete columns and piers and stays in place, acting as permanent axial and shear reinforcement for the structural member. It also provides resistance to environmental damage for both the concrete and reinforcing bars.
Proprietary systems are used to support vertical formwork while concrete cures, consisting of a series of tubes and ties.
Related articles on Designing External references edit]
edit]Formwork specifications
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edit]Beam formwork
edit]Column formwork
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edit]Buildings
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Introduction to System Formwork & why the adoption ...
Well, before a blog on System Formwork is written, it is imperative that I mention certain basic things about Formwork itself.
Formwork essentially means that "It's a mould that holds as well as gives shape to the concrete. In the process, Formwork keeps supporting the concrete structure until the structure attains enough strength to carry it's own weight"
Why Formwork is so important?
- It consumes 70% of the Structural construction time
- It contributes to 10-15% of the Building structural cost
- Major part of Quality & Safety governed by Formwork
A good Formwork system should...,
- Enable quick & easy Shutter assembling & dissembling
- Achieve quality Concrete surface finish
- Only require optimum labour & material
- Ensure Safety is integrated into the system
- Contribute significantly towards pace of the Project
- Ultimately contribute towards significant cost savings for the Project
Now, What is System Formwork?
It's a type of Formwork that.....,
- Is Factory made, which means no making at Project Site
- Enables labour to be highly productive
- Requires only optimum materials to execute the job
- Made of materials that are flexible, versatile, high on re-usability count etc.,
- Has safety in-built into the System
- Only requires semi-skilled labour to execute the work
- Is most cost-effective in the long-run
- Produces quality finish, hence no re-work
How well has INDIA been faring in using System Formwork?
Conclusion
As one can easily infer from the above presented information, adoption of system formwork is growing at a very rapid pace. This is more so important for a country like India, where factors like demand for faster construction, necessity for skyscrapers, especially in a space constraint cities like Mumbai & Bangalore, scarcity of skilled labour, high end form finishes etc., are absolutely becoming the driving force. Therefore, earlier one understands & adopts system formwork, better are there chances of delivering the Projects on-time.
Contact us to discuss your requirements of concrete slab formwork. Our experienced sales team can help you identify the options that best suit your needs.
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