Power point presentation on the topic formwork

Formwork

1. Form work SEMINAR PRESENTATION

2. GROUP MEMBERS • SANJANA P • SNEHA MB • SREELAKSHMI J • THASLEEMA NP

3. FORM WORK Introduction Requirements of good formwork Classification Slip form Conclusion

4. INTRODUCTION •Form work is a mould or open box, like container into which fresh concrete is poured and compacted. •When the concrete is set, the formwork is removed and a solid mass is produced In the shape of the inner face of the formwork. •The top of the formwork is normally left open. •False work is the necessary support system that holds the formwork in the correct position.

5. Requirements of good formwork Good form work for concrete structures should satisfy the following requirements: 1. It should be strong enough to resist the pressure or the weight of the fresh concrete and the superimposed loads due to equipment.
2. It should be rigid enough to retain the shape without undue deformation. Therefore it should be so designed that deflection does not exceed 1/900 th of span in normal cases.
3. It must be made or constructed as tight as possible so that it doesn’t allow the cement paste to leak through the joints.
4. The space enclosed by the form should be true to the size as designed .The form should therefore not warp, bulge or sink, to meet this requirement.
5. The inside surface of form work should be smooth so as to give good appearance to the resulting concrete surface.
6. The entire formwork should be so made that it can be removed easily without causing least Injury to the surface or edges of the concrete
7. As the form work doesn’t contribute anything to the stability of the finished structure ,it should , therefore, be made economical by reducing the cost through proper design, construction and use of form work

6. Materials and sizes of forms Materials: - the materials to be used for making formworks are decided either by economy or requirements of the job or both. The materials most commonly used are timber, plywood, steel and Aluminum . In case of specific structures such as round columns, curved surfaces etc. Steel is preferred Formwork materials can be classified as: 1. Timber
2. Metals 3. Plastics

7. FORM WORK TYPES (BY SHAPE) Considering shapes, Form work types can be classified as: Column Formwork Beam Formwork Slab Formwork Wall Formwork

8. Column Formwork

9. Column Formwork • Column formwork is made usually with either timber or metal panels. • The principle is to create an enclosed box with frames at the exact size of the column and fix it tightly on the kicker left from base or at the last stage of column concreting. • The box is held in position by steel column clamps or bolted yokes and supported by
timber studs or props

10. Beam Formwork • Beam formwork consists of open through section and because it is not closed at the top requires more supporting framework to restrain the sides.
• The supports need to be maintained to the soffit and also provide lateral support to the sides.
• In timber this is done by the use of ahead tree across the top of a vertical member.
• Metal panels are used with corner pieces, but timber head trees are needed for vertical support.

11. Slab Floor Formwork • Floors require a large area of formwork to be provided usually from beam to beam.
• Timber floor formwork consists of timber boards or plywood sheets supported on a Frame work and resting on a series of timber joists.
• Again timber and metal props can be used for vertical supports.
• Metal panels can be used and bolted or clipped together and held in place by a system of metal beams or a tabular scaffold system. • Adjustable props need for levelling purposes

12. Wall Formwork • Wall formwork is a simpler than for other concrete units as the actual forces against it are less, most of the load being carried vertically downwards.
• The panels at both sides are held in position by ties.
• Ties are also used as spacer, arranging wall thickness.
• Wall support systems are usually sloping props at satisfactory intervals.

13. SLIP FORM CONSTRUCTION Slip form construction is a continuous construction technique in which concrete is poured into a continuously moving form. Slip form is used for tall structures (e.g.: bridges, towers, buildings, lift shafts and dams) as well as horizontal structures such as roadways. Slip forming enables continuous, non-interrupted cast-in-place flawless concrete structures which have superior performance characteristics. It also results in saving of time. Slip forming relies on the quick setting properties ofconcrete and requires a balance between quick setting capacity and workability. Concrete needs to be workable enough to be placed into the form and consolidated, yet quick setting enough to emerge from the form with strength. The height of the formwork is designed in such a way that while the top of the formwork is being filled by concrete the lowest layer of concrete poured earlier has already gained an initial set. When the formwork is moved upwards the concrete that is then exposed remains firm. In vertical slip forming , concrete form may be surrounded by a platform on which workers stand,placing steel reinforcing rods into concrete ensuring a smooth pour concrete form and platforms are raised by means of hydraulic jacks. Slip form raise at a rate which permits the concrete to harden by the time it emerges from the bottom of the form. In horizontal slip forming for pavements and traffic separation walls, concrete is laid down, vibrated, worked and setted in place while the form itself slowly moves ahead at a rate of about 300mm/h. This method can be used to form any regular shape or core. It supports itself on core and does not rely on support from other parts of the building or permanent works.

14. Procedure Slip form methods of construction can also be adapted to horizontal structures and are used for paving, canals, and tunnelling.The technique is more in use for structures that have continuous walls like silos, chimneys, and piers for very tall Bridges.It has also been successfully used for construction of buildings, although this requires the manner of leaving inserts for openings like doors and windows to be decided well in advance, as well as also any necessary inserts to support floor slabs after the walls are constructed.

15. Commonly the formwork has 3 platforms 1. The upper platform act as a storage and distribution area.
2. Middle platform, which is the main working platform, is at the top of the poured concrete level.
3. The lower platform provides areas for concrete finishing.
• Assembly can only start once the foundations are in place and the wall starter is in correct
alignment.
• Slip form shuttering is aligned with the help of yokes.
• Horizontal crossbeams connect these yokes.
• Hydraulic jacks are attached to these crossbeams for simultaneous upward movement.
• Height of the slip form ranges from 1.1 to 1.5 meters.
• Yokes and crossbeams also used to support the working platform.
• Structure should be rigid and shape maintained at all times.
• Make sure there is no lag or else it prevents the structure from free upward movement
• It is also possible to reduce wall thicknesses
• as the construction gains height and arrangements have to be made in the slip form structure that will enable such reduction at regular intervals

16. CONCLUSION By understanding the importance of formwork materials and adopting best practices, construction professionals can ensure successful project outcomes, improved quality, and reduced costs.

17. THANK YOU ...

18. REFERENCE Referred from: Sharma S.K (2019) civil engineering construction materials Google Chrome, chat gpt