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Formwork is a mold in which concrete is filled until it sets, which is supported by verticle and horizontal members. The safety during installation of shuttering, pouring concrete, and removal is critical as the load of the fresh concrete must be withstood by the formwork.

Formwork for Column
Fig 1: Formwork for Column.

In this article, we have discussed the safety measures that shall be followed for shuttering works.

Safety measures for formwork installation

  1. The formwork shall be designed after taking into consideration spans, dead load, setting the temperature of concrete, and working load to be supported and safety factors for the materials used for formwork. 
  2. The timber formwork shall be carefully inspected before use, and members having cracks and excessive knots shall be discarded.
  3. The timber centering usually sinks when loaded with concrete, thus while designing, allowance for this factor shall be considered.
  4. The vertical supports must be sufficiently braced or secured in position so that they don’t fail when the load is released, or the supports are accidentally hit.
  5. When timber centering and tubular steel is to be used in combination, necessary precautions must be taken to avoid any unequal settlement of shuttering under load.
  6. A thorough inspection of tubular steel centering must be carried out before its installation, and members showing evidence of excessive resting, dents, kinks, or damaged welds shall be removed.
  7. The buckled or broken members of the shuttering shall be replaced.
  8. All the locking devices shall be checked for their efficient working, and coupling fins should be appropriately aligned with the frames.
  9. After assembling the basic skeleton of the shuttering, adjustment screws shall be set to their final levels and plumb.
  10. The shuttering frames must be tied together with sufficient braces to make rigid struts, and diagonals braces should be installed in the proper position so that frames develop full load-carrying capacity.
  11. The connections shall typically be made with bolts and nuts.
  12. The use of rusted or spoiled threaded bolts and nuts shall be avoided.
  13. The centering layout must be made by a qualified engineer and shall be followed strictly.
  14. The bearing capacity of the soil must be considered for every centering job.
  15. The effect of weather conditions shall also be taken into consideration as dry clay may become very plastic after a rainfall and show a marked decrease in its bearing capacity.
  16. The stability of the props shall be assured by setting the sills firmly on the soil.
  17. Precautions shall be taken not to disturb the soil under the supports.
  18. Proper drainage shall be ensured to drain away water due to the washing of forms, rains, or during the curing of the concrete to avoid displacement in the supporting soil strata.
  19. All centering shall be inspected/checked to ensure that:
    1. All the footings or sills under every post of the centering are sound.
    2. All lower adjustment screws or wedges are snug against the legs of the panels.
    3. All adjustment screws or heads of jacks are in full contact with the formwork.
    4. Panels are plumb in both directions.
    5. All cross braces are correctly placed, and locking devices are in a closed and secure position. 
    6. In the case of chajjas and balconies, the props shall be adequate to transfer the load to the supporting point.
  20. During the pouring of the concrete, the centering shall be continuously inspected and strengthened.
  21. If required, the wedges below the vertical supports tightened, and adjustment screws adjusted adequately as necessary.
  22. Adequate protection for the shuttering shall be secured from moving vehicles or swinging loads.
  23. Destripping of forms shall not be allowed before the time specified in the relevant codes until it is certain that the concrete has developed sufficient strength to support itself and all loads that will be imposed on it.
  24. Only workers engaged in removing the formwork shall be allowed in the area during these operations. 
  25. Those engaged in removing the formwork shall wear helmets, gloves, and heavy-soled shoes and approved safety belts if adequate footing is not provided above 2 m level.
  26. While cutting any tying wires in tension, care shall be taken to prevent backlash, which might hit a worker.
  27. The particular order in which the supports are to be dismantled should be followed according to the instructions of the site engineer.

FAQs on Safety Measures of Formwork

What are the design consideration for designing formwork?

The formwork shall be designed after taking into consideration spans, dead load, setting the temperature of concrete, and working load to be supported and safety factors for the materials used for formwork. 

What are the inspections and checks to be carried out in formwork?

The formwork shall be inspected/checked for-
1. All the footings or sills under every post of the centering are sound.
2. All lower adjustment screws or wedges are snug against the legs of the panels.
3. All adjustment screws or heads of jacks are in full contact with the formwork.
4. Panels are plumb in both directions.
5. All cross braces are correctly placed, and locking devices are in a closed and secure position. 
6. In the case of chajjas and balconies, the props shall be adequate to transfer the load to the supporting point.

Read More:
1. Formwork -Technical, Functional, Economical, and Safety Requirements
2. How to Achieve Economy in the Cost of Formwork Construction?
3. What are the Causes of Concrete Formwork Failures?

Fasi Ur Rahman

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