The reduction of formwork construction is essential in declining the total cost of the project because it accounts for up to 60% of the entire cost of concrete structure. Decision made at the design phase can play crucial role in this regard. New materials, accessories, and prefabricated formwork components may enable designers to achieve their design goals at a lower cost.
The Concrete Reinforcing Steel Institute provided several recommendations to achieve economy in the cost of formwork construction. For instance, utilize one form scheme throughout the project, orient all framing in one direction to save time in one-way system, employ standard form sizes, and use the same level for all beams and joists.
How to Achieve Economy in the Cost of Formwork Construction?
- Use single framing scheme for the entire project. This would improve learning of labors and cut mobilization and formwork material cost. Two framing schemes are justifiable only on large projects.
- Use the same depth for all beams and joists since reduced cost would surpass the increased cost of steel and concrete. when beams are heavily loaded, their width can as four or five times as their depth.
- Stick with the same beam outlines even if the loads and spans are not the same, and modify reinforcement ratio to resist the load.
- Space columns uniformly to achieve uniform sizes for columns, joists, and beams, thus saving money by simplifying forming.
- Increase reuse of forms by using the same size for columns, horizontally in one storey and vertically in one stack. Change reinforcement and concrete strength to accommodate loads.
- It is recommended to use constant floor-to-floor height. However, if change is needed, reduce the height in upper storeys. It would cheaper and easier to cut column form than its extension.
- Employ small drop panels instead of tapered column in flat plates to cut forming cost. it recommended to utilize steel shear heads to avoid capitals and drop panels provided that the slab thickness is not less than 200 cm.
- Make the height of drop panels fit standard lumber dimensions.
- To save time and money, orient all framing in one direction in case of one-way system construction.
- Use standard form sizes for one-way joists and two-way domes to avoid special form fabrication charges.
- Make full use of capacity of minimum-sized members by arranging forming member sizes and spacing. Slabs of minimum thickness controlled by fire ratings should span at least as far as the minimum reinforcement will permit. Walls of minimum thickness and reinforcement may carry column loads, act as grade beams or transfer girders, resist lateral loads, and serve as petitions or exterior walls-all at the same time.
- Consider flat plate for spans up to 7.6m since its forming system is comparably cheapest, fastest, and shallowest.
- Tight tolerances increase labor work and cost. So, permit reasonable tolerances, specify strict tolerances only in locations where they are needed.
- Determine when forms are stripped. Use a time limit for walls and columns and a strength requirement for beams and slabs. Nonetheless, consider requiring reshoring until design strength has been reached to prevent excessive deflection.