Modular and Design Factors for Selecting Flying Formwork
There are many factors that affect the selection of the flying formwork system for a concrete building. Some of these factors are related to economy, site condition, architectural, and structural considerations. The following section will focus on some of the dimensional considerations for selecting flying formwork. Architects and design engineers should be aware of these considerations so they can reduce building costs.
1. Standard modular flying tables are available for contractors to rent or purchase. Flying table width ranges from 15 to 30 ft (4.6 to 9.1 m), with the most economical width for flying tables being 22 ft (6.7 m). Standard aluminum truss height ranges from 4 to 6 ft (1.22 to 1.83 m). Total height with extension legs can reach 20 ft (6.10 m). As a result, flying formwork is limited to story height of 20 ft (6.10 m) maximum. It should be also noted that small flying tables are not economical.
Large flying tables can reach a length of up to 120 ft (36.6 m) and a width of up to 50 ft (15.2 m). For long spans, two flying tables can be bolted together. For wide bay size, three aluminum trusses are needed to support wider tables. However, two trusses are sufficient for tables of up to 30 ft (9.1 m). Flying tables longer than 120
ft (36.6 m) are difficult to handle with average crane capacity.
2. Column size and location perpendicular to the flying table (i. e., the bay width) should be the same from floor to floor to avoid changing the formwork dimension by adding filler panels. It should be noted that a flying formwork system is not an economical alternative if the filler panels between flying tables exceeds 20 percent of the total area formed. The labor cost and time spent to add filler panels will negate the savings realized by using flying formwork.
3. Beam sizes and location should be the same from floor to floor on a modular building grid. Also, the depth of spandrel edge beams should be minimum, and cross beams should be avoided.