Figure 3-3. - Diagonal bracing supports.
American Concrete Institute (ACI) or the Architectural Graphic Standards (AGS) for more information on designing of forms.
As with wall forms, column forms are designed according to step-by-step procedures. Wooden forms for a concrete column should be designed by the following steps:
1. Determine the materials available for sheathing, yokes, and battens. Standard materials for columns forms are 2 by 4s and 3/4-inch plywood.
2. Determine the height of the column.
3. Determine the largest cross-sectional dimension of the column.
4. Determine the yoke spacing, as shown in table 3-4, by reading down the first column until the correct height of the column is reached. Then read horizontally across the page to the column headed by the largest cross-sectional dimension. The center-to-center spacing of the second yoke above the base yoke will be equal to the value in the lower interval that is partly contained in the column height line. All subsequent yoke spacings may be obtained by reading up the height column to the top. This procedure gives maximum yoke spacings.
Table 3-4 is based upon use of 2 by 4s and 3/4-inch sheathing. For example, if you had to construct a 9-foot column, the spacing of the yokes starting from the bottom yoke would be 8", 8", 10", 11", 12", 15", 17", 17", and 10". The space between the top two yokes has been reduced because of the limits of the column height.
Because of their height and relatively small cross-sectional area, column forms require four-way bracing to ensure alignment and resistance to wind and various other lateral forces that may occur during the placement of the concrete.
The general goal of slab form design is a balanced form design. Careful consideration must be given to the design of the formwork due to the danger of failure caused by the weight of the concrete and the live load (LL) of the equipment and personnel on the forms. The following procedures uses some of the same figures used in the wall form design.
See figure 3-4 for the nomenclature for a typical overhead form.Continue Reading