Formwork for Columns
Conventional formwork for columns is made of sheathings nailed together to form rigid sides. Typically, formwork for concrete columns has four sides. Column form sides are held together by yokes or clamps (see Figure 6.2). Another function of these yokes is to prevent the buckling of sheathing resulting from the horizontal lateral pressure when the fresh concrete is placed.
Concrete lateral pressure is greater near the bottom of the form. As a result, yokes are spaced at smaller intervals near the bottom than near the top of the form. Column form sides may also be tied by straps or steel angles. In order to prevent breaking of the corners or edges, it is common practice to add a triangular fillet to the form along the edges of the columns. This practice also facilitates stripping of column forms.
Columns can take several shapes: round, rectangular, L – shaped, or various irregular shaped cross sections. Irregular shapes are frequently formed by attaching special inserts inside square or rectangular forms.