Fig. 154A shows the common way, or some modification of it, of constructing forms for columns. The plank may be 1 inch, inches, or 2 inches thick; and the cleats are usually 1 by 4 inches and 2 by 4 inches. The spacing of the cleats depends on the size of the columns and the thickness of the vertical plank.
Fig. 15413 shows column forms similar to those used in construct ing the Har yard stadium. The planks forming each side of the column are fastened to gether by cleats, and then the four sides are fast ened together by slotted cleats and steel tie-rods. These forms can be quickly and easily re m oved.
Fig. 155 shows a col umn form in which con crete is placed and rammed as the form is constructed. Three sides are erected to the full height, and the steel is then placed. The fourth side is built up with horizontal boards as the concrete is placed and rammed.
Round columns are often desirable for the interior columns of buildings. Fig. 156 shows a form that has been used for this type of column. The columns for which these forms were used were 20 inches in-diameter, and had a star-shaped core made of structural steel. The forms for each column were made in two parts and bolted together. The sides were made of 2 by 3-inch plank surfaced on all four sides, beveled on two, and held in place by the steel bands, which were + by inches and spaced about 21> feet apart. One screw in the outer plank at each band of both parts, to gether with a few intermediate screws, held the plank in place. The building for which these forms were made was ten stories in height. Enough forms were provided for two stories, which was sufficient, as they could be removed when the concrete had been in place one week. Later these same forms were used in construct ing the interior columns of a six-story building. Some difficulty was experienced in removing these forms, owing to the concrete sticking to the plank. But had these forms been made in four sections, instead of two, and well oiled, it is thought that this trouble would have been avoided. Columns constructed with forms as shown in Fig. 156 will not have a round sur face, but will consist of many flat surfaces, 2+ inches wide. If a perfectly round column is desired, it will be necessary to cut the surface of the plank next to the concrete to the desired radius.
Forms for octagonal columns can be made in a somewhat similar manner to these just described.
353. Forms for Beams and Slabs.
A very common style of form for beam and slab construction is shown in Fig.
157. The size of the different mem bers of the forms depends upon the size of the beams, the thickness of the slabs, and the relative spacing of some of the members. If the beam is 10 by 20 inches,and the slab is 4 inches thick, then 1-inch plank supported by 2 by 6-inch timbers spaced 2 feet apart, will support the slab. The sides and bottom of the beams are enclosed by li-inch or 2-inch plank supported by 3 by 4-inch posts spaced 4 feet apart.
In Fig. 158 arc shown the forms for a reinforced-concrete slab, with I-beam construction. These forms are constructed similarly to those just described.
A slab construction supported on I-beams, the bottom of which is not covered with concrete, may have forms constructed as shown in Fig. 159. This method of constructing forms was designed by by Mr. William F. Kearns (Taylor and Thompson, "Plain and Rein forced Concrete").
The construction of forms for a slab that is supported on the top of I-beams is a comparatively simple process, as shown in Fig. 160. In any form of I-beam and slab construction, the forms can he con structed to carry the combined weight of the concrete and forms. When the bottom of the I-beam is to be covered with concrete, it is not so easily done as when the haunch rests on the bottom flange (Fig. 159) or is a flat plate (Fig. 160).
354. Forms for Locust Realty Company Building. The forms used in constructing the building for the Locust Realty Company (the mixing plant has already been described), present one rather unusual feature. The lumber for the slabs, beams, girders, and columns was all the same thickness, 1 inches. Fig. 161 shows the details of the forms for the beams and slabs. The beams are spaced about 6 feet apart, and are S by16 inches; the slab is 4 inches thick. A notch is cut into the 1 by 6-inch strip on the side of the beams, to support the 2 by 4-inch strip under the plank which supports the concrete for the slab. The posts supporting the forms are 31 by 3'-inch, and are braced by two 1 by 6-inch boards spaced about 3 feet apart, and extending in the direction of the beams.