Fig. 186.—Form for Octagonal Column for a Factory Building.
The form shown by Fig. 186 was used for interior columns of octagonal section with hooped reinforcement for a factory building. This form for a 12-ft. octagonal column 24 ins. across between sides requires approximately 325 ft. B. M. of lumber. The form shown by Fig. 187 was used by the same engineer in another building; it is, as will be noted, in four units coming apart in joints at diagonally opposite corners. This form for an octagonal column 18 in. across between sides required about 13 ft. B. M. of lumber per foot of column length, with yokes spaced 3½ ft. apart.
The form shown by Fig. 188 was used in a large warehouse at Chicago, Ill. It will be noted from the dotted lines that one yoke clamps the sides a a, the next the sides b b and so on. This does away with triangular blocking to hold the corner boards that is used in the form shown by Fig. 187. Six pairs of yokes were used for each column so that the yoke spacing was about 2 ft. With 2×6-in. yokes and 1½-in lagging a form for a column 18 ins. between sides would require some 17 ft. B. M. per foot of column length.
Fig. 187.—Form for Octagonal Column for Factory Building.
Fig. 188.—Form for Octagonal Column for a Warehouse, Chicago, Ill.
Circular Columns.—Circular columns have been most frequently molded in steel forms, and these are by all odds the best for general work. Made in two parts of sheet steel and in sections that are set end to end one on another a form is obtained which is easy to erect, remove and transport. Wood forms for circular columns are rather clumsy affairs and are expensive to construct. Such a form, Fig. 190, is described in the succeeding section; another is shown by Fig. 189. This form was used successfully for filling and encasing steel columns for a fireproof building in Chicago, Ill., and is a favorite circular form construction in Europe. It is apparent that the hooping needs to be very heavy and that the form is one that will be hard to handle and rather expensive to make.