The form construction shown in Fig. 196 was employed in building the slab and girder floors for the United Shoe Machinery Co.'s factory at Beverly, Mass. In these buildings the main girders cross the building at 20-ft. intervals and midway between the main girders is a bridging beam also reaching across the building. Floor beams span the 10-ft. spaces between bridging beams and main girders at intervals of 3 and 4 ft. Referring first to the main girder form, tall horses are set up at 3-ft. intervals and connected by stringers laid on the caps. These stringers carry a cross piece, with a cleat at each end, over each horse. The bottom boards of the mold rest on these cross pieces and the side pieces are set up between verticals wedged tight between the cleats. The beam molds are a modification of the girder molds. The slab centers consist of panels just large enough to span the openings between beams and girders and composed of 1-in. boards fastened together by four 1×5-in. cleats. Except in attaching the quarter round and triangular moldings for fillets no nailing is necessary in erecting and taking down the forms.
Fig. 197.—Girder and Slab Form for Concrete Building Work.
The form construction shown by Fig. 197 is one used by a large firm of reinformed concrete builders. The slab centers can be struck and the sides of the girder mold removed without disturbing the support for the bottom of the beam. This form runs quite low in lumber, requiring for a 9×12-in. beam box including posts some 9 ft. B. M. per lineal foot of box. The joists and lagging as shown require about 2 ft. B. M. per square foot of floor slab. The practice is to give these girder boxes a camber of ½-in. in 10 ft.
The construction shown by Fig. 198 is designed to provide adjustability, to enable quick erection and removal and to do away with all nailing. The construction is as follows: Wooden posts carry at their tops steel T-beam cross-arms knee braced to the posts by steel straps. The cross-arms carry the two jaws of a clamp, each consisting of a vertical plate, and two diagonal braces, slotted so as to slide on the T-beam. A cut nail or other piece of metal driven into the slots fastens the jaws on the T-beam. The cross-arms carry the bottom boards of the girder molds and the vertical plates of the jaws support the side pieces. A blocking piece slipped between the braces carries the end of the joist for the floor slab centers. This form is the invention of Mr. W. H. Dillon and was used in constructing the nine-story, 260×150-ft. wholesale hardware store Of Farwell, Osman & Kirk Co., St. Paul, Minn.
Fig. 198.—Girder and Slab Form for Warehouse at St. Paul, Minn.
Fig. 199.—Girder and Slab Form for Factory Building, New York, N. Y.