| Per sq. yd. | |
| Lumber at $20 per thousand | 28 cts. |
| Carpenter work at 30 cts. per hour | 10 cts. |
| Labor tearing down at 15 cts. per hour | 4 cts. |
| ——— | |
| Total per square yard | 42 cts. |
Figure 194 shows an arrangement of centering between steel beams which is novel in that it provides for molding a slab with girders. The form was used in building the roof of a locomotive roundhouse. This roundhouse was of the usual circular form and had a radial width of 80 ft. Each radial roof girder, which was an 18-in. I-beam was carried by an outside wall pier and three I-beam columns encased in concrete. The space between main roof girders was spanned by reinforced concrete girders and roof slab. The center illustrated was employed for molding the concrete girders and slab, and carries out the idea of making a stiff and light center for considerable spans of slab without support by staging. The truss construction of the frames supporting the girder box will be noted.
Fig. 194.—Form for Slab and Girder Floor Between I-Beams
Concrete Slab and Girder Floors.—The construction of forms for this type of floor should be such that the slab centers and the sides of the girder molds can be removed without disturbing the bottoms of the girder molds. This permits the beams to be supported as long as desirable and at the same time releases the greater part of the form work for use again. It is of advantage also to lay bare the concrete as soon as possible to the hardening action of the free air. The slabs may be similarly supported by uprights wedged up against plank caps; no very great amount of lumber is required for this staging and it gives a large assurance of safety. It is well also to give the girder molds a camber or to crown them to allow for settling of the falsework.
The form shown by Fig. 195 was used in constructing girders from 14 to 23 ft. long in a factory building at Cincinnati, O. The sides are separate from the bottom, being supported at the ends by cleats on the column form and at intermediate points by struts under the yokes. The floor lagging is carried by 2×4-in. stringers supported by the yokes. Uprights set under the bottom plank keep the girder supported after the sides and slab centers are removed. It will be noted that the form is given a camber of 1-in. The structural details are evident from the drawing. The form shows a method of molding a bracket for wind bracing; a simple modification fits it for molding girders without brackets. A rough computation gives 10 ft. B. M. of lumber per lineal foot of girder form as shown.
Fig. 195.—Girder and Slab Form for Factory Building, Cincinnati, O.
Fig. 196.—Girder and Beam Forms for Factory Building, Beverly, Mass.