SEPARATELY MOULDED MEMBERS. The usual method of constructing reinforced concrete buildings by moulding in place is expensive on account of the cost of the forms, and is also compara tively slow on account of the time that must be allowed for the concrete to harden. To overcome this objection buildings are some times built of members moulded separately in advance, the erection proceeding very much as with timber or steel construction. The beams must have. both tension and compression reinforcement to permit of handling. Several types of patented beams specially designed for this form of construction have been put upon the market.
The important advantages of this form of construction are that many members can be moulded in the same forms, and the work can be done on the ground under cover in all kinds of weather with facil ities for securing a good and economical product. The objection to this form of construction is the difficulty of securing rigid con nections between the columns, girders, and beams. However, the joints are made with neat portland cement, and therefore the struc ture has a considerable degree of stiffness.
. In Europe this method has been employed to a considerable extent, but has not attained much popularity in America. For an account of the most important example in this country, see Engi neering News, Vol. lviii, pages 5-7,—July 4, 1907.
A recent extreme example of this of construction was the moulding of the whole side of a building and erecting it in a single piece.* The building is a two-story mess hall, 76 by 170 feet, for the state militia at Camp Perry, Ohio, erected in the summer of 1908. The walls are 26 feet high and 4 inches thick with 10-inch
pilasters. A platform of 2-inch lumber was laid upon a steel frame which was supported on screw-jacks operated by a tumbling-rod run by an engine. The reinforced-concrete window frames, door frames, cornice, etc., having been previously moulded separately, were placed in their proper position on the platform, the reinforcing rods of these being allowed to project to give a good bond with the body of the wall. Four-inch boards were set edgewise on the four sides of the platform to complete the forms, and half of the concrete for the wall proper was poured; and then the reinforcement con sisting of }-inch rods 6 inches apart both ways was placed, after which the remainder of the concrete was poured and then the surface was finished by troweling. Forty-eight hours after the concrete was placed, the wall was tilted into a vertical position upon the founda tion by operating the screw-jacks. Two adjacent sides of the building were joined by building suitable forms at the corner and filling them with concrete, the reinforcement from the sides being allowed to project into this concrete. The interior columns, the girders, the floor beams, were separately moulded and hoisted into place. The cost of the building is said to have been only a little more than that of a wood one.