Systems of Reinforcement — concrete, floor, system, construction, steel, fig and reinforced

Systems of Reinforcement - concrete, floor, system, construction, steel, fig and reinforced

Systems of Reinforcement

concrete, floor, system, construction, steel, fig and reinforced

For light roof construction where the steel work need not be protected, a continuous slab is built over the beams, reinforced with flat steel bars, 3/16 in. by in. placed edgewise and held in position by spacers, as shown in Fig. 75.

For floor construction this system also uses segmental arches of cinder concrete laid upon permanent stiffened wire lath centering, or upon wood centering which is car ried on steel tees and supported by the steel I-beams of the floor system, which are generally placed about 7 feet on centers. The concrete is placed upon the centering without puddling or tamping, in order to obtain a light porous concrete of high fire-resisting quality.

The Standard System is shown in Fig. 76.

The general scheme is to build floors of light-weight I-shaped or T-shaped joists of reinforced concrete to replace wood joists or reinforced concrete slabs, and rest the ends of the joists upon walls made of vertical inter locking concrete studding or concrete blocks. Columns are formed in the wall in light construction by filling the hollows between the vertical studs, or blocks, with concrete reinforced with steel rods. For heavy buildings, the floor-joists may rest upon monolithic reinforced con crete girders and columns, or upon structural steel gird ers and columns fireproofed in the factory with concrete. One T form of standard joist section is 16 inches wide by 81/2 inches deep, with horizontal reinforcement for tension, and webbing of metal mesh to provide for shear and the stresses which are liable in transportation. Mem bers of other dimensions are made to suit the span and loading required.

A nailing piece is imbedded in the top of the joist for laying wooden floors. If the floor is to have concrete finish, the joists are made I-shaped. The ceilings are plastered upon the lower flanges, the concrete being left rough for the purpose.

Three styles of «Standard» floor construction are illustrated in Fig. 76. The top floor is laid with joists just described; the two middle floors, of separately moulded arches; and the bottom floor of cast slabs, with reinforced ribs moulded on the bottom surface. The thin slabs are also well adapted to roof construction.

An important feature of the «Standard» system is the method of connecting the individual members. The reinforcement is allowed to project, and is mechanically connected after placing. The connection is finally im

Systems of Reinforcement - concrete, floor, system, construction, steel, fig and reinforced

bedded in fresh concrete so as to give strength and rigidity.

In Europe the Siegwart System of floor con struction has been developed quite extensively, using for floor slabs a series of adjacent hollow beams formed by the use of collapsible cores.

Fig. 77 shows the construction of these hollow beams, and also their reinforcing rods. The top face of these beams forms the floor slab, and the bottom face forms the ceiling for the rooms be low. These beams are moulded individually in sections about ten inches wide. As shown by the figure, they have an open space extending nearly to the lower surface on each side of the beam, or, are narrower across the top than across the bottom. When they are placed in position in the structure, these open spaces are filled with cement grout, thereby making the floor prac tically one continuous mass.

The American System consists in the use of plain round rods underneath woven wire fabric, both of high-carbon steel. Fig. 57 shows the type of fabric, and the clamp used in joining ends of sheets. Floors are designed in some in stances by stretching the parallel rods across steel girders, and simply laying the wire fabric on top of these, embedding all in concrete. In other structures, the monolithic type of caged concrete column and connected girder, all formed of rods and fabric embedded in concrete, is used, as in Fig. 78. In short spans and for light loads, the wire fabric is often used without the rods.

The manufacturers of these materials claim advantages on account of ease and cheapness of handling and laying the rolls of fabric, together with the absolute assurance of proper spacing of reinforcing and ideal distribution of metal, The Vaughan System of floor construction is shown in Fig. 79. Other details of this system are shown later under the heading of «General Building Construction.» The Vaughan system consists of reinforced concrete «joists» made in an exaggerated I-beam shape. For ordinary construction, the upper and lower flanges are 12 inches wide, and the total height of joist is 8 inches. The upper flange is made somewhat thicker than the lower. Any good system of reinforcement combining tension and horizontal shear members may be used.

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