To bend a bar with this device, the bar is placed against the steel strap with the point of the bar at which the bend is to be made opposite the steel pin. The lever is hooked on the pin, while being held at right angles to the bar to be bent. The lug on the lever rests against the bar; and by moving the lever towards the end of the timber,• the required bend is given to the bar. For smaller sizes of bars, a washer should be placed over the pin so as to reduce the space between the pin and the bar to be bent.
372. Beams and Girders. Fig. 176 shows the bending details of the bars for a beam or girder in which six bars are required for the reinforcement three of which arc turned up, one at a distance of 3 feet, and two at a distance of 4,1 feet from the center of the span. The light lines indicate the depth of the beam, including the thickness of the slab; the vertical dash-and-dot lines, the center of the supports of the beam; and the heavy full lines, the bars.
When plain bars are used for reinforced concrete, architects and engineers very of ten require that the ends of all the bars in the beams and girders shall be hooked as shown in Fig. 177. This is done to prevent the bars from slipping before their tensile strength is fully developed.
373. Slab Bars. To secure the advantage of a continuous slab, it is very often required that a percentage of the slab bars, usually one-half, shall be turned up over each beam. Construction companies have different methods of bending and holding these bars in place; but the method shown in Fig. 17S will insure good results, as the slab bars are well supported by the two longitudinal bars which are wired to the tops of the stirrups. Fig. 179 shows the bending details of slab bars, the beams being spaced six feet center to center.
374. Stirrups. Fig. 1S0 shows the bending of the bars for stirrups. The ends of the stirrups rest on the forms and support the beam bars, which assist in keeping these bars in place. The ends of
the stirrups seldom show on the bottom of the slab of the finished floor. Sufficient mortar seems to get under the ends of the stirrups to cover them. Type a is much more extensively used than type b.
The latter type is generally used when a large amount of steel is required for stir rups, or if the stir rups are made of very small bars.
375. Column Bands. In Fig. 1S1 two types of column bands are shown.
Type a shows bands for a square or a round column; and type b, bands for a rectangular column. The bar which forms the band is bent close around each vertical bar in the columns, and therefore assists in holding theSe bars in place. The bands for the rectangular column b are made up of two separate bands.
376. Spacers. Spacers, Fig.
182, for holding the bars in place in beams and girders, have been successfully used. These spacers arc made of heavy sheet iron. They are fastened to the stirrups by means of the loops in the spacers. The ends of the spacers which project out to the forms of the sides of the beams, should be made blunt or rounded. This will prevent the ends of the spacers being driven into the forms when the concrete is being tamped. The number of these spacers required will depend on the lengths of the beams; usually 2 to 4 spacers are used in each beam.
377. Unit=Frames. Among the pa tented methods of fastening the bars together for beams and girders, is the Unit Girder Frame System. The loose bars are bent and made into a frame as shown in Fig. 1S3. All this work is done in a shop; and the frames arc sent to where the building is being constructed, ready to The stirrups are made of round or flat bars, and are hot-shrunk on the longitudinal rods. The girder, beam, or column unit is shipped to the site of the building being constructed, bearing a tag numbered to correspond with a number on the plan showing the proper position of the reinforce ment.