BENDING OR TRUSSING BARS 369. Bending Details. The full bending details of the bars should be made before the reinforcing steel is ordered for any rein forced-concrete work that is to be constructed. It has been the common practice for contractors to make these details, if they are made; and they may or may not submit them to the designing archi tects or engineers for their approval. Very often the plans or specifications do not state how long the bars arc to be, or even state what lap of the bars is required; or they may not be very definite in the number of bars to be turned up in the beams and girders. If architects and engineers would make these details and submit them with their general drawings, the contractors could then make a very definite estimate on the amount of steel required for the work, and these details should also assist the contractor in estimating the cost of the bending of the bars. With the assistance of these details be ing made very definite, it should not only assist the contractor in making his bid on the work, but would often result in better work being done.
The angle at which the diagonal bars are turned up, varies from about 10 degrees to 45 degrees, and sometimes to a greater angle than 45 degrees. A great deal depends upon the length and depth of the beam or girder. If the beam is very short and deep, the bars are usually turned up at an angle of about 45 degrees, or perhaps a little greater; but if the beam is long and shallow, the angle at which these bars are turned is very small. This angle, in the average practice, is about 30 degrees.
The bending of the bars is usually a simple matter, and generally can be easily and quickly done. If bends of 30 degrees or more, with short radii, are required of large bars-1 inch to 11 inches square—it is usually necessary to heat the bars. This makes the bending more expensive, as it requires the use of forges and black smiths to do the work.
370. Tables for Bending Bars. The usual outfit for bending the bars cold consists of a strong table, a vise, and a lever with two short prongs. The outline to which the bar is to be bent is laid out on the
table, and holes are bored at the point where the bends are to be made. Steel plugs 5 inches to G inches long are then placed in these holes. Short pieces of hoards are nailed to the table where necessary, to hold the bar in place while being bent. The bar is then placed in the position A-B, Fig. 173, and bent around the plugs C and D, and then around the plugs E and F, until the ends Eli and FG are parallel to AB. When bends with a short radius are required, the bars are placed in the vise, near the point where the bend is wanted, and the end of the bar is pulled around until the required angle is secured. The vise is usually fastened to the table. The lever shown in Fig. 174 is also used in making bends of short radii. This is done by placing the bar between the prongs and pulling the end of tne lever around until the required shape is secured.
371. The Hunt Bender. The bar-bending device shown in Fig. 175 was devised by Mr. R. S. Hunt, C. E., and has been used by him to bend 11 inch bars. In bend ing bars of this size, it is not necessary to heat them; and the size of bars that can be shaped by this bender depends largely on the proportions of the materials of which the bender is In constructing this device, a timber 1.0 inches by 10 inches and about 10 feet long is supported on posts and well braced, the top of the timber being about 3 feet high. A 2 by 4-inch plank is spiked on one edge of the 10 by 10-inch timber, the smaller timber extending to within 12 inches of the end of the larger, as shown in the figure. On the edge of the 2 by 4-inch timber, is fastened a +-inch by 2-ineh steel strap, which is the same length as the timber to which it is fastened. Opposite the end of the timber, and 3 inches from the timber, is a steel pin 1 inches in diameter. The lever is usually about 31 feet long, and made as shown in the figure.