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STATE GEOLOGIST. LAX 
Weber System.—tIn the Weber system steel T bars are used for re- 
inforcing the concrete, the advantage being, that the T form gives a 
much greater surface contact for union with the concrete, than do round or 
square bars. having the same cross-section. The T shape also resists a 
much greater bending force for equal amounts of metal. This being one 
of the standard shapes is readily obtained at reasonable prices. Longi- 
tudinal and lateral bars are easily clamped together, back to back, by spe- 
cially designed clamps which work very simply so that the reinforcing 
skeleton is quickly put in place. Figure 72 shows the details of this 
system. 
Kahn’si System.—This is one of the later developed systems, and 
seems to have some excellent features to commend it to engineers. In the 
first place it is a form which can be easily rolled and easily cut and pressed 
into the shape desired. In the second place it seems to offer a reasonable 
solution of furnishing the tension member at every position where it is 
most needed. It amounts to the same reinforcement furnished by the 
Hennebique system, and doés it with a much simpler piece of metal to 
place in position. Its fori readily fits it for a great variety of structural 
purposes. It would seem to be especially adapted for floors, beams and 
walls. Figure 73 shows the shape of the metal member. 
Columbian System.—The Columbian system is another method of 
using bars and strives by the shape of the bar used to gain in rigidity 
and in binding union with the concrete. The bar is ribbed, having a 
central web from which three to six ribs running longitudinally of the 
bar set out at right angles on each side. As it is an unusual form, 
it can only be obtained at the few rolling mills which may install 
the necessary rolls. Being an unusual form it will probably cost 
more than the simpler and customary forms. The claims made 
for it are: The greater surface presented for adhesion of concrete, 
the rigidity of the metal piece itself, and the additional rigidity given 
when supported by concrete firmly imbedded between the ribs or flanges. 
Figure 74 shows a section of the metal. 
Cumming’s System.—This system employes round iron rods in 
place of the Kahn system of flat ribbed bars. These rods are bent into 
sets of long, slim parallelograms. Each parallelogram is sufficiently 
narrower than the one preceding it to lay within it and is considerably 
shorter. A short portion of the ends of each parallelogram is then bent 
up to make an angle with the horizontal of about 45 degrees. This nest 
of bent parallelograms is then laid into the form with its lower edges about 
two inches from the lower surface of the beam. The concrete is then 
tamped into place. The result accomplished is the same as with the 
Kahn reinforcement, but the accomplishment is not so simply and easily 
attained. Figure 75 illustrates the metal forms. 
