Arizona republican., 1907-07-27

congresses under pressure and the
lower side stretches or pulls apart
Now concrete" explained Mr.. RACER
is strong in compression while steel is
Estrong in tension. The steel is there
| fore placed in the lower half of the
girder The size of the steel and the
girder can be determined by the strain
it will be called upon to bear. In the
Noble building 4, and IA inch twist
ed steel rods will be used which can
be loaded up to 100000 pounds. The
advantage of twisted steel rods is first,
| the anchorage that is obtained, the
same as in a screw, and second that
the twisting process tests the unifor-
nifty of the strength of the rod, and
imperfect steel can be discerned by
the naked, eye and cast aside"
Another thing that is interesting to
note as Showing upon what scientific
basis this making of concrete Orders
is founded: All these supports have
tendency to split at the end, hori-
Zontally. To overcome this, a stirrup
of strap iron is placed in the ends of
the girder. Viewed from the end. this
stirrup looks like a w, and it wraps
the concrete above. Mr. Roger further
explained that when Orders break,
the break occurs generally near the
column on which it rests. and not in
the middle. To strengthen at this
point, two of the rods in the gkder
are carried to the upper side over the
column. or rather through the column,
since it is one to the top of the roof
and to the under side of the girder on
the other side.
To elucidate the mystery of the col
umn. Mr.. Roger then took the reporter
out to the pile of skeleton steel frames,
sixteen feet long. and sixteen inches
wide, two inches less in width than the
column form, and composed of four
steel rods bound together by many
bands Of IA inch steel. These skele-
ton frames are placed in the wooden
forms and the concrete poured in. This
concrete cannot be crushed by any
load il will have to bear. and the col
umn cannot shear off, break on a
slant or buckle. until the upright steel
rods pop out. which cannot occur I'M
til the bands which bind them break
from the tension. in which steel is very
SthCht' hN NVHNlttt VII the
of the steel frame does not enter into
the calculations as to strength, as it
Is merely to protect the rods from fire,
as the rods weaken when subjected to
heat.
You have seen the column to the
first floor" said Mr.. Roger Here
the steel frame is Joined to the one
above by an iron pipe or joint. which
fits closely, and at every floor is a
joint similar, all being filled with con-
orete"
Mr.. Roger in the laboratory, again
gave some interesting figures as to
what loads this construction. will car
~. These statements are founded on
facts, for it has been positively DEM
onstrated what every different size of
steel rod will stand in tension. what
amount of compression, every inch of
concrete both without reinforcement.
and with it. will bear.
Beginning at the SOIL" said Mr..
Roger. ''its character determines how
large must be the footings of the col
umns to support a certain dead weight.
the weight of the building plus the live
weight, that may be added This soil
'oBP'AN Il hteiu NfiEIl VI D.VVU
pounds per square foot The twenty
inch columns will carry 500 pounds
per square inch, or 81 tons. The steel
must stand tension of $4,000 pounds
and the concrete the same amount.
We use safety factor of IA in
steel, of Is in concrete: in other
words, we estimate to build n floor or
beam. the breaking load of which will
be four or five times what the dead
and live loads will be.
1.-The steel is all tested at the fac
tory, but here is where we test the
cement and concrete. The first test
of the cement is for fineness,-it must
be as fine as flour,-and second for
tension
Mr.. Roger then showed how briquets,
shaped like a figure s, one inch i'm
diameter in the narrowest part, were
nodded. allowed to harden under
water. then on a scale tested for
strength If the cement in any car
does not come up to the standard il
is refused. A briquet is placed in the
clutches of the testing machine. and
shot is poured into a RECEPTACLE at the
end of one of the compound levers.
which for every pound of weight of