Evening star. [volume] (Washington, D.C.) 1854-1972, 1896-07-31
SUSTAINING GREAT WEIGHT
Test Of Arches In the New City Post
Office.
How Their Strength II Ascertained-
Other Items of Interest In Re-
gard to the Construction.

Two hundred and twenty men can &C
eomplish q large amount Of work when
they have ths necessary knowledge and
skill and the incentive to labor. Two hum
drsd and twenty men comprise the work.
ing force on the new city post office build
ing. and they are industriously engaged at
their occupations. Much has been done in
the matter Of interior finishing, but a great
deal more remains to be done.
To the public generally the only pro-
erosion noticeable in the construction
work Is the completion Of the tower. which
Is rearing its head high above the other
parts Of the building. There yet remains
only a portion Of a story to be built of
stone. after which the pitched roof will be
put on. Already the post office tower Is one
of the conspicuous points In the local land
scape. and from it a splendid view Of the
city and surrounding country can be OBJ
tanned
But only a small portion of the SIN al
force Is at work on the tower. Ihe major
part is pdtting IN the floors. painting the
iron beams that have already received one
or more coats Of the oily mixture. stating
the inflammable fireproof roof and roofing
the great court with large plates OF heavy
hammered glass.
The first floor has been laid with brick
arches. over which filling Of cement has
been set The other stories are to be laid
in tile arches. and considerable portion
Of the work has already been done. The
second and third floors have been finished,
and work Is soon to commence On the
fourth story.
Testing the Arches.
There has just been completed severe
test Of the strength Of one of these arches.
and other tests are TO be made this week.
The specifications require that test shall
be made Of three selected arches picked out
at random. on every floor, by the govern
ment inspectors. The test Just completed
was made of an arch on the first floor, in
the great court of the structure near the
tower. 1t Is one of the few tile arches on
the first story.
1t measures feet from beam to beam, and
is feet wide, with a total surface area Of
20 square feet. Upon this arch were piled
1890 ordinary bricks. The height of the
brick column was equal to that Of good
sized man, and its weight was approXi-
mately 1900 pounds or nearly SIX tons.
Each square foot of the arch sustained a
weight of nearly half a ton. To add to the
severity OF the test, the sustained weight
was allowed to remain on the arch for two
weeks yet there was not the slightest sign
of any weakness nor crumbIing Twenty
square feet OF box-like terra Gotta tiling 9
inches thick. sustained for two weeks a
solid pile of bricks feet high.
The further tests to be conducted are to
be upon three selected arches on the second
floor This time the sand test will be adopt
ed On the 18th street side, near C street,
is the first arch which will be subjected to
the weight Of tons of sand This arch is
3 feet by feet inches. A box of about
that size has been made and placed SQUARE
~ on the arch. and is to be filled with sand
1t is calculated that one cubic foot of sand
weighs 100 pounds. and enough sand is to
be piled on top of the arch until it will sus-
tain 1.40o pounds of the heavy material
One box will not be sufficient to hold this
amount of sand, and after the first has been
filled to Its level another box is to be placed
on top, and ii, too. loaded down with the
earth and gravel The column of sand
walled in by the box frames will be : feet
high, feet wide and feet inches long.
Made of Terra Gotta.
1t seems remarkable to one unaccustom-
ed to such things that the arches con-
structed as they are of terra Gotta, can
sustain such tremendous weights. The
arches-which, indeed, are not the bow-like
curves which the term usually signifies,
but fiat surfaces-are made Of baked clay
or terra Gotta, sometimes called fireproof-
ing" The material is brittle and easily
breaks when dropped to the ground. yet
when the several parts are cemented to-
gether and the key-bricks put in, 1t takes
a very severe strain to crush it. Each
piece IS like a box without ends, with two
interior walls dividing 1t into three COM
partments. When large number are piled
up side by side they present a honeycomb-
ed appearance like SO many pigeon holes
Nevertheless, these hollow. clay boxes are
being filled in between the skeleton beams
of the post office to make the floors, and
the tests already made show conclusiyely
that they are capable of sustaining any
weight likely to be required of them.
Those who have watched the course Of
construction of the building are aware that
concealed beneath the protecting slate is
a roof CT pine boards, which has been de-
clared by the same authority to be both in
fiammable and fireproof. This unique ar
sir Of he
great building; over the court another
roof Is to be put on. This is certainly non
combustible. 1t Is to be of glass-hammer-
ed glass-half an inch thick, transparent
and not easily broken. Some of it is al
ready being put on the east side of the
great roof that spans the court at such
a dizzy height. The cortile roof Is also to
be of glass, so that over the city post
masters force-when it moves into its new
quarters-will be two immense skylights,
one at the height of the second story and
the other high above, at the top of the
building.