The Portland daily press., 1897-04-09
WEIGHING SKY-SCRAPERs.
Every Bolt and Bar Considered in the
Plan.

Plan.
Even the Weight of the Paint, Oil, Solder
Tenants, and Casual Visitors Calculated
before a Stone Is Set Up-Solid Rock in
Foundations and the Way of Making Ii
The city of the future will be built
upon solid rock Modern conditions
point that way. The solid rock may not
necessarily exist at the surface of the
earth. If 1t does, so much the better. Il
1t is deep underground the foundations
Of buildings will have to be carried dowr
to 1T. The latter day sky scraper and
the practice of building Ouses of the
heaviest materials render this compulsory
even now. There are men in New York
and other large cities whose sole business
| 1t is to test the character of the ground
on which tall buildings are to stand.
They are experts, and no thorough going
architect would trust to his own discern
nlent in the matter Uf his groundwork.
In fact, the construction of sky scrapers
has vastly extended the calling Of the
architect, and compelled him to do some
things of which the constructor of by
gone days never dreamed. Most inter
esting of these newly acquired habits is
the weighing of tall buildings.
The average person might not fully ap.
probate the necessity for weighing tall
building. In fact. many persons would
calmly assert that it could not be done,
yet the practice of Weighing Immense
buildings, bridges, heavy ordnance, and
pondrous objects generally is science in
itself. 1t Is all done by computation,
but the actual weight of the structures
is accurately computed. In heavy
ordnance not only is the weight COM
puted without putting the gun on the
scales, bat the center of gravity is deter
mined within such fine point that
when hung on its trunnions the gun IL
so nicely balanced that 1t can be moved
up and down by the hand Of one man.
Swinging bridges which move upon a
pivot are 30 accurately balanced that
hardly pound Of difference exists be-
tween the two 0utstretohed arms.
4 1T il necessary for an architect to know
the weight Of his building long before ii
ia put up. The character of his founda-
tion depends upon it. Yet the estima-
ton of this weights Is SO simple a matter
that an under clerk or An apprentices in
an arohiteDt's office often gets the task
of calculating it. His grand total may
reach, as in the case of the twenty one-
story Surety building in this city, 30, 00C
TINS, or in the case of some big bridges
like thu one at Poughkeepsis 1000 or o.
600 tons. How is it dones In the first
place, the weight of everyspieee of mate
rial to become part of the structure is
furnished by the manufacturers.
Whether it be Z-bar girders or white
lead, it is all brought into the total
Even such an insignificant thing as n
difference in the quality and kind OF
paint may make a ton of difference in
the general weight of the structure.
Every rlvet in the building is accounted
for, and If the ends are fused or ham,
mered down on the opposite side of q
girder instead of being merely bolted oil
the fact must be taken into account. II
the roof is covered with tin the solder
which holds the plates together is put
down as weighing so much per ton. In
| laying the tin plates on the roof the
edges of each plate are Tapped over the
adjoining plates of the extent Of a omar
ter of an inoh on all sides. This quarter
inoh of necessary lap adds large num-
Der Of pounds to the general weight OF
the roof. so the process continues
through the whole building. The weights
| of this olapboards, the plaster, the wall
paper, the window glass. the gas or cleo
| trio fixtures, the cOrnioe ornaments, and
of the thousand and one materials aud
| appnrtenances which 20 to make up q
| building are considered and accounted
| for. Iii the aggregate these weights,
| Thousands OF tons, constitute merely the
| dor oiYhf Of tha h,,rI lh4
weight suoh as the weight of the tenants
the furniture, and their other belongings,
must be added to the total.
| An Office building with capacity OF
5000 persons would be about 1856 sons
| lighter at night. when it is deserted,
than in TIE daytime, when it is occupied.
In office buildings it is customary to es-
innate about 100 pounds of live weight tc
| the square foot. 10 manufacturing es.
adjustments it is customary to allow TO,
| at least loo pounds to the square foot.
The buildings themselves press down
| upon the earth at the various rates of
| from four tons to the square foot to
twelve sor fourteen tons to the square
foot. The tall st. Paul building Ia esti.
mated at the last named figure The
Surety building, mentioned above, is es-
timated to exert a pressure of six tons tt
| the SO uare foot.
| A curious part of this business In the
TESTING of the ground Oh which tall
| buildings are to stand. Nearly every
tester has his own method of ascertain
| ing earth resistance. Some do it by n.y.
draulic pressure, some by pile driving,
some bysdrivina down Einto the earth a
worn" which picks up dirt and grnvel
and sand at various distance and conveys
them to the surface to be examined. The
hydraulic method ia pursued by con.
structing box or casing, which is fas-
tened tightly to the ground. In it a
plunger, operated by water pressure, is
made to press down upon the earth. The
force with which it presses on the ground
| is determined by It's resistance to the in.
flow of the water. which is asoertained
beforehand. In driving piles these are
forced down simply until they will go nc
further. This Is done at various points
over the ground on which the structure
] Is to be built. Of course, the depth Of
this point of greatest resistance can be
marked of on the beam of wood which
has gone down. The worm resamh1es 9