The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-10-02

terial IN the United States in ISL, shortly
after the great Chicago fire. Its peculiar
advantages caused it to undergo many i'm
proyements IN rapid succession affecting
Its use IN floor construction and in the pro-
lection OF metal columns and beams from
nre, and also adapting it to the needs OF a
lighter and more rapid construction
throughout. Reduction in weight. great
increasing qualities. peculiar adapta-
blllty to all conditions of position and
form, Its susceptibility TO modelling, its
readiness OF manufacture in shapes con-
venlent Tor transportation and ection,
ana It's enduring qualities, ell combined 10
bring 1t into extensive use The latest i'm
provement proposed is an enameled terra
Gotta, which would be of peculiar value in
soot-ln1ested cities like Chicago and Pitts
burg, as exteriors constructed OF such ma
terial could be readily cleansed.
Everybody has noticed the extraordin-
airy rapidity which the skeletons OF the
new buildings rise after the foundations
have once been laid. Two stories can gen
orally be erected IN six days of ten hours
each. In the Unity building, CHICAGO. the
metal work for the seventeen stories, from
the basement to TIE roof, was put in place
IN nine weeks. The rapidity of building
operations possible with the new type OF
construction is shown by the following
data IN regard to the New YORK Life build
ing in Chicago:
July z. Old building torn down
July 81. New footings laid out.
umns.
September 5. Started setting the floor arches.
september le' Started laying the terra colt.
september 2s. The steel skeleton finished.
November 8. All the tile floors set
November II. Terra COTS all set
turned on.
There were 671 separate columns in this
bulIdlng. An average OF twenty-five work
ing hours was required 10 set the steel work
Tor compete story. AS the exterior walls
OF such buildings are supported wholly or
IN part by the metal framework, their con-
struetlon can proceed simultaneously at
several stories. Thus, in the Manhattan
building IN Chicago, the main cornice was
completed before the wall was built up be-
meath II. On another building the granite
base wall was built at the first and second
hoor, the pressed brick face was placed at
the twelfth-story level, and the hollow tile
arcnes were set Tor the fifteenth story all
al the same time. Several gangs OF work
men may be seen frequently at different
levels constructing the exterior walls of
such buildings. Modern requirements of
plenty OF light and air and broad windows
made necessary this plan OF supporting the
walls by the framework Piers of solid
masonry carrying all the floor and roof
loads, as IN ordinary structures, would be
lmpTactlcable IN twenty-story sky-scrap ers,
because they would take up too mach
valuable room. Thus in the twenty-one
story Masonic Temple in Chicago the maxi
mum allowable pressure of twelve tons per
square foot on the brickwork was reached
al the fifth story, and this without any
floor or roof loads
The expedient was therefore adopted OF
carrying the masonry work on brackets
attached TO the metal columns at the six
tenth and fifth story levels. Thus the
pier consisted of three separate columns of
masonry and one continuous metal coll
unn. Brick and terra Gotta have driven
stone from the field of skeleton construc-
ton IN exterior walls save in the lower
stories where it serves as base for the
superadded brick or terra Gotta. The OBJ
lection 10 stone is the difficulty OF prop
erly anchoring or attaching it to the metal
framework. The load carried by some of
the metal columns used as substitutes for
masonry piers are tremendous. In the
Schiller Theater, Chicago. columns 90 feet
10 inches long were used TO carry weight
of 3, 600 pounds. 1t is not uncommon TO
have SQ0tons or more on single column.
with q sectional area of 15s square inches.
The foundations for these great build
ings call for all the skill of the architect
ard engineer. Some wonderful things haze
been done, especially in Chicago in the
way OF erecting twenty-story buildings on
uncertain and shifting layers of mud, clay
and sand. One development has been the
so-ealled raft footing. The name describes
il we'll On bed OF concrete a raft or grill
OF railroad rails or steel or iron beams IS
built in layers placed crosswise One such.
footing Is prepared for each column, and so
a tTenty-story sky-scraper is made 10
float in safety On steel rats in sea OF mud
and clay. In New York and elsewhere
pneumatic caissons have been used 10 PEN
citrate TO bedrock for the foundations. and
daring expedient. have been resorted to in
the way of balancing great structures ON
cantllevers in order TO distribute the weight
OF the building over all the available space.