Montgomery County sentinel. [volume] (Rockville, Md.) 1855-1974, 1956-02-23
Local Firm Produces
Structural Concrete ,

Long, slender construction
beams cast of concrete? A seem
ing impossibility.
But a new Rockville manufac-
turing operation will soon be
turning out concrete beams that
have already been used to build
an entire bridge in an hour and
As minutes of actual construction
time. Prestressed Structures Inc.
is preparing its casting beds" on
a two acre tract near the Wash
ington Gas Light Co. plant on
WeStmore Road.
Obviously plain concrete beams
would crumble beneath h e
weight of bridge traffic. Pre-
stressed Structures Inc. strength
ems its beams by a process from
which the company takes its
name: prestressing. Stretched
steel cables are embedded in the
concrete beams at the time of
casting.
Prestressed beams are not a fly
by-night invention. In a variety
of forms they have been used in
Europe for 30 years. But only
since 1915 have they been used
extensively in the United States.
Philadelphia Has First
The Walnut Lane Bridge in
Philadelphia was the first major
bridge in this country constructed
with prestressed concrete beams.
The five and a half mile Tampa
Bay Bridge in Florida is another
example of prestressed beam con-
struction.
After a period of research and
development in its Bethesda
plant, Prestressed Structures, Inc.
has apparently convinced Wash
fngton area Jurisdictions that
brid ges constructed of pre-
stressed concrete beams are eco
IIOIIllCdl anu sale.
The company erected a vehicu-
lar bridge across a small stream
at Valleywood Drive in the Con-
necticut Avenue Estates 70 r
Montgomery County. Construc-
ton time: three and a half hours,
not counting hauling and I'M
loading.
Company officials say the Val
leywood Drive bridge would have
taken -four or five weeks" to
erect using old poured-concrete
methods.
Several Up Here
Prestressed Structures has also
erected bridge across a stream
near Wheaton for Rockingham
Builders, widened a bridge in
Arlington County, and put a num-
Der of foot bridges, all in amaZ-
ingly short times.
The company hopes to use its
new construction method on the
Back Lick Run bridge and the
Four Mile Run five-span bridge,
both in Virginia. They are bid
ding on the projects.
Company president MILFORD
F u e of Wheaton, says,
Bridges made of prestressed
concrete beams show a consid-
cradle saving in initial cost, in
maintenance coast, and in time of
erection"
Shaped Like &C.
Looked at endwise, pre-
stressed concrete beam appears
like a square letter &C" Other
companies make "T'' and III"
shaped beams. The beams are
made in lengths from 30 TO 70
feet. A so foot section made by
the Prestressed Structures meth
cd weighs 46 tons. Company Off
Gals say concrete beams made
by other methods may weigh al
most 10 times as much.
Three-eighths inch, seven-strand
steel cable is used in the beams.
Eleven cables run the length of
short beams; fifteen cables run
the length of long beams. The
cables are pulled taunt by 10000
pounds pressure.
Prestressed Structures hopes TO
begin full-scale operations with
four casting beds each 225 feet
long. Mr.. Fuller says the plant
will turn out 1000 feet of beams
per week. The Valleywood Drive
bridge took 1850 feet Of beams
The bottom of the casting bed
is slate, the sides are concrete.
The cables are stretched along
the length of this trough and
then it's filled with concrete. A
wooden form" is pressed down
on the wet concrete, giving the
beams der u" saape.
-------J --....IciiJ
AIR % no.-s the concrete /:
hand l.i t.g cables are released