Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1917-01-28
.P|LE-BENT BRIDGES TO
Be MADE OF CONCRETE
Deputy State Engineer of Minnesota
Tells of Changes in Types Of
Bridge Construction.
WOOD is BEING sUppLANTED
Serious Consideration in Building
With Material as Permanent aS
Concrete Is the Matter OF Fountia-
lions. Which Streams Undermine

Writing OF the subjcc; O: Concrete
Nagcl. dcru,y state engineer OF Min
re~o's. says.
study OF the types Of construction
tina; have been used for highway
bridges shows that they have developed
as mex materials have become avail
able. First lame wood pile bent
bridges and wood ,russes. which were
'''i wrought iron construction. Then
followed a 'o1 period In which steel
bridges were used TO q great extent.
and sill. more recently concrete bridgcs
have come [ use.
streams Undermine Foundations.
y serious consideration III building
with 81 material as permanent as CON
cot" IS 'ho matter cf foundations
Many streams arc continually cutting
decpsr r drainage bitches arc dug
nader The b-;IEes. and foundations
which were carried w.ll below the bed
Of The stream u; tho time cr coustruc-
'ion n undermined Ever though
piles 's2'" been Gsod obey sometimes
rot oT hscrUSr the low water level
is lowered. |; appears TO the writer
That We must come back 10 the Old pile
her' bridges IN a LITTLE different form
"a.
With concrete the economical length
OF I'll" span between tho hen:s or cross
rows OF piles figures abou; twenty
feet. carried by three piles per hent.
each pile driven until i; will carry
twenty tons. Should II be determined,
after one p'le has been driven, that
twenty tons cannot te carried by piles
, OF tho length provided. four Or even
Gvn piles can be driven Ter bent where
necessary &c give the required sup
port.
\ concrets cap is cast across the
tons OF The piles and serves 70 carry
the ends OF IN" spans. No ahu;men's
are used and tho bridge is made long
enough to provide sufficient waterway.
af,sr allowing the loose material of
the approach ~ each enc Of the bridge
10 run through tho end h"nt on--a
orc-to-onc slore. For the supcrstruc-
turc the Minnesota Highway Cc,ums-
sion has designed slabs with their ur
der side cored ON, by means Of corru
gated arch forms. resulting III saving
OF orc-third tho volu;Nr Or concrete
that would he used in solid slab.
How to Make Trrrtic Bridges.
roucrctc pile ,rcs,lc bridges can hc
, built by using multiple number %
spans % standard length. rendering
ii possible to make repeated use OF
tho same metal forms ard metal false
work Intermediate wood piles, IS
scDtial for IL IScuork under present
conditions. are not needed. This fac'.
taken toEcthc- with the ahscnc" Of
ccTcrdar1 work TO- pjcrS and abut-
nents. makes il possible to construct
/. this type ot bridge even Whom tho
:. wa'or level Is above normal. or when
!; freshcts are likely to occur. so that
: The working season Will he heightened
consderah bly,.
For driving concrete piles. more ma
> chincrv and less hand Ia hor arc uercS.
sarN than FOR constructing "rdu,rv
suhstructurcs. which Is "a decided ad-
vantage with the present uuSa.!S:ar.
tory labor conditions. The la bor that is,
cmrloycd Will necessarily 10 higher
paid and more reliable. Much less
time will be NECESSARY to construct
these bridges. for tho excavation work
will nc eliminated and tho Standa rti
s"'s 30 '"rms and f.l$.work can hc
nut 'n ''a"" r"sdy for concrete in a
shorter t,tn" thnu the timber talScwork
for tho usual types OF coucrci" bridges
This viii raus" less Inconvenience to
;rafNc. which is either detourcd or
carried over temporary bridge with
tn" approa chcs barely pas,ablc.
IN the past there has been a CON
tinued increase in width Of roadway,
and there is likely TO he a demand for
s'il greater widths on main trunk
lines as ira f'ic increases in volume
Concrete Sird"r bridges canno; be
"'dened, but with the type described
and - haph rail and curp can b.,
removed ind additional width obtained