The Monmouth inquirer., 1925-12-10
ROAD
Bull DING
NEW ROADS REQUIRE
PERMANENT BRIDGES

Traffic conditions on our roads to-
day are so different from those Of
few years ago that highway officials
have found it difficult to comply with
the ever increasing demands made by
automobile and truck. One of the most
important features Of good road is
the construction and design of the
bridges The good bridge of today
must be a permanent structure, free
from maintenance expense. and wide
enough for all the traffic which the
road carries under ordinary condi-
tions. The wise highway official will
not only build his bridges for the
present, but will also keep an eye
on the future
Bridges, like roads. are for the
traffic of today and tomorrow They
grow stronger as they grow older.
They will not rust. rot burn. nor
deteriorate in any way. They need
no painting, no Tightening of bolts,
nuts or rivets, no repair of masonry
joints, no periodical replacement OF
worn-out parts, no rebuilding after
floods.
Permanent highway bridges, desir-
able in ordinary times, serve an inn
perative need in times Of expansion
or of emergency. Quick, certain, and
economical movement of food and
other products from farm to town,
or of goods between widely separated
manufacturing plants, is required by
the new conditions under which we
live, and these demand highways able
to withstand any kind Of traffic every
day in the year.
Every bridge location involves some
special study to best meet the needs
Of the particular situation. Designs
for small culverts and for bridges up
to 16 or 20-foot span can in large part
be standardized Larger and more inn
portant bridges should be designed by
competent engineers, able to obtain
first-hand knowledge of all conditions
that are to be fulfilled.
Bridges or culverts should be cor
rectly located with respect to the high
way and the stream. They should be
on the center line of the highway.
The abutment walls should be parallel
to the highway. It is often advisable
to change the channel of waterway
for a short distance in order to OBJ
tain q better approach for the stream
to the bridge opening, and better
angle of crossing. The objects to be
attained are, as nearly a straight
course as possible on the upper side
of the bridge and the same for a
short distance at least on the lower
side This will reduce the danger OF
the bridge being undermined or it's
adjoining embankment being washed
away by high water. In locating
bridge, due consideration should be
given also to securing as nearly level
and straight approaches on the high
way as possible.
Large bridges should be founded on
rock or on piles driven to refusal.
Smaller structures may rest on good
firm earth, provided footings are so
spread that the pressure on the soil
is well within the limits of safety.
In general, foundations should extend
below possible frost penetration, but
otherwise need not be carried deeper
than to firm-bearing soil or to a depth
necessary to prevent undermining.
All bridges require an abutment on
top of this to support the main bridge
structure and to retain in place the
roadway embankment Wing walls
also are needed to retain the slopes Of
the embankment 1t is best that the
wing walls be monolithic with the
abutment proper. In very long abut-
ments vertical expansion joints should
be placed every 80 to so feet to pre-
vent cracking due to expansion and
contraction under changing tempera-
ture conditions It is also important
that suitable drainage be provided for
the fill behind the abutment.