The Abbeville press and banner. [volume] (Abbeville, S.C.) 1869-1924, 1891-12-16
doctor to plead an intricate case at law

, the plans and specifications fora bridg
Some committees have the good SEM
to see that this is out of their line an
: that it requires a technical knowledg
which they do not possess, and the
calm an engineer who is expert o
such matters, to draw up general plan
and specifications, to see that CONTRACT
and bonds are in proper form, and
the expert understands his bushes:
the county is sure to get a safe and du
rable bridge, suited to the locality an
at the lowest market price.
BY the average specification an
contract as submitted to the committe
by the bridge company the contracto
binds himselfto receive his pay prompt
Ily and does not bind himself to d
much of anything else. He general
agrees to furnish a bridge according t
strain sh &c is submitted, which, inter
preted, m cans that he will furnish tn
fightest sections of the various shape
that the mills are capable of rollind
When q bill is presented it il a good
business policy before payment to in
vestigate it, and make sure the good
have been received and that they ar,
of the quality ordered, but when
strain sheet is presented bya bridg,
company the committee are poor judg
es of the goods, and are in consequence
likely to be cheated. If a strain shee
claims to be based on a live load o.
l,4O0 lbs. per lipeal foot of bridge and
|1s really based on a load of 800 lbs. Pc
lineal foot, which discrepancy is by NJ
means an unusual occurrence, how are
the. committee to. find it out. If sec.
lions marked Is lbs. per foot are given
on strain sheet and sections. weighing
10 lbs. per foot are furnished how are
the committee to find it out?
1t has been estimated by some au'
thorities who have given considerable
attention to the subject, that an aver
age of thirty highway bridges give
way every year in the United States,
sometimes under a considerable load
but often under next to no load at all.
The amount of risk which some bull
ders will assume under brisk competi.
ton in cutting down their material
and cheapening their structures con-
sidering that human life is at stake, is
really surprising. That much larger
number of bridges do not fall is due
to the fact that they have never re-
ceived anything approaching the load
which under exceptional circumstan-
ces they may be required to carry and
which they should be- designed to car
ry with perfect safety. 1t is safe to as
sert that not twenty-five per cent. of
the highway bridges standing to-day
are
WELL DESIGNED AND SAFE BRIDGES,
by which Is meant bridges which un-
der the maximum load for which they
should have been designed will not
give way or be permanently injured
by straining the material beyond its
elastic limit. Railroad bride construc-
ton for the past twenty years has been
very progressive. There has been a
steady improvements specifications,
details, class and quality of material,
mode of manufacture, inspection and
supervision, as we'll as the great in
crease in loads provided for, so that no
railroad engineer could be found to-day
who would accept bridges of the same
as were common twenty
years ago. At that time cast iron was
generally used for all members in COM
preston, the effect of wind was not
considered, and the Lateral systems
were designated by rule of thumb,
c%onnectors were often made greatly
inferior in strength to the members
connected; the size of the pins were
fixed by their bearing any shearing
values only, while the usually much
greater bending stress was not consid-
cred; YIELDS were allowed in all the
principal tension members structures
ambiguity of stress were common
the effect of wheel or concentrated
loads was not we'll understood and
floor systems were made much inferi-
Or in strength to the trusses; eXcen-
of stress was allowed to an a
Iarming extent, its effect being neither
or understood. These and
many other defects that might be
mentioned and which are found to u
or less extent in all old bridges
are not found in designs made by ca
Dable engineers or in bridges built by
CpuI3biS ioilAod'A oltSSO OlhpohiC
1t the present time. With
HIGHWAY BRIDGES
the case is very different, the use of
cast iron has been discarded to a large
extent, but designs are not much bet
ter, neither, as q rule, are the bridges
than they were twenty years ago
and so long a each is allowed to sub
his own designs on his own speci-
fication, use such material as he pleases
and manufacture and erect it without
supervision, they will never be.
Attempts have been made in some
States to correct present abuses, and
safe practice by statute, but so far as
the writer can learn very little has
been accomplished. There is no ques.
ton that if each State employed an
expert bridge inspector by whom his
plans for highway bridges should be
examined and approved and who
would be required to inspect all bridges
after erection, and who would have
power to condemn and replace all un'
safe structures the object would be &C.
complished; but in the absence of
such State action, each county must
protect itself from blackmail and from
unsafe and worthless structures in the
manner indicated or suffer the conse'
quences.
IT'S Worth 1t All.
Yes, to get hold of the grand truth
a. h. -.~.Il