The Abbeville press and banner. [volume] (Abbeville, S.C.) 1869-1924, 1879-02-19
Building Bridges.
Correspondent Union 7Imes.

I built stone abutments en- the piling wood
en- foundation plan on Fair Forest, near Gen.
line. The situation had no hard foundation
Mt q depth of some fifteen feet, the mire
%soundings showed the banks to be very soft,
sandy and deep. The many bridge builders
around that place, Frank West, JAS. Williams
Mr.. Maro, Maj. Mcdowell. Gen. Glenn, and
persons generally, strongly asserted that
these stone abutments, could not be made to
STEMS sian he e e@Weaer,sg sd us 'h rcst do a oo Jew two do dsGt
soft sand. The June and other freshcts have
not moved the abutmcnts the eighth OF an
inch. The first cost of this improved plan
the future cost to rebuild the wood will not
extend one-ffth cost, to rebuild on the old
plan. The first leading wantin bridge econo-
my is stone and dirt abutmcnts, TO shorten
the bridge as much MS practicable ms above
said; ncXtto this Is stone piers. their distance
apart to vary as the varied circumstances of
the situation may demand. The Howe Truss
or the Lattice. or the Utlcy bridge, can he
many wagon bridges with lU feet spans, the
older ones built on the Lattice plan, the more
recent built on the Howe truss plan, which.
or the lattice bridge, and advise itsadoption.
Where the situation calls for n span l50 feet,
the bottom cords, especially. should be made
much larger: the braces. however, not to he
increased In size but little. as IT. would give
them al unnecessary weight on the long span,
they to he much longer. the top cord to be
much higher on long than short spans, and
much less than the.bottom cord in any length
OF span, as its functions require much less
strength han the bottom cord. When the
lower cord Is u inches square the top cord
should be about by 10. The usual practice,
however, Is 10 by II for tho top: Iintroduced
burg County In 1856, but IN every instance
specified the top cords, braces, needle beams
and short Slccpers to be much lighter tl ,,n
,rlp 7 nn,ct1nrn1 Ann1 Sltninht Snnf a re- or
the freshct OF 81, q Northern man built n sort
OF self sustaining bridge Mt the Hurricane
Shoals, PacOlet River, using very long, heavy
and very. fiat running braces: rising only
about 81 feet in 20; soon after this the same
plan was adopted at two other places on the
river. one close above. the other close below
Trough Shoals, and all three OF them were re-
both the first and second building, as soon rs
the work began to get Il little old, and 1t took
twenty years to school these people, that the
to show how long n time Is frequently re-
quircd to teach n people whnt Is worthless or
inferior. II is now entirely abolished, and
the once lovers Of II can now look back upon
1t and their blindness. l never did like 1t,
because the plan was contrary to the clear
teachings Of the science OF mechanics.
1t Is laid down by an able author that the
strength of IL stick of timber is MS the square
vcrscly as the length. I presume the author
means these laws of course only to apply to
short length sticks, rs the freight Of one 10 or
70 feet long would so largely enter intoit ms to
it follows. according to my theory, that great
lengths, either In a sleeper or s~clfSuppOrting
span, on the Howe truss, the Lattice. or The
Utly plan, that all dead weight should be dis
clrdeu; that the dimensions and proportions
of the different parts should be such rise only
aS to perform the respective functions Of the
different parts. The bottom cords Of any Of
the truss spans performs n different function
Z "a fhnt nc tho fnY, cords Tho fnnf nf tho
braces on the former strains them to make
them longer. while with the latter the braces
push to make them shorter. With this diff
ference, the bottom cords require to be much
stronger to make them safe from giving down
or breaking.
4 very similar principle exist with regard
that a sleeper Of great length will he stronger
to have the top cdgc not more than 1 or
inches thick and the bottom edge 5 or 10.
The effect Of weight on the under edge is to
strain 1t apatt where the break first begins,
while or the top edge it is pressed together.
Therefore, with these quite different func-
lions, much less material is required to per-
form the demands Of the upper than the low
but / am very sure am correct. got out
my Trough Shoal bridge slcepers in this
shape in 81. But, however, the old sleeper
bridge Is In many places passing away, and
have mainly referred TO 1t US above to call at-
~tcntion. that II very similar principle applies
to the Truss bridge, not to weight 1t down
with disproportionate weights. &c: If this
be not attended to, with other defects in the
planning, with sorry workmanship, the ma
tcrial o little inferior, put up on wooden
trusels and they on bad foundations. the mon
cy had nearly as we'll be thrown in the river
or the fire. But, on the other hand, with
stone abntments, and in some places stone
piers, with q Truss bridge Oh this, covered In.
with all paris well planned and the work well
executed, would lake a bridge that would
last the county half n century; while the
first cost would little more than double the
cost of the inferior, the latter being much
more subject to frcsllct damages, in cOnncc
tion with its rapid delay. and much more ok;
say. to invest so much In q bridge and 1t so
liable to wash away. would not pay. In reply
to his l beg to say That to no part of meclnil-
and study, than Hydraulics, or, in other
words, the laws of water In motion, and can
truthfully say that l have never had n piece
of my work to give way by frcshcts, bridges.
mill DAMS, or mills, where the work was
doneas directed when. too, much of 1t I have
lone at the most difficult places. In several
cases my stone abutmcnts, In Spartanburg
County. were damaged by the June freshet
very defective work. The other two Commits
Sioncrs requested me to Xamin plans and
specifications of several bridges In their d.
visions. but, very strangely they saw fit not
to hive me to the work, and they
received the most defective work even went
so far ms to over-rule by majority the exccp-
ton of sorry work or line bridges between us,
X x(tsr tG of e1 1hcy u gaIs som mey of ~ ibe tb br,d frex ena:
tractors combined and placed the fault in my
plans. instead Of bad work, and 10 my sur
prise they succeeded In moulding much Opin-
ion to their very ERRONEOUS view. l mention
this to show how easy 1t Is for men of limited
experience and opportunities In mechanics to
be gulled with sorry work. boldly challenge
p Sest onf ll TO in5w' a nS stome mason 1" ih fhis op
~Spartanburg COunties-that the fault of this