Ellsworth American. [volume] (Ellsworth, Me.) 1855-current, 1902-07-30
FAsoiSAr1se DANGER
The periis That fgesef the builders
Of Big Bridges.

Of Big Bridges.
The design of iDng bridge span Is
one Of the most elaborate mathemat.
icaI problems that arise IN constructive
work. The stresses produced BY rs
own weight. BY the weight of trafyie.
by locomotive drivers. hy the hammer
ing 81 fiattaBed wlisels. ~ tie action
Of brakes on an express iraln. hy tie
high speed on curved track. ~ she
wind and b. the expansion and con.
traction 81 the steel In summer ard
winter are ali accurately calculated.
The DETECTION Of the loaded aid mn
loaded bridge is determined. ard com
plese drawings are made Of every mem
Der Of It. The bars Of steel are tested
ia machines which will pail Ia two
hursaElaif or q steel bar strong enough
to lift half score Of the heaviest To-
comotiyes at once, and which will
crush an eggBbell or steel column.
and accurately measure the stress in
each case. The different kinds Of menu
bers are forged. riyeted, bored. or
planed in perhaps half dozen remote
shops. and, although usually not fitted
together there, are examined and meas
ured by specialists TO see that they are
correct, and are then shipped by scores
Of carloads TO the site of the proposed
structure, where steam derricks unload
them and pile them many feet high in
stacks covering acres Of ground.
The bridge piers may rise above the
water hundreds Of feet apart II re-
mains TO place them On thousand ton
structure. high ai,oYe savage ciasm.
over an impossible current or roaring
tide, where the water ~ deep. the bot
t0m Of jagged rocks or tFeaeberous
quicksaDd. OF where an Old bridge must
be removed and the new one built in
Its place without InteFruptiBg traffic
on the bridge. To accomplish fl1is the
engineer las timber. bolts and ropes.
holsting engines. derTieks and band
Of intrepid builders who have perhaps
followed hin for years through more
hardship and danger than faII 70 tie
bot of aiFDoss any other calling.
The complicated framework Of
great span Is q skeleton with many
accurate joints and thousands OF steel
sinews and bones, each OF which naase
go IN exactly the right place 10 exact,
~ the right order. The builder naaxt
weave Int the trusseS pieces larger.
heavier and far mare iaEexibse fhan
whole tEee tgunks. swiftly host and
swing them TO place hundreds Of feet
high. CT together the massive giFtlera
and huge forged bars with watcsmak-
erz accuracy. support the ugwfel3y
masses Until they are keyed together
and self sustaining. and under nil
Hons Of pounds Of stress must adjust
them az dizzy bessfsS To mathematical
Lines This he may need 70 % not de-
EbeTafely. bat "a dangerous eraexgez-
eses. at utmost speed. putting forth hls
ws0Se strength On narrow, SpT1nglnz
pisnks Ia a fgrl01s tempest. In bitter
e0ld or "a blazsng heat He gsaT b.
"a the hear. Of an African desert, Esea-
aeed - bBoodfh3rsty fanatics. 81 Ia a
EO=ze ~ the A2des. buadrets q niles
from tools Or SUPPLIES. ~h@re tAere L.
ahsz0saEely 10 sgyptezGent 10 his owB
resources Under such cyn1ifAoa8
hrfG9s bssfldsnS - ore Of tie assst fas-
efEatiag ard G.fycGlt u eazazesrfaz
pro5aesss and reqslres a different ~
lGstsoa for almost sTery ease.-FraaE
w. Sklznsr 90 CsgszEy.