New-York tribune., 1907-09-05
STRAIN THEORY WRONG?
Strength Not Increasing zcith Bulk,
Theory of Bridge Collapse.

The collapse Of the great cantilever bridge oTe<
rhe s.. Lawrence at Quebec, which cost seventy
r.ize lives and puzzled the engineering world.
discussed length in editorial published to-day
n The Engineering News" The cause is still a
puzzle but the main point made is that while engi-
reers know the material that goes into the make
pp OF such gigantic structures, they do not know
.he composite the structure In other and les1
technical words. engineers can decide by rule the
st-ess and breaking strain OF materials up to a
certain point Beyond that other elements enter.
and the chief Of these is whether the increase IL
strength is commensurate or proportionate 10 the
tacreasc IL bulk
q-se editorial deprecates The blow this accident
t.s struck to the engineering world and the Jar Il
gives pubic confidence in engineering projects
After throwing at length those things that
could :sot possibly caused the collapse OF the
hsldEe IL continues;
Al the time this is written. at Quebec, on the
fourth Say after The wreck The initial cause q inc
sioa member IN the anchor arm Of the cAi1tilever
The expert in snalyzing the reasons for this con-
clasion. points cat many things The nam pier
fnd tie anchor ple- show no signs of settlement or
failure IN PROOF Of his conclusion that no tension
,7,1naber vas the cause OF the initial bIeak that
t.cuch- shout tho entire collapse. t.le writer
unuc.:
Isad tension member failed frat it would have
snapped with a loud. sharp report or series or
which would have impressed every eyewitness. All
silent The tirst warning was when ias IIsen fel;
lie aocr sinking beneath them
Had 81 tension member failed, especially Of
rhe top chord members the structure would have
dropped instantly, like falling body Tho failure
cid not occur IN this way. The hazy accounts
g.rer by eycwftaesses agree iu the fact that
fhe cnl.suts was gradual least In
stages. A ZINE OF ten 10 fifteen seconds is indi-
Gated. TIE tiIaekeeper. who was near the anchor
end AID RAD to uphill TO safety. must have
occupi-d az least this before he turned
around This man, by the way, ooeS not report
5uTllpsas a gap the archoraSs, although gap
Rave opened there 1T once II The anchor arm
vns the seat OF the failure But there
hanging from, the approach span three long strings
os track rail, about seventy-fiVe feet long, which
bridge: these doubtless carried their ties with
them for time and b:idged q gap, is a gap did
fcyrl- The absence or gap. therefore. argues
neither for against compression failure or
anchor arm failure. Bat the slowness Of the fall
points 10 a compression member the one TO give
wey- The gradual fan could not possibly occur IA
the case os sudden swapping OF eye52r, or.
rather. a panel of eyessre.
OF importance 10 engineers who have been con-
STEERING the matter is the statement by this eye
witness that .fn all that pile ~ torn and twisted
cnc wsenched steel Is only single broken eye-
h2- thus far discovered and that IS only one eye
bar o@t CT tgenty-stz composing thse particular
top chord r:ernbef''
tssc- taxing up Eeveral other possible causes and
ess.izsas fisenl o;.t OF the oues stlsn The En-
gia>eEs-s &rvs" returns to the main question IS
f5Iioxx
sses tsc dcuat lies furthsr lack. We step up