New-York tribune., 1907-12-19
HUDSON BRIDGE PLANS.
ENGINEER FILES REPORT.
Ans1cers Criticisms of Mechanical
Features of Structure.

Leon S. Moisseif. engineer in charge OF the de-
signs for the proposed Henry Hudson Memorial
Bridge, submitted a report yesterday to Chief En-
gineer IngersoI OF the Department of Bridges on
the engineering features of the structure In It's
issue of to-day Engineering News" critcises the
designs already prepared for the bridge. The re-
port of Mr. Mosseiff takes up and disposes or the
questions raised in the editorial of Engineering
News
The designs call for concrete bridge about 2,s4o
feet long consisting of seven circular arches OF
about los feet clear span each with corresponding
piers. main arch of 103 feet clear span De
tween skewbacks 1anked by two monumental piers
about los feet wide and $50 feet high. The ap-
proaehes are designed 10 be of concrete masonry
reinforced b. embedded steel wherever required
the piers being faced with natural stone.
The bridge Is designed with an upper and lower
deck providing for surface and subway traffc- Inc
upper deck has clear width OF ~ feet oet"ee"
balustrades occupied by q 50-foot roadway and two
sidewalks of 10 feet each The lower deck is 20
feet wide from outside to outside Of walls ana
about 50 feet the inside. 1t is occupied by iour
railroad tracks and has sufficient space Tor pipe
galleries and the like The subway tracks on the
main span are supported by steel beams and posts
resting In turn on the secondary relieving arches
and on the vertical piers designed to be OF rein
forced concrete
The editorial in Engineering News" says in part:
We do that the great structure 9 e9nld noy
is permissible. or that II built it might no. Six x
" hat we 90 say Is l4dt t4Ie dSSotItN'N
pGrience and knowledge of the engineering proies-
is sufficient TO build concIeie 1911 alIi
tht tle PuDc Pd9t 3 Ii3 hHge arch involves serious
risk and we can find no adequate reason why the
city OF New York should run such risk. TIC. IN
There is to be considered also the risk to life m
VOWED III a great structure whose margin oL Sc
Tn bud II Concrete arch of 7o3 is not
mere step forward but flying leap ana pan thsFe in The
dark Not only Is there no precedent whate@tei @ 80, o
the construction of a stone or concrete ai Gu V' III
m mas sisaa' less than one-thifd this span,
The recent accident the quebec bridge Is, Is
startling Illustration. In that the conclusions
of sound and conservative designers pdseu o.,
tlce with structures Of ordinary size pIoFu ntEay
erroneous when applied to a structure OF anottet
order OF maentude In Ihe pss6 Feet snan can be
bUilt In satisfactory manner without great flsh S
assertion that 76Ofoot span is feasible Inc n'IG lie
serious risks involved. ii is to De n9tGu 90 ~ iii
~ ~ % IL The manner in which the designers appear TO
carried out their plans anq eco aIn has been
chosen nv the designers for the WORKING Sti1@t I;1@t
in the concrete $50 pounds square men ms Is s, @ IS
are here involved, where the dlStt.ou'o bicb ~ we
over t1a1Iv Know little But with great care, rigid
selection OF f saFtv to render this safe
NAV he realized Arrayed against 'he s.o, fctors
IN fe m ebv Of the centerins. its settlement and
elastic motion under load ana teInPerali
subject 10 similar influences and 90 9aSa t1qny in in
the growing mass OF concrete. oue !" & Iit tnn16era
scum ro cnees e1i The same problem. of course is en-
@ i short spans it's difficulties are relatiyeIy
small AS the spans grow iTeg a. ibe iargest arches
Tins far built they have made the problem VIZ
difficult With the Iehgam t 1I oer+ein to nrove
multiplied by three. the problem Is certain u Pt''
The o s3e be detes produced by the expansion
ana contraction of the concrete during tne the con-
ta dm1 ' jtb the important exception however INA.
Iaiue built SeIl-Suppo tiI9 rIci'
introduces complication not present IN IN t hj.beTto
ton OF any of the large concrete aIche' H''''''
The arch spuyten D9yv ~ atae f1eek co1ern a:
some fortv feet of soft mud under !2la by sn6
an @ q,.ries from 10 to l.J feet AS the crown OF
tbr arch is $50 feet above the water ] cent5'iS @ 70
er+ e!ir 81 n If founded on solid rock would nave
@ fPpe e nearly 22o feet hirh abcu The altitude of Of
New York Citys tairS1 oet m to carry the weight
~ fhe arch ring alone, the totai ioao upon II viii
oe rs aso" " %h bs osTred 81 ted on as Faad
rary centrne 100 feet long ." - dor Area The
1ecessary openings in the oentrn ing for 51e pa
Tay tracks Ear on naViraton would still further com
pcate its construction
Mr. Moisseiff's report answers this argument IN
part follows:
For reinforced concrete arch Of the dimensonf
Brdee dIse an mrnovable. incomDressih.e and IN
pershable foundation is prereqciSieI 1 ali ON dry
land with the hard rock on the average - Ten 80
/ f.al6x r1Han
bt3, nf the foundation at Level Of twenty feet
IofoU damn The abutments, which VIII oe OF c9ll-
crete will thus rest on the nara TOE aifo 80 80
abtt a"aInst wall of the same mater a. a. , nc
~, yaefstsnee and displace the abutfIlehts ne
rool-,, Y1ountainS behind them Wouiu na' ~ 49,
ci,SS Tba foundations thus VIII furfish an apao
Iutelv irrnovable abutnent. os tho structure
= raoIizad that the Importance OF tne ST. dci u
an,iree Ihat ali possible causes OF Stress IN ne ne
arc1 he foreseen and PROVIDED ior. ,nora u +re
~ Jorafora the effect of change OF teille1 taat
;4Lir rnaeonable limits computed, put even 'tS -
wllhn mn sTbe shrinkage of the concrete AFTER rne
OF tre po5r swung free of its falseWofk ihe
tDaeses caused in the arch by IT'S Ri5d in the
ticn from the original curve are dlSo i''' "
resulting total x.,.-. ;s made bv the assurnp
,on of high moving loads for boih sle Pe-cb is
IIou VI dSs Tho tctal moving toad the trcu 20
lnoYonuted for is 1900 POUNDS pei Iod ase,med
Siage 1-on1pared with the moving i0an hrdee
bflosSS, Sganbattan or BIackweHs tsiand oruse. .
Dbch are designed for the heaFiesI yoIsrt H NV
Mi5o5 IN long span bridges, the equlVfITiIp pisa III
ing icad for the Henry Tucson s n5asted
yvouId be l4000 pounds q Hnear 10 Io1e y. "a t9i 0o
iop oaterias Of the main arch are 70 oe S In
- and steel The arch Is 20 De ior!hso 49, ~ a,
solid rib of concrete 40 Ieei VIZ , 10 a thick
@ suiu nyyn and gradually increasing 70 Ia IN en n
tDe oio ~ 90 faat ri the skewbacks trnpedaen ~
~ oo,crete are forty-eight rectansuaI .;s..
~ fonr hv inch angles each acea on ail n,s or
They are arranged in W. .wt' connected both YER
.i,,,, ,nd horizontally. TO each othef py
~ Forming huge steel cage CT s.eNr Iss ~;
~. steel members of the VertCa DC e;.,a.a cor
eted to the steel frames above fhe
aetoT for the part Of the srnctut 49, ns
~ 1sba steel units with sutaole
a,roc+lv an the rock and are anchorto ~
S,s.rthution of the steel in the concIe.e eli t,s
thTorghout its mass. completely soppoi'ns " 40
parts Intended to specify for the main structure