New-York tribune., 1908-05-22

the dia gram. and the strain figures are given un-
derneath the particular panel TO which they reler
The first important point in connection with
these two strain sheets is that the revised sheet
which Chief Engineer Ingerson of the Bridge De-
partment explained had been prepared before
pound of steel rolled for the bridge bears the
official stamp Of having been received IN the de-
partnent on March Is 1906 The first shipments OF
lower chord sections for the structure were re
ceved March q, 1905. or just about year oe-
fore the strain sheet appears 20 have been re
cefved the department, and after ten lhousaIld
tons of steel for the bridge had been fabricated III
tho ebons This not only shows that the res 4sed
strain sheets not prepared in the Depart
ment of Bridges but that little care or super
vision taken by the departmental engineers
either during after their preparation
An examination of the figures accompanying the
diagram shows that in the original strain sheet the
assumed dead load for the first panel OF the lower
chord nearest the pier was 10.44o units OF l""
pounds each and in the revised strain sheet 1t
is given AT II $40 units Of 100 pounds each 1hls
j. an increase of 10 per cent. Yet the actual
weight of the bridge increased under the re-
vised plans from 100000 pounds to lo5"moo
pounds an increase of about p per cent. Ihere IS
here an increase in the actual weight Of the new
structure of - per cent, which Is not proNloed lo
in the revised strain sheet
The assumed live load for the panel given
in the original strain sheet is $50 units OF LOU
pounds each. In the revised strain sheet 1t IS
given at 4.o2 units This is a reduction In the re-
,ised strain sheet of about 81 per cent allhouSh
the Bridge Department in the revised plans made
,,rov:son for considerable increase In the tralfc
facilities over those provided for in the original
plans Either there was q serious error III 'he
strains allowed in the original strain sheet or the
live load stresses for the bridge as erected nave
been arbitrarily underestimated by at least 90
per cent.
The stresses allowed foT wind in the same
-s,al vere reduced from 61S4 units in the original
strain sheet 10 5529 units in the revised, or re-
d,,ctio, of about is per cent. Yet the structure
,,,der the revised plans is supposed 10 contain a
,oreidorabIy larger area of metal TO offer resist
80 IN the wind than bridge as originally
damned Instead Of = decrease there ought 10 oe
~ increase in this stress of at least 10 per cent
r.es an error was made in the original strain
sheet.
1-ra mast significant figures however. are those
r Tho total Ioadings resultant stresses. or
-, - ers+ nanel the total loadings are given
- IT. original strain sheet at 22,50i units. ana IN
r. -.,.ieed strain sheet no total loauh8S aie
-. b,,t worked out from the figures that are
- u comes TO q 2ll units. Still the Bridge
- eII.,o,,. enpineers state that in the ne"
,is,a there is a greater bearing area D! - pi
cent Here again some one hau eiieu' "
4g,,res for the bridge as erected nave oee u',
'is -, .duced If it was found that the 9o
So 4,obes Of bearing area PROVIDED IN 'he '
TT sheets was too little. II Is dlnicui'
It u,b,, If was necessary TO cut down lhe
a for live load and wind IN 'Ee IeNlSeu
strain sheets -, -,,a-.a suggest
- so,,res throughout when cornpaIeu 9-e9
10, ,bera has beer an attempt !" i -
5c,;ons In the assumed stresses appear 1-'i
conservative by Juggling "i'' '