from points named on its own line of road or on the Eureka Springs
PURDON OX THE \'AN BUREN" BRIDGE. 187
Eailway to Tan Buren, but the contractor shall pay for transportation
over the Little Kock and Fort Smith Kailway, or from the quarries to
the nearest side track by teams or otherwise.
3. Stone, however, for rip rap, concrete and slope-wall, shall be
taken from quarries near the bridge site and transported by the con-
tractor at his own cost and expense.
4. The contractors shall furnish all tools, machinery and plant of
every description — both at the quarry and at the bridge site.
5. The stone shall be cut at the quarries, and the contractor shall
promptly load and unload the cars furnished for transportation of stone
or other materials.
6. The railway company will furnish free transportation for timber
from stations south of West Fork, Arkansas, to Van Buren, over its own
line of road.
7. The railway company will also furnish free transj^ortation be-
tween stations on its own line of road for men, tools and material and
supplies actually needed for this work, except as more particularly
sjjecified for stone and timber.
1. No material shall be measured or included in the estimate which x.
does not form a part of the permanent structure. ^Works'^
2. And all such material or temporary works shall be removed as
dii'ected by the engineer, leaving the bridge free and unobstructed on
comi)letion of the work.
All material furnished shall be sound, and free from any defect that xi
will injure its strength or durability, and sixbject to the inspection and
acceptance of the engineer before being used. If rejected by him it
shall be promjitly removed.
1. The contractor shall not sub-let or transfer his contract, or any ^jj
part thereof, without the written consent of the engineer. General.
2. The contractor shall, at his own cost and expense, take down,
remove and rebuild any work which, in the opinion of the engineer,
has been imperfectly executed.
3. All extra work other than that to be paid for as herein set forth
required by the engineer, and not embraced in the items and prices set
forth in the contract, shall be done by the contractor only on the writ-
ten order of the engineer, who shall return with each monthly estimate
a bill for the same, based on the actual cost of labor and material used,
such as in his judgment is reasonable and just. And 10 per cent, shall be
added to the same for the use of tools, superintendence and all other
expenses. The acceptance of such bill by the contractor shall be
deemed and taken as waiving any further claims for or on account of
extra work done during the month referred to in said bill.
4. No charge shall be made by the contractor for hindrances and delays
from any cause whatever in the progress of the work, but it may entitle
him to an extension of the time allowed for the completion of the work
Defective Ma-
terial.
188
PUKDON ON THE VAN BUREN BRIDGE.
XIII.
Form of Bid.
XIV.
XV.
XVI.
Engineer.
XVII.
equal in length to the detention, to be determined by the Chief Engineer
of the St. Louis and San Francisco Railway Comjoany; provided, h&
shall give the said chief engineer immediate notice in writing of the
cause of the detention.
1. Bids will be received for the substructure hereinbefore as speci-
fied either with a lump sum to be paid for the whole such substructure
complete; or
2. With specific prices to be i^aid for the several classes of work as
enumerated below.
3. Said prices shall cover and include all material, barges and ma-
chinery or other plant, tools, labor, temporary work or other expense
used or inciirred in the i^rogress of this work.
4. No constructive or conventional measurement will be allowed.
5. Quantities of timber in estimates shall include only the actual
cubic contents of the timber turned into board measure, and as placed
permanently in the structure.
6. Quantities of masonry shall include only the actual cubical con-
tents of tlie masonry inside the draft lines and according to the plans.
The contractor shall employ persons exiserienced and skilled in the
various kinds of work sijecified; and shall use the best tools and ma-
chinery to be obtained for rapid and efficient progress.
Any or all of the work herein specified shall be carried on night and
day if so directed by the engineer. In which case the contractor shall,
within ten days after being so directed, provide at his own cost ami
expense sufficient electric or other artificial light, and a force adequate
to keep three full shifts of men successively employed during the whole
of each twenty-four hours; and shall maintain such force until, in the
judgment of the engineer, the necessity for so doing shall have passed.
Whenever the word engineer occurs in these si>ecifications, it shall
have reference to the Chief Engineer of the St. Louis and San Francisco>
Railway or his authorized assistants on the work.
1. Timber in caissons shall include all timber of every kind furnished,
framed, and placed in caissons which are sunk to bed-rock.
2. Timber in cribs and open caissons shall include timber of every
kind (excepting piles and grillage) furnished, framed and jjlaced in
cribs and open caissons for foundations of masonry.
3. Timber in grillage shall include all oajjs for piles and timber,
or platforms resting thereon, or other platforms for foundations of
masonry.
4. Piling shall include only such part of the piles as remain in the
foundations of the masonry and below the level of the bottom of the
grillage resting on them, and such price includes furnishing, driving
and cutting oft' the tops of the piles level as hereinbefore specified..
5. Sinking caissons shall be measured per foot, vertically from the
average level of the bottom of the cutting edge to low-water level cs
PURDON ON" THE VAN" BUREN BRIDGE, 180
already estaljlislied by the engineer, and shall include all excavation
from the interior of the caissons or elsewhere of all classes of material
encountered in sinking them excepting the bed-rock.
6. Wrought-iron shall include all wronght-iron bolts and their
attachments, drift-bolts, dowels, washers, plates, cutting-edges, nail?,
spike or other wrought-iron furnished and used in the foundations and
masonry and remaining in the permanent structure.
7. Cast-iron shall include all cast washers, plates or other castings
furnished and used in the permanent structure.
8. Concrete in working chamber of caisson shall include only such
concrete as is furnished and used in the working-chamber jjroper of the
caissons sunk to bed-rock.
9. Excavations above water shall include all excavations of founda-
tions and other excavations incidental thereto, and will include all
classes of material except as hereinafter more particularly specified.
10. Excavations under water shall only apply to excavation of
foundation pits and deepening of channels under water where required
by the engineer, and shall cover all classes of material encountered, and
include draining, bailing, pumping, and all matei'ial, labor or other
expense connected with such excavation.
1. The river shall, at all times during the construction and erection xviii.
of the substructure, be kept free for navigation.
2. All coffer-dams, staging and other obstructions must be removed
by the contractor when directed by the engineer, leaving the river
entirely unobstructed excej^t by actual space occupied by the masonry.
1. In case the elevation of the underlying bed-rock above datum line Bed-rock
of levels is less than that shown on plans, the contractor shall be en-
titled to the sum of SlOO per vertical foot for the difference of level so
found at the sites of Piers 1, 2, 3, 5 and 6, and the sum of S600 per
vertical foot at the site of Piers No. 4.
2. In case the elevation of the underlying bed-rock above datum line
of levels is greater than that shown on plans, the railway company
shall be entitled to a credit of $400 per vertical foot for the difference
of level so found at the sites of Piers 1, 2, 3, 5 and 6, and the sum of
25er vertical foot at the site of Pier Xo. 4.
19U
PURDON ON THE VAN 13UREX BRIDGE.
hi
i
P
rt
P
O
•I9SJS aSpijg
Pounds.
190 009
190 000
220 570
190 009
80 147
80 147
80 147
80 147
•noji aSpug
Pounds.
237 452
237 452
520 483
237 452
129 102
129 102
129 102
129 102
1 749 247
noiiBABOxa
1
Cu Yds.
225
410
480
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1
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379.8
430.2
491.0
987.4
471.0
434.2
385.7
380.7
378.5
173.4
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377.5
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300
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3 903
6 000
8 270
9 008
8 496
8 202
3 221
3 378
3 171
m
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31.40
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2 319
2 210
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41 5.59
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29 704
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37 400
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S 1
DISCUSSION" ON" THE VAN" BUREN BRIDGE. 191
DISCUSSION.
Charles Macdonald, M. Am. Soc. C. E. — The interest attaching to
bridges of the character described in this paper, is perhaps more of a
commercial than professional nature. There were really no engineering
difficulties worth mentioning, in the construction. The rock was about
30 feet below the water, overlaid with sand, and easily reached by
pneumatic caissons in that portion of the river where scour was liable
to take i)lac3. Ou the south side pile foundations were used, for the
reason that a large excess of waterway had been provided for, and there
was no probability of scour at those points. I may mention a point,
connected with the testing of cement, which might be of interest to the
Committee ou Tests of Cement. The cement was made at Louisville,
Ky. The fii'st car load received was carefully tested, and about 10 per
cent, of the barrels were reported as falling below the specifications.
For the purjjose of verifyiui;- these tests, I had two samples taken from
each of the rejected barrels. The first sat was mixed in exact accord-
ance with the practice which had been observed in the original tests;
and was tamped in a briquette, with a moderate amount of pressure.
Tests made upon these samples all fell below the specifications. The
second set of samples was treated in the same way, except that the
tamping was a little more decided than in the first case. Every one of
these tests came above the specifications. It appeared evident that the
pressure exerted in tamping- was the controlling element, and that a
slight difference in amount would give very different results on the test
piece. It would seem as if the most important question, in connection
with testing cement, is the manner of preparing the test pieces.
In sinking caisson No. 3 an interesting exjierience was encountered.
After the caisson had been sunk a few feet into the sand, the water in
the river rose rapidly, completely covering the work, and obliging a
suspension of operations.
During the high water the sand scoured out under the up-stream end
of the caisson, until it dropped down 6 feet out of level and the whole
caisson moved 2 or 3 feet down stream.
After the water had receded sufficiently to renew operations, Messrs.
Sooysmith, who had undertaken to do the pneumatic work, succeeded in
righting the caisson, and, at the same time, crowding it back into place
by a system of inclined structures placed in the working chamber on the
upstream side of the center. Upon releasing the air pressure suddenly
the caisson descended and worked up stream at the same time.
Mr. Sooysmith will doubtless be able to describe this operation more
in detail.
It was an ingenious method of overcoming what appeared to be a
serious difficulty.
192 DISCUSSION ox THE VAN BUUEN BRIDGE.
Charles Sooysmith, M. Am. Soc. C. E. — When we are working in a.
location where the grounl will p â– rtnit iis to pile the material higher on
one side than on the other, the most eftective way to move the caisson is.
to bring about a greater pressure on one side than on the other,
and this is done by simply piling the material higher on that side.
When we had about 40 or 50 feet of material about the caisson, we
found that a difference of 5 or G feet in the height of the material on
one side had a tendency to work the caisson away from the high side.
Throughout the sinking of the caissons we often change the height of
the material every day or so and find it very effective.
We had an interesting case at the Randolph Bridge over the Mis-
souri, at Kansas City. A channel caisson had gotten 2 or 3 feet out of
position when it was but a few feet from the rock; the masonry had beeu
started on it and it was very desirable to get it more nearly in jiosition.
There was too much material around it to enable us to push it, and there
was not enough distance still to sink to permit us to move it in the man-
ner just describid. It was moved into position in the following way:
12 X 12 timbers resting on plank pLitforms on the sand were set up in-
side the caisson; these were all inclined in the direction in Avhich we-
wished to move the caisson. After excavating under the cutting edges-
a portion of the pressure was let off, bringing the weight of the caisson
on the inclined posts, and the result Avas that the caisson moved slightly
in the direction we wished it to go, and two or three repetitions of this
method brought it into position.
F. CoLLiNGwooD, M. Am. Soc. C. E.— In sinking the Brooklyn-
caisson of the East River Bridge, there was a decided excess of pressure
on the land side. The ultimate depth reached was 44 i feet l)elow mean
high tide, and the surface of the earth on the land side was about feet
above the water surface. The bottom had been dredged to 18 feet
depth, and sloped to a greater depth at a short distance in the stream.
The resultant of the weight of the caisson and this difference of side
pressure was, therefore, outward, and when the full depth was reached
the caisson was found to have moved two feet towards the river.
The caisson had been made purposely abundantly large (for this,
among other reasons), and as the masonry base was also made largo,
there was no difficulty in adjusting the tower above water to its true
l^osition.
As the resultant from the cables was also outward, the final effect
was favorable rather than otherwise.
Joh:^ Bog\rt, M. Am. Soc. C. E.— Did the piers of the Pough-
keepsie Bridge get out of line at all?
T. C. Clarke, M. Am. Soc. C. E.— The caissons of the Pougbkeepsie
Bridge were sunk to a depth of 136 feet. We found that the river- bed
consisted of soft sand, so soft that everything that sunk disappeared at
DISCUSSION ON THE VAN BUREN BRIDGE. 193-
once. The soil grew harder as it went down iiutil some gravel was found
with it, and just before reaching the bed-rock it turned into a very hard,
solid gravel.
The piers of the Poughkeepsie Bridge were very large; the base was-
60 feet wide by 100 feet long and they were about 130 feet high. We
inaele the size on the bottom 60 by 100, which gave a j)ressure on the-
bed of the river of about 3$ tons to the square foot. Then, for the
reason that so much size was not required as we went up, we drew this-
in to 100 by 50 feet on the top. Whether this had anything to do toward
keeping the bridge piers perj^endicular I think no one could tell. I am
certain of one thing, that our experience there shows that we must not
overload the piers if we want them to go down without deviating from
their normal position. We must keep the excavation below the cutting
edge. When the weight overcame the side friction the thing dropped
just like a plumb-bob. But, as a matter of fact, they did not get out of
line.
Joseph P. Davis, M. Am. Soc. C. E. — Can you give any data as to-
the friction of the sand on the side of the caisson?
Mr. CiiAKKE. — I think, if my memory is correct, it took, to overcome
the friction, a weight of about 800 pounds per square foot, between 700'
and 800 pounds to the square foot. I am not quite certain. On re-
ferring to my note books I find that when the caisson was sunk 45 feet-
below the river-bed its perimeter was 320 feet. 45 x 320 = 14 400'
square feet of exterior rubbed surfaqe. Its immersed weight was then
8 000 tons = 16 000 000 pounds, ^vi-tt^tt— = 1 100 pounds per square-
14 4U0
foot of rubbed surface, equals the downward pressure. This was-
not enough to make the caisson move, until a hole was dredged below it.
When that hole was dredged, and the support under the base taken
away, the caisson sank down. Hence the friction on the rubbed surface
could not have been as much as 1 100 pounds. We called it 700 or 800-
pounds, but it is not i^ossible to state it exactly.
Mr. CoiiiiiNGWOOD. — Was there any increase as you went down?
Mr. Clarkk. — No; we could not see that there was.
C. D. PuRDON, M. Am. Soc. C. E. — I may mention, in connection
with the subject of caissons being out of place, that at the Rob Pioy
Bridge (over the Arkansas River on the St. Louis, Arkansas and Texas
Railway), where cylinders of 7 feet diameter were sunk to a depth of
60 feet below low water, the method employed to bring a cylinder back
to place was to first get it out of plumb, with the bottom pointing in
the direction in which it was necessary to move it; to sink it thus in-
clined until calculations of inclination and position together showed
that the bottom was in the right place, and then to jjlumb it; this was.
done with twelve cylinders.
104
DISCUSSION ON THE VAN BUREN BRIDGE.
To throw the cylinders out of plumb and afterwards to plumb them,
pieces of 12 x 12 inch timber were clamped on the cylinders, and in-
clined struts placed from these to either sills on the sand-bar or to caps
on clumps of piles driven for the purpose.
At the Junction Eailwav Bridge, over the Arkansas Kiver, at Little
Hock, Ai'k., of which I also had charge, one of the caissons was brought
back to its place by sinking it out of plumb; it was thrown out of plumb
and righted by simply excavating below the cutting edge on one side
only.
This caisson was but little out of place, however.
The following are the illustrations of the jjaper by Mr. Purdon on
the Van Buren Bridge:
Plate XYIII.
" XIX.
" XX.
" XXI.
'' XXII.
" XXIII.
" XXIV.
" XXV.
" XXVI.
'' XXVII.
^' XXVIII.
" XXIX.
" XXX.
" XXXI.
" XXXII.
" XXXIII.
^' XXXIV.
" XXXV.
" XXXVI.
^' XXXVII.
*' XXXVIII.
" XXXIX.
Photograph of Bridge.
Location.
Triangulation.
Caisson and Crib of Fixed Piers.
(( (( ((
Pier 2.
Water Gauge Profile.
Ravine Section.
Process of Leveling Caisson of Pier 3.
Caisson and Crib of Pier 4.
Pier 4; Elevation and Section.
Plan of Courses, Pier 4.
Pier 7.
Pier 10.
Profile showing Sinking of Caisson.
Profile showing Progress of Masonry.
Superstructure of 252-feet 9-inch Spans.
Superstructure of 162-feet Spans.
Superstructure of Draw Span.
PLATE XIX
TRANS. AM. SOC. CIV. ENG'RS
VO L XX. N9 •i+12
PURDON ON
VAN BUREN BRIDGE
PLATE XX
TRANS.AM.SOC.CIV. ENG'RS.
VO L XX . N9 ^'.2.
PURDON ON
VAN BUREN BRIDGE.
PLATE XXI
rRANS.AM.SOC.CIV. ENGRS.
VO L XX . N9 ^12.
PURDON ON
C/^/SSOA/ /7A//] CA/3
PLATE XXII
TRANS. AM. SOC. CIV ENG'RS
VO L XX. NO ^12
PURDON ON â–
VAN BUREN BRIDGE
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TRANS.AM SOC.CIV. ENGRS.
VO L XX . N9 •^l 2.
PURDON ON
VAN BUREN BRIDGE.
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TRANS. AM. SOC. CIV. ENGRS
VOL XX. N? ^12.
PURDON ON
VAN BUREN BRIDGE.
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TRANS AM SOC. CIV. ENGKS.
VOL XX. rgo ^12.
PURDON ON
VAN BUREN BRIDGE.
7*rcce^s cf let/eHtn^ Ccii^so/v
PLATE XXVI
TRANS. AM, SOC. CIV ENG'KS
VO L XX. N° -^12
PURDON ON
VAN BUREN BRIDGE
C/9/SSOAf ^^o C/{/S
PLATE XXVII
TRANS.AM.SOC.CIV. ENG'RS.
VOL XX. iN 9 ^12.
PUROON ON
VAN BUREN BRIDGE.
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TRANS.AM.SOC.CIV. ENGRS
VO L XX. NO ^12
PURDON ON
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PLATE XXIX
SOC.CIV.ENG'RS
?DON ON
REN BRIDGE
C^„7e.r,t ZJ'/z Ills.
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PLATE XXX
TRANS. AM. SOC.CIV.ENGRS
VOL XX. N9 ^12
PURDON ON
VAN BUREN BRIDGE
,e r,eeol A u.^. H'T^ /".Vr. j-Aeo/ Au.^3/^
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