Fort Worth gazette. [volume] (Fort Worth, Tex.) 1891-1898, 1891-11-07

| sion that suspension bridges are to be
| chosen as rule only where great length is
required, or where some other special cir
| cumstance render them desirable. Such is
not the case at this point
| Finally the absence of any strain sheet
| makes it impracticable to institute exact
| comparisons between the proposed design
and others, but ]. consider the design to
lack so thoroughly In all the elements which
go to make up sound and lasting work,
| that | have no hesitation in condemning it
| absolutely. Respectfully submitted,
| Signed F. CoLLINGwooD,
| NJ Am. Soc. G. E.
| AMERICAN SOCIETY OF CIVIL ENGINEERS,
127 EAST TwESTy-THIRD STREET
NEW YORK, Sept. %, 1891.
| H. H. Kerr, Esq, City Engineer, Fort Worth.
DEAR SIR incIose herewith my report
on the plans and specifications sent by you
| fora suspension bridge IN Fort Worth across
| Trinity river After writing it, to see how
| it would seem to another bridge engineer,
| submitted it to a friend, and he simply
| remarked, ''Tou have not said half enough,
as the plan is insufferably bad" | thought
| it best to point out the salient defects, and
| 60 no further.
never saw the design before; but it is
| one of many made manifestly by a man
without training as an engineer; and is well
calculated to please the fancy of body of
| laymen.
| What | mean in the report by saying that
| suspension bridges are not chosen now for
| short spans. is this: Wherever the anchor
| ages have to be artificial, the extra masonry
on short spans is very large item of cost
| Then again, it is difficult to make short
| spans stiff enough, as the dead load and
| light load are too nearly alike for inertia to
| bear an important part, and when you come
| TO add stitching trusses, the cost is greatly
| increased. As an example. the Allegheny
AZ &c ic NO
| being removed, after some forty years serv-
| ice, to give place to a modern type of truss
! bridge. The suspension bridge is strong
| enough, but the vibrations under rapid
| movement of loads is very unpleasant, and
might become dangerous This had stifen-
| ing truSses, but they We're not de p enough
to be thoroughly effective. In the example
| before US there is an effort to make the
| main cables and auXiliaries perform this
| Office but it is not well carried out, and is
| destined to failure.
When there are so many well tried de-
| signs to be had, there is no excuse for seek
| ing novelty. # il must be done, it should
certainly be under the guidance and control
of a trained engineer.
No engineer is provided for in the speci-
fications, and it would seem that his pres
ence would not be welcome.
l ought to add in reference to the strain
sheet so conspicuously absent, that really
make one. Yours truly,
Signed. F. CoLLINGwooD.
AMERICAN SOCIETY OF CIVIL ENGINEERS.
ia EAST TwENTY-THIRD STREET.
NEW YORK, Oct. |, 1891.
II. H. Kerr, Esq, City Engineer. Fort Worth.
DEAR STR-In the multiplicity of calls
upon me during the past few days, | neg
lected to mention in my report except in
cidentally) that no inspection of any kind is
provided for in the specifications, and no
person named who is TO decide any Ques-
tions which may arise.
Also that the description of the steel wire
is such, that the most brittle wire pr0cura-
bic would comply with the requirements,
provided it had the strength.
This is a very important matter. On the
East River bridge it was only by the ut
most watchfulness that we prevented the
contractor for the wire from furnishing
surreptitiously an exceedingly poor quality
of wire. Yours truly,
Signed F. CoLLINGwooD.
FORT WORTH, Oct. ., 1891.
To the Hon. Mayor and Council, city OF Fort
Worth.
GENTLEMES-I beg leave to submit the
following criticism on Mr.. COllingwood's
so-called report on the plans and specitica-
tions for the proposed Trinity river bridge.
First, he states that it is impossible to
tell whether the sizes given in the plans
are COTEGtI NllllOuL SOlIlS luEOusl lHt cllIlIc
computation" Now, supposing the strains
had been given, would it not have been Mr..
C.'S duty TO have verified the calculations?
All of the data necessary to make such COM
putation is embodied in the plans and Speci-
tications submitted, and it was certainly in
cumbent on him to make them, and if Mr..
e. has not made the calculations necessary
to determine the strength of every part of
the structure, on his own responsibility,
whether have supplied HIN with figures
on this point or not, he has not done what
was properly to be expected of him, and
what he would be entitled to pay for. And
in the absence of the necessary computation
as to the correctness of sizes, ETC., any OBJ
servations which he has made as to the
merit of the plans is gratuitous and un-
founded assertion. 1t is legitimate to
conclude that an engineer will back
his opinions with figures, and his
failure to do so is tantamount to
an admission of inability to produce the
proof.
2 His remarks relative to the tension of
the backstays are subject to the same criti-
cism involved in his failing to make compu-
tation on the strength of the members of
the proposed structure. The tension of the
backstays is given. Mr.. C. knows, or
ought TO know, as well as do, that in this
case the tension on the backstays is the
same as the tension on the main cables at
the towers.
B. The remarks in regard to wrapping the
cable entirely are entitled to more consider
alton than all the rest OF this so-called re-
port combined, though the manner of wrap
ping specified is the same as that of SuS-
pension bridge across the Schuylkill at
Philadelphia built in 1872 and which be-
ieve is still in service, the only repairs to
which have been the renewal of the floor
and other woodwork and an occasional ap-
plication of paint.
t. Asphaltum is mentioned as preserva-
tive TO be used only when the backstays
come in contact with the earth. and in that
way is the best preservative known, not
withstanding MIR. C's. assertion to the con-
trary.
5. The manner OF fastening does ad-
nit of the proper adjustment of the sus-
penders and diagonals.
6. The tie-rods for the hand-rail can be in
creased to five-eighths or three-quarters
iron if deemed necessary.
:. The thickness of the courses of stone
in the masonry is shown approximately in
the drawing, and as bounding is always
considered necessary and essential in this
class of work it was not necessary to men-
ton it in the specifications The retaining
walls are simply to hold a bank of earth
five to six feet high, and minute specitica-
tons are not necessary. The thickness of
the walls shown in drawing is sufficient.
S. The cast-iron bed plates are to be two
inches thick where the towers rest, and
taper to three-quarter inches at outer
edge. AS it would be impossible to fit
twenty-four inch column to bed plate cal
culated for a .nineteen-inch column, it fol-