Fort Worth gazette. [volume] (Fort Worth, Tex.) 1891-1898, 1891-11-12
MIR. KERR'S REPORT.
What the City Engineer Says in Regard
to the Bridge.


The following is the report of City En-
gineer Kerr on the Trinity bridge matter,
which was crowded out of the council re-
port yesterday, owing to the lack of room
and the lateness of the hour at which the
council adjourned:
Tot the Honorable Mayor and City Council
GENTLEMEN-In the matter of the suspen-
sion bridge referred to the committee. beg
to report: l. / do not consider, nor does it
seem to me that it was intended by MeSsrs.
johnson Il Flad, that their paper is to be
considered as a detailed specification such
as is complete enough for the oasis of a
contract They say, s'of course it is as
sumed that the details of construction will
be carefully worked out, many of which
are not even shown in the drawing as throw
ing light on the matter" l am borne out by
what they say about the general specifca-
lions they prepared for the Topeka bridge.
They would not serve as a basis of 4 con-
tract, but We're only intended for general
description of the design. They state they
have answered inq uiries put; this is very
different from a complete set of drawings
and specifications. The details make up a
bridge more than anything else about it.
The plans presented cannot be considered
anything more than a general top and side
design. No details Except wind bracing
between towers) and no figured dimensions
are given.
2. AS 10 the strain sheet, still conspicu-
ously absent. 1t does not appear that the
auxiliary cables are attached anywhere to
anything except at the center of the bridge
where they cross each other How then
does two-ninths of this go to the auxiliary
cables?
3. The strain on the back stays is not nee
essarily equal to that in the cables. In the
case of dead men for derricks it is some
times double. This strain is complicated
by the union of the lower auxiliary before
il reaches the anchorage. At this point
again the drawings are entirely deficient in
details. I must say again that l cannot
think johnson Il Flad intended this for a
part of a contract.
t. The objection abort not having the
cables fully wrapped is reiterated.
8. The diagonals are not cut. Now moth
ing is said about sequence in building, and
it is evident that the suspenders and dag
onas must be all on before the floor can be
laid. vet we know that until the load is all
on the cables are changing form from
cotenary to Il close approximation to
parabola.
g. 1t is admitted that the towers are so
small they have not great deal of Stabil-
ity on their bases. Has it been settled that
the resultant will certainly remain axial?
If not. with the extremely narrow base,
there is great danger of Gripping; why not
construct the towers as usually done with
wide bases2
Z. AS to the diagonals slipping suppose
drove of cattle to come on one end, the d.
agonals will be in a state of unequal ten
sion There will be resultant in direction
of the cable. nothing but friction to resist
it. As friction of steel on steel is but
degrees there must be slipping. In East
river bridge and others built by Mr..
Roebling there are no diagonals and sus-
penders are attached by strong iron bands,
which are screwed up so as to powerfully
compress the wires underneath and pre-
vent all possibility of movement.
5. Nearly all suspension bridges do not
have two or more cables over each other.
The usual arrangement is a single cable at
each side of the roadway. The Niagara
bridge was the only one built by the older
Roebling with two cables at one side, but
he never built another that way and did not
consider it his best work. When there are
men like the Roeblings who will get up
plans according to the best practice, why
try a new device. and one also inferiorl
9. In repairing the Allegheny suspension
bridge, it was found that the cable attach
ments at the anchorage had been protected
by the best quality prepared coal tar, but
in process of time had lost its virtue and
rusting had taken place extensively. In re-
pairing it was protected by parafine.
Asphaltum will follow the same experience
if time be given it.
TO- The ambiguity. This is one OF the
principal points of criticism. l merely
quote FRONT Messrs. johnson & Flad. ''In
the design submitted, which has no stiff
ening truss, the only means of preventing