iolation of the
principles of sound engineering.

Mr. Mensch mentions the failure of the Quebec Bridge as an example of
the unknown strength of steel compression members, and states that, if
the designer of that bridge had known of certain tests made 40 years
ago, that accident probably would not have happened. It has never been
proven that the designer of that bridge was responsible for the accident
or for anything more than a bridge which would have been weak in
service. The testimony of the Royal Commission, concerning the chords,
is, "We have no evidence to show that they would have actually failed
under working conditions had they been axially loaded and not subject to
transverse stresses arising from weak end details and loose
connections." Diagonal bracing in the big erection gantry would have
saved the bridge, for every feature of the wreck shows that the lateral
collapse of that gantry caused the failure. Here are some more simple
principles of sound engineering which were ignored.

It is when practice runs "ahead of theory" that it needs to be brought
up with a sharp turn. It is the general practice to design dams for the
horizontal pressure of the water only, ignoring that which works into
horizontal seams and below the foundation, and exerts a heavy uplift.
Dams also fail occasionally, because of this uplifting force which is
proven to exist by theory.

Mr. Mensch says:

"The author is manifestly wrong in stating that the reinforcing
rods can only receive their increments of stress when the concrete
is in tension. Generally, the contrary happens. In the ordinary
adhesion test, the block of concrete is held by the jaws of the
machine and the rod is pulled out; the concrete is clearly in
compression."

This is not a case of increments at all, as the rod has the full stress
given to it by the grips of the testing machine. Furthermore, it is not
a beam. Also, Mr. Mensch is not accurate in conveying the writer's
meaning. To quote from the paper:

"A reinforcing rod in a concrete beam receives its stress by
increments imparted by the grip of the concrete, but these
increments can only be imparted where the tendency of the concrete
is to stretch."

This has no reference to an adhesion test.

Mr. Mensch's next paragraph does not show a careful perusal of the
paper. The writer does not "doubt the advisability of using bent-up bars
in reinforced concrete bea