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 beams.”  What he does condemn is bending up the bars with a sharp bend and ending them nowhere.  When they are curved up, run to the support, and are anchored over the support or run into the next span, they are excellent.  In the tests mentioned by Mr. Mensch, the beams which had the rods bent up and “continued over the supports” gave the highest “ultimate values.”  This is exactly the construction which is pointed out as being the most rational, if the rods do not have the sharp bends which Mr. Mensch himself condemns.