The last-mentioned argument is as old as Engineering; it is the “practical man’s” mainstay, his “unanswerable argument.”  The so-called practical man will construct a building, and test it either with loads or by practical use.  Then he will modify the design somewhere, and the resulting construction will be tested.  If it passes through this modifying process and still does service, he has something which, in his mind, is unassailable.  Imagine the freaks which would be erected in the iron bridge line, if the capacity to stand up were all the designer had to guide him, analysis of stresses being unknown.  Tests are essential, but analysis is just as essential.  The fact that a structure carries the bare load for which it is computed, is in no sense a test of its correct design; it is not even a test of its safety.  In Pittsburg, some years ago, a plate-girder span collapsed under the weight of a locomotive which it had carried many times.  This bridge was, perhaps, thirty years old.  Some reinforced concrete bridges have failed under loads which they have carried many times.  Others have fallen under no extraneous load, and after being in service many months.  If a large number of the columns of a structure fall shortly after the forms are removed, what is the factor of safety of the remainder, which are identical, but have not quite reached their limit of strength?  Or what is the factor of safety of columns in other buildings in which the concrete was a little better or the forms have been left in a little longer, both sets of columns being similarly designed?

There are highway bridges of moderately long spans standing and doing service, which have 2-in. chord pins; laterals attached to swinging floor-beams in such a way that they could not possibly receive their full stress; eye-bars with welded-on heads; and many other equally absurd and foolish details, some of which were no doubt patented in their day.  Would any engineer with any knowledge whatever of bridge design accept such details?  They often stand the test of actual service for years; in pins, particularly, the calculated stress is sometimes very great.  These details do not stand the test of analysis and of common sense, and, therefore, no reputable engineer would accept them.

Mr. Turner, in the first and second paragraphs of his discussion, would convey the impression that the writer was in doubt as to his “personal opinions” and wanted some free advice.  He intimates that he is too busy to go fully into a treatise in order to set them right.  He further tries to throw discredit on the paper by saying that the writer has adduced no clean-cut statement of fact or tests in support of his views.  If Mr. Turner had read the paper carefully, he would not have had the idea that in it the hooped column is condemned.  As to this more will be said later.  The paper is simply and solely a collection of statements of facts and tests, whereas his discussion teems with his “personal