“The tests were planned with a view of determining the amount of stress (tension and bond) developed in the stirrups.  However, for various reasons, the results are of less value than was expected.  The beams were not all made according to the plans.  In the 1907 tests, the stirrups in a few of the beams were poorly placed and even left exposed at the face of the beam, and a variation in the temperature conditions of the laboratory also affected the results.  It is evident from the results that the stresses developed in the stirrups are less than they were calculated to be, and hence the layout was not well planned to settle the points at issue.  The tests, however, give considerable information on the effectiveness of stirrups in providing web resistance.”

     “A feature of the tests of beams with stirrups is slow failure, the
     load holding well up to the maximum under increased deflection and
     giving warning of its condition.”

“Not enough information was obtained to determine the actual final occasion of failure in these tests.  In a number of cases the stirrups slipped, in others it seemed that the steel in the stirrups was stretched beyond its elastic limit, and in some cases the stirrups broke.”

“As already stated, slip of stirrups and insufficient bond resistance were in many cases the immediate cause of diagonal tension failures, and therefore bond resistance of stirrups may be considered a critical stress.”

These quotations seem to indicate much more effectiveness in the action of vertical stirrups than the author would lead one to infer from his criticisms.  It is rather surprising that he advocates so strongly the use of a suspension system of reinforcement.  That variety has been used abroad for many years, and numerous German experiments have proved with practical conclusiveness that the suspension system is not as efficient as the one in which vertical stirrups are used with a proper arrangement.  An example is the conclusion arrived at by Moersch, in “Eisenbetonbau,” from a series of tests carried out by him near the end of 1906: 

“It follows that with uniform loads, the suspended system of reinforcement does not give any increase of safety against the appearance of diagonal tension cracks, or the final failure produced by them, as compared with straight rods without stirrups, and that stirrups are so much the more necessary.”

Again, with regard to tests made with two concentrated loads, he writes: 

“The stirrups, supplied on one end, through their tensile strength, hindered the formation of diagonal cracks and showed themselves essential and indispensable elements in the * * * [suspension] system.  The limit of their effect is, however, not disclosed by these experiments. * * * In any case, from the results of the second group of experiments can be deduced the facts that