Faults in the Theory of Flexure, and an Epitome of Certain I-Beam Tests Made at Ambridge, Pa.

As the ordinary theory of flexure is almost universally used, not only in proportioning simple beams, but in the solution of all questions involving the elastic deformation of structural members, the nature and influence of its faults, by reason of which it is not rigidly accurate, but only approximate, should be generally understood. It is generally recognized that the ideal material and conditions assumed are not wholly achieved, and it is shown in some elaborate treatises on the theory of elasticity, but not ordinarily realized, that, even if it were possible to have ideal material and conditions, the theory would still be faulty; for instance, it is shown by Professor C. Bach, that a cross-section originally plane does not remain plane during flexure, as is ordinarily assumed, but is forced into a reversed curve somewhat like a long, only much less pronounced in ordinary materials; and Professor A. E. H. Love states that the ordinary equation for shear distribution gives an average intensity across the breadth of the section, and that actually the distribution is not uniform, as is tacitly assumed in nearly all textbooks.