The theory of elasticity applied to the strain and stress of material is the basis of nearly all structural design.
It cannot be considered completely satisfactory, for a deeper insight into molecular physics, in certain particulars, leads investigators to feel that it is not a finality.
However, granting that it is even a crude rendering of deeper truths, the fact remains that it offers a reliable and practically satisfactory process to the engineer.
_~ny one who is at all sceptical regarding the truth of this theory, or has had his faith in it shaken by discussion, can readily satisfy himself of its reliability by simple experiment upon that phase of it relating to flexure. There are few instances in which the processes of the calculus, applied to physical laws, find a more pleasing and direct corroboration from practical experiment, than in the case of the flexure of beams.
The following description concerns a simple but effective apparatus that I have devised for experimentally testing certain flexure formulae for beams under peculiar conditions of support.
It was easily and cheaply made, and can be readily adapted to a wide range of conditions of support and loading of beams.
Any one who has had experience in teaching the laws of resistance of materials will appreciate the practical value of such an apparatus in the class-room. Let the student work out his formulae in the case of restrained beams, for instance, and then check the calculation of reaction, bending moment and deflection by actual experiment. The mathematics will then cease to be a mere abstraction for him, and become a personal possession.
Such exercises are easily possible with the apparatus illustrated.