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Tests of some girder hooks
the degree of supersaturation is shown to vary between 160 per cent. for the very fluid honeys to 290 per cent. for those in which the granulation has proceeded to complete solidification. From the statistical data a rough generalization is suggested which may make possible a prediction in regard to granulation if restricted to sirups of a similar degree of clarity. A knowledge of the solubilities of sucrose in the presence of invert sugar and of invert sugar in the presence of sucrose makes possible a determination of the composition which is saturated with both. Such a sirup contains the maximum concentration which can be produced by the partial inversion of sucrose. Thus at 23.2” C. such a sirup should contain 36.3 per cent. sucrose, and 39.9 per cent. invert sugar; and at 30’ C., 33.6 per cent. sucrose, and 45.4 per cent. invert sugar. Methods of partial inversion of sucrose are reviewed. In tropical America the inversion is accomplished by addition of The more scientific cane juice soured by acetic fermentation. methods consist of enzymic inversion for cane juices and hydrochloric acid inversion for pure sugar free from any considerable inorganic impurities. TESTS
OF SOME GIRDER
By Herbert L. Whittemore
HOOKS.
and Ambrose
H. Stang.
[ABSTRACT.]
MILD-STEEL hooks having rectangular cross-sections are often used for lifting steel girders. Two hooks with their curved ends together are placed on a link carried by the crane hook. Hooks of this kind are usually designed by combining the To determine the safety of hooks tensile and bending stresses. designed in this way, nine were tested, three each for the following loads : 5, IO and 15 tons. The hooks were supplied by the mechanical engineering department of the American Bridge Company, Ambridge, Pennsylvania. The hooks were loaded using several increments up to the proportional limit of the material, which was obtained from coupon specimens cut from each hook. The stresses on the inside and outside surfaces of the hooks were measured, experimentally, __-‘Technologic Papers, No. 260. Price, ten cents.
U. S. BUREAU OF STANDARDS NOTES.
54s
[J. I;. I. .
with strain gauges, having two-inch gauge lengths. Readings were taken along practically the entire length of each hook. The stresses for the same gauge lines were also found, theoretically, by adding algebraically the stress due to the component of the load normal to a right section of the hook and the stress due to bending at that section. The bending stress was computed using the ordinary beam formula. The experimental and theoretical stresses were plotted for comparison in load-stress diagrams for each hook. The maximum stresses in the hooks were also computed from the Winkler-Bach and the Andrews-Pearson formulas derived from theory of curved beams. CONCLUSIONS. ( I ) The stresses obtained from strain-gauge measurements on girder hooks of rectangular section agreed well with the stresses computed by the ordinary theory of combined tension and bending, except at the critical section. (2) The experimental stresses at the critical section were higher than the values computed by the ordinary theory of combined tension and bending for all hooks except K-9. The results indicate that the Winkler-Bach and the Andrew+Pearson formulas, which take into account the curvature of the hook, give correct values for the stress. (3) The stress computed by the Winkler-Bach and the Andrews-Pearson formulas was in no case more than 20 per cent. greater than the stress computed by the ordinary theory of combined tension and bending. If the factor of safety used in designing hooks of this kind is sufficiently large, it is believed that the use of the more exact formulas is not necessary. (4) It is impossible to determine by visual inspection whether any part of the hook has been stressed beyond the proportional limit. LOGGING
AND
SAWMILL
CODE.
[ABSTRACT.]
THIS code is one of a series of safety codes being prepared under the plan of procedure of the American Engineering Standards Committee. The Bureau of Standards accepted the sponsorship and the work has been carried on with the assistance of a representative sectional committee. “Handbook
No. 5,
Price,
sixty cents.
OF SOME GIRDER
By Herbert L. Whittemore
HOOKS.
and Ambrose
H. Stang.
[ABSTRACT.]
MILD-STEEL hooks having rectangular cross-sections are often used for lifting steel girders. Two hooks with their curved ends together are placed on a link carried by the crane hook. Hooks of this kind are usually designed by combining the To determine the safety of hooks tensile and bending stresses. designed in this way, nine were tested, three each for the following loads : 5, IO and 15 tons. The hooks were supplied by the mechanical engineering department of the American Bridge Company, Ambridge, Pennsylvania. The hooks were loaded using several increments up to the proportional limit of the material, which was obtained from coupon specimens cut from each hook. The stresses on the inside and outside surfaces of the hooks were measured, experimentally, __-‘Technologic Papers, No. 260. Price, ten cents.
U. S. BUREAU OF STANDARDS NOTES.
54s
[J. I;. I. .
with strain gauges, having two-inch gauge lengths. Readings were taken along practically the entire length of each hook. The stresses for the same gauge lines were also found, theoretically, by adding algebraically the stress due to the component of the load normal to a right section of the hook and the stress due to bending at that section. The bending stress was computed using the ordinary beam formula. The experimental and theoretical stresses were plotted for comparison in load-stress diagrams for each hook. The maximum stresses in the hooks were also computed from the Winkler-Bach and the Andrews-Pearson formulas derived from theory of curved beams. CONCLUSIONS. ( I ) The stresses obtained from strain-gauge measurements on girder hooks of rectangular section agreed well with the stresses computed by the ordinary theory of combined tension and bending, except at the critical section. (2) The experimental stresses at the critical section were higher than the values computed by the ordinary theory of combined tension and bending for all hooks except K-9. The results indicate that the Winkler-Bach and the Andrew+Pearson formulas, which take into account the curvature of the hook, give correct values for the stress. (3) The stress computed by the Winkler-Bach and the Andrews-Pearson formulas was in no case more than 20 per cent. greater than the stress computed by the ordinary theory of combined tension and bending. If the factor of safety used in designing hooks of this kind is sufficiently large, it is believed that the use of the more exact formulas is not necessary. (4) It is impossible to determine by visual inspection whether any part of the hook has been stressed beyond the proportional limit. LOGGING
AND
SAWMILL
CODE.
[ABSTRACT.]
THIS code is one of a series of safety codes being prepared under the plan of procedure of the American Engineering Standards Committee. The Bureau of Standards accepted the sponsorship and the work has been carried on with the assistance of a representative sectional committee. “Handbook
No. 5,
Price,
sixty cents.