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Page 126 - The effect of differences of design was most noticeable with respect to differences in the bridge floors. An elastic floor, such as furnished by long ties supported on widely spaced stringers, or a ballasted floor, gave smoother curves than were obtained with more rigid floors. The results clearly indicated a cushioning effect with respect to impact due to open joints, rough wheels and similar causes. This cushioning effect was noticed on stringers, floor beams, hip verticals and short-span girders.
Page 275 - ... results are obtained by placing the angles in the form of a T. 18. In all main members having an excess of section above that called for by the greatest combination of stresses, the entire detailing is to be proportioned to correspond with the utmost working capacity of the member, and not merely for the greatest total stress to which it may be subjected. In this connection, though, the reduced capacity of single angles connected by one leg only must not be forgotten. 19. Designs must invariably...
Page 126 - The impact due to the rapid application of a load, assuming smooth track and balanced loads, is found to be, from both theoretical and experimental grounds, of no practical importance. (12) The impact caused by balanced compound and electric locomotives was very small and the vibrations caused under the loads were not cumulative. (13) The effect of rough and flat wheels was distinctly noticeable on floor beams, but not on truss members. Large impact was, however, caused in several cases by heavily...
Page 126 - The maximum impact on web members (excepting hip verticals) occurs under the same conditions which cause maximum impact on chord members, and the percentages of impact for the two classes of members are practically the same. (7) The impact on stringers is about the same as on plate girder spans of the same length and the impact on floor beams and hip verticals is about the same as on plate girders of a span length equal to two panels. (8) The maximum impact...
Page 126 - ... hip verticals) occurs under the same conditions which cause maximum impact on chord members, and the percentages of impact for the two classes of members are practically the same. (7) The impact on stringers is about the same as on plate girder spans of the same length, and the impact on floor beams and hip verticals is about the same as on plate girders of a span length equal to two panels. (8) The maximum impact percentage as determined by these tests is closely given by the formula 2OOOO in...
Page 126 - This cushioning effect was noticed on stringers, floor beams, hip verticals and shortspan girders. (10) The effect of design upon impact percentage for main truss members was not sufficiently marked to enable conclusions to be drawn. The impact percentage here considered refers to variations in the axial stresses in the members, and does not relate to vibrations of members themselves.
Page 1022 - ... mixed in the proportion of one part of cement to two parts of sand. The wash should be applied with a brush.
Page 68 - ... in the manufacture of nickel steel. There is a fact concerning nickel steel known to the profession, but which, as far as the author can learn, had not until a very short time ago been stated in print, viz., that the Pennsylvania Steel Company has obtained control of an iron mine containing a small percentage of nickel; and is, consequently, able to place upon the market a low grade nickel steel at a reasonable excess cost above that of carbon steel. This steel has been denominated by its makers...
Page 125 - Bulletin: (1) With track in good condition the chief cause of impact was found to be the unbalanced drivers of the locomotive. Such inequalities of track as existed on the structures tested were of little influence on impact on girder flanges and main truss members of spans exceeding 60 to 75 feet in length. (2) When the rate of rotation of the locomotive drivers corresponds to the rate of vibration of the loaded structure, cumulative vibration is caused, which is the principal factor in producing...
Page 194 - ... stress in the first truss will be twice the percentages in the second truss. (3) The more uniform the proportions of a truss the less, in general, will be the secondary stresses. Sudden changes in length, width, or in moment of inertia, are likely to result in relatively large secondary stresses. (4) Trusses consisting of approximately equilateral triangles, and without hangers or vertical struts, present the most uniform conditions and will have, in general, the lowest secondary stresses. A...