. The strength of materials; a text-book for engineers and architects. ge = P = -933Then for whole strutk,,. = 3-77 = 3-1832 + -9942. •. k,, = 3-33 Length _ 26 x 12 c = Least radius of gyration 3*33 93-6 • / ^ 6 • • ^ 93-6 X 93-6^ 6000 2-46 = 2-44 . Safe load = 2-44 x area = 2-44 X 2 X 8-296 = 40-4 say 40 tons. STRUTS WITH ECCENTRIC LOADING Simple Approximate Method.—If the thrust in thestrut is out of the centre, where there is bendingmoment as well as direct thrust on the strut, we cannot usethe same rules for design as in the ordinary case. In such case we may obtain approximate result
. The strength of materials; a text-book for engineers and architects. ge = P = -933Then for whole strutk,,. = 3-77 = 3-1832 + -9942. •. k,, = 3-33 Length _ 26 x 12 c = Least radius of gyration 3*33 93-6 • / ^ 6 • • ^ 93-6 X 93-6^ 6000 2-46 = 2-44 . Safe load = 2-44 x area = 2-44 X 2 X 8-296 = 40-4 say 40 tons. STRUTS WITH ECCENTRIC LOADING Simple Approximate Method.—If the thrust in thestrut is out of the centre, where there is bendingmoment as well as direct thrust on the strut, we cannot usethe same rules for design as in the ordinary case. In such case we may obtain approximate results by pro-ceeding as follows— Let the load P be at distance e from the centroid of thecross section, then M = P . e (Fig. 136). Case 1. Very Short Struts.—If the length is less than 302 THE STRENGTH OF MATERIALS 10 times the least diameter of the strut, the stresses areobtained as shown on p. 237. i. e. /, A ^Z. f, M PZ, A In this case /,. V Vx K^ Z,. P P . e . d, ~ A ^ Ak A V^ ^ k^ ) P•• A ed. IZy^a Y Ccniroia L D ?Cff^—*? -<+ B F. Fig. 136.—Columns with Eccentric Loads, This gives the safe load P for a compressive stress /,. Thisease is fully dealt with in Chap. VIII. Case 2, Struts Longer than 10 J)iameters.—In thiscase we must make some allowance for buckling tendencies,and ^\e may proceed as follows— As in the previous case we have Combined compressive stress = . (l + ,2 j Now in this case this compressive stress should not be more COLUMNS, STANCHIONS AND STRUTS 303 than the safe stress x>er sq. in. obtained by considering thebuckling formulae, A , , ed,. Safe central load on Safe eccentric load on strut = 7———^ (1 + i where e = eccentricity of load dr = distance from centroid to edge of section nearest loadk = radius of gyration about axis perpendicular to theplane containing the centroid and the formula may be put into a form which is sometimesmore useful as follows— Let P^ be the central load, which is
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