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ye ey April, 1909 in fourth column, and moment in f&fth column. Moment 12,474.64 -- equals Area of section 925.15 13.48 equals neutral axis above under- side of keel plate. Calculation of moment of inertia for hogging strain are shown in the table in columns as follows: First column--Items in girder, Second column--Section area in sq. in. A. Third column--Distances of center of gravity from neutral axis h. Fourth column--Squares of § dis- trnces hh. Fifth column--Products of A X h?, Sixth column--Depth of webs d. Seventh. column--Squares of depths d'. Eighth column--Products AX @ The sectional areas: i equals vertical ii the ~calcala-- tions are for one-half of the section of the vessel. It is thus necessary to multiply the moment of inertia, column 5, for the half section by 2 in order to obtain the total moment of inertia. The finding of the moment of iner- tia is the second stage of the calcu- lation but before the stress upon either the top or bottom of the vessel can be ascertained, the bending' moment must be found. One-eighty-fourth the length of the load water line multiplied by the dis- placement in tons is found to give a fairly accurate approximation to the maximum bending moments experienced, and which is developed when the. vessel is supported upon the crests of waves and enduring a hogging strain. The vessel whose midship section shown in Fig. 49, and moment of iner- tia calculation 1s. 532 56°. x 31'and has a displacement of 13,600 tons on a draft of 20 ft. The neutral axis being 18.52 below the top of girder and 13.48 above the underside of the keel plate, the maxi- mum tensional stress on the top of 86,133 X 18.54 the sheer strake will be 145,464 equals 10.96 tons per sq. in. And the maxinium compressive stress on the bottom plating will be 86,133 X 13.48 -- equals 7.96 tons per sq. 145,464 in. 10.96 X 2,000 equals 21,920 pounds the maximum tension on the top sides. The breaking strength of the mate- rial is 62,000 pounds and elastic limit half of same 31,000 pounds. This gives TAE Marine REVIEW 41 CALCULATION OF MOMENT OF INERTIA FOR HOGGING STRAIN. LE 2: $8, 4. 5 6. 'le 8. Distance Sectional of C. G. area in from Depth of Prod- Square neutral Squares of Vertical Squares of ucts. inches axis distances Products webs dépths <1 Items in Girder-- . A. ao sac AOS? ad: d Ax d2, Keel plate and <angles....... 20.80 13.00 169.00 3,427.32 piles plating, IB. . be 48.00 13.30 176.89 8,490.72 shell plating © and -D..7... 88.12 13.40 179,56 15,821.72 Hell plating Ih Gece; 40.12 12.40 153.76 6,168.85 % center keelson and angle 17.09 10.30 106.09 858.26 Gitder eplattes; ete. 4s 52rd '10.20 104.04 5,423.56 7735 25 227 piel plating' Go 40.20 9.50 90.25 3,618.05 dank<top a,b,c and: das. = 104.50 8.40 70.56 7:;300-52. Bilge stringer. os. 25; 48 3.50 8.30 68.89 210.11 Tank side "Strake e752. ; 40.12 6.20 38.44 1,543.21 shell plating: i024 3 36.09 4.20 17.64 636.72 side -strinpen' NO...) 0 ios: 7.34 3.50 12.25 42.87 : Wank Sidexf <5.) es 272000. 0.50 0.25 6.75 + 16 256 4,523 Shell -platingeG- ri. pea 38.67 1:20 1.44 55.68 vide 'Stringer No, 2....5:.. 7.34 1°70 2.89 2120. Tank side OU Te Mie ess 13.87 5.40 29.16 304.04 ell plating Ka) er. ale 4 38.84 6.20 38.44 1,493.00 ank Side top. Mb D.., o. 34.68 7.20 51.84 1,797.81 wide stringer No; 32.2.5. 7.34 11.80 139.24 1,643.03 shell seams and MG, 4, 110.38 14.00 196.00 2,034.48 § 11.00 Ii L187 par deck <i ee 150.00 18.00 3.24 5,832.00 : 66,794.91 5,937 5,937 72,731.91 = moment of inertia for Length, 532. Breadth, 56. Depth; si, Load draught, 20' 0". Load displacement, 13,600 tons. Wx L Y section. 2 for both sides of vessel. 145,464 Total moment of inertia. Maximum bending moment -- ee BO. 133 a: 84 Moment of inertia, 145,464. Neutral axis from top £8.52) Neutral axis from bottom Maximum tension on top, 10.96 tons. Maximum compression on bottom, 7.96 tons. approximately a factor of safety of - three over the breaking strain. Through the unreliability of rivet points I have been unable to find any authority on the value of a rivet in tension, ATE a oo 13.48 § depth of girder In this article all the intercostals have been omitted. The thatch coaming has been considered but it is very doubtful if it is of any consequence in assisting the area of section seeing that it only runs to the hatch opening. gd : # TIGURPE 49 8 Kaek