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Jo" 10° BEAM KNEE WITH 10-2" RIVETS THE Maro ne REVIEW Figo: 8" BEAM KNEE WITH 8 -3°RIVETS 9° BEAM KNEE WITH 10-3" RIVETS aS 'See 7° BEAM KNEE WITH 7-2" RIVETS_ 5" BRACKET WITH 6-2 RIVETS WITH 6-2" RIVETS des 43° BRACKET WITH 4-% RIVETS WS ie °, Ci ° io o = i! fle i 'ot ie ¢_] Sees fio] " THe ft g ° ; of | Fic 4 | a _ Fig. 5. oo "J GRAM NEE s" cee WITH 7-2° RIVETS Fi6.8 WITH 4-2 RIVETS Beam Knees AND BRACKETS TAKEN From PRACTICE. Columns: 10; 11 and 13. of Table' I show that, with the knees ordinarily used in the United States naval ves- sels, the resistance to shearing of the fivets in the majority..of cases,is from sixty to eighty per cent of the resistance to shearing of the beams. The resistance to shearing of the riv- ets would therefore limit the load that could be concentrated at the end of a beam under ordinary conditions. This load is, however, large in comparison with the load that can be concentrated at the middle of the beam even when considered with the weight of the beam itself. The deck beams of the Vermont are 10 in. x 33% in. x 33% in. x 218 Ib. and are allowed to have a maximum span of 18 ft. between Supports. Under this condition, the load which, when concentrated at the middle of the span, will rupture the beam by bending is 16.7 tons. This load added to the weight of the beam, 0.18 tons, gives a total load of 16.88 tons. From the tabic, column I1, we find that the rivets in one knee have a resistance to shearing of 98.6 tons, and will support a load six times as large as the total load given above. The vertical' stresses. on. the rivets due to loading the beams at the middle were found to be smaii when com- pared with the maximum horizontal stresses due to the bending moments. The resultants of the stresses due to the loads and bending moments were found to be but little iarger than the stresses due to the bending moments alone. &n ihe above case of the Ver- mont's deck beam, the following stres- ses were found :-- : g way (7 he s bao, @8 H ee : ne Bo 22 "25 Ow HH dh ead: on O ov oa. Sa a Co Oba ae ro Poo vo AH ARF Co Shearing stress --++++:> Lon 18.09 18.13 Crushing stress in front Of "wivets2f<..5--= +. .50 28.43 28.47 The differences between the result- ant stresses in the table and the stres- ses due to the bending moment are less than one-half of one per cent of i the resultant stresses. Since these dif- ferences are so small, the stresses due to the loads have been neglected. The resisting moments of the beams and the riveting in the knees only have been compared. The resisting moments of the beams were calculated .without taking into ac- count the deck plating riveted to the beams, but considering one 34-in. rivet hole in the shorter flanges at the sec- tions of the beams. The deck plating was omitted because of the wide varia- tion of thickness used on the same beam under different conditions. Columns. 15, 16"and 18 of fable 1. Plate 1, give the moments required to rupture the beams and cause failure of the riveting by shearing or crushing of the metal. For comparison, the moments that will cause failure of the riveting required by Lloyds rules for the same knees are also given in col- umns 17 and 19 of the same table. These moments were calculated by the My formula f = ----, where f equals I 63,000 Ib: per sq.. im. tensile stress, 50,000 lb. per sq. in. shearing stress, and 96,000 Ib. per sq. %m.. crushing stress, and are expressed in foot-tons. The moment of inertia of the rivets in every knee has been taken about a pole through the center of gravity of the area of all the rivets in the knee. Columns 16, 17, 18 and 19 show 'that the riveting of beam knees as required by Lloyds Rules gives ap- proximately the same resistance as the riveting according to _ the ordinary practice in United States naval ves- sels. In general, however, the rivet- ing for knees having a greater depth than 18 in. as required by Lloyds Rules, is slightly stronger than that used in United. States naval vessels, and the riveting for knees having a depth of 18 in. and less, as required by Lloyds Rules, is somewhat weaker than that used in United States naval vessels. If we exclude the fast four beams and the protective deck beam of the Olympia, the resisting moments of the riveting have a ratio to the resistitg moments of the respective beams varying from 1.14 to 22. for United States naval vessels and 0.97 to 235 for Lloyds Rules in the case of shearing, and from TAS to 2A) for United States naval vessels, and 118 to 246 for Lloyds Rules in the case of crushing the metal in front of the rivets. The largest ratios oc- curred in the 7-in. and 6-in. angle bars. The variations in the above ratio appear too large. It seems. more logical to design the riveting and depth of ~