io8 



An analysis of tests of water-tight bulkheads. 



Mx=Mj, + Ty- P^x + Iwhx^ + Iwo^. 



(22) 

 (23) 



The value of T used in this case is again that denoted by Tq, deter- 

 mined by equation (4) . 



Numerical Example — To Determine Tension, Deflection, Stresses, etc., in 

 Stiffener No. 62 of C. L. B. H. Illinois, Test No. i, Plate I. 



Z=22.i6 feet, h = 2.']6 feet, w = ^ ton per foot run per foot head. 

 A = 8.44 square inches, 7=128 (in.)^ square inches, £'=13,170 tons per 

 square inch. 



The elastic deflection was measured: — 5=1.38 inch. \ 



Considering the stiffener fixed at both ends we find from (4) : — 





.86 tons per square inch. 



Hence T = 7.23 tons. Further fe= .0253. 



If we reckon the bending moment at the middle of the stiffener = 

 ^(Pi+Pz)/ we find M = 389 inch-tons, which would give the maximum 

 stress due to simple bending: — /=i9.4 tons per square inch, to which the 

 tension .86 tons per square inch should be added. 



Using the complex formulas (18), (19), (20), (21), (22) given above for 

 combined tension and bending we find the results given in the first column of 

 the following table, while the second column gives the results for simple 

 bending. 



It is seen that the difference between the results in the two columns 

 is insignificant in this case, although the deflection is greater than usual 

 and the stiffener has been strained beyond the elastic limit. In general, 

 therefore, we may use the formulas for simple bending and to the stress 

 so found we may, if desired, add the tensional stress determined as explained 

 above by means of the observed or calculated deflection. 



