AND THOSE MEASURED WHILE RECEIVING CARGO. 121 



enced in making strain gauge measurements on engineering structures; therefore it 

 is believed that these results are trustworthy in a higher degree than generally 

 expected, that the strains were substantially as reported. In deducing the stresses 

 corresponding to the measured strains, a value of 30,000,000 pounds per square 

 inch was used for the modulus of elasticity of the steel plates. 



A full cargo of 10,217 tons was carried on the outward voyage, while on the 

 return voyage the cargo was only 3,000 tons. 



Observations on the live load strains of the deck plating were made on both 

 the outward and the return voyages. Good weather generally prevailed, hence the 

 measured strains refer to conditions as they were found on a smooth sea with a 

 minimum pitching of the ship. A few observations, however, were made on the 

 outward voyage with a moderate sea running. With a low freeboard, when the 

 ship carries a full cargo, the decks were generally wet in a moderate sea, and with- 

 out protection it was impracticable to make many observations. The few meas- 

 urements which were taken showed strains of increased magnitude, corresponding 

 to the greater pitching of the ship which then occurred. 



Tables i and 2, Plates 71 and 72, give the results of the measurements made 

 at sea. Certain of these measured strains are entered upon diagrams of the deck 

 plates and appear in Plate 67. 



Referring to the observations in detail, and beginning at the forward deck, 

 neither the solid metal of plate C 27 (Table i), over which the breakwater passed, 

 nor that of the next plate aft developed strains of sufficient magnitude to be meas- 

 urable. At the first lap joint aft the breakwater and across all succeeding joints 

 there was measurable deformation. The solid metal of plate C 25 and those aft 

 displayed measurable longitudinal strains due either to the vibrations of the en- 

 gines or to the pitching of the ship or to their combined effect. 



The magnitude of the strains in general increased as the bulkhead of the 

 superstructure was approached, although the rate observed was not a uniformly 

 increasing one. The presence of hatches probably influenced the magnitude and 

 distribution of the stresses. The smooth sea was favorable for acquiring compara- 

 tive results on different parts of the ship. At times the engines on one shaft would 

 gain in the number of rotations over those of the other, and dififerences in strains 

 were noted which were attributed to the effects of the heavier pistons when those 

 of both shafts were in the same phase. 



Strains across the lap joints of courses C and D were substantially the same 

 and much greater than those of the stringer plates. This behavior calls for the de- 

 velopment of longitudinal shearing stresses at the seams between the stringer course 

 and the adjacent course, but measurements necessary to follow these shearing 

 strains were not included in the present series. 



Pitching strains were not of sufficient magnitude to admit of measurement on 

 the deck amidship, covered by the superstructure, but those caused by the engines 

 were followed to a point nearly abreast the boiler hatch. 



On the after deck the strains reached a maximum near the bulkhead. The 



