AND THOSE MEASURED WHILE RECEIVING CARGO. 125 



It is not improbable that some effect resulted from taking this amount of cargo 

 aboard and bringing the ship nearly to an even keel, but the part belonging to tem- 

 perature effects and that belonging to the cargo do not admit of being separated. 



On the 20th of June the usual complement of readings was taken in the morn- 

 ing, supplemented by observations on the bulwark rails during the day, the tem- 

 perature in the meantime having risen from 60 degrees to 90 degrees on the star- 

 board side and 62 degrees to 87 degrees on the port side. 



On the starboard side the stress changed from 900 pounds per square inch 

 tension to 1,650 pounds per square inch compression, and on the port side from 450 

 pounds per square inch tension to 1,950 pounds per square inch compression. These 

 changes again clearly represent temperature effects. 



Higher stresses were developed in the more rigid stringer plates and the bul- 

 wark rails than in the plates having lap joints, a result to be expected whether 

 caused by temperature changes or by taking aboard the cargo. 



The maximum range in stresses observed were 4,800 pounds per square inch 

 on starboard stringer plate No. 10 and 4,050 pounds per square inch on the corre- 

 sponding port stringer plate. The range in temperature for all places observed was 

 from 60° to 116° F. 



Four of the gauged lengths spanned joints in the plating. There was greater 

 apparent rigidity in the butt joints of the stringer courses than in the solid plates, 

 and less rigidity in the lap joints of courses C than in the solid plates. Dotted lines 

 on the diagram connect plotted points showing the movements at the joints, located 

 according to the same scale as the plotted strains in the solid plates. 



It will be noted, for example, that the changes in strains from June 13 to 15 

 on the port side were much greater for the gauged length spanning the lap joint of 

 course C than the strains in the solid plate — more than twice as much — while on the 

 stringer course the reverse was true. Here again the general looseness of the lap 

 joints appears in evidence. 



Complex thermal conditions prevailed throughout this series of observations, 

 but no more than would be experienced on other occasions. The ship floated in 

 water at about 60 degrees, setting deeper and deeper as the cargo was received, 

 while the temperature of the deck plates reached 116 degrees on one occasion. 



In conclusion, attention is invited to the opportunities afforded by engineer- 

 ing structures of all classes in the acquisition of information upon the behavior of 

 materials in service, the distribution of stresses, and verification of computed 

 stresses, along the lines of inquiry illustrated in these strain gauge observations. 



