8 R. F. GWYTHER, Specification of Stress. Part IV. 



under statical conditions is to be employed, without 

 making use of surface-traction conditions which have not 

 as yet been introduced, it is necessary to make some 

 general assumption on which to base an illustration. 



St. Venant has discussed the case when /' = 0, = f/O, 

 ^ = 0, and has given the general method on which surface- 

 conditions may be treated. 



I select the case of a strut connecting parts of a 

 structure, considered to be straight, or, at any rate, to have 

 a definite axial direction, which I shall take to be the axis 

 of ^'. The object of a strut is to convey a state of stress 

 from one part of a structure to another. I shall suppose 

 as describing the conditions of the special case to be con- 

 sidered that all stresses are independent of .s', so that the 

 stresses are communicated without change from section 

 to section of the strut. 



The conditions to be made use of are (13) and the 

 fundamental static equations 



^P ZU . oU -bQ r. dT ^ dS n 



ox vy dx dy ' ?^x ?i' 



The relations obtained from (13) become 

 P = P„~ J^!L^ xl{P-^Q^ P) , 



or 



(^5). 



