NOTATION. 



The same letter is sometimes used to denote entirely differ- 

 ent quantities which can not possibly be mistaken for each other. 

 Sub-scripts and super-scripts denote particular values or 

 values referred to particular axes, origins, or points. 



In general, capital letters denote totals, small letters denote 

 units and distances, and Greek letters denote angles. 



Max. and min. written as sub-scripts denote maximum and 

 minimum values. 



A = total area of cross section (square inches). 

 Af = net area of one flange (square inches). 

 A w = gross area of the cross section of the web = th. 

 a = distance shown in the figure. 

 I = width of a rectangular cross section. 

 = width center to center of supports. 

 = distance shown in the figure. 

 C = centrifugal force per pound. 

 Cii 2, C', etc. = constants of integration. 

 c = distance shown in figure. 



D = total direct stress in posts with portal attached. 

 DI, D 2 ,, >3, etc. = stresses in diagonal members. 

 D = degree of curve of track. 

 D. L. = dead load or dead load stress. 

 d = distance from the neutral axis to a parallel axis. 

 = depth between centers of gravity of the flanges of a girder. 

 = depth between centers of chords of trusses. 

 = differential when written in connection with and preceding 



a variable. 



dA = an infinitesimal element of area. 

 E = modulus of elasticity in tension or compression (pounds 



per square inch). 



= equilibrant of two or more forces. 



E a = modulus of elasticity in shear or shear modulus (pounds 

 per square inch). 



XV 



