PLATE GIRDERS. 581 



tq. in. are given in Table 7. The I-Beams could have been selected directly from the moment 

 making use of these valu< 



The safe uniform load, in tons, for I-Beams is given in Table 12, using a fiber stress of 16,000 

 Ib. per sq. in. The I-Beams could have been selected directly from the load using this table. 



If the girder is not supported to prevent lateral deflection the allowable fiber stress must be 

 reduced by the compression formula as shown in Table 120. 



The separators for Carnegie I-Beams are given in Fig. 4, page 83, Chap. II. The separators 

 for lU-thlfhrm beams are given in Table 158. 



Plate Girders. The full discussion of the design of plate girders would require more space 

 tli.in is available. The following notes will be of value. 



References. The following references should be consulted. 



Weights. P. 115; p. 150; p. 151; p. 152; p. 153; p. 155; p. 156; p. 158. 



Bending Moments and Shears. Pages 159, 163, 164, 165, 166, 167, 173, 174. 



Unit Stresses 33, 35, 36, p. 57; 42, 43, p. 58; 36, 37, 39, 40, 41, 44, p. 

 Hi; 50, 51. 52, 53. 54. P- 142; 14. 2 9. P- 206; 14, 15, 17, 18, 19, p. 209; 29, 

 30, p. 210. 



Proportion of Parts 3, p. 55; 43, p. 58; 3, p. 137; p. 202; p. 203; 26, 29, 30, 77, 

 p. 206; 79, p. 207; 26, 27, 29, 31, 32, 38, p. 210; 57, p. 21 1 ; 77, 78, 79, p. 212; 



80, p. 213; pages 220, 221, 222. 



Details. Pages 54, 123, 124, 189, 190. 



The gross and net areas of angles are given in Table 29; Area of Plates, Table I ; Areas to be 

 Deducted for Rivet Holes, Table 116; Moments of Inertia of Angles, Tables 32, 33 and 34; 

 Moments of Inertia of Web Plates, Table 3; Moments of Inertia of Cover Plates, Table 5; Prop- 

 erties of Plate Girders, Table 87; Centers of Gravity of Plate Girder Flanges, Table 88. 



Nomenclature. The following nomenclature will be used. 



M = resisting moment of section. 



V = vertical shear at section. 



/ = allowable unit fiber stress. 



/ = moment of inertia of gross section. 



/' = moment of inertia of net section. 



/ = moment of inertia of gross section of web plate. 



/' = moment of inertia of net section of web plate. 



AF = gross area of one flange. 



Af = net area of tension flange. 



A w = gross area of web. 



h = distance between centers of gravity of flanges. 



V = distance between gage lines of rivets in tension and compression flanges. 



d = distance back to back of angles in flanges. 



c = distance from neutral axis to extreme fiber. 



p = pitch of rivets in flanges. 



r = allowable resistance of one rivet. 



w = concentrated load per unit length of rail = P/l where P = concentrated load and 

 / = distance over which the load, P, is considered as distributed (see 5, p. 202). 



2 = number of rivets on one side of web splice. 



Resisting Moment. There are four methods now in use for determining the resisting moment 

 ot a plate girder section. 



(1) Assuming that all the bending moment is carried by the flanges (see 29, p. 206), 



M = A F '-}-h (i) 



(2) Assuming that one-eighth the gross area of the web is available as flange area (see 42, 

 P- 58; 50, p. 142; 29, p. 206), 



lAJ-f-h (l') 



