226 



MODERN BRIDGE TRUSSES. 

 C D 



Art. 123. 



/ i 



SUB-D/I//DED WARREN TRUSS 



Fig. 167. 



In the Warren truss the compression members of the web are 

 longer than in the Pratt truss, and some of them are subject to 

 alternating stresses of tension and compression. These disadvan- 

 tages lose their importance, however, when the number of panels 

 is small, as there are but few such members (see Fig. 167). The 

 usual limit of span for this style of truss is about 150 feet. 



While multiple intersection trusses are not in general favor, 

 multiple intersection Warren trusses are used on several lines of 

 railways on account of the severe treatment they will stand, with- 

 out actual collapse, in cases of derailment. Fig. 168 shows a 



DOUBLE INTERSECTION WARREN TRUSS 



Fig. 168. 



double intersection Warren truss $ this is sometimes sub-trussed 

 by inserting short suspenders from the intersections of the diag- 

 onals to the lower chord. The stresses are calculated upon the 

 assumption that the two systems act independently (135.) 



Fig. 169 shows a combination of four trusses with the neces- 

 sary modifications at the ends to allow inclined end posts. The 

 four systems are assumed to act independently. 



The term " lattice girder " is commonly applied to either the 

 single or multiple intersection Warren truss when the connections 

 are riveted; but it would be more appropriate to designate 

 trusses, with more than two systems of web bracing, as lattice 

 trusses. In such trusses when the web members are connected 



