

TYPES OF TRUSS BRIDGES. 



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nation of isosceles triangles as shown in (d), Fig. 3 and in (c) and (d), Fig. 4. The Pratt truss 

 has its vertical web members in compression while its diagonal web members are in tension, as 

 shown in (b), Fig. 4. The Warren truss is commonly built with riveted joints while the Pratt 

 truss is usually built with pin-connected joints. The Warren low truss with riveted joints as 

 shown in (d) is generally preferred in place of the low Pratt truss in either (e) or (f), Fig. 3. The 

 Howe truss has its vertical web members in tension, and its inclined web members in compression 

 as shown in (a), Fig. 4. The upper and lower chords and the inclined members of a Howe truss 

 commonly made of timber, while the vertical tension members are iron or steel rods or bars. 



(a) THROUGH HOWE TRUSS 



(b) THROUGH PRATT TRUSS 



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(c) THROUGH WARREN TRUSS 



(d) QUAOKANGULAR THROUGH WARKEN TRUSS 



THROUGH WHIPPLE TRUSS 



(F) CAMEL BACK TRUSS 



THROUGH BALTIMORE TRUSS 



(h) K-TRUSS 



(i) THROUGH PETIT TRUSS (j)K-TRUSS 



FIG. 4. TYPFS OF HIGH TRUSS STEEL BRIDGES. 



The Whipple truss, (e) Fig. 4, is a double intersection Pratt truss. This truss was designed 

 give short panels in long spans which have a considerable depth. The stresses in the Whipple 

 truss are indeterminate for moving loads, and its use has been practically abandoned, the Balti- 

 more truss, (g) Fig. 4 being used in its place. The quadrangular Warren truss with riveted joints 

 is used by the American Bridge Company as a standard truss for through highway bridges, with 

 spans of from 80 to 170 ft. Like the Whipple truss its stresses are indeterminate for moving loads. 



For spans of from, say, 170 to 240 ft. it is quite common to use pin-connected trusses of the 

 Pratt type having inclined chords as in (f), Fig. 4. The K-bracing in (h) or (j) is more economical 

 of material and gives smaller secondary stresses than the subdivided bracing in (g) and (i), and 

 is rapidly replacing both forms of bracing shown. 



The Baltimore truss, (g) Fig. 4, is a Pratt truss with parallel chords in which the main panels 

 have been subdivided by an auxiliary framework. The auxiliary framework may have struts 

 as in (g), or ties as in (i), Fig. 4. The Baltimore truss with inclined upper chords, (i) Fig. 4, is 



