298 STRESSES IN A PRATT TRUSS FROM WHEEL LOADS. Art. 153. 



=0.31. 



2050 



Live load, Cooper's E4Q loading. 



The dead load coefficients are shown in Fig. 207. 



For the live load stresses in the chords it will be necessary 

 to get the maximum moments at joints 4, 5, and 6. For joint 6, 

 using the loading strip with the principles enumerated in Art. 

 143 in mind, it is seen that one of the drivers of the first engine 

 will probably give the maximum moment. The criterion, equa- 



Fields of Shear 

 Fig. 207. 



tion (84), may be simplified in application somewhat by dividing 

 both sides by the panel length, making it read 



Using this criterion for joint 6, we get the following results: 

 For joint 6, the panel in question is 6-7, N =7 and n = 1. 

 Wheel 2 at joint 6, 31 ft. of uniform load on: 



- ! = 10. 



=30. 



As the first term does not fall between the limits of the 

 other two, the criterion is not satisfied. 



