QUESTIONS AND PROBLEMS. CHAPTER XIII. 



315 



1. It what parts of structures are longitudinal forces im- 

 portant ? 



2. What is "impact" and how is it taken into account? 



3. In a railroad bridge how are loads actually applied? 

 How are they usually specified ? 



4. The stress in a main diagonal of a bridge, due to Cooper's 

 #40 loading, is 420,000 Ibs. What would be the live load stress 

 in this diagonal if the loading were increased so that one engine 

 and tender weighed 150 tons ? 



5. Find the maximum span for which the four drivers of 

 Cooper's engine will give a maximum moment and the minimum 

 span for which the four drivers and the first tender wheel will 

 give a maximum. 



6. Find the position of Cooper 's Loading which will give a 

 maximum stress in the top chord 2'-3', of Fig. 204. Span= 

 120 ft. Find the position for maximum shear in panel 2-3. 



7. Prove equation (93). 



8. Why should the panel lengths be about 19 ft. for a bridge 

 having two systems of webbing, if Cooper's loading is used? 



9. Find the equivalent uniform load for center moment, 

 and for shear in the end panel, for the truss of Fig. 207, for 

 Cooper's "60 loading. 



