I 



284 ()l ESTIONS AND PROBLEMS. CHAPTER XII. 



1. How do the weights of the various parts of a bridge 

 vary from the supports to the center? 



2. How is the dead load estimated in a railroad bridge? 



3. How are the panel loads of dead load assumed to act? 



4. How much variation is usually allowed between the 

 assumed dead load and the final estimated weight? 



5. Make sketches of some bridge in your vicinity, showing 

 the manner of supporting the floor covering, the joists and the 

 floor beams. Make an estimate of the weight of the floor per 

 panel, and of the steel work. 



6. What stresses are required in a bridge design? 



7. When a partial live load is on the bridge, how is the 

 partial panel load at the head treated? 



8. What is the relation of the stresses in two trusses 

 similar to Fig. 167, if the span and height of one are 120 ft. 

 and 24 ft., and of the other are 105 ft. and 21 ft., respectively, 

 if the panel loads are 24,000 Ibs. in each case? 



9. In Fig. 167, what position of the live load will give a 

 maximum stress in BC'l What will the maximum stress in BC 

 be if the span is 120 ft., height 24 ft., dead load 400 Ibs. per lin. 

 ft., live load 600 Ibs. per lin. ft. of truss? 



10. In the case of Problem 9, what will be the position of 

 the live load for a maximum tension in Bel 



11. Where must the center of moments for a member 

 lie in order for its stress to be a maximum for full load? 



12. What is represented by a coefficient of stress? 



13. Write the dead and live load coefficients on a Howe 

 truss of 9 panels, all loads assumed to act at the upper chord. 



14. Write the dead and live load coefficients on a clock 

 sub-divided Warren truss of 8 panels; one third of the dead 

 load assumed to act at the lower chord and two thirds at the 

 upper. 



15. Write the dead and live load confidents on a deck 

 Baltimore truss of fourteen panels with vertical end posts. 



16.' What is the condition for maximum tension in V 2 , 

 Fig. 194? In 7 3 ? 



17. Make sketches illustrating the four different trusses 

 possible with different loadings, us affecting V 2 in Fig. 194. 



