232 QUESTIONS AND PROBLEMS. CHAPTER XI. 



1. Name two types of trusses that usually have two diag- 

 onals in at least some of the panels. 



2. What causes a reversal of stress in some members of a 

 truss? Can the stresses in any of the chord members of a truss 

 simply supported at the ends ever reverse? In what kind of a 

 truss may there be a reversal of stresses in the chords? 



3. If the stress in a counter tie is 25000 Ibs. when there is 

 no initial stress, what will it be when the initial stress is 10000 

 Ibs.? What when the initial stress is 15000 Ibs.? 



4. What types of trusses are best adapted to construction 

 in wood? 



5. Classify the trusses illustrated in the preceding chapter 

 as to web bracing. 



6. When was the first book on stresses in trusses published? 



7. What was the development of bridge building as to 

 materials used? 



8. Why did each type of truss mentioned in Art. 122 go 

 out of use? 



9. What are the economic reasons for using trusses with 

 curved chords for the longest spans only? 



10. What types of trusses are commonly made with riveted 

 connections and what with pin connections? 



11. Does the cantilever bridge have any advantage over a 

 series of simple spans so far as the substructure is concerned? 

 For a series of equal spans; what is the advantage of the simple 

 trusses over the cantilever trusses? 



12. What kind of trusses are used in the Queensboro 

 bridge over the East River in New York? 



13. What traffic is provided for in the plans of the canti- 

 lever bridge over the St. Lawrence River near Quebec? 



14. What are the two arch bridges over the Niagara River ? 

 What are the lengths of their spans? What the number of 

 hinges? 



