QUESTIONS AND PROBLEMS. CHAPTER V- 89 



1. What is the difference between a stress diagram and a 

 force polygon? 



2. Explain fully how the signs of stresses are determined 

 when algebraic methods are used and when graphic methods 

 are used. 



3. What should be the uniform practice with regard to the 

 angles giving the inclinations of the members of a truss and their 

 functions ? 



4. Find, graphically, the stresses in a truss like that of 

 Fig. 61, with panel loads, at joints 3, 5, 7, and 9, of 15000 Ibs. 

 each, the panels being 15 ft. and the depth d, 1\ ft. Also for a 

 single load at joint 9 such that #i = 1000 Ibs. 



5. Find the stresses in problem 4 algebraically and com- 

 pare the results. 



6. Take a truss similar to that of Fig. 51 with a span of 

 60 ft. (six panels of 10 ft. each), a height at the center of 15 ft., 

 and vertical panel loads at joints 2, 4, 6, 8, and 10 of G400 Ibs. 

 each. Find the stresses algebraically and graphically and com- 

 pare them. 



NOTE. This style of truss is called a Howe truss. When the 

 diagonal web members are inclined in the opposite direction, it 

 is a Pratt truss. The instructor may assign individual problems 

 by varying the span, the pitch, and the panel load. The above 

 truss is one-fourth pitch because the ratio of height to span is \. 



7. Find the stresses in the truss of problem 6 when the sup- 

 port is at joint 9 in place of joint 12 and a half panel load is 

 added at joint 12. 



8. If the reaction R\ were known, would it be possible to 

 draw a stress diagram for a full arch like that shown in part in 

 Fig. 60? 



9. What is the bending moment at the middle of a beam 

 of 24 ft. span for a load of 8000 Ibs. at its middle? 



10. What is the maximum bending moment in the above 

 beam for a load of 9000 Ibs. 8 ft. from one support? What the 

 maximum shear? 



11. At which load, in the beam of Fig. 41, is the bending 

 moment a maximum? 



12. At which joint of the truss, Fig. 50, is the bending 

 moment a maximum? Where does the shear pass through zero? 



