QUESTIONS AND PROBLEMS. CHAPTER X. 



1. What is a truss element? What is a truss? 



213 



2. What assumption with regard to the joints of a truss 

 is made in calculating the stresses? 



3. Make a sketch of some roof truss in your vicinity, showing 

 the manner of attaching the purlins and the points of appli- 

 cation of the loads to the truss. Are there any live loads carried 

 by the truss? Are the roof loads applied at the panel points? 



4. Consult Kidder's " Architects and Builders' Pocket- 

 Book/' and Ketchum's " Structural Engineer's Handbook," for 

 examples of roof trusses and roof construction. 



5. What are purlins? Rafters? Kneebraces? 



6. In what way do the stresses in a rafter usually differ 

 from those in the other members of a roof truss? In a knee 

 brace? 



7. What types of trusses are commonly used for steel mill 

 buildings? For drill halls? For churches? For timber con- 

 struction? For flat roofs? For shops where columns are not 

 objectionable? 



8. How may the saw-tooth roof be modified to eliminate 

 intermediate columns? 



9. How are the stresses in roof trusses usually determined? 



10. For what different loadings are the stresses in roof 

 trusses calculated? What combinations of these loadings are 

 possible? 



11. How is lateral stability secured when the trusses are 

 supported on columns? 



12. Determine the stresses in the truss of Fig. 151 (6) 

 for the following data : 



Span 60 ft. Depth at center, 12 ft. Depth at eaves, 8 

 ft. Height to bottom chord, 20 ft. Dead load panel load, 

 10000 Ibs. Snow load panel load 5000 Ibs. Horizontal wind 

 load at eaves, 12000 Ibs. 



