24 



The Atlanta Lumber Company, of Atlanta, Ga., quote the following 

 relative prices for longleaf-pine timber such as would be used for 

 stringers: For sizes 12 inches or under, $8 per 1,000 feet, B. M. For 

 sizes over 12 inches add $1 per inch per 1,000 feet, B. M. 



Assuming that these prices represent the average conditions, tig-. 5 

 shows the relative cost of stringers of different heights but of equal 

 cross-bending strength and stiffness. 



o in ?n an 40 



Fig. ">. — Diagram showing relative cost of stringers of different heights. 



The heavv line shows the relative cost of stringers of different 

 heights, but designed to develop the same safe unit stress in the 

 extreme liber, while the light line shows their cost when designed to 

 develop the same maximum allowable deflection of one two-hundredth 

 of the spun. 



COST OF STRINGERS OF EQUAL STRENGTH. 



For uniform load in cross bending: 



3WZ 



R 



* 



4 h Ir 



7 3 W U i • 1 7 i a 3 W I 



or h = - . T » ,„ from winch l> k = A 



4 R !r 



4R// 



See Appendix 1. 



