Without corbels: 



23 



Factors of safety. 



Stringers in cross breaking 5 4- 



Stringers in deflection , J 5 span 2 + 



Stringers in end bearing 3 4- 



Cap in bearing value 3 + 



Posts in endwise crushing 7. 4+ 



Strs.LongieafPine 

 Caps.Wmite Oak 



RedCypress 



DBJPHOLES 



< SlLLS. 



White Oak 



Scale:- i- Inch * I Foot . 

 Pig. 4. — Example, of proposed practice without corbels. 



Bill of material. 

 TIMBER, EXCLUSIVE OF TIES AND GUARD RAIL. 



IRON. 



STRINGERS. 



The stringer is the first thing- to be considered in the design of tim- 

 ber trestles. It is the most important member of the structure and the 

 most difficult to design economically. The cost of a stringer is a func- 

 tion of not only the number of feet, B. M., contained therein, but also 

 of the height or maximum cross-sectional dimension. 



