296 



TIMBER BRIDGES AND TRESTLES. 



CHAP. VII. 



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^ Hole for T,e Rod ^ 



-*p/i^i^- 



1^'r 



h- 





7; Counter* 



IgHo/g} 4 



FIG. 13. DETAILS OF A TIMBER HIGHWAY BRIDGE. 



DETAIL SPECIFICATIONS. 



12. Piles. Piles shall be carefully selected to suit the place and ground where they are to 

 be driven. When required by the engineer, pile butts shall be banded with iron or steel for 

 driving, and the tips with suitable iron or steel shoes; such shoes will be furnished by the railroad 

 company. 



13. Piles shall be driven to a firm bearing, satisfactory to the engineer, or until five blows 

 of a hammer weighing 3,000 lb., falling 15 feet (or a hammer and fall producing the same mechan- 

 ical effect), are required to cause an average penetration of one-half Q) in. per blow, except in 

 soft bottom, where special instructions will be given. 



14. Batter piles shall be driven to the inclination shown by the plans, and shall require but 

 slight bending before framing. 



15. Butts of all piles in a bent shall be sawed off to one plane and trimmed so as not to 

 leave any horizontal projection outside of the cap. 



1 6. Piles injured in driving, or driven out of place, shall either be pulled out or cut off, 

 and replaced by new piles. 



17. Caps. Caps shall be sized over the piles or posts to a uniform thickness and even bearing 

 on piles or posts. The side with most sap shall be placed downward. 



1 8. Posts. Posts shall be sawed to proper length for their position (vertical or batter), and 

 to an even bearing on cap and sill. 



19. Sills. Sills shall be sized at the bearing of posts to one plane. 



20. Sway Braces. Sway bracing shall be properly framed and securely fastened to piles or 

 posts. When necessary for pile bents, filling pieces shall be used between the braces and the 

 piles on account of the variation in size of piles, and securely fastened and faced to obtain a 

 bearing against all piles. 



21. Longitudinal Braces. Longitudinal X-braces shall be properly framed and securely 

 fastened to piles or posts. 



