FOUNDATIONS 337 



10ft.; and the width of the course next above it is 3ft. (a) 

 What is the maximum bending moment? (b) What size 1 

 beam may be used, assuming an extreme fiber stress of 15,000 

 Ib. persq. in.? 



SOLUTION. (a) The projection at each end qf the bottom 

 course is 



10 3 



- = 3Ht.,or42in. 



There are eighteen I beams in the course; therefore, the load 

 on each is 360,000 -5- 18 = 20,000. Substituting these values in 

 the formula, gives 



4 



(6) Referring to a steel manufacturer's handbook, it is 

 found that the moment of inertia of an 8-in. I beam weighing 

 18 Ib. per ft. of length is 56.9. The resisting moment of the 

 beam is therefore 



therefore, an 8-in. I beam may be used. 



SUPPORTING POWER OF PILES 



Assume that R is the resistance or bearing capacity of a pile; 

 s, the set of pile, .T distance, in inches, that the pile is driven 

 during last blow; w, the weight of pile hammer; and k, the fall, 

 in feet, of hammer during last blow. Then, for drop-hammer 



pile drivers, 



2wh 



R - 5 -. (1) 



For steam-hammer pile drivers, 



Formula 1 is called the Engineering News formula, because 

 it was first published by that engineering journal. It has been 

 very extensively adopted, as experience has proved that it is 

 as reliable as any formula can justifiably claim to be. The 



