330 Rural Architecture. 



408. Breaking Constants of Transverse Strength of Differ- 

 ent Materials. 



WOODS. 



American White Ash 650 Ibs. 



Black Ash 600 Iba. 



American Yellow Birch 850 Ibs. 



American Hickory ani Bitter n it 800 Ibs. 



Larch and Tamarack 400 Ibs. 



Soft Maple., 750 Ibs. 



American White Pine 450 Ibs 



American Sellow Pine 500 Ibs. 



Poplar 550 Ibs. 



American White Oak 600 Iba. 



American Red Oak 810? Ibs. 







METALS. 



Cast iron 1,500 to 2, 700 Ibs. 



Wrought iron, bends at 1,900 to 2,600 Ib3. 



Brass 8501bs. 



409. To Find the Quiescent Center Breaking Load of Mater- 

 ials having Rectangular Cross-sections, when Placed Hori- 

 zontally and Supported at Both Ends. In placing joists and 

 beams in barns it is important to know the breaking load of 

 the timbers used. This may be determined with the aid of 

 the following rule and the table of constants given in 

 (408) : 



Rule. Multiply the square of the depth in inches by 

 the breadth in inches and this by the breaking constant 

 given in (408) ; divide the result by the clear length in 

 feet and the result is the load in pounds. 



But in the case of long heavy timbers and iron beams 

 one-half of the clear weight of the beam must be deducted 

 because they must always carry their own weight 



Breaking load = 



Square of ") 

 ^depth 

 in inches 



depth C X breadth in inches X Constant 



Length in feet. 



What is the center breaking load of a white pine 2x1 : 

 joist 12 feet long? 



