SHOETLEAF PINE : IMPORTANCE AND MANAGEMENT. 



9 



purpose. Other woods much used for structural timbers are Doug- 

 las fir, western hemlock, tamarack, Norway pine, loblolly pine, and 

 western larch. Comparative tests of these in both a green and an 

 air-seasoned condition, and for both structural sizes and small, clear, 

 straight -grained pieces, 1 give shortleaf a relatively high place in all 

 strength values, including bending, compression, and shearing. The 

 values found in the various tests are shown in Table 6 : 



Table 6. — Average strength values of shortleaf pine, air seasoned, and green 

 structural timbers ivith ordinary defects, and small, clear specimens cut from 

 them. 1 



Condition and 

 size. 



Rings 

 per 

 inch. 



Hori- 

 zontal 

 shear 

 per 

 sq. in. 



Bending. 



Fiber 

 stress at 

 elastic 

 limit 

 per 

 sq. in. 



Modu- 

 lus of 

 rupture 



per 

 sq. in. 



Medu- 

 lusof 

 elas- 

 ticity 

 per 

 sq. in. 



Compression parallel to 

 grain. 



Crushing 

 strength 

 at elastic 

 limit per 

 sq. in. 



Crushing 

 strength 

 at maxi- 

 mum 

 load per 

 sq. in. 



Modu- 

 lus of 

 elas- 

 ticity 

 per 

 sq. in. 



Com- 

 pression 

 perpen- 

 dicular 

 to grain. 



Crushing 

 strength 

 at elastic 

 limit per 

 sq. in. 



Shear. 



Shearing 

 strength 



per 

 sq. in. 



Air seasoned struc- 

 tural sizes 



Small specimens . . 



Ratio 



Green structural 



sizes 



Small specimens . . 

 Ratio 



Pounds. 

 364 



12.1 



332 



Pounds. 



4,675 



7,780 



60 



3,237 

 4,350 



74 



Pounds. 



6, 573 



12, 120 



54 



5,548 



7,710 



72 



IfiOOlbs, 

 1,726 

 1,792 



1,473 



1,395 



106 



Pounds. 

 4,070 



2,460 



Pounds. 



6,030 



6,380 



95 



3,435 

 3,570 



IfiOOlbs. 

 1,961 



1,548 



Pounds. 

 796 

 926 



351 

 400 



Pounds. 



1,135 



704 



" Tables 1, 2, and 10 to 15, Forest Service Bulletin 108, "Tests of Structural Timbers." 



Though true longleaf pine averages heavier, stronger, and tougher, 

 many pieces of shortleaf have greater density, strength, and tough- 

 ness than the average longleaf pine. Also some longleaf pine lacks 

 density and is weaker than the average of the other species, the den- 

 sity or dry weight of the wood being a much better criterion of the 

 strength than the species. 



USES. 2 



The general uses of shortleaf pine are as varied as those of long- 

 leaf and the two go together without preference or prejudice for many 

 purposes. For heavy building and structural work, however, where 

 the architect desires timber to sustain pressure and withstand shocks, 

 longleaf is usually preferred. Because of a high degree of strength 

 and elasticity, the heavier classes of shortleaf 3 are being substituted 

 for longleaf and are giving practically the same service. This recent 



1 Conducted by iinr Fores! Products Laboratory, Madison, Wis. 



d in pari upon State cooperative wood manufacturing studios and Korcst Service 

 Bulletin 99, " Uses of the Commercial Woods of the United states: Pines," pages 17 to 20. 



■Timber having the same density as longleaf. 



6 197°— Bull. .'{08—15 2 



