44 



"breaking unit stresses recommended by your committee and the following factors 

 of safety, viz: 



Tension with and across grain 10 



Compression with grain 5 



Compression across grain 4 



Transverse rupture, extreme fiber stress 6 



Transverse rupture, modulus of elasticity 2 



Shearing with and cross grain 4 



In conclusion, your committee desires to emphasize the importance and great value 

 to the railroad companies of the country of the experimental work on the strength 

 of American timbers being conducted by the Forestry Division of the United States 

 Department of Agriculture, and to suggest that the American Association of Railway 

 Superintendents of Bridges and Buildings indorse this view by official action and 

 lend its aid in every way possible to encourage the vigorous continuance of-this 

 series of Government tests, which bids fair to become the most reliable and useful 

 work mi the subject of strength of American timbers ever undertaken. With addi- 

 tional and reliable information on this subject far-reaching economies in the design- 

 ing of timber structures can be introduced, resulting not only in a great pecuniary 

 saving to the railroad companies, but also offering a partial check to the enormous 

 consumption of timber and the gradual diminution of our structural timber supply. 



Walter G. Berg, Chairman. 

 J. H. Cummin. 



JOHX FOREMAX. 



H. L. Fry. 



Average safe allowable working unit stresses in pounds per squart inch recommended by 

 the committei on "strength of bridge and trestle timbers," American Association of Rail- 

 way Superintendents of Bridges and Buildings, fifth annual convention, New Orleans, 

 October, 1895. 



Kind of timber. 



Factor of safety 



White oak 



White pine 



Southern, longleaf, or Georgia 

 yellow pine 



Douglas, Oregon, and Wash- 

 ington fir or pine: 



Yellow fir 



Red fir 



Northern or shortleai yellow 

 pine 



Red pine 



Norway pine 



Canadian (Ottawa) white pine. 



Canadian (Ontario) red pine... 



Spruce and Eastern fir 



Hemlock 



Cypress 



( leuar 



Chestnut 



< talifornia redwood 



California spruce 



Tension. 



Compression. 



With grain. 



With 



grain. 



10 



Across 



grain 



10 



1,000 

 700 



1,200 



1,200 

 1,000 



900 

 900 



800 

 1,000 

 1,000 

 800 

 600 

 600 

 800 

 900 

 700 



200 

 50 



60 



50 



50 



50 



End 

 bear- 

 ing. 



1,400 

 1,100 



1,600 



1, 600 



Col- 

 umns 

 under 



lodiam- 

 eters. 



1.200 

 1,200 

 1, 200 



1,200 



1, 200 

 1, 200 



900 

 700 



1,000 



1.200 



800 



800 



800 



1,000 



1,000 



800 



800 



son 



800 



1,000 



800 



Slid 



Across 



grain. 



Transverse rup- 

 ture. 



Ex- 

 treme 

 fiber 

 stress. 



Modulus 



of elas- 

 ticity. 



500 1,000 

 200 700 



350 



300 



250 

 200 



1,100 

 800 



1,000 



Mill 



550,000 

 500, 000 



1,200 ; 850,000 



700, 000 



Shearing. 



With Across 

 grain, grain. 



i;i in. i ii ii i 

 600,000 



200 

 100 



1,000 

 500 



150 1,250 



150 



100 



1.000 



100 

 100 

 100 

 100 



750 



600 



150 

 100 



400 

 400 



