UNITED STATES DEPARTMENT OF AGRICULTURE 



j\J9*^?Lru 



BULLETIN No. 286 



Contribution from the Forest Service 

 HENRY S. GRAVES, Forester 





Washington, D. C. 



PROFESSIONAL PAPER 



September 27, 1915 



STRENGTH TESTS OF STRUCTURAL TIMBERS TREATED BY 

 COMMERCIAL WOOD-PRESERVING PROCESSES. 



By H. S. Betts and J. A. Newlin, Engineers in Forest Products, Forest Products 



Laboratory. 



CONTENTS. 



Object of the tests '.. 1 



Material tested 2 



Methods of treatment 3 



Method of testing 4 



Results of tests , 6 



Deductions. 14 



Publications relating to strength tests of 



various woods 15 



OBJECT OF THE TESTS. 



This bulletin presents the results of tests made by the Forest 

 Service, in cooperation with the Illinois Central Railway and one 

 eastern and two western wood-preserving companies, to determine 

 how the strength of bridge stringers is affected by commercial creo- 

 sote treatments. To do this, comparison was made between the 

 strength of treated and untreated stringers of the same size and 

 quality. The test timbers were selected by representatives of the 

 Forest Service from stock furnished by the cooperators. The For- 

 est Service requested that the treatments given the timbers by each 

 of the cooperators be that used in its regular commercial practice. 

 A Forest Service representative was present during the treatments 

 and kept a record of the various conditions to which the material 

 was subjected. The woods used were loblolly pine, longleaf pine, 

 and Douglas fir. After treatment the loblolly and longleaf pine were 

 shipped to the Forest Service timber- testing laboratory at Lafayette, 

 Ind., 1 and the Douglas fir to the Forest Service timber-testing sta- 

 tion, Seattle, Wash. 2 



1 Formerly conducted in cooperation with Purdue University. 



2 Conducted in cooperation with the University of Washington. 



Note. — This report is of interest to users of timber where strength is an important consideration. 

 1035°— Bull. 256—15 



