UNITED STATES DEPARTMEJNTOF AGRICULTURE 
raw BULLETIN*?^ 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 
Page. 
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 
