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West Coast Issue New "Douglas Fir Use Book"

A new and practical book for the use of architects ancl engineers in designing with structural Douglas fir has just been published by the West Coast Lumbermenls Association and is now available for distribution. Its title is "Douglas Fir Use Book". The book contains design tables and supporting .techni,cal data which enable a designer to figure loads and specify sizes of Douglas fir for a structure easily and with assurance. The price of the book is $1.00 per copy. It may be obtained from the West Coast Lumbermen's Association, 364 StuartBuilding, Seattle, Washington.

The new book supersedes'the "Structural Timber Handbook on Pacific Coast Woods", published by the Association in 1916, and which has been out of print for a number of years. It ,contains a number of valttable features not in the old handbook.

Since publication of the 1916 edition of the "Structural Timber Handbook", which incorpora,ted grades of No. I Common, Selected Common and Selected Structural for structural purposes, a great deal of progress has been macle in the development of structural grades. In 1923 the United States Departmen't of Agriculture issued Circular 295 of. theUnited States Forest Products Laboratory, entitled "Basic Grading Rules and Working Stresses for Structural Timbers". This circular which was published at the time the American Lumber Standards were being formulatetl was adopted as the basis for structural grades of the beforenrentioned lumber standards. It was carefully studied arrtl worked over by the American Railway Engineering Association and the American Society for Testing Materials, in cooperation with the Forest Products Laboratory ancl cotunrittees of the standardization project.

Out of this rvork came amplifica'tions of the basic systerrr established in Cir,cular 295 and the detailed provisions necessary in c,omplete sets of structural grades for the manufacture, grading and use of structural timbers, a record of the laws of structural grading, the factors ne€essar)' of in,clusion in them, notes useful to a designer in using the grading rules and working stresses recommencled for them, and a detailed analysis of the determination and caleulation of working stresses from the basic values for the various species. The results and findrngs of these bodies are dealt with in the nerv "IJse Book" under the sections entitled "Basic Laws for Structural Grades", "Determination of Working Stresses for Structural Grades", a table showing the basic working stresses for green clear wood iu structural sizes to which grade-strength ratios can be applied to determine rvorking stresses for grades containing defects; "Calculation of Working Stresses for Structural Grades", "Grade-Ratio Values of Structural Grade Examples of American Lumber Standards", "Working Stresses for Structural Grade Examples of American Lumber Standards", and "Notes on Working Stresses for Structural Grades Complying with American Lumber Standards."

, The Douglas fir standard structural grades presented in the "tlse Book" have been reproduced from the Number Nine rules of the West Coast Lumbermen's Association, the latest rules for grading West Coast woods and, therefore, .conform to the "Basic Provisions of American Lumber Standards for Structural Material". The working stresses shown are based on the recommendations of the United States Forest Products Laboratory, all of which have been developed since the old handbook was published.

The dressed sizes shown in the design tables of the "IJse Book" conform to American Lumber Standards. During the time prior to the inception of American Lumber Standards, the West Coast standards for West Coast material were in effect, being /g" off for dimension 2" thick and tl" oft for material 3" and thicker. In widths, the West Coast standards were %" ofr up to 6" and f" off for material 8" and u'ider. The finished sizes shorvn in the old handbook were based on West Coast standards. Norv, since Ameri'can Lumber Standards have been adopted, %" ofr is allorved for material 2" to (' thick, and in widths, /s" off up to 7" and f" over 8". In the case of Beams and Stringers 5"x8" and larger and Posts and Timbers 6"x6" and larger, tl" oft each way is allowed for dressing conforming to American Lumber Standards.

Other neu' sections are "Stresses in Compression or Tension Only"; the offering of a recently developed formula to determine compression stresses on surfaces inclined to the fibers; "Grading of Timber for Preservative Treatment", Working Stresses for Treated Douglas Fir", "Com-

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parison of Cost and Utility Values" and'a cross reference of equivalent grades of Douglas fir of American Lumber Standards, American Society for Testing Materials, American Railway Engineering Association and West Coast Lumbermen's Association.

Another section which will be of help to specifiers and designers is that showing recommended uses of standar<l grades of the West Coast Lumbermen's Association for Douglas fir, West Coast Hemlock, Western red cedar and Sitka spruce, and the supplementary section of explanatory notes.

Other new sections show the working stresses for the West Coast Lumbermen's Association standard structural grades of Douglas fir cross-referenced with those of the American lumber Standards and notes pertaining to them.

In the design tables for Joists and Beams appearing in the !'{Jse Book", the loads given are for uniform l<lading and include the weight of the memlter, rvhereas in the old book, only the superimposed load ll'as shown. In order to facilitate the use of the tables for other loading, however, loads are extended to the spans next beyond those giving shear stresses fifty per cent greater than the grade values, and to deflections trventy-five per cent greater than at one thirty-second inch per foot of span, so that by using the proportional relations between load, span, shear and deflection for various kinds of loading, loads can be determined from the formulae offered for these methods of loading. In the case of the old book, the shear stresses and deflections were confined to their actual limit. Also. in the old handbook, loads given were based on abstract values whereas in the new tables they are based on grade values. In the new "IJse Book", besides conversion factors for rough materi.al, conversion factors appear in the design tables for material surfaced two sides and also for material surfa€ed two edges whereas in the old book, conversion factors for only rough material were shown.

Two column tables were used in the old handbook. one based on a formula adopted by the American Railway E,ngineering Association and theother based on a formula established by the Fores't Service. A few years ago, the Forest Products Latioratory developed a new column formula which has been generally adopted as a definite larv governing the strength for timbers used as columns, and upon which the tables for posts and struts in the new book have been based.

The old handbook included a table of maximum spans and maximum deflections for laminated floors uniformly loaded. In the new handbook the order was reversed, and there is shown instead, a table of loads for plank and laminated floorsuniformly loaded, and which includes a column showing the load required to extend the floor to a deflection limit of l/16" per foot of span. Together with the table for plank and laminated floors is a section explaining its application.

The "Douglas Fir Use Book" was prepared by the technical staff of the West Coast Lumbermen's Association under the direction of Chester J. Hogue, in charge of the Association's Trade Extension and Field Service Department. Mr. Hogue is a member of the American Society of Civil Engineeri and a graduate of Massachusetts Instiiute of Technology. For a number of years he was practicing architect and engineer. Mr. Hogue is recognized as one of the outstanding n'ood nse authorities in the United States.

The design tables were prepared by or under the direction of Professor E. S. Harrar, College of Forestry, University of Washington, Seattle, Washington.

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