Osdind Deflection Chart lor Douglas Fit Plywood

This diagram is designed to show deflection of Dougla-s Fir plywood rough or-sanded, in any- thickness from r/s" to I'i/16" inclustive, uniformly loaded with from 20ft t9. iOCO# per sq. ft. and freely supported on from 12" to 36" centersi the grain of the faces running either parallel or perpendicular to the sPan.

The four ctlrves, marked "Douglas Fir Plywood"- were constructed by plotting the EI value for each thickness, kind and grai.t direct;dn. l|he value of Modulus of Elastiliiy, E, i"as taken at 1,600,000.-.The Moment of Inertia, I, *'ar calculated as that of the plies having grain direction parallel to the span plus one-twentieth that of the plies ira.oitrg grain direction perpendicular to the s-pan' Douglas Fir Piyfi'ood Association standards were used for thickness of plies.

The curves representing "uniform lo. ading"- (w)we.r9 constructed by plotting thi value of. w/EI-against the .EI values. The scale tor w/EI was used for the construction of the chart only and is not shown on the chart' The scale was approximaiely I inch equal to w/100,000 EI on the full size chart.

The straight lines representing the span, 1, were.located by plotting the deflection against the rv/EI, using the formula: d : 5WL^/384F] for simple beam loading' Th9 scales showing deflection for continuous beam loading .1nd in concrete foims were constructed on the basis of doubling the deflection of simple beam to obtain that of contin-uous beam and adding 2O/o to the latter for wet concrete lorm'

As added featirres to the chart, there is a weight curve showing approximate mill weight of Douglas Fir plywood oer 1006 toifo." feet and letters under thickness scale indicate the sizes that are stock items and those that are special and made to order only. The Supplementary Chart is- an enlargement of a portion of the main chart for use when the piywood in question is too thin to permit a close enough reading of the main chart.

The directions for using the diagram are shown on the chart. It is as easy to find the most economical plyw-ood for a given set of ionditions (including permissible deflection) is to find the deflection of the plywood, other factors being known, by direct readings of the. chart without any adjuitments of ioad factor to suit special conditions.

This chart was preparecl by Benjamin Ostlind, staff engineer of California Panel & Veneer Company, P.O. Box N96, Terminal Annex, Los Angeles 54. Copies of the cha.rt will be sent without charge to those who have use for it, if request is sent on their firm's letter head.

Mcrnufccturers

Robert Gray Shingle Co.

Yes, these gnrls oI ours in the vcrrious brqnches of the service cne elficient. We owe them a lot oI prcise lor their work.

And while we are mentioning this word, elficient, may we remind you there,s no mcrtericl being used tor wcr purposes thct has a better claim to this adiective thcn plynrood.