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FEB-13-2003 THU 10;09 RM ENGINEERING TECHNICAL FAX N0, 6054981299 P. 06
<br /> ' Thls r�wciuction is to provfde against buckling of EI� = s�iffness factor compi.steci in ��?Ction
<br /> th� skir�s, i; a�plies to working stre;sses in both 3.4.3 fur deflection (ib•ir�.�'�
<br /> � t��siqn and compression parallel to grain, but not and other symbols aro as ab�ve,
<br /> to ro!ling-shear stresses.
<br /> lf th2 spllce is ir► an area af hic�h mom�ai��t, ,�r�:S !s �'
<br /> 3.a.5 Aclawabfe 4eac1 found to control the destgn, often th� b<;��t thing
<br /> , to do fs to change thE location of the splic�� io an
<br /> t�t�st str�ssed-skin panels with spaced stringers area of lower stress.
<br /> are n�t symmetrical about the neutr�l axis. For
<br /> such "►,nb�la�ceci secfions," it wil! be necessary 3.6 Rolling sfit8�r
<br /> lo fi�ur� tYtie allowabie load in bending as deter-
<br /> rr�inecl f�oth by tho to� skin and by tho bottom.7he 3.6.1 Location ol 4;ritica! Strass
<br /> lisv��r ot theso values wili then govern, unless When the plywc�od skin has Ets face c�rain p:j�,�llel
<br /> there fs r� �plice in an area of high moment. (�t to the ion��iu�inal frarning rnemUers,as f� usually
<br /> tl7er� ia, �n �dditionat check on the s�lice w�tf bo
<br /> ��qi���.�� � the case, the critica! shear plane lies witl�iEn it�e
<br /> plywood. It fs betwcen the Inner face pIy ac,cl the
<br /> F=or unifc�rm ioad:, the general equation M = �Fj-• ad3acent perpendicEala� ply (��t A or E3).
<br /> red�ces to the foflowing: °
<br /> 8� tEI�)
<br /> � wb " �g ��2 E Locatiar► qF Critical Rolling Shear SEre��
<br /> , whe-,r� t—I N� •-�t�- B
<br /> , wb - al�owable load based on bending (psf) �� � ---=�'�-" `���'-�-�ry��-�
<br /> � � - a(lowablo stress (�ither t�nsion or com- �' ��� �
<br /> ression a ' t in ���_... .. �_
<br /> � d�us ed accordancewEth Sea .�.__._.____._....,_._w__ �._._._ A
<br /> 3.5.4� tPSi)
<br /> �,,,
<br /> �=1�-, � stiifness factor computed in Section 3.5.3 � ! B ��'
<br /> � fc�r bendin9 (Ib-in.�} , ,.�,,,..
<br /> , �. . . .,� ;r.� .��' 1
<br /> � c = cii,tance from neutral�xis to extreme ten- ��%"-���� � .�,c�-.��r.-,x.�r�
<br /> ,- --�--i r-----�+
<br /> sion or comprQssion fib�:r (in.) t � c �
<br /> � l = span (tt) �. ....�
<br /> +
<br /> , � � �ppropriate modulus �f elasticity ior the
<br /> �kln beir�g considered (p�i).
<br /> ' When tho (ace grain of the skin Is perpendic��l��r to
<br /> 3.5.6 S�li�;c•�iate l�eslgn tha framing memr�ers, the; critical r��llinc�•�;P�e.ir
<br /> Rasisti�i morr,�nt of tho s lico rnust bo com uted plane lies between thc Itincr f�ce anci tt�r. fr�m�ng
<br /> � P P member (at A or Q )_
<br /> usir�g' lho allawable stresses from PLYWpOD
<br /> ' DESiGPJ S!'�:rf�lCA�'ION Section 5.6. In the case af Tt�e stan�iar�7 eyitation for shear �s �� _ ��<1
<br /> ; ��alic�r pE���tes,ih�is all4wablo stress is applied aver only [�! �
<br /> i��e wic�t.h �f skin actual{y covered by splice pfates. An "unbatariced" stressed-skin panei f��js twa
<br /> The gros; Z fs used for calculating this splice-plate valuns for 4� — one for the ihicker slcin, r�n;i one
<br /> resi,.tin� rr�oment, sirtce full widlh of skins is effec- for the thinner. Since the R of the th(ci.E,r �b:�n is
<br /> tiv��at ihi:�point,due to the stiffening offect of splice almost aiw;�ys larqar than tliat of the Shinner skir�,
<br /> �fata �atid i'�locking. it is gerterally sufficisnt to cornpute rollirtc� s+�e;�r
<br /> onfy for tho tt;ick�er ski�.
<br /> � �"he fntic�w+ng oc{uation i, vafid f�r a splico plate at
<br /> tfte paiirt ofi rn�xlrnurn momeni. 3.6.2 Transfurnticd Saction
<br /> tn calculating C,�, as irt calcul�ting nPc�tr��i rs:�ciw :arrcl
<br /> 8F (Et�) mament of {nertia, it is necess�.ry to usi; �
<br /> . wha�� w�� 48 cL2 E "transforrried :;ec(ion." '1'i�a tschn{c�uF �E:>itS h�ro
<br /> ls differFnf, howevcr. lnstead of treatinc� tl�o ��kin
<br /> w� - �Uawable toad based on splice stress as a homo��neous stieet, it niu,t �ie "t�ralcen
<br /> {psf) down" into fts corr�pc�nent paris. 'fhe i��llowing ��
<br /> F � allowable spllCe•pldte stress tab�e olimfi�:�[rr; tho ca���plic�tion wh�cl� �vc���1c1
<br /> rnultipfied by ttio proportion of the UtherwisE: t'�C InvUlved in calculating iftc t�l ft7r thl;; �-!,'
<br /> width aCtually spliced {psi) transf�rmera sectio�. / !�.
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