ANSI/ASAE EP484.2 JUN1998 (R2008) Diaphragm Design of Metal-Clad, Wood-Frame Rectangular Buildings
S T A N D A R D
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ANSI/ASAE EP484.2 JUN1998 (R2008) Approved August 1998; reaffirmed February 2008 as an American National Standard
Diaphragm Design of Metal-Clad, Wood-Frame Rectangular Buildings Developed by the ASAE Diaphragm Design of Metal-Clad, Post-Frame Rectangular Rectan gular Buildings Subcommittee of the Structures Group; approve approved d by the Str Structu uctures res and Env Enviro ironmen nmentt Div Divisi ision on Sta Standar ndards ds Com Committ mittee; ee; adopted by ASAE September 1989; revised December 1990; reaffirmed December 1994, 1995, 1996, 1997; revised June 1998; approved as an American National Standard August 1998; revised editorially February 2000; reaffirmed February 2003 by ASAE and ANSI; revised editorially August 2003; reaffirmed by ASABE and ANSI February 2008. Keywords: Buildings, Structures, Terminology, Wood-frame
1 Purpose and scope 1.1 This Engineering Engineering Practice is a consensus document document for the analysi analysiss and design of metal-clad wood-frame buildings using roof and ceiling diaphragms, diaphr agms, alone or in combination. The roof (and ceiling ceiling)) diaphragms, endwalls, endwal ls, intermediate shearwalls, shearwalls, and buildi building ng frames are the main structural elements of a structural system used to efficiently resist the design lateral (wind) loads. This Engineering Practice gives acceptable methods for analyzing and designing the elements of the diaphragm system. provisionss of this Engineer Engineering ing Practice Practice are limited limited to the 1.2 The provision analysis analys is of singlesingle-story story buildings of rectang rectangular ular shape.
2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions provisions of this Engineering Engineering Practic Practice. e. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Engineering Practice are encouraged to investigate the possibility of applying the most recent editio edi tions ns of the stan standar dards ds ind indica icated ted belo below. w. Stan Standar dards ds orga organiz nizatio ations ns maintain mainta in regist registers ers of current currently ly valid standards. AF&PA AF&P A (American Forest & Paper Association) Association) (1991), National (1991), National Design Specification ® (NDS ® ) for Wood Construction. (AF&PA. Washington, D.C.) ASAE EP486 DEC97, Post DEC97, Post and Pole Foundation Design ASAE AS AE EP EP558 558 DEC DEC98 98,, Load Load Tes ests ts fo forr Me Metal tal-C -Cla lad, d, Wo Wood od Fr Frame ame Diaphragms
3 Definitions (see figures 1 and 2) 3.1 diaphragm: A structural structural assembly of metal cladding, including including the wood or wood product framing, metal cladding, fasteners and fastening patter pat terns, ns, capa capable ble of tra transf nsferri erring ng inin-plan planee shea shearr for forces ces thr through ough the cladding claddi ng and framing members members.. 3.2 diaphragm design: Desi Design gn of roof (and cei ceiling ling)) diap diaphra hragm(s gm(s), ), sidewallll posts, endwalls, shearwalls, component connect sidewa connections, ions, chord splices, and foundation anchorages, for the purpose of transferring lateral (e.g., wind) loads to the foundation structure. 3.3 Diaphragm dimensions 3.3.1 diaphragm length, d length, d : Length of a building diaphragm in the plane of the diaphragm. 3.3.2 diaphragm span, b h : Horizontal Horizontal span of a building diaphragm having length, d length, d . 3.3.3 3.3 .3 diap diaphra hragm gm wid width, th, s : Dis Distanc tancee betw between een indi individ vidual ual bui buildin ldingg frames; see also 3.10. ASABE STANDARDS 2008
3.3.4 model diaphragm length, b length, b : Length of a model diaphragm diaphragm as measured parallel to the direction of applied load. 3.3.5 model diaphragm width, a : Leng Length th of a mod model el diaphrag diaphragm m as measured perpendicular to the direction of applied load. 3.4 diaphragm fasteners: The various fasteners fasteners and fastener patterns patterns used to connect the several components of the endwalls, shearwalls, and diaphr dia phragms agms.. The These se incl include ude fas fastene teners rs bet between ween clad claddin dingg and pur purlins lins,, between bet ween cla claddin ddingg and endw endwall all gir girts, ts, bet between ween diap diaphra hragm gm fra framing ming members, and between individual sheets of cladding (stitch fasteners). 3.5 Diaphragm shear stiffne stiffness ss 3.5.1 mod 3.5.1 model el dia diaphra phragm gm she shear ar sti stiffne ffness, ss, c : The in-plane in-plane shear stiffness of a model diaphragm. Defined as the slope of the shear loaddeflection curve between zero load and the load corresponding to the diaphragm diaphr agm allowab allowable le shear strength. c p : The in-plane in-plane shear stiffness stiffness of an 3.5.2 in-plane shear stiffn stiffness, ess, c individual roof or ceiling diaphragm. 3.5.3 horizontal shear stiffne stiffness, ss, c c h : The horizontal horizontal shear stiffness stiffness of an ind individ ividual ual roof or cei ceiling ling diaphragm diaphragm.. It is obt obtain ained ed by adj adjusti usting ng diaphragm diaphr agm in-plan in-planee shear stiff stiffness, ness, c c p , for slope. 3.5.4 total horizon horizontal tal diaphragm shear stiffn stiffness, ess, C C h : The horizontal shear stiffness of the roof and ceiling assembly is calculated by summing the hori horizon zontal tal shea shearr stif stiffne fness ss val values ues of ind indivi ividual dual roof and ceil ceiling ing diaphragms. Alternatively, this stiffness can be obtained from full-scale building tests. 3.6 dia diaphra phragm gm shea shearr str strengt ength, h, V a : The allowable allowable design shear strength (see ASAE EP558) of a diaphragm in the plane of the cladding. 3.7 eave load, R: load, R: A concentrated concentrated (point) load, horizontall horizontallyy acting, that is located at the eave of each frame, and results in a horizontal eave displacement identical to that caused by application of the controlling combination of design loads. R R is numerically equal to the horizontal force required to prevent horizontal translation of the eave when the controlling combination of design loads is applied to the frame. ratio of a horizonta horizontall 3.8 endwall and shearwall stiffness, k e : The ratio force applied at the eave to the corresp corresponding onding deflection deflection of an individual unatta una ttached ched wall. A wall is una unattac ttached hed when it is not connected connected to components that lie outside the plane of the wall. 3.9 frame stiffness, k : The ratio ratio of a hor horizo izontal ntal force force applied applied at the eave to the corresponding deflection of the individual unclad post-frames. 3.10 frame spacing spacing,, s : The distance between between frames. In the absence of stiff frames that resist lateral loads, the frame spacing is generally equated to the distance between adjacent trusses (or rafters) or to the model diaphragm width. Frame spacing defines the width (and therefore stiffness properties) of roof/ceiling diaphragm sections. Frame spacing may vary within a building. 3.11 metal cladding: The metal exterior and interior interior coverings, coverings, usually cold-formed aluminum or steel sheet, fastened to the wood framing. 3.12 model diaphragm: A laboratory laboratory tested diaphragm diaphragm or a diaphr diaphragm agm analyzed using a validated structural model that is used to predict the behavior of a building diaphragm. Laboratory tested diaphragms should be sized, constructed, supported and tested in accordance with ASAE EP558. 3.13 post frame: A structural structural building building frame consisting of a wood roof truss or rafters connected to vertical timber columns, or sidewall posts.
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Figure Figure 1 – Definition Definition sketch sketch for terminology terminology
3.14 sidesway restraining force, Q force, Q : The total force force applied to to a frame by the roof/ceiling diaphragm. 3.15 shear transfer: The transfer of the resultant shear forces between indiv ind ivid idual ual sh sheet eetss of cl clad addin ding, g, bet betwe ween en th thee en ends ds of roo roof/ f/ce ceililing ing diaphragms and frames and shearwalls, or between the bottom of the shearwalls and the base of the posts or foundation. 3.16 shearw shearwall: all: An endwall or intermediate intermediate wall designed to transfer shear from the roof/ceiling diaphragm into the foundation structure. 3.17 wood frame: A structural structural building frame consisting consisting of wood or wood-based wood-bas ed materials. Wood trusses over studwalls and post and beam are examples of wood frames.
4 Diaphragm stiffness
When the frame spacing, s spacing, s ,, or roof/ceiling diaphragm construction varies along the length of a building, C h may vary, and the building requires special analysis (see clause 7.3). 4.2.1 Excludi Excluding ng diaphrag diaphragms. ms. Diaphra Diaphragm gm analyses may be simplified simplified by excluding from an analysis any diaphragm that is considerably less stiff than others in the roof/ceiling system. For example, where a ceiling diaphragm diaphr agm is much stiffer than the roof diaphra diaphragm(s), gm(s), the stiffness of the roof diaphragm(s) diaphragm(s) may be excluded from total stiffness stiffness calcula calculations tions (i.e., equation 1). Nonstructural diaphragms that are framed or attached to a structural frame and/or structural diaphragm in a manner that requires the nonstructural nonstructural diaphr diaphragm agm to transla translate te with the structural frame and/or struct str uctural ural diaphragm diaphragm shou should ld not be excl exclude udedd fro from m the anal analysi ysis. s. A nonstructural diaphragm that is relatively stiff is likely to attract more load than it can safely support.
4.1 Gen Genera erall prov provisi isions. ons. Thi Thiss se sect ction ion ou outltline iness pr proce ocedu dure ress fo forr determining the total horizontal shear stiffness, C stiffness, C h , of a width, width, s s ,, of the roof/ceiling assembly. This stiffness is defined as the horizontal load requiredd to cause a unit shift (in a direct require direction ion parallel to the trusses trusses/rafter /rafters) s) of the roof/ceiling assembly over a spacing, s spacing, s (figure (figure 1). This stiffness can be obtained directly from full scale building tests (Gebremedhin et (Gebremedhin et al .,., 1992), validated structural models, or using procedures outlined in clause 4.2.
4.3 Horizontal shear stiffness of an individual diaphragm, c c h , i . The horizontal shear stiffness of an individual diaphragm can be calculated from the diaphragm’s in-plane shear stiffness (equation 2) or from the in-plane in-pla ne stiffness of a model diaphragm (equation (equation 3). Model diaphragms diaphragms used to predict the horizontal stiffness of a building diaphragm shall be functionally equivalent to the building diaphragm. ASAE EP558 gives laboratory test procedures for obtaining model diaphragm shear stiffness.
4.2 Tota otall hori horizon zontal tal shea shearr sti stiffn ffness, ess, C h . The total hor horizo izontal ntal diaphragm shear stiffness, C h , for the fra frame me spa spacing cing,, s , of the roof/ ceiling assembly is defined as:
c h , i c p , i cos2 i
(2)
c h , i G cos i b h , i /s
(3)
where:
n
C h
c i 1
(1)
h , i
c p , i is
where:
2
c h , i is
c h , i
is
n
is
horizontal horizon tal shear shear stiff stiffness ness of of diaphra diaphragm gm i i with a width, s , from clause 4.3, N/mm (lbf/in.); number numb er of ind individ ividual ual roof and ceil ceiling ing diap diaphrag hragms ms in the roof/ceiling assembly (figure 2).
i is G is b h , i is
s
is
horizontal shear horizontal shear stiffness stiffness of diaphra diaphragm gm i i with with width, s width, s ,, and horizontal span b span b h , i , N/mm (lbf/in.); in-plane in-pla ne shear stiffn stiffness ess of diaphragm diaphragm i i with with width, s width, s ,, and horizontal span b span b h , i , N/mm (lbf/in.); slope slo pe from the hori horizon zontal tal of diap diaphra hragm gm i; i; c ( a / b b ), ), effective shear modulus; horizontal horizo ntal span span of diaphra diaphragm gm i i as as measured parallel to trusses/rafters, m (ft); fram fr amee spa spaci cing ng,, m (f (ft) t);;
ANSI ÕASAE EP484.2 JUN1998 „ R2008…
ASABE STANDARDS 2008
Figure 2 – Building cross section showing showing four individual diaphragms
Figure Figure 3 – Definition Definition sketch sketch for frame stiffness, stiffness, k k ASABE STANDARDS 2008
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Figure Figure 4 – Structural Structural analog analog for obtaining obtaining eave load, R
c
is
a
is
b
is
in-plane in-pla ne she shear ar stif stiffne fness ss of the mode modell diaph diaphrag ragm, m, N/m N/mm m (lbf/in.); length len gth of the mode modell dia diaphra phragm gm as mea measure suredd perp perpenendicular to the direction of applied load, m (ft); depth dep th of the mode modell diaph diaphrag ragm m as as measu measured red para paralle llell to to the direction of applied load, m (ft).
5 Frame Frame,, endw endwall, all, and shear shearwall wall stiffness 5.1 Gen General eral pro provisi visions ons.. Fra Frames, mes, end endwall walls, s, and inte interme rmediat diatee shearwalls transfer roof/ceiling loads to the foundation. The amount of load that a frame, endwall, or shearwall attracts is dependent upon its in-plane stiffness. 5.2 Frame stiffness, k stiffness, k . A horizontal horizontal force, P force, P , applied at the eave of a building buildi ng frame will result in a horizon horizontal tal displacement displacement of the eave, (fig. 3). The ratio of the force P force P to to the horizontal displacement is defined as the horizontal frame stiffness, k stiffness, k . Frame stiffn stiffness ess is general generally ly obtained withh a plan wit plane-f e-frame rame str structu uctural ral anal analysi ysiss prog program ram,, e.g. e.g.,, PPSA (Purdue (Purdue Research Resear ch Foundat Foundation, ion, 1993), METCLAD (Gebremedhin, (Gebremedhin, 1987b), and SOLVER (Gebremedhin, 1987a). Frame stiffness is equal to zero when all posts in the frame are pin connected to both the truss and the base/foundation. 5.2.1 Fram Framee sti stiffn ffness ess can be calculate calculatedd usin usingg equa equatio tionn 4 when when:: (1) trusses/rafters are assumed to be pin-connected to the posts, and (2) the base of each post is assumed fixed. n
k 3
E I / H i 1
where: k n E i I i H i
4
i i
3 i
(4)
Endwa wallll and shea shearwa rwallll 5.3 Endwall and shearw shearwall all stiffness, k e . End stiffness, stiff ness, like frame stiffness, stiffness, is defined as the ratio of a horizon horizontal tal force, P , app applie liedd at the eav eavee of the wal wall,l, to the resultin resultingg hori horizon zontal tal eave displacement, . Endw Endwall all and she shearwa arwallll sti stiffn ffness ess can be obt obtaine ainedd directly from full scale building tests (Gebremedhin et al, 1992), validated structural struct ural models, or from tests of functionally equivalent equivalent assemblies (Gebremedhin (Gebrem edhin and Jorgens Jorgensen, en, 1993). ASAE EP558 gives laborat laboratory ory test procedures that can be used to determine the stiffness of functionally equivalent walls.
6 Eave loads diaphra hragm gm anal analysi ysis, s, bui buildi lding ng load loadss are 6.1 Gener General al provisi provisions. ons. In diap replaced by an equivalent set of horizontally acting, concentrated (ie, point) loads. These loads are located at the eave of each frame, endwall, and shearwall (ie, they are spaced a distance, s distance, s , apart), and therefore are referred to as eave as eave loads . Eave loads and applied building loads are equivalent when they horizontally displace the eave an equal amount. 6.2 Eave loads, R loads, R , by plane-frame structural analysis. A horizontal horizontal restraint (vertical roller) is placed at the eave line as shown in figure 4 and the structural analog is analyzed with all externa externall loads in place. The horizontal reaction at the vertical roller support is numerically equal to the eave load, R load, R . Note that the vertical roller should always be placed at the same location that horizontal load P load P was was placed when determining frame stiffness (clause 5.2). 6.3 Eave load calculation using frame base fixity factors. Eave loads resulting from wind loads can be estimated using equation 5. R s h wr q wr h lr q lr h ww f w q ww h lw f l q lw
is
is is is is
frame stiffn stiffness, ess, N/mm (lbf/in. (lbf/in.); ); number numb er of post postss in the post post-fr -frame ame (no (normal rmally ly 2); 2 modulus modu lus of ela elastic sticity ity of post post i i ,, N/mm (lbf/in.2); 4
4
moment of inertia inertia of post post i i ,, mm (in. );
(5)
where: R s
is is
hwf
is is
distanc dist ancee from from base base to pin pin conne connecti ction on of of post post i i , mm (in.).
eave lo eave load ad,, N (l (lb) b);; framee spacin fram spacingg for inte interior rior fra frames mes and and shear shearwall walls, s, m (ft); one-hal one -halff the frame spacing spacing for for endwalls, endwalls, m (ft); (ft); windw win dward ard roo rooff heigh height, t, m ft); ft);
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h lr h ww h lw q wr q lr q ww q lw f w f l
is is is is is is is is is
intermediate shearwalls and with constant values of: diaphragm stiffness, C h ; frame stiffness, k k ;; endwall stiffness, k e ; and eave load, R . Input paramet par ameters ers for tab tables les 1 and 2 inc includ lude: e: num number ber of bui buildi lding ng fra frames mes (endwalls are counted as frames); ratio of diaphragm to frame stiffness, C h / k ; ; and ratio of endwall to frame stiffness, k stiffness, k e / k . When establishing establishing the values in tables 1 and 2, it was assumed that the eave load, R , for the endwalls was one-half the load applied to each interior frame.
leeward leewa rd roo rooff heig height ht,, m (ft (ft); ); wind wi ndwar wardd wall wall heig height ht,, m (ft); (ft); leewa le eward rd wall wall he heig ight, ht, m (ft); (ft); design desi gn wind windwar wardd roof roof pres pressur sure, e, N/m N/m2 (lbf/ft2); design des ign lee leeward ward roof pre pressur ssure, e, N/m2 (lbf/ft2); design des ign wind windward ward wal walll pressur pressure, e, N/m N/m2 (lbf/ft2); design desi gn leew leeward ard wall pre pressur ssure, e, N/m2 (lbf/ft2); windwar win dwardd post fixi fixity ty fac factor tor;; leeward lee ward post fixi fixity ty fac factor tor..
Inward acti Inward acting ng win windd pres pressur sures es have pos positiv itivee sig signs, ns, outw outward ard acti acting ng pressures are negative (see figure 4). Equation 5 shall be modified for cases where pressures are not uniform over a wall or roof surface. In buildings buildi ngs with variabl variablee frame spacings, set s set s equal equal to the average of the frame spacings on each side of the eave load. The frame base fixity factor(s), f factor(s), f w and and f f l , will equal 3/8 for substantial fixity at the groundline. The frame base fixity factor(s) will equal 1/2 for all other cases (see ASAE EP486). For symmetrical base restraint and frame geometry, equation 5 reduces to: R s h r q wr q lr h w f q ww q lw
(6)
where: h r h w f
is is is
roof he roof heigh ight, t, m (ft (ft); ); wallll hei wa heigh ght, t, m (ft (ft); ); leeward lee ward and win windwar dwardd post post base base fixi fixity ty fact factor or..
6.4 Maximum total diaphragm shear, V h . A conservative conservative value value of maximum total diaphragm shear, V shear, V h , due to wind load may be calculated by multiplying the equations in clause 6.3 by one-half the building length instead of the frame spacing, s spacing, s . 1 V h R L/s 2
(7)
where: V h R L
ablee 1 contains contains shear shear 7.2.1 Maximum total diaphragm shear, V shear, V h . Tabl force modifiers or mS or mS values. values. Multiply the appropriate mS appropriate mS value value by eave load R load R from from clause 6.2 or 6.3 to obtain maximum total diaphragm shear. This value is the total shear, V shear, V h , in the endwalls and in the diaphragm sectio sec tions ns adja adjacen centt to the endwalls. endwalls. This value will be less than the conservative estimate calculated using the equations in clause 6.4. 7.2.2 Sidesway restrai restraining ning force, Q . Tabl ablee 2 con contai tains ns sid sideswa eswayy restraining force factors or mD or mD values. values. Multiply the appropriate mD appropriate mD value value by eave load R load R from from clause 6.2 or 6.3 to obtain the sidesway restraining force, Q force, Q . The sidesway restraining force is the total force applied to the critic cri tical al fram framee by the roo roof/ce f/ceili iling ng asse assembl mbly. y. The cri critica ticall fra frame me in a symmetric building without interior shearwalls is always the one closest to the building midlength. 7.3 Load distri distribution— bution—detaile detailed d analyse analyses. s. The for force ce dis distri tributi bution on method (Anderson et al, 1989) and computer program DAFI (Bohnhoff, 1992) are two methods that can be used to determine load distribution in a building in which the stiffness of individual frames differ, endwalls differ in stiffness, intermediate shearwalls are present, and eave loads and diap di aphr hragm agm st stififfn fness ess val value uess va vary ry fr from om fr fram amee to fr fram ame. e. The for force ce distri dis tributi bution on meth method od is an ite iterati rative ve meth method od for hand hand-ca -calcul lculati ating ng loa loadd distri dis tributi bution on that is pro procedu cedural rally ly ide identi ntical cal to the clas classic sical al met method hod of moment distribution. Computer program DAFI automatically formulates and solves a set of equations to obtain eave deflections. Both methods output individual frame, shearwall, endwall, and diaphra diaphragm gm forces. 7.4 InIn-plan planee shea shearr for force ce in ind individ ividual ual diap diaphrag hragms, ms, V p , i . The maximum in-plane in-plane shear force in an individual diaphragm, V V p , i , is given given as V p , i c h , i / C h V h / cos i
is is is
maximum total maximum total diaph diaphrag ragm m shear, shear, N (lbf) (lbf);; eave ea ve load load give givenn by equa equatition on 5, N (lb (lbf) f);; builildin bu dingg leng length th,, m (f (ft) t)..
where: V p , i is c h , i is
For sym symmetr metrica icall base res restrai traint nt and fram framee geom geometr etryy, the max maximum imum diaphragm shear is conservatively estimated by: 1 V h R L/s 2
(9)
(8)
where:
maximum in-plan in-planee shear force force in diaphrag diaphragm m i i ,, N (lbf); horizontal horizo ntal shear shear stiffness stiffness of diaphra diaphragm gm i i with with spacing s from clause 4.3, N/mm (lbf/in.); total horizontal horizontal diaphrag diaphragm m shear stiffness stiffness,, C h , for a spacing s of the roof/ceiling assembly, N/mm (lbf/in.);
C h
is
V h
is
maximu max imum m total diaph diaphrag ragm m shear from from cla clause use 6.4 6.4,, 7.2 7.2.1, .1,
i
is
or 7.3, N (lbf); slope from the hori slope horizon zontal tal of diap diaphra hragm gm i i .
R is R is eave load given by equation 6, N (lbf).
7 Load distribution 7.1 Genera Generall provisi provisions. ons. The distribu distribution tion of hor horizo izontal ntal loads to the vari va riou ouss fr fram ames, es, wal walls ls,, an andd dia diaph phrag ragms ms can be det deter ermi mined ned af after ter diaphragm, frame, shearwall, and endwall stiffness values have been calculated and eave loads have been established. Use the procedure outlined in clause 7.2 to determine load distribution in a building without intermediate shearwalls and with constant values of: diaphragm stiffness, C h ; frame stiffness, k stiffness, k ;; endwall stiffness, k stiffness, k e ; and eave load, R load, R . When one or more of these variables is not fixed, use methods referenced in clause 7.3. If the number of individual roof and ceiling diaphragms in the roof/ceiling assembly exceeds one, use the equation in clause 7.4 to determine the distribution of roof shear, V shear, V h , to the indivi individual dual diaphragms, diaphragms, and use the equation in clause 7.5 to determine the horizontal restraining force associated with each diaphragm. 7.2 Load dis distrib tributi ution on usi using ng tab tables. les. Tabl ables es 1 an andd 2 ar aree used to determine the maximum total diaphragm shear V h , and the maximum sidesway side sway res restra trainin iningg for force, ce, Q , res respe pect ctive ively ly,, in bu build ildin ings gs wi witho thout ut ASABE STANDARDS 2008
7.5 Sidesw Sidesway ay restrai restraining ning force— force—individ individual ual diaphra diaphragms, gms, Q i . The total tot al sid sideswa eswayy for force ce appl applied ied to the critical critical fram framee by an ind indivi ividual dual diaphragm is given as Q i c h , i / C h Q
(10)
where: Q i c h , i
is is
C h
is
Q
is
sidesway restraining sidesway restraining force for diaphragm diaphragm i i ,, N (lbf); horizontal horizo ntal shear stiffness stiffness of diaphragm diaphragm i i with with spacing s from clause 4.3, N/mm (lbf/in.); total horizontal horizontal diaphragm diaphragm shear stiffness, stiffness, C C h , for a spacing s of the roof/ceiling assembly, N/mm (lbf/in.); sidesway sidesw ay restraining restraining force for the roof/ceiling roof/ceiling assembly assembly from clause 7.2.2 or 7.3, N/mm (lbf/in.).
8 Building diaphragm and shearwall design 8.1 General General.. All building components components shall be checked checked to ensure that actual loads do not exceed allowable design values.
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