modelguidelinesengineeredpanelizedwalls appendices

7/28/2019 ModelGuidelinesEngineeredPanelizedWalls Appendices

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Evaluation of site conditions and local building code regulations

Selection of a design approach

Prescriptive Design Engineered Design Alternate Means and Me

Based on site conditions,building classification, and

building configuration, selectstructural wall parameters fromthe local prescriptive building

code provisions.

Required wall parametersinclude, but are not limited to,

framing member types andsizes, sheathing types and sizes,framing and sheathing fasteningschedules, fastener types,

anchorage specificationincluding anchor types and

spacings.

Panelized walls are required tobe inspected on site by a localbuilding official in accordancewith Section 3.4.3.

Determine gravity and lateral loads

according to Section 4.3.

Design walls, including member sizing andlateral wall analysis, to resist the determinedloads in accordance with Section 4.4.1.

Use design methods and wall configurationsspecified in the governing building code or

Appendices B, C, and D of this Guide.

Based on design results, develop a set ofpanel shop drawings that include information

specified in Section 2.5.1.

Panels are required to be inspected in the

factory in accordance with Section 3.3.2.

Panelized walls are required to be inspected

on site by a local building official inaccordance with Section 3.4.3.

Develop a panel configuratio

design criteria.

Validate the proposed config

accordance with Section 4.4.2

Design walls using the propo

accordance with Section 4.4.

Based on design results, deve

shop drawings that include in

in Section 2.5.1.

Panels are required to be inspin accordance with Section 3

Panels with innovative confirequired to be a subject to a t

assurance program (Section 4

Panelized walls are required

site by a local building officiwith Section 3.4.3.

Based on design results, developa set of panel shop drawings that

include information specified inSection 2.5.2.

Determine gravity and lateral

Section 4.3.

Wall Panel Design

A-1


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APPENDIX B

SUPPLEMENTAL DESIGN DATA

B1. General This appendix provides supplemental technical data for wall design in accordance

with this document, but which is not provided in the reference documents listed in Section 1.6 or

in the model building codes. The scope of this appendix covers shear wall resistance values anddesign information for wall bending members. The objective of this appendix is not to

incorporate all the information necessary to complete design of a wall, instead, it is intended to

supplement the material design specifications as set forth by the governing building code orspecified in Section 1.6 of this Guide.

B2. Shear Wall Resistance Data Characteristic shear wall values are presented in Tables B1and B3 for light-frame wood and cold-formed steel, respectively. To compare with design loads,

characteristic shear wall values should be modified as specified in Section 4.4.3 of this Guide.

The characteristic shear wall values reported in this section were measured experimentally bytesting of full-scale shear walls or obtained analytically by interpolating or extrapolating test data

using the connection yield theory. The test shear walls were fully restrained against uplift so thatthe failure mode was predominantly governed by degradation of sheathing fasteners rather than

restraint connections of the shear wall assembly. Therefore, to use these values the designershould detail the shear walls to resist the uplift forces or should reduce the wall resistance to

account for partial restraint (see Appendix D).

The capacity of shear walls sheathed on opposite faces with the same sheathing materials using

identical fastening methods shall be permitted to be calculated as a sum of capacities of each

side. The capacity of shear walls sheathed on opposite faces with the same sheathing materialsusing different fastening methods shall be permitted to be calculated as a capacity of the stronger

face or twice the capacity of the weaker face whichever is greater. For wind design, the capacityof shear walls sheathed with structural wood panels on one side and gypsum wallboard panels on

the other side shall be permitted to be calculated as a sum of capacities of both sides. If the

resistance of gypsum wallboard panels is used in the structural analysis, the gypsum wallboardinstallation method shall be specified on the shop drawings and the walls shall be inspected upon

gypsum wallboard installation for conformance with the wall design.

B2.1 Wood Shear Walls The characteristic shear wall values (Table B1) are adopted fromNEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA Publication 273, BSSC

1997). These values are allowed to be modified using the nail size adjustment factors (Table B2)

to determine the unit shear resistance of wood shear walls assembled with pneumatic or boxnails. The values are based on wall segments that are fully restrained from overturning.

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TABLE B1

CHARACTERISTIC SHEAR VALUES FOR WALLS FRAMED WITH

DOUGLAS-FIR-LARCH OR SOUTHERN PINE1, 2, 3, 4, 5, 6, 7, 8, 9

Characteristic shear wall values, lb/ft

Nail Spacing at Panel Edges (inches)10

Panel Grade

Minimum

Nominal

Panel

Thickness(inches)

Minimum

Nail

Penetration

in Framing(inches)

Nail Size11

(Common)

6 4 3

12

2

12

5/16 1 1/4 6d 700 1,010 1,130 1,200

3/8 750 1,080 1,220 1,540

7/16 815 1,220 1,340 1,590

15/32

1 1/2 8d

880 1,380 1,550 1,620

Structural I

15/32 1 5/8 10d 1,130 1,500 1,700 2,000

5/16 650 700 900 1,200

3/81 1/4 6d

680 800 1,000 1,350

3/8 700 880 1,200 1,500

7/16 720 900 1,300 1,560

15/32

1 1/2 8d

820 1,040 1,420 1,600

15/32 900 1,400 1,500 1,900

C-D, C-C Sheathing,

plywood panel

siding and othergrades covered in

US DOC PS1 and

PS2.

19/32

1 5/8 10d

1,000 1,500 1,620 1,9501Panels applied vertically or horizontally directly to framing and blocked at all edges.2Nominal framing thickness shall be a minimum of 2 inches. Studs are spaced a maximum of 24 inches on center.3Values extrapolated from cyclic testing.4Values can be adjusted for intermediate nail sizes or nail penetration less than specified using the connection yield theory.5Use 80 percent of values for yield strength.6For framing member species other than Douglas-Fir-Larch or Southern Pine the values shall be reduced using the Specific Gravity Adjustment

Factor = [1-(0.5-SG)] 1, where SG is specific gravity of lumber species.7Minimum nail edge distance of 3/8 inch shall be provided along panel edges.8Maximum allowable aspect ratio of a shear wall segment is 3.5:1. Resistance of wall segments with aspect ratios between 3.5:1 and 2:1 shall be

adjusted using the following reduction factor: 0


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B2.2 Light-Gage Steel Shear Walls - The characteristic shear wall values (Table B3) are

adopted fromNEHRP Recommended Provisions for Seismic Regulations for New Buildings andOther Structures (FEMA Publication 368, BSSC 2001). Cold-formed steel walls are assembled

using self-drilling self-tapping screws and sheathed using structural wood-based panels.

TABLE B3

CHARACTERISTIC SHEAR VALUES FOR WALLS

FRAMED WITH COLD-FORMED STEEL 1, 2, 3, 4, 5, 6, 7, 8Characteristic shear wall values, lb/ft

Nail Spacing at Panel Edges (inches)Panel Sheathing Type

6 4 3 2

15/32-inch-thick Structural I plywood 780 990 1,465 1,625

7/16-inch-thick oriented strand board 700 915 1,275 1,7001Panels applied vertically or horizontally directly to framing and blocked at all edges.2Studs shall be a minimum 1 5/8 inch by 3 1/2 inch C-section with 3/8 inch return lip. The studs shall be capped on both ends using

track section measured minimum 1 1/4 inch by 3 1/2 inch.3Wall studs and track shall be made of a minimum 33 mil (20 gage) steel with a minimum galvanized coating of G 60 in accordancewith ASTM A 653 or equivalent.4Framing screws shall be minimum 5/8-inch-long No. 8 with wafer head. Sheathing screws shall be a minimum 1-inch-long No. 8

with bugle head with a minimum head diameter of 0.292 inches.5Minimum fastener edge distance of 3/8 inch shall be provided along panel edges.6Studs are spaced a maximum of 24 inches on center.7Maximum fastener spacing in the panel field is 12 inches.8Screws extend through the steel member a minimum of three exposed threads.

B3. Repetitive Member Factors and Composite Action Factors The repetitive member

factors and composite action factors set forth in this section are only applicable to the design ofbending members consisting of an assembly of dimension lumber as specified.

B3.1 Repetitive Member Factors When three or more parallel solid-sawn wood members are

spaced a maximum of 24 inches on center and connected with structural sheathing or other load

distributing elements, they comprise a structural system with more bending capacity than thesum of the single members acting individually. Because the nominal design values tabulated in

the NDS are based on performance of individual members, an increase in allowable stress is

permitted to account for load redistribution between repetitive members. System assembly testssupport the range of repetitive member factors shown in Table B4 for the specified design

applications. With the exception of the 1.15 repetitive member factor, the NDS does not

currently recognize the values in Table B4. Therefore, the values in Table B4 are provided foruse by the designer as an alternative method based on various sources of technical information

including standards, code recognized guidelines, and research studies. For more information on

repetitive member effects and composite action, consult the references provided in Section B3.4.

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TABLE B4

REPETITIVE MEMBER FACTORS FOR USE WITH DIMENSION LUMBER1, 2, 3

ApplicationRecommended Cr

Value

References

(Section 1.6 or D3.3)

Two adjacent members sharing load4 1.1 to 1.2AF&PA,1996

HUD, 1999

Three adjacent members sharing load

4

1.2 to 1.3 ASAE, 1997Four or more adjacent members sharing load4 1.3 to 1.4 ASAE, 1997

Three or more members spaced not more than 24 inches oncenter with suitable surfacing to distribute loads to adjacent

members (i.e., decking, panels, boards, etc.)5

1.15 NDS, 1997

Wall framing (studs) of three or more members spaced notmore than 16 inches on center with minimum 3/8-inch-thick

wood structural panel sheathing on one side and 1/2-inch thick

gypsum board on the other side subjected to wind pressure 6

1.52x4 or smaller1.352x6

1.252x8

1.22x10

AF&PA, 1996

SBCCI, 1999Polensek, 1975

Source: Residential Structural Design Guide, U.S. Department of Housing and Urban Development,Washington D.C., 2000.1 Factors shall be used to determine adjusted allowable bending stress.2NDS recommends a Cr value of 1.15 only as shown in the table. The other values in the table were obtained from various codes, standards,

and research reports referenced in Section B3.4 of this Appendix.3

Dimension lumber bending members are to be parallel in orientation to each other, continuous (i.e., not spliced), and of the same species,grade, and size. The applicable sizes of dimension lumber range from 2x4 to 2x12.4Cr values are given as a range and are applicable to built-up columns and beams formed of continuous members with the strong-axis of all

members oriented identically. In general, a larger value of Crshould be used for dimension lumber materials that have a greater variability in

strength (i.e., the more variability in strength of individual members the greater the benefit realized in forming a repetitive member system

relative to the individual member strength). For example, a two-ply built-up member of No. 2 grade (visually graded) dimension lumber mayqualify for use of a Cr value of 1.2 whereas a two-ply member of No. 1 dense mechanically graded lumber may qualify for a C r value of 1.1.

The individual members should be adequately attached to one another such that the individual members act as a unit (i.e., all members

deflect equally) in resisting the bending load.5Refer to the NDS and the NDS Commentary for additional guidance on the use of the 1.15 repetitive member factor.6The Cr values are based on wood structural panel attachment to wall framing using 8d common nails spaced at 12 inches on center. For

fasteners of a smaller diameter, multiply the C r values by the ratio of the nail diameter to that of an 8d common nail (0.131 inch diameter).

The reduction factor applied to Cr need not be less than 0.75 and the resulting value of C r should not be adjusted to less than 1.15. Doubling

the nailing (i.e., decreasing the fastener spacing by one-half) can increase the Crvalue by 16 percent.

B3.2 Header System Effect Factors The system effect factors for header systems discussed in

this section include a combination of repetitive member (load sharing) effect and compositeaction effect. This appendix considers a header consisting of double members to be a repetitive

member system; therefore, a repetitive member factor, Cr, of 1.1 to 1.2 is applicable (see TableB4). Headers are generally designed to support all loads that are within the tributary length of the

header including loads from upper stories and roof. However, typical platform construction uses

a double top plate above the header that creates a composite member with resistance greater than

the resistance of the individual header. When an upper story is supported, a floor band joist andsole plate of the wall above also resist the load and reduce the forces in the header. Testing

results (HUD, 1999) show that a repetitive member factor is valid for headers constructed of only

two members as shown in Table B4 and that additional composite effects produce large increasesin capacity when the header is overlaid by a double top plate, band joist and sole plate.

Consequently, an overall system factor of 1.8 was found to be a simple, conservative designsolution (Table B5). That system factor is applicable to the allowable bending stress value, Fb,

of the header members only. The above adjustment factor is not currently recognized in the NDS

and should be used at the designers discretion as an alternative means and method of design.

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TABLE B5

HEADER SYSTEM EFFECT FACTORS

Header Type and Application1 Recommended Cr Value2

2x10 double header of No. 2 Spruce-Pine-Fir 1.30 3

Header with double top plate, 2x10 floor band joist, and sole plate

of wall located directly above.1.8 4

Source: Residential Structural Design Guide, U.S. Department of Housing and Urban Development, Washington D.C., 2000.1For other applications and lumber sizes or grades, refer to the Crfactors in Table B3.

2Apply Cr in lieu of factors in Table B3 to determine adjusted allowable bending stress.3Use Cr= 1.35 when the header is overlaid by a minimum 2x4 double top plate without splices. This factor is higher than the

factors recommended in Table B4 because it is based on testing of the specific system configuration. The factors in Table

B4 are recommended for a wide range of applications and represent conservative estimates of the actual system response.4Includes repetitive and composite effect of other members in the specified system.

B3.3 Horizontal Shear Factor The horizontal shear factor, CH, in the NDS was developed

based on the assumption that shear design values for dimension lumber, Fv, did not incorporate areduction for end splitting of lumber. During recent re-evaluation of this assumption, the ASTM

D7 Task Committee assigned to this topic found that shear design values did incorporate a

reduction for the effect of end splitting. Therefore, a CH factor of 2.0 should be used with the1997 NDS provisions (and previous editions of NDS) until this error is corrected in the futureNDS editions. The CH factor applies to parallel-to-grain shear stress, Fv, in bending members.

B3.4 References

AF&PA, National Design Specification for Wood Construction, American Forest and Paper

Association, Washington DC, 1997.AF&PA, Wood Frame Construction Manual SBC High Wind Edition, American Forest and

Paper Association, Washington DC, 1996.ASAE, Design Requirements and Bending Properties for Mechanically Laminated Columns (EP

559), American Society of Agricultural Engineers, St. Joseph, MI, 1997.BSSC, NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA-273), BuildingSeismic Safety Council, Washington, DC, 1997.

BSSC, NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other

Structures (FEMA-368), Building Seismic Safety Council, Washington, DC, 2001.

Bonnicksen, L.W. and Suddarth, S.K., Structural Reliability Analysis of Wood Load SharingSystems, Paper No. 82, American Society of Testing and Materials, Fifth National Meeting,

Philadelphia, Pennsylvania, 1965.

Douglas, B.K. and Line, P., System Effects in Wood Assemblies, Proceedings of theInternational Wood Engineering Conference, New Orleans, LA, 1996.

FPRS, Wall & Floor Systems: Design and Performance of Light Frame Structures, Proceedings

7317, Forest Products Research Society, Madison, WI, 1983.HUD, System Performance of Wood Header Assemblies, prepared by the NAHB Research

Center, Inc., for the U.S. Department of Housing and Urban Development, Washington, DC,

1999.NAHBRF, Stress and Deflection Reduction in 2x4 Studs Spaced 24 Inches on Center Due to the

Addition of Interior and Exterior Surfacings, NAHB Research Foundation, Rockville, MD,

July 1974.

National Evaluation Service, Inc. Report No. NER-272, Power Driven Staples, Nails, and AlliedFasteners for Use in All Types of Building Construction, Council of American Building

Officials, Falls Church, VA, 1996.

B-5


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Polensek, A., Rational Design Procedure for Wood Stud Walls under Bending and Compression

Loads, Forest Research Laboratory, Oregon State University, September 1975.Rosowsky, D. and Ellingwood, B., Reliability of Wood Systems Subjected to Stochastic Live

Loads, Wood and Fiber Science, Society of Wood Science and Technology, Madison, WI,

1992.

SBCCI, Standard Building Code, Southern Building Code Congress International, Birmingham,AL, 1999.

Wolfe, R.W., Performance of Light-Frame Redundant Assemblies, Proceedings of 1990

International Timber Engineering Conference, Vol. 1, 124-131, 1990.Wolfe, R.W., Structural Performance of Light-Frame Truss-Roof Assemblies, Proceedings of the

International Wood Engineering Conference, Vol. 3, Omnipress, Madison, WI, 1996.

B-6


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APPENDIX C

LATERAL LOAD DISTRIBUTION MODELS

C.1 General This appendix presents methods for distribution of lateral building forces to shear

walls in light-frame construction. Each method is briefly summarized and the assumptions

involved in formulation of the methods are presented. The appropriate method should bedetermined by the building designer or wall designer in accordance with the provisions of the

governing building code.

C.2 Methods Load distribution methods are presented with sufficient detail to allow the user to

implement each method without consulting other sources. However, to obtain a better

understanding of the methods and related research, the reader is referred to more detailed reportsspecified in Section C4 of this Appendix.

C2.1 Tributary Area Method (Flexible Diaphragm Method) The tributary area method isused to distribute the story lateral load between the shear walls based on tributary areas assigned

to each shear wall. In wind design, the tributary areas are associated with exterior wall surfaces,whereas in seismic design, the tributary areas are associated with plan configurations. The

tributary area method assumes that the diaphragm acts as a flexible beam and does not provide amechanism to distribute forces between the walls. Due to extensive experience, this method is

considered as accepted engineering practice and is widely used with lateral load analysis of

residential buildings.

Although the tributary area method is simple to use and in most cases it provides conservative

solutions, according to recent research findings (Section C4) it misrepresents the response oflight-frame construction and can result in misguided design decisions. For example, the method

lacks the ability to effectively use the resistance of intermediate and short wall segments that areabundant in the irregular-shaped residential buildings. In addition, the method can result in

nonconservative designs of shear wall components on the element level due to underestimation

of loads acting on individual walls.

C2.2 Rigid Diaphragm Method without Torsion This method is used to distribute the story

lateral load between the shear walls based on the relative shear wall stiffnesses. The principal

assumption is that the diaphragm stiffness is relatively high compared to the stiffness ofsupporting shear walls. Thus, the rigid diaphragm distributes loads to the supporting walls in

proportion to their relative stiffnesses. The wall capacity is typically used as a measure of its

stiffness. The total story shear load is distributed to individual shear wall lines according to theratio of the wall capacity (stiffness) to the total capacity of all parallel walls on the story under

consideration. Recent research findings (Section C4) have shown that the rigid diaphragm

method is a more accurate model for light-frame wood construction compared to the tributaryarea method. However, insufficient information is available on performance of buildings with

significant plan irregularities to assess appropriate limitations on use of this method, if any. The

reader is further referred to NEHRP Recommended Provisions for Seismic Regulations for NewBuildings and Other Structures (FEMA 368, BSSC 2001) for detailed descriptions of

irregularities that affect the building response.

C2.3 Rigid Diaphragm Method with Torsion This method is an extension of the methoddescribed in Section C2.2. In addition to distributing the total story lateral force to the shear

C-1


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walls based on their relative stiffnesses, an additional force is assigned to each wall due to

rotation of the rigid diaphragm. The rotation occurs when the load vector and the resistancevector are not collinear, resulting in a force couple in addition to direct shear. This method is

typically used to model response of irregular buildings with complicated branched plans. The

torsion force component can either increase or offset the direct shear force component. However,

model building codes do not allow for a reduction of the direct shear force due to the torsioneffects. Current model building codes also limit the degree of lateral resistance that can be

provided by torsional response through limits on building plan aspect ratio (length to width)

where torsional analysis is permitted. When designing buildings with branched plans, theengineer should exercise judgement on whether sections of an irregular diaphragm are

sufficiently interconnected to provide a unit action or the diaphragm should be modeled as a

group of individual diaphragms. The magnitude of the torsional component is determined asfollows:

J

VrMV iiTT = (C.E1)

=n

i

2ii rVJ (C.E2)

where:VT = torsional shear load on a wall line;

MT = torsional moment a product of total story shear load and perpendicular distance

between the load vector and resultant resistance vector for load direction under

consideration;ri = distance from the wall to the center of stiffness (center of resistance);

Vi = design shear wall capacity (or consistent measure of stiffness);

J = torsional moment of inertia of the story.

C2.4 Plate Element Method This method models a diaphragm with two-dimensional elementsformulated using plate theory. The diaphragm movement is restricted by imposing springreactions that represent shear walls. The in-plane stiffness of the plate elements and stiffness of

connections between the plates can be adjusted to improve accuracy of the model. This modelcan be solved by commercial or proprietary computed-aided structural analysis procedures.

Recent research demonstrated that the plate element method accurately models light-frame wood

construction (HUD 2001).

C3. Alternative Rational Analyses This section is not intended to limit the use of alternate

design methods that use recognized principles of mechanics and engineering. Examples of such

methods include finite element analysis, matrix analysis, energy-based formulations, closed-from

solutions, and others.

C4. Publications Relevant information regarding methods for distribution of lateral forces inlight-frame construction can be found in the following publications:

Building Seismic Safety Council, NEHRP Commentary on the Guidelines for the SeismicRehabilitation of Buildings (FEMA Publication 369), Washington, DC, 2001.

Building Seismic Safety Council, NEHRP Recommended Provisions for Seismic Regulations for

New Buildings and Other Structures (FEMA Publication 368), Washington, DC, 2001.

C-2


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Fisher, D., Filiatrault, A., Folz, B., Uang, C., and Seible, F., Shake Table Tests of a Two-Story

Woodframe House. Report No. SSRP 2000/15. Division of Structural Engineering,

University of California, San Diego, 2000.

HUD, Residential Structural Design Guide, U.S. Department of Housing and UrbanDevelopment (HUD), Washington, DC, 2000.

HUD, Whole Structure Testing and Analysis of a Light-Frame Wood Building (Three Reports),U.S. Department of Housing and Urban Development (HUD), Washington, DC, 2001.

Kasal, B., and Leichti, R. J., Incorporating Load Sharing in Shear Wall Design of Light-FrameStructures. Journal of Structural Engineering, Vol. 118, No. 12, pp. 3350-3361, 1992.

Phillips, T. L., Itani, R. Y., and McLean, D. I., Lateral Load Sharing by Diaphragms in Wood-

Framed Buildings, Journal of Structural Engineering, Vol. 119(5), pp. 1556-1571, 1992.

C-3


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APPENDIX D

METHODS FOR ANALYSIS OF SHEAR WALL RESISTANCE

D1. General Resistance of shear walls to in-plane lateral loading may be determined according

to one of the methods presented in this Appendix. Each method is briefly summarized and the

assumptions involved in formulation of the methods are presented. The appropriate methodshould be determined by the building designer or wall designer in accordance with the provisions

of the governing building code.

D2. Methods Analysis methods are presented with sufficient detail to allow the user to

implement each method without consulting other sources. However, to obtain a better

understanding of the methods and related research, the reader is referred to more detailed reportsspecified in Section D3 of this Appendix. The first three methods (Sections D2.1, D2.2, and

D2.3) need input of unit shear resistance values that can be determined from Appendix B or

measured experimentally in accordance with the provisions of Section 4.4.2. Alternatively, theshear wall resistance can be estimated using analytical methods (Sections D2.4 and D2.5).

D2.1 Perforated Shear Wall Method. This method relates shear capacity of a wall with

perforations (i.e., doors or windows or both) to a wall of identical configuration withoutperforations through an empirical reduction factor, F, determined as follows:

r23

rF

= (DE.1)

lH

A+1

1=r

i

o

(DE.2)

where:

F = reduction parameter;r = sheathing area ratio;

Ao = total area of openings;

H = height of the wall; and,

li = summation of length of all full height wall segments.

To implement this method, the designer shall multiply the shear wall resistance calculated based

on the total wall length (including the length of perforations) by the reduction factor, F 1.0,determined with Equation DE.1. The total shear resistance of a shear wall line is determined as

follows:

vLFV = (DE.3)where:V = total lateral resistance of a perforated shear wall line;F = reduction parameter determined using Equation DE.1;

L = total length of a shear wall line including length of perforations;

v = unit shear resistance determined from Appendix B or Sections 4.4.2, D2.4, orD2.5.

The method requires that overturning restraints are installed at the wall ends that typicallycoincide with building corners. The method has been validated for light-frame wood and cold-

D-1


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formed steel shear walls sheathed with wood structural panels with the maximum wall unit shear

capacity (unfactored) not exceeding 1,200 lb/ft (See Appendix B).

D2.2 Segmented Shear Wall Method - This method uses resistance of fully sheathed segments

located between wall openings. Each segment should be fully restrained against overturning. The

contribution of the components above and below openings is ignored. The unit shear resistance ismultiplied by the segment length to determined shear resistance of the segment. The total

resistance of a shear wall line is determined as a sum of the resistances of all individual segments

as follows:

=

=n

1iii vlV (DE.3)

where:

V = total lateral resistance of a shear wall line;li = length of an individual shear wall segment;

vi = unit shear resistance of an individual shear wall segment determined from

Appendix B or Section 4.4.2, D2.4 or D2.5;

n = number of shear wall segments in a shear wall line.

D2.3 Ni-Karacabeylis Method This mechanics-based method is formulated such that theresistance of a nonperforated shear wall segment with a partial overturning restraint is expressed

as a fraction of the resistance of an identical shear wall segment with a full restraint. The shear

capacity ratio for a wall with a partial overturning restraint and the full overturning restraint can

be determined as follows:

++= 221 (DE.3)

10,CM

R

N

= (DE.4)

where: = ratio of the lateral load capacity of a wall segment with partial uplift restraint to

the capacity of a wall segment with full uplift restraint;

= wall segment aspect ratio; = uplift restraint effect which is equal to unity for the walls fully restrained against

overturning;M = total number of nails along the end stud of a shear wall segment;

CN = capacity of a single nail connection that can be measured experimentally or

estimated using the connection yield theory;R = uplift restraint force on the end stud of shear wall that can include contribution of

partial overturning restraint, gravity load, corner effect, and other system effects.

The total resistance of a shear wall line is determined as a sum of the resistances of all individual

segments as follows:

ii

n

1ii vlV

== (DE.5)

where:

V = total lateral resistance of a shear wall line;

= see Equation DE.3;li = length of an individual shear wall segment;

D-2


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vi = unit shear resistance of an individual shear wall segment determined from

Appendix B or Section 4.4.2, D2.4 or D2.5;n = number of shear wall segments in a shear wall line.

D2.4 Shear Through Panel Rotation - This method is used to determine shear resistance of a

fully restrained light-frame nonperforated shear wall segment through modeling the rotationresponse of individual sheathing panels that are fastened to the wall framing with nails or screws.

The method is formulated with an assumption that a sheathing panel rotates around its center as a

rigid body (infinite in-plane shear modulus). The contribution of an individual nail to the totalshear resistance is determined based on the distance from the nail to the center of panel rotation

and relative nail displacement. The unit shear wall value (characteristic strength) of an individual

shear wall panel is determined as follows:

B

KC

v

total

1iiN

== (DE.5)

2

i

2

ii sin

Hycos

Bx)(sinK

+

= (DE.6)

where:

CN = peak resistance of individual sheathing fastener that can be measuredexperimentally or determined using the connection yield theory;

B = sheathing panel width;

H = sheathing panel height;

= angle between the diagonal and the vertical edge of individual sheathing panel;i = sheathing fastener enumerator, i changes from 1 to the total number of sheathing

fasteners in a panel;

xi = horizontal coordinate of i-th fastener relative to the panel center;

yi = vertical coordinate of i-th fastener relative to the panel center;Ki = geometric characteristic of fastening schedule of a sheathing panel.

The total resistance of a shear wall line can be determined using methods described in Sections

D2.2, D2.3, or D2.4 of this Appendix. The resistance of an individual sheathing fastener, CN, canbe measured experimentally or estimated analytically using the connection yield theory. Narrow

shear wall segments with aspect ratio greater than 2:1 can have significant bending component intheir response and should not be analyzed with Equations DE.5 and DE.6 unless the bending

contribution is included. Because this method does not model wall ductility, energy dissipation

mechanism, and other failure modes, the designer should detail the wall configuration so thatnone of these factors can negatively affect the wall response under a design event.

D2.5 Alternate Rational Analyses This section is not intended to limit the use of alternatedesign methods that use recognized principles of mechanics and engineering. Examples of such

methods include finite element analysis, matrix analysis, energy-based formulations, closed-from

solutions, and others.

D3. Publications Relevant information regarding methods for estimating resistance of light-

frame shear walls can be found in the following publications:

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Dolan, J., and Heine, C., Monotonic Tests of Wood Frame Shear Walls with Various Openings

and Base Restraint Configurations, Prepared for the NAHB Research Center, Inc. byVirginia Polytechnic Institute and State University, Blacksburg, VA, 1997.

Dolan, J., and Heine, C., Sequential Phased Displacement Cyclic Tests of Wood Frame Shear

Walls with Various Openings and Base Restraint Configurations, Prepared for the NAHB

Research Center Inc. by Virginia Polytechnic Institute and State University, Blacksburg,VA, 1997.

Dolan, J., and Heine, C., Sequential Phased Displacement Tests of Wood Framed Shear Walls

with Corners, Prepared for the NAHB Research Center, Inc. by Virginia PolytechnicInstitute and State University, Blacksburg, VA, 1997

Dolan, J., and Johnson, A., Cyclic and Monotonic Tests of Long Shear Walls with Openings,

Prepared for the American Forest & Paper Association by Virginia Polytechnic Instituteand State University, Blacksburg, VA, 1996.

NAHB Research Center, Inc., Monotonic Tests of Cold-Formed Steel Shear Walls with

Openings, Prepared for the U.S. Department of Housing and Urban Development,American Iron and Steel Institute, and the National Association of Home Builders by the

NAHB Research Center, Inc., Upper Marlboro, MD, 1997.NAHB Research Center, Inc., The Performance of Perforated Shear Walls with Narrow Wall

Segments, Reduced Base Restraint, and Alternative Framing Methods, Prepared for theU.S. Department of Housing and Urban Development and The National Association of

Home Builders by the NAHB Research Center, Inc., Upper Marlboro, MD, 1998.

NAHB Research Center, Inc., Perforated Shear Walls with Conventional and Innovative BaseRestraint Connections, Prepared for the U.S. Department of Housing and Urban

Development and The National Association of Home Builders by the NAHB Research

Center, Inc., Upper Marlboro, MD, 1999.HUD, Residential Structural Design Guide: A state-of-the-art review and application of

engineering information for light-frame homes, apartments, and townhouses, Prepared forthe U.S. Department of Housing and Urban Development (HUD) and The National

Association of Home Builders by the NAHB Research Center, Inc., Upper Marlboro,

MD, 2000Ni, C., and Karacabeyli, E., Effect of overturning restraint of performance of shear walls,

Proceedings of the World Conference on Timber Engineering, Whistler Resort, British

Columbia, Canada, 2000.

Ni, C., Karacabeyli, E., and Ceccotti, A., Design of shear walls with openings under lateral andvertical loads, Paper prepared for PTEC'99, Draft v. 4, December 2, 1998.

Salenikovich, A. J., The racking performance of light-frame shear walls, Ph.D. dissertation,

Virginia Polytechnic Institute and State University, Blacksburg, VA, 2000.Sugiyama, H., and Matsumoto, T., Empirical Equations for the Estimation of Racking Strength

of a Plywood Sheathed Shear Wall with Openings, Summary of Technical Papers,

Annual Meetings, Trans. of A.I.J. Japan, 1994.Sugiyama, H., and Yasumura, M, Shear Properties of Plywood Sheathed Wall Panels with

Openings. Trans. of A.I.J., No. 338. Japan, 1984.

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APPENDIX E

DESIGN EXAMPLE

This example demonstrates the design methods for analysis of the lateral force resisting system

of a one-story house (Figure E1). The design lateral load is distributed between the shear walls

according to two methods: flexible diaphragm method and rigid diaphragm method (seeAppendix C for description of the methods). Figures E2 and E3 show a graphical representation

of analytical models for both methods. Then, the shear resistance of Wall 4 (Figures E1 and E4)

is analyzed using three methods: segmented shear wall method, perforated shear wall method,and Ni-Karacabeylis method (see Appendix D description of the methods).

Figure E1

Shear Wall Schedule for a One-Story House

DESIGN INPUT

Design Format ASD

Load Direction North-South (NS)Wind Load in NS direction 20,000 lb (assumed)

Design Basis Capacity

Reduction Factor 0.5 (Table 4.2)Load Duration Factor 1.0 (Wind Load)

Shear Wall Parameters:Structural Sheathing Panels Structural OSB panels

Sheathing Nails Common nails

Lumber Species SPF (SG = 0.42)Stud Spacing 16 inches o.c.

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Shear Wall Height 8.1 ft

Interior Sheathing noneWall configurations See Table E1

TABLE E1

WALL CONFIGURATIONS

Parameter Wall 1 Wall 2 Wall 3 Wall 4

Total length 32 ft 9 ft 21 ft 20 ft

Number of openings 1 none 1 1

Opening type Window Window Door

Opening length 3 ft 6 ft 4 ft

First segment 6 ft 9 ft 11 ft

Second segment 21 ft 6 ft 5 ft

LATERAL LOAD DISTRIBUTION

Flexible Diaphragm Method

The total lateral load is distributed between the shear walls based on the tributary areas

associated with each wall on a purely geometric basis. Figure E2 is a graphical representation of

the mechanical model based on a simple beam approach. Table E2 summarizes individual shearwall loads.

Figure E2

Flexible Diaphragm Method Model

TABLE E2

SHEAR WALL LOADS ACCORDING TO FLEXIBLE DIAPHRAGM METHOD

Shear Wall #Tributary Area of

Associated Wall, ft2

Fraction of Total

Tributary Wall AreaShear Wall Load, lb

Wall 1 (6.0)(8.1) = 48.6 0.125 2,500

Wall 2 (19.5)(8.1) = 157.95 0.410 8,125

Wall 3 (18)(8.1) = 145.8 0.375 7,500

Wall 4 (4.5)(8.1) = 36.45 0.090 1,875

TOTAL 388.8 1.0 20,000

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Rigid Diaphragm Method

The total lateral load is distributed between the shear walls based on the relative capacities.

Figure E3 is a graphical representation of the mechanical model based on a continuous rigid

beam approach. For the first iteration, the segmented shear wall method is used to determine thewall capacities. Table E3 summarizes individual shear wall loads.

Figure E3

Rigid Diaphragm Method Model

TABLE E3

SHEAR WALL LOADS ACCORDING TO RIGID DIAPHRAGM METHOD

Shear Wall #Segmented Shear Wall

Length, ft

Fraction of Total Wall

LengthShear Wall Load, lb

Wall 1 29.0 0.42 8,400

Wall 2 9.0 0.13 2,600

Wall 3 15 0.22 4,400

Wall 4 16 0.23 4,600

TOTAL 69.0 1.0 20,000

Table E4 compares results of flexible vs. rigid diaphragm methods. The flexible diaphragmmethod both underestimates and overestimates the shear wall loads as compared to the rigid

diaphragm method. While providing a more conservative design, the flexible diaphragm method

requires an impractical shear wall schedule for this building configuration (Figure E1). Forexample, Wall 2 has to be excluded from the analysis, because it is impractical to design a short

wall segment that accounts for only 13 percent of the total shear wall length of the building in the

North-South direction to resist as much as 41 percent of the total story shear load. AlthoughWalls 3 and 4 have practically the same lengths, according to the flexible diaphragm method,

Wall 3 should have capacity four times greater than that of Wall 4. The differences between the

two methods diminish in significance for simple rectangular buildings that resist shear loads byonly two exterior walls. Appendix C discusses the methods of lateral load distribution and

examines aspects and limitations of various methods of analysis.

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TABLE E4

COMPARISON OF FLEXIBLE AND RIGID DIAPHRAGM METHODShear Wall Load, lb

Shear Wall # Flexible

Diaphragm

Rigid

Diaphragm

Absolute

Difference, lb

Relative1

Difference, %

Wall 1 2,500 8,400 5,900 70

Wall 2 8,125 2,600 -5,525 -213Wall 3 7,500 4,400 -3,100 -70

Wall 4 1,875 4,600 2,725 59

Total 20,000 20,0001Rigid diaphragm method is used as a basis.

Shear Wall Analysis

Results of the rigid diaphragm analysis are used to design Wall 4 (Figure E4). The shear wall is

designed using three methods: segmented, perforated, and Ni-Karakabeylis (see Appendix D for

description of the methods).

Figure E4

Wall 4

LOAD

Load: P = 4,600 lb (Table E3)

Segmented Shear Wall Method

Minimum required unit shear wall capacity:

( ) ( )ft/lb575

5115.0

600,4

ll

Pv

21

=+

=+

=

where:P, lb = load;

= 0.5 = reduction factor for ASD design format (Table 4.2);(l1 + l2), ft = total length of wall segments.

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Characteristic unit shear wall resistance adjusted for lumber species:(650) [1- (0.5-0.42)] = 598 lb/ft (Table B1 of Appendix B)

Wall Characteristics:

Structural sheathing 5/16 wood structural panelNail size 6d common (D = 0.113 inch)

Nail spacing 6 inch o.c. on perimeter and 12 inch o.c. in field

Stud spacing 16 inches o.c.Lumber species SPF lumber

Holddowns: at the end of each segment four holddowns overall for

two segments

Perforated Shear Wall Method

Empirical perforation reduction factor, F:

62.0)83.0()2(3

83.0

r23

rF =

=

=

83.0

)115)(1.8(

)5.6)(4(1

1

lH

A1

1r

i

o

=

++

=

+

=

where:Ao = total area of openings;

H = shear wall height;

li = summation of lengths of all full height wall segments.


ft/lb742)62.0()20()5.0(

600,4

FL

Pv ==

=

Characteristic unit shear wall resistance adjusted for lumber species:

(820) [1- (0.5-0.42)] = 754 lb/ft (Table B1 of Appendix B)

Wall Characteristics:Structural sheathing 15/32 wood structural panel

Nail size 8d common (D = 0.131 inch)Nail spacing 6 inch o.c. on perimeter and 12 inch o.c. in field

Stud spacing 16 inches o.c.

Lumber species SPF lumberHolddowns: at the wall corners two holddowns overall

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Ni-Karacabeylis Method

The wall is analyzed in both directions:

Direction of Loading: Left-to-Right (Figure E4)

Segment 1:

Segment length l1 = 11 feet

Uplift restraint effect: 1 = 1.0 holddown bracket is installed

Capacity ratio: 1 = 1.0 segment is fully restrained

Segment 2:


Uplift restraint effect: 2 = 0 no overturning restraint at door openingSegment aspect ratio: 2 = 8.1/5 = 1.62Capacity ratio:

28.062.162.1)62.1()0(2121 22 =++=++=


ft/lb740)5.0()]5)(28.0()11)(0.1[(

600,4

]ll[

Pv

2211

=+

=+

=

Direction of Loading: Right-to-Left (Figure E4)

Segment 2:Segment length l2 = 5 feet

Uplift restraint effect: 2 = 1.0 holddown bracket is installedCapacity ratio: 2 = 1.0 segment is fully restrained

Segment 1:


Uplift restraint effect: 1 = 0 no overturning restraint at door opening

Segment aspect ratio: 1 = 8.1/11 = 0.75Capacity ratio:

50.075.075.0)75.0()0(2121 22 =++=++=


ft/lb874)5.0()]11)(50.0()5)(0.1[(

600,4

]ll[

Pv

1122

=+

=+

=

The Right-to-Left direction governs the design.

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Characteristic unit shear wall resistance adjusted for lumber species:

(1040) [1- (0.5-0.42)] = 956 lb/ft (Table B1 of Appendix B)

Wall Characteristics:Structural sheathing 15/32 wood structural panel

Nail size 8d commonNail spacing 4 inch o.c. on perimeter and 12 inch o.c. in field

Stud spacing 16 inches o.c.

Lumber species SPF lumberHolddowns: at the wall corners two holddowns overall

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APPENDIX G

METRIC CONVERSION FACTORS

The following list provides the conversion relationship betweenU.S. customary units and the International System (SI) units. A

complete guide to the SI system and its use can be found in ASTM

E 380, Metric Practice.

To convert from to multiply by

Length

inch (in.) micrometer () 25,400inch (in.) centimeter 2.54

inch (in.) meter (m) 0.025foot (ft) meter (m) 0.3048yard (yd) meter (m) 0.9144

mile (mi) kilometer (km) 1.6

Area

square foot (sq ft) square meter (sq m ) 0.09290304 Esquare inch (sq in) square centimeter (sq cm) 6.452 Esquare inch (sq in.) square meter (sq m ) 0.00064516 E

square yard (sq yd) square meter (sq m ) 0.8391274square mile (sq mi) square kilometer (sq km ) 2.6

Volume

cubic inch (cu in.) cubic centimeter (cu cm) 16.387064cubic inch (cu in.) cubic meter (cu m) 0.00001639cubic foot (cu ft) cubic meter (cu m) 0.02831685

cubic yard (cu yd) cubic meter (cu m) 0.7645549gallon (gal) Can. liquid liter 4.546gallon (gal) Can. liquid cubic meter (cu m) 0.004546

gallon (gal) U.S. liquid* liter 3.7854118gallon (gal) U.S. liquid cubic meter (cu m) 0.00378541fluid ounce (fl oz) milliliters (ml) 29.57353

fluid ounce (fl oz) cubic meter (cu m) 0.00002957

Force

kip (1000 lb) kilogram (kg) 453.6

kip (1000 lb) Newton (N) 4,448.222pound (lb) kilogram (kg) 0.4535924

pound (lb) Newton (N) 4.448222

Stress or pressure

kip/sq inch (ksi) megapascal (Mpa) 6.894757

kip/sq inch (ksi) kilogram/square 70.31centimeter (kg/sq cm)

pound/sq inch (psi) kilogram/square 0.07031centimeter (kg/sq cm)

pound/sq inch (psi) pascal (Pa) ** 6,894.757pound/sq inch (psi) megapascal (Mpa) 0.00689476pound/sq foot (psf) kilogram/square 4.8824

meter (kg/sq m)pound/sq foot (psf) pascal (Pa) 47.88

To convert from to multiply by

Mass (weight)

pound (lb) avoirdupois kilogram (kg) 0.4535924ton, 2000 lb kilogram (kg) 907.1848

grain kilogram (kg) 0.0000648

Mass (weight) per length)

kip per linear foot (klf) kilogram per 0.001488meter (kg/m)

pound per linear foot (plf) kilogram per 1.488meter (kg/m)

Moment

1 foot-pound (ft-lb) Newton-meter 1.356

(N-m)

Mass per volume (density)

pound per cubic foot (pcf) kilogram per 16.01846cubic meter (kg/cu m)

pound per cubic yard kilogram per 0.5933(lb/cu yd) cubic meter (kg/cu m)

Velocity

mile per hour (mph) kilometer per hour 1.60934

(km/hr)mile per hour (mph) kilometer per second 0.44704

(km/sec)

Temperature

degree Fahrenheit (F) degree Celsius (C) tC = (tF-32)/1.8

degree Fahrenheit (F) degree Kelvin (K) tK= (tF+ 459.7)/1.8

degree Kelvin (F) degree Celsius (C) tC = (tK-32)/1.8

* One U.S. gallon equals 0.8327 Canadian gallon** A pascal equals 1000 Newton per square meter.

The prefixes and symbols below are commonly used to form namesand symbols of the decimal multiples and submultiples of the SI

units.

Multiplication Factor Prefix Symbol

1,000,000,000 = 109

giga G1,000,000 = 106 mega M

1,000 = 103 kilo k0.01 = 10-2 centi c

0.001 = 10-3 milli m

0.000001 = 10-6

micro 0.000000001 = 10-9 nano n

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