EWPAA Structural Plywood and LVL Design Manual - Engineered ...

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the hygroscopic movement of structural plywood along and across the grain. The dimensional stability ofplywood is beneficial in many structural applications and is particularly important in concrete formplyapplications where large areas of structural plywood formply are subjected to high temperatures and moisturecontents at the time of the concrete pour.PlywoodThickness(mm)Numberof PliesDirection*ofMovement5% - 12% 12% - 17%Moisture Content Range %17% -SaturationAverage.5%toSaturation12 5II⊥0.0160.0210.0090.0080.0060.0050.0110.01115 5II⊥0.0160.0220.0080.0100.0040.0090.0100.01317 7II⊥0.0170.0220.0090.0100.0050.0100.0110.01422 9II⊥0.0170.0180.0120.0100.0040.0080.0120.014• Direction II is along the face grain• Direction ⊥ is across the facegrainExampleDetermine the hygroscopic expansion in mm across the grain of a 1200mm wide,17mm thick structural plywood panel, when installed at 10% moisture content andused in a fully exposed application in which the plywood could become fullysaturated with water. Assume fibre saturation is 28%.1. As the range is 10% - 28% the correct selection from Table 4.1 is from the‘average’ column, and is 0.014% per % change of moisture content.2. Total change in moisture content = 28% - 10% = 18%3. Movement in mm of 1200mm panel width = ( 0.014/100) x 1200 x 18 = 3.0 mmTABLE 4.1: Percent Movement of Structural Plywood Per Percent Change of Moisture Content4.4 Thermal PropertiesFire Resistance is the ability of a building component to resist a fully developed fire, while stillperforming its structural function. Fire resistance in the form of a fire rating, can only be applied to atotal building element incorporating plywood. For example, a fire door or wall or roof system. Aproduct cannot be fire rated.Plywood is quite acceptable as a material used in fire resistant components provided it is combined with othermaterials so as to meet the fire resistant requirements. This can be achieved by combining plywood with noncombustiblematerials such as fibrous cement or fire grade plasterboard.Early Fire Hazard Indicies provide a measure of the plywood's surface characteristics relating to spreadof flame, heat evolved, smoke emission and ignition. A low index value indicates better early firehazard properties. The early fire hazard indices as defined in AS 1530 Part 3, for untreated pine plywoodare given below. The possible index range is given in brackets.Ignitability index (0 - 20) 14Spread of Flame index (0 - 10) 8Heat Evolved index (0 - 10) 9Smoke Developed index (0 - 10) 215
The early fire hazard indicies of plywood permit it to be used untreated in most typical building applications.Plywood is suitable for use in most building linings, walls, ceiling partitions and floors. Building codes mayrestrict its use in areas of severe hazard such as flues, hearths, public exits, public corridors, lift wells andcertain public areas and buildings.The use of intumescent finishes and paints to reduce the early fire hazard indicies is not acceptable undercurrent building regulations.For further information concerning fire see Error! Reference source not found..Thermal Expansion: Wood, including LVL and plywood expand upon heating as do practically all solids. Thethermal expansion of plywood is quite small. The average co-efficient of thermal expansion of plywoodis in the range 4.5 x 10 -6 to 7 x 10 -6 mm/mm/ 0 C.Thermal Conductivity: The ability of a material to conduct heat is measured by its thermal conductivity, k.The higher the k value, the greater the ability of the material to conduct heat; the lower the k, the higher thethermal insulation value. k varies with timber species, moisture content, the presence of knots and othernatural characteristics, and temperature. However an average value of k=0.1154 W.m/(m 2 . 0 C) for softwoodtimbers is sufficiently accurate for determining the overall co-efficient of heat transmission (U value) of aconstruction assembly.Thermal Resistance: The thermal resistance or insulating effectiveness of LVL and plywood panelsbased on k=0.1154 W.m/(m 2 . 0 C) is its reciprocal, i.e., R=8.67 (m 2 . 0 C)/(W.m). The higher the R value, themore effective the insulation. For example, the R value for 12mm pine plywood = (12/1000) x 8.67 = 0.10m 2 . 0 C/W. Similarly, the R value for 25mm thick pine plywood is (25/1000) x 8.67 = 0.22 m 2 . 0 C/W.Vapour ResistanceCondensation occurs when warm moisture laden air comes in contact with a cooler surface. In coldclimates, vapour barriers should be used on or near the warm side of exterior walls clad with plywood.Plywood also provides good resistance to vapour transmission. Where an additional vapour barrier isrequired on the warm side, internal plywood linings may be considered to act as a secondary vapour barrier.For further information on the topic of thermal transmissions see Error! Reference source not found..4.5 Acoustical PropertiesPlywood has unique properties which allow it to be effectively used in sound control and reduction forresidential and industrial applications. Audible sound is a propagation of energy and is usually measuredin terms of decibels (dB). 1 dB is the lower threshold of human hearing while 130 dB is considered thethreshold of pain.Sound waves in air is energy in motion and may be absorbed or reflected by a surface. Plywood, like othermaterials will absorb some of the sound energy and reflect the remainder. A material which exhibits perfectabsorptivity is rated as 1.0; a perfect reflector of sound would have a co-efficient of sound absorption of0.0. The acoustic properties of plywood will vary with density, moisture content and surface coatings,however for most practical purposes plywood can be considered a reflector of sound. Relative co-efficients ofsound absorption are given in TABLE 4.2. For further information see Error! Reference source not found..Material CoefficientOpen Window 1.0Brick 0.03Window glass 0.03Plywood 0.04TABLE 4.2: Sound Absorption Co-efficients of Various Building Materials4.6 Electrical PropertiesPlywood and LVL are excellent electrical insulators, provided they are in the dry condition. Resistancefalls off considerably with an increase of moisture content. The glueline in plywood and LVL is not as16
Page 2 and 3: Structural Plywood & LVL Design Man
Page 4 and 5: Table of Contents1 Plywood & LVL -
Page 6 and 7: 11 Plywood Stressed Skin Panels ...
Page 8 and 9: Table of FiguresFIGURE 4.1: Plywood
Page 10 and 11: Part OneProduct Production & Proper
Page 12 and 13: PeelingAfter conditioning, the logs
Page 14 and 15: Sanding, Trimming and BrandingAfter
Page 16 and 17: through to applications where aesth
Page 18 and 19: 2.7 Identification CodeThe plywood
Page 20 and 21: 2.10 Non Structural PlywoodsInterio
Page 22 and 23: 3.5 Veneer QualityVeneer quality us
Page 26 and 27: effective an insulator as the wood
Page 28 and 29: 5 Structural Plywood - Design Princ
Page 30 and 31: 12 - 13 40015 - 19 45020 - 25 52026
Page 32 and 33: TABLE 5.3: Standard Structural Plyw
Page 34 and 35: TABLE 5.5: Indicative Stiffness Val
Page 36 and 37: Strength Limit StateStrength LimitS
Page 38 and 39: Application of Structural memberAll
Page 40 and 41: FIGURE 5.5 shows an I-beam defining
Page 42 and 43: j 2- Duration of Load Factor for Cr
Page 44 and 45: Using the theory of parallel axes a
Page 46 and 47: 6 Structural LVL - Design Principle
Page 48 and 49: I (neutral axis(NA)-stiffness= (bd
Page 50 and 51: Serviceability Limit State:Calculat
Page 52 and 53: Strength Limit State:Strength Limit
Page 54 and 55: Equilibrium Moisture Content (EMC)P
Page 56 and 57: (c) For shear k 11 = 1.0(d) For com
Page 58 and 59: Chapter 6 AppendixSlenderness Co-Ef
Page 60 and 61: FIGURE A6.3: Continuous restraint a
Page 62 and 63: Stability factor.The stability fact
Page 64 and 65: 7.4 Structural Plywood Flooring - D
Page 66 and 67: 5. Critical Load Action EffectsLoad
Page 68 and 69: 5. Serviceability limit state - Des
Page 70 and 71: 7.10 Structural Plywood Residential
Page 72 and 73: Because of the obvious difficulty a
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1.2 m roof load width)0.25 kPa x 1.
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Concentrated Imposed Load (Q)M max
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5. Serviceability Limit Stateand [A
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8 Structural Plywood Webbed Box Bea
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AdhesivesBeams relying only on an a
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5. Check Beam Stiffness:Check beam
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1. Initial beam trial size:(a)(b)Fr
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Required nail spacing s = øN j / q
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Figure 8.5 shows a discontinuous pl
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A8Chapter 8 AppendixBending / Compr
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where:A= h3.5 3D .1032 N. mJ12.440.
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FIGURE A8.2: Guide for Selecting In
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Table A8.6: Unit-Load Deflection Sp
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9 Structural Plywood Diaphragms & S
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FIGURE 9.3 shows a plywood panel na
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The following are the design steps
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Wind force, w on diaphragm w = 1.86
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Converted to Limit States CapacityC
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4. Chord Size and SplicesThe chords
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Load/Nail (N)Nail Deformation (mm)2
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• The horizontal force is 1.9 x 2
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= 5 kN/m v oR = 15/5 = 3 kN/m107
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ELEVATIONFIGURE 9.12: Shows shear f
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As previously mentioned the shearwa
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Assuming the applied racking load t
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In this instance let the two panels
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A9 CHAPTER 9 APPENDIXPlate 1Plate 2
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Plate 7Plate 8Plate 9119
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REFERENCES CITED:1. Timber Shearwal
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“nailability” by increasing res
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(a) (b) (c)FIGURE 10.3: Actual and
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Re-arranging the torsion equation r
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The polar moment of area (I p ) of
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Design Example - Plywood Gusseted P
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• assuming width of lines paralle
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hence:where:ΦMj⎡ Ip⎤= (0.8 x1.
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A10 Chapter 10 AppendixPhotographs
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MOMENT JOINTSPlate 7Plate 8Plate 9(
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REFERENCES CITED:1. Investigation o
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11.2 MaterialsPlywoodPlywood used i
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FIGURE 11.3: Effective widths of pl
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Transformed SectionSince the plywoo
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FIGURE 11.5: Bending stresses in st
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FIGURE 11.6: Stressed skin panel tr
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Flexural Deflection Long Term Servi
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Compression SpliceUsing 17mm F11 st
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REFERENCES CITED:1. Design & Fabric
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12 Exotic Structural Forms12.1 Intr
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displacement between diaphragms eac
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The section modulus (Z) is:ZZ=Iy1=1
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FIGURE 12.9: A parabolic arch (not
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F AFFFASS= (374.4 + 166.4)kN= 540.8
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12.11 Hypar Design - GeometryTo dev
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FIGURE 12.16: Reactive force compon
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12.14 Methodology - Principal Membr
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Many braced dome geometries exist b
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θasphere= is the angle subtended b
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AndNNNxyxyP=L21P=L12P=L33L2P3⎤+
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• whether or not to force the ply
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A12Chapter 12 AppendixEXAMPLES OF E
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EXOTIC STRUCTURAL FORMS DESIGN AIDS
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Type 1 joints referred to in AS 172
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FIGURE 13.3: Two and Three member T
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SECTION 4 : AS 1720.1-1997 : Clause
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connection load carrying capacity c
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13.5 Design of Type 1 Nailed Connec
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The following unfactored loads are
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nnaa=nnr42=5= 9 rowsThe assumed val
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13.11 Design of Type 2 Screwed Conn
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The reasons k 13 and k 14 are not c
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Type of JointSeasoned TimberUnseaso
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13.16 Design of Type 2 Bolted Conne
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where:Δ = Δi +h33j14xh35Q *Qkpfor
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The exploded view in Figure 13.11 s
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FIGURE 13.12: Edge, end and bolt sp
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13.21 Design of Type 2 Coach Screwe
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REFERENCES CITED:1. AS 1720.1-1997,
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Plate 3Plate 4219
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Plate 7Plate 8221
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14 Noise Control14.1 IntroductionTh
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The absorption process of a single
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When it is required to add more tha
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FIGURE 14.5: Types of cavity wallsT
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15 Condensation & Thermal Transmiss
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15.4 Thermal TransmissionThermal tr
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15.5 Thermal Transmission - Design
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REFERENCES CITED:1. Condensation, C
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The early fire hazard test indices
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ISO 9705 AND AS/NZS 3837These tests
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General InformationDesign of struct
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SpeciesAsh, Alpine - Eucalyptus del
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Results of recent tests organised b
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FlooringConstructionLVL(Substrates
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as expressed in the BCA.Species Ave
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ClosurePlywood Thickness for:Dougla
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Borers are rarely a problem with st
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HazardClassH1Exposure Specific serv
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17.3 Durability and Finishing Appli
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EWPAA MembersPlywood and Laminated
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