Structural Design of SIPs - WoodWorks · Structural Design of SIPs Example 1: DeflectionExample 1:...

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Structural Insulated Panels (SIPs)Structural Insulated Panels (SIPs)for Engineersfor Engineers

Eric Tompos, P.E., S.E., C.B.O.Eric Tompos, P.E., S.E., [email protected]@ntainc.com

Structural Design of SIPsStructural Design of SIPs

“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be

t d t AIA/CES f AIA b C tifi t f C l ti freported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professionalThis program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using,material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials methods and services will beQuestions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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di t ib ti di l d f th t tidistribution, display and use of the presentation without written permission of the speaker is

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© The American Wood Council 2010

Learning ObjectivesLearning ObjectivesLearning ObjectivesLearning ObjectivesAt the end of this program, participants will be able to:

1. Assess design limits state applicable to SIP panels in commercial and

residential projects.

2. Estimate SIP deformations, including shear deformations, for the purposes

of checking serviceability requirements.

3 Account for creep deformation situations where sustained loads are applied3. Account for creep deformation situations where sustained loads are applied

to the panel.

4. Assess the strength of various support details which may be encountered in

walls and roofs.

What is a SIP?What is a SIP?What is a SIP?What is a SIP?Rigid Foam Insulation

Structural Facings

Structural AdhesiveStructural Adhesive

Optional Electrical ChChases


What is a SIP?What is a SIP?What is a SIP?What is a SIP? OSB faced SIPs with EPS cores are most OSB faced SIPs with EPS cores are most

common; however other materials exist:common; however other materials exist:common; however, other materials exist:common; however, other materials exist:

OSB Metal Cementitious/


Composite

Brief HistoryBrief HistoryBrief HistoryBrief History Development began in the 1930’s with Development began in the 1930’s with

engineering and durability testing at the Forestengineering and durability testing at the Forestengineering and durability testing at the Forest engineering and durability testing at the Forest Product Laboratories (FPL)Product Laboratories (FPL)

FPL constructed a small house of SIPs inFPL constructed a small house of SIPs inFPL constructed a small house of SIPs in FPL constructed a small house of SIPs in 19371937——house is still in usehouse is still in use

Another structure was built in 1947 using Another structure was built in 1947 using corrugated paperboard corescorrugated paperboard cores——it was it was disassembled periodically over a 31 year period disassembled periodically over a 31 year period to observe changes in the panelsto observe changes in the panelsto observe changes in the panelsto observe changes in the panels


Brief HistoryBrief HistoryBrief HistoryBrief History Foam cores introduced in 1969 creating first Foam cores introduced in 1969 creating first

modern panelsmodern panelsmodern panelsmodern panels Prescriptive code requirements added to the Prescriptive code requirements added to the

2007 IRC supplement, Section R6142007 IRC supplement, Section R614pp ,pp , Walls OnlyWalls Only

2009 SIPA code report developed with NTA2009 SIPA code report developed with NTA——f t d SIPf t d SIPperformance rated SIPsperformance rated SIPs


Designer’s RoleDesigner’s RoleDesigner s RoleDesigner s Role The design professional & engineered designThe design professional & engineered designg p g gg p g g Assesses suitability for specific useAssesses suitability for specific use Ability to check conditions that cannot be evaluated Ability to check conditions that cannot be evaluated

in the laboratoryin the laboratoryin the laboratoryin the laboratory Evaluates allowable properties against code Evaluates allowable properties against code

required loadsrequired loads


Engineering GuidelinesEngineering GuidelinesEngineering GuidelinesEngineering Guidelines SIP Code ReportsSIP Code Reportspp Summary of test dataSummary of test data Interpolated values not identifiedInterpolated values not identified Method of interpolation not providedMethod of interpolation not provided Limited explanation of how to use dataLimited explanation of how to use data

2007 IRC Prescriptive Provisions2007 IRC Prescriptive Provisions Prescriptive onlyPrescriptive only——not a design methodnot a design methodp yp y gg Method for deriving prescriptive values not providedMethod for deriving prescriptive values not provided Very restrictive limitationsVery restrictive limitations


Engineering GuidelinesEngineering GuidelinesEngineering GuidelinesEngineering Guidelines APA Plywood Design Specification APA Plywood Design Specification y g py g p

Supplement 4 Supplement 4 –– Design & Fabrication of Design & Fabrication of Plywood Sandwich PanelsPlywood Sandwich Panels

C d d t dC d d t d Code adoptedCode adopted No properties providedNo properties provided Only addresses most basic aspectsOnly addresses most basic aspects——insufficient forinsufficient forOnly addresses most basic aspectsOnly addresses most basic aspects insufficient for insufficient for

complete designcomplete design Very conservativeVery conservative----does not correlate well to tested does not correlate well to tested

assembliesassembliesassembliesassemblies


Engineering GuidelinesEngineering GuidelinesEngineering GuidelinesEngineering Guidelines

NTA IM 14 TIP 01 Engineered Design of SIPNTA IM 14 TIP 01 Engineered Design of SIPNTA IM 14 TIP 01 Engineered Design of SIP NTA IM 14 TIP 01 Engineered Design of SIP Panels Using NTA Listing Report DataPanels Using NTA Listing Report Data Basis for SIPA code report (currently applies Basis for SIPA code report (currently applies

ONLYONLY to SIPA report)to SIPA report) Provides design values that are correlated to test Provides design values that are correlated to test

datadatadatadata Sufficient details to permit designSufficient details to permit design Provisions based on NTA’s judgment and NTAProvisions based on NTA’s judgment and NTAProvisions based on NTA s judgment and NTA Provisions based on NTA s judgment and NTA

opinion as to best practiceopinion as to best practice


Design Example 1Design Example 1SIPA Report Table 3:

Allowable Uniform Transverse Loads4-5/8-inch Thick SIP 6-1/2-inch Thick SIP

D fl ti Li it2 D fl ti Li itPanel Length

(ft)

Deflection Limit2 Deflection LimitL/180 L/240 L/360 L/180 L/240 L/360

8 WAB 50.8 40.9 27.3 73.8 64.7 43.1

8 68.8 51.6 34.4 80.6 80.6 56.6

10 45.1 33.8 22.5 62.0 57.9 38.6

12 30 8 23 1 15 4 50 4 40 9 27 312 30.8 23.1 15.4 50.4 40.9 27.3

14 21.7 16.3 -- 39.6 29.7 19.8

16 -- -- -- 29.4 22.1 14.7

18 -- -- -- 22.4 16.8 --


Design Example 1Design Example 1

Design Limit StatesDesign Limit StatesDesign Limit StatesDesign Limit StatesFlexural strengthFlexural strengthShear strengthShear strengthggDeflectionDeflection


Example 1: Flexural StrengthExample 1: Flexural StrengthExample 1: Flexural StrengthExample 1: Flexural StrengthDesign Guide 4.3.Design Guide 4.3.gg

PropertyWeak-Axis Bending

Strong-Axis Bending

SIPA Report Table 1: Mechanical Properties

Allowable Tensile Stress, Ft (psi) 245 495Allowable Compressive Stress, Fc (psi) 340 580


Example 1: Flexural StrengthExample 1: Flexural StrengthExample 1: Flexural StrengthExample 1: Flexural StrengthSIPA Report Table 2: Section Properties

Panel Thickness, h

(in.)

CoreThickness, c

(in.)

Shear Area, Av

(in.2/ft)

Moment of Inertia, I(in.4/ft)

SectionModulus, S

(in.3/ft)

4.63 3.75 50.25 46.03 19.90

Solve for w:

45.6 psf


Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthDesign Guide 4.4.2.Design Guide 4.4.2.gg

PropertyWeak-Axis Bending

Strong-Axis Bending


Allowable Core Shear Stress, Fv (psi) 4.5 5.0

SIPA Report Table 2: Section Properties

Panel Thickness, h

(in.)

CoreThickness, c

(in.)

Shear Area, Av

(in.2/ft)

Moment of Inertia, I(in.4/ft)

SectionModulus, S

(in.3/ft)


4.63 3.75 50.25 46.03 19.90

Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthDesign Guide 4.4.3: Size Adjustment, Design Guide 4.4.3: Size Adjustment, CCFvFvg j ,g j , FvFv

Property Weak-Axis Bending

Strong-Axis Bending


Bending BendingReference Depth, ho (in.) 4.625 4.625

Shear Depth Factor Exponent, m 0.84 0.86


Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear Strength18

20

)12

14

16

, Fv (p

si)

6

810

12S

treng

th

24

6

She

ar

02 4 6 8 10 12 14

Overall Thickness, h (in.)


, ( )

Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthDesign Guide 4.4.4.3: Bearing ConditionDesign Guide 4.4.4.3: Bearing Condition

Bearing Support


Spline Support

Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthDesign Guide 4.4.5: Shear SpanDesign Guide 4.4.5: Shear Span


Span Reduction

Example 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear StrengthExample 1: Shear Strength

Solve for w:

45.8 psf


Example 1: DeflectionExample 1: DeflectionExample 1: DeflectionExample 1: DeflectionDesign Guide 4.5.2Design Guide 4.5.2

Si l t d d fl ti ti i l di h dSi l t d d fl ti ti i l di h dSimply supported deflection equation including shear under Simply supported deflection equation including shear under uniform loads:uniform loads:

Bending deformation

Shear deformation

Shear deformations can not be neglected in SIPsShear deformations can not be neglected in SIPs


Example 1: DeflectionExample 1: Deflection12

Example 1: DeflectionExample 1: Deflection

8

10

06

OSB Weak-Axis

4

6

1/E

a x 1 Slope, 1/G

2

4

OSB Strong-Axis

Y-Intercept, 1/Eb0

0 500 1000 1500 2000 2500 3000

1/Ks x106

p , b

1/Ks x10


Example 1: DeflectionExample 1: DeflectionExample 1: DeflectionExample 1: Deflection


Property Weak-Axis Bending

Strong-Axis Bending

Elastic Modulus (Bending) E (psi) 738900 658800


Elastic Modulus (Bending), Eb (psi) 738900 658800Shear Modulus, G (psi) 270 405

SIPA Report Table 2: Section Properties

Panel Thickness, h

(i )

CoreThickness, c

(i )

Shear Area, Av

(i 2/ft)

Moment of Inertia, I(i 4/ft)

SectionModulus, S

(i 3/ft)(in.) (in.) (in.2/ft) (in.4/ft) (in.3/ft)

4.63 3.75 50.25 46.03 19.90


Example 1: DeflectionExample 1: DeflectionExample 1: DeflectionExample 1: Deflection

Substitute and Solve for w:


Example 1: Overall ResultExample 1: Overall ResultExample 1: Overall ResultExample 1: Overall ResultAllowable Uniform Loads (psf)Allowable Uniform Loads (psf)

L/180 L/240 L/360

Flexure 45 6Flexure 45.6Shear 45.8

Deflection 30 8 23 1 15 4Deflection 30.8 23.1 15.4

Deflection governsDeflection governsLoads match those given in SIPA report Table 3Loads match those given in SIPA report Table 3


Example 2 & 3Example 2 & 3Example 2 & 3Example 2 & 3Design Guide 4.4.4.3 & 4.4.5: Bearing Condition & Design Guide 4.4.4.3 & 4.4.5: Bearing Condition & Shear ForceShear ForceShear ForceShear Force

Bearing Support Spline Support

Zero bearing condition has two effectsZero bearing condition has two effectsReduction in strengthReduction in strengthIncrease in design shear loadIncrease in design shear loadIncrease in design shear loadIncrease in design shear load


Example 2 & 3Example 2 & 3Example 2 & 3Example 2 & 3


Example 2 & 3Example 2 & 3Example 2 & 3Example 2 & 3Total shear strength can (and should) beTotal shear strength can (and should) beTotal shear strength can (and should) be Total shear strength can (and should) be calculated as the summation ofcalculated as the summation ofTested SIP shear strength without fasteners Tested SIP shear strength without fasteners (example 2)(example 2)Calculated fastener withdrawal strength Calculated fastener withdrawal strength adjusted to account for fastener spacingadjusted to account for fastener spacingadjusted to account for fastener spacing, adjusted to account for fastener spacing, sheathing continuity, and prying (example 3)sheathing continuity, and prying (example 3)


Example 4: CreepExample 4: CreepExample 4: CreepExample 4: CreepDesign Guide 4.5.4: LongDesign Guide 4.5.4: Long--Term LoadingTerm LoadingCreep is an increase in strain (deflection) Creep is an increase in strain (deflection) under constant loadunder constant loadExcept for metalsExcept for metals allall structural materials creepstructural materials creepExcept for metals, Except for metals, allall structural materials creep structural materials creep and are designed for creep and creep ruptureand are designed for creep and creep ruptureDesign guide recommendations are based on Design guide recommendations are based on g gg gpublished study conducted by SIPApublished study conducted by SIPA


Example 4: CreepExample 4: Creep6 0

7.0cr

Example 4: CreepExample 4: Creep

4 0

5.0

6.0

ctio

n, K

c

Urethane

3.0

4.0

nal D

efle

c

EPS

1.0

2.0

Fact

ion

0.00 100 200 300 400 500 600 700

Duration of Load (months)( )Taylor, S.B., Manbeck, H. B., Janowiak, J. J., Hiltunum, D.R. “Modeling Structural Insulated Panel

(SIP) Flexural Creep Deflection.” J. Structural Engineering, Vol. 123, No. 12, December, 1997.


Example 4: CreepExample 4: CreepExample 4: CreepExample 4: CreepComparison of Material Creep Potential

MaterialMaterialFraction Deflection, Fraction Deflection,

KKcrcr

EPS, XPS Core SIPEPS, XPS Core SIP 4.04.0

Urethane Core SIPUrethane Core SIP 7.07.0

Seasoned LumberSeasoned Lumber 1.51.5

OSB or ‘Wet’ LumberOSB or ‘Wet’ Lumber 2.02.0

‘Wet’ OSB‘Wet’ OSB 6.06.0

Reinforced ConcreteReinforced Concrete 2.02.0


Example 4: CreepExample 4: CreepExample 4: CreepExample 4: CreepProposed Creep Equation for SIPsProposed Creep Equation for SIPsp p qp p q

Consider Consider KKcrcr based on load typebased on load typeLoad TypeLoad Type Creep Coefficient, Creep Coefficient, KKcrcrLoad Type Load Type (ASCE 7)(ASCE 7)

pp crcr

EPS/XPSEPS/XPS UrethaneUrethane

D, F, H, TD, F, H, T 4.04.0 7.07.0

S, LS, L 3.03.0 5.05.0

E, W, R, LE, W, R, Lrr, F, Faa 1.01.0 1.01.0


Design Example 5Design Example 5SIPA Report Table 5:

Allowable Uniform Axial LoadsAllowable Uniform Axial LoadsLateral Brace

Spacing

Panel Thickness

Spacing(ft) 4-5/8-inches 6-1/2-inches 8-1/4-inches

8 WAB 2320 2470 25308 3630 4070 42408 3630 4070 4240

10 3260 3890 413012 2810 3660 400014 -- 3390 383016 -- 3090 364018 -- 2790 343020 -- -- 3190


Design Example 5Design Example 5Design Example 5Design Example 5

Design Limit StatesDesign Limit StatesDesign Limit StatesDesign Limit StatesFacing strength under eccentric loadFacing strength under eccentric loadGlobal bucklingGlobal bucklingGlobal bucklingGlobal buckling


Example 5: EExample 5: E--StrengthStrengthExample 5: EExample 5: E StrengthStrengthDesign Guide 5.1.1: Load EccentricityDesign Guide 5.1.1: Load Eccentricityg yg y


Example 5: EExample 5: E--StrengthStrengthExample 5: EExample 5: E StrengthStrengthProperties from Table 1 and Table 2Properties from Table 1 and Table 2Minimum eccentricity from Design Guide:Minimum eccentricity from Design Guide:

To find maximum load iterative process requiredTo find maximum load iterative process requiredTo find maximum load iterative process requiredTo find maximum load iterative process requiredGood first guess:Good first guess:


Example 5: EExample 5: E--StrengthStrengthExample 5: EExample 5: E StrengthStrengthTrial AxialLoad P

Eccentricity Factor

CalculatedAxial Load PLoad, Pe

(lbf)Factor

Ce

Axial Load, Pe(lbf)

1 3045 0.627 38182 3818 0.595 36223 3622 0.603 36744 3674 0.601 36605 3660 0.602 3664

3664 0 601 36636 3664 0.601 36637 3663 0.601 3663


Example 5: BucklingExample 5: BucklingExample 5: BucklingExample 5: BucklingDesign Guide 5.1.2: Global BucklingDesign Guide 5.1.2: Global Bucklingg gg g

Where:


Example 5: Overall ResultExample 5: Overall ResultExample 5: Overall ResultExample 5: Overall ResultAllowable Uniform Axial Loads (plf)Allowable Uniform Axial Loads (plf)

Eccentric Load 3663

Global Buckling 4975

SIPA Report 3663

Strength under eccentric load governsStrength under eccentric load governsAxial Loads in SIPA report Table 5 rounded down to Axial Loads in SIPA report Table 5 rounded down to nearest 10 plfnearest 10 plfnearest 10 plfnearest 10 plfCalculated load matches SIPA report Table 5Calculated load matches SIPA report Table 5


Design Example 6Design Example 6Design Example 6Design Example 6Same as Example 5 except consider Same as Example 5 except consider increased design eccentricityincreased design eccentricity


Example 6: EExample 6: E--StrengthStrengthExample 6: EExample 6: E StrengthStrengthLoad Eccentricity Calculated

ExEccentricity, Pe

(in.)Factor

Ce

Axial Load, Pe(lbf)

5 1.083 0.601 3663

6 3.25 0.385 2186

Identical wall with sideIdentical wall with side--hung framing 36% hung framing 36% reduction in strengthreduction in strengthreduction in strengthreduction in strength


Example 7: Combined LoadsExample 7: Combined LoadsExample 7: Combined LoadsExample 7: Combined LoadsMust Use ASCE 7 Load CombinationsMust Use ASCE 7 Load Combinations——transient loads transient loads ne er applied conc rrentl at f ll magnit dene er applied conc rrentl at f ll magnit denever applied concurrently at full magnitudenever applied concurrently at full magnitude7 loading ‘conditions’ (not to be confused with ASCE load 7 loading ‘conditions’ (not to be confused with ASCE load cases)cases)))


Example 7: Combined LoadsExample 7: Combined LoadsExample 7: Combined LoadsExample 7: Combined Loads

Axial only, Axial only, PPTransverse only (C&C), Transverse only (C&C), TTP+T (max bending)P+T (max bending)P+T (max bending)P+T (max bending)0.75(P+T) (max axial)0.75(P+T) (max axial)P+T+V (max bending)P+T+V (max bending)P+T+V (max bending)P+T+V (max bending)0.75(P+T+V) (max axial)0.75(P+T+V) (max axial)P+V (seismic load combinations)P+V (seismic load combinations)


Design SoftwareDesign Software

Commercial packagesCommercial packages Isotropic material properties Don’t adequately consider shear deformations Don t adequately consider shear deformations Difficult to consider creep


Future ImprovementsFuture Improvements

Future editions will includeFuture editions will include Lateral design recommendations Seismic detailing recommendations Seismic detailing recommendations Design procedure for panels with structural

reinforcement (dimensional/engineeredreinforcement (dimensional/engineered lumber splines) Recommendations for holesRecommendations for holes LRFD (US) & LSD (Canada) methodologies


Questions?Questions?Questions?Questions?This concludes The American Institute of Architects Continuing This concludes The American Institute of Architects Continuing

Education Systems CourseEducation Systems CourseEducation Systems CourseEducation Systems Course

Eric Tompos, P.E., S.E., C.B.O.Eric Tompos, P.E., S.E., [email protected]@ntainc.com


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