Resolving Wood Shear Wall Design Puzzles with Force ...€¦ · Resolving Wood Shear Wall Design...

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Resolving Wood Shear Wall Design Puzzles with Force Transfer Around Openings


Presented by: Jared S. Hensley, P.E.Disclaimer: This presentation was developed by a third party and is not funded by

American Wood Council or the Softwood Lumber Board.

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“The American Wood Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #50111237.

Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non‐AIA members are available upon request.

This course is registered withAIA 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, distributing, or dealing in any material or product.

______________________________Questions related to specific materials, methods, and services will be addressed atthe conclusion of this presentation.


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Course Description

This presentation provides an overview of the Force Transfer Around Openings (FTAO) shear wall design approach, recent research in this area, and a side-by-side comparison of design results between segmented, perforated, and FTAO design methods. This methodology is based on a joint research project of APA – The Engineered Wood Association, University of British Columbia (UBC), and USDA Forest Products Laboratory that examined variations of shear walls with code-allowable openings. The study evaluated internal forces generated during testing and assessed the effects of opening sizes, full-height pier sizes, and different construction techniques, including the segmented, perforated, and FTAO methods. Asymmetric piers, multiple openings, and C-shaped sheathing were investigated and rational design methodologies in accordance with the International Building Code have been created.

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Learning Objectives

1. Participants will investigate past and current methods for determining force transfer around openings for wood shear walls through discussion of the joint research project of APA – The Engineered Wood Association, the University of British Columbia (UBC), and the USDA Forest Products Laboratory (FPL).

2. Participants will compare the effects of different opening sizes, full-height pier sizes, and their relationships to the three industry shear wall approaches by illustrating use of the segmented, perforated, and FTAO methods.

3. Participants will observe how the study examined internal forces generated during loading by reviewing full-scale wall test data as well as analytical modeling performed in determining statistical accuracy.

4. Participants will conclude that research results obtained from this study can be used to support different design methodologies in estimating forces around openings accurately.

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Audience Poll

1. What is your profession?A. Architect

B. Engineer

C. Builder

D. Building Official

E. Other

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Audience Poll

2. How would you describe your knowledge of Force Transfer Around Openings?A. Expert

B. Intermediate

C. Novice

D. What am I doing here?

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Agenda

1. Shear Wall Design Challenges

2. History of FTAO Research at APA

3. Advancements in FTAO Asymmetric Pier Widths

Multiple Openings

C-shaped Panels

Deflection Calculations

Conceptual Keys

4. Benefits of FTAO with Continuous Wood Structural Panels

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Shear Wall Design Challenges

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Segmented1. Aspect Ratio of

2:12. Aspect ratio up to

3.5:1, if allowable shear is reduced by 2b/h

Force Transfer1. Code does not

provide guidance for this method

2. Different approaches using rational analysis could be used

Perforated1. Code provides

specific requirements

2. The capacity is determined based on empirical equations and tables

15 SDPWS 4.3.5

1010

H H H Hvv

Vbs

Only full height segmentsare consideredHold-downs at each

wall segmentMax aspect ratio 2:1 – without

adjustment 3.5:1 – with

adjustment New to SDPWS-15

Aspect ratio h:bs as shown in figure

h

15 SDPWS Section 4.3.5.1


Segmented Wood Shear Walls

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1111

Openings accounted for by empirical adjustment factorHold-downs only at

endsUplift between hold

downs, t, at full height segments is also required Limited to 870 plf H H

V


t t

15 SDPWS 4.3.5.3


Perforated Shear Walls

vmax vmax

h

bs

1212

Openings accounted for by strapping or framing “based on a

rational analysis”

Hold-downs only at endsH/w ratio defined

by wall pier

15 SDPWS 4.3.5.2


FTAO Shear Walls

H H

V


v

h

bs

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Audience Poll

3. How often do you use FTAO when designing a building utilizing wood shear walls?A. > 50% (Frequently)

B. 0-25% (At least once per job)

C. 0% (I only use segmented or perforated)

D. N/A (I don’t design wood buildings.)

1414h:b ratio Perforated

Excerpt Fig 4Ch:b ratio Segmented

Excerpt Fig 4D


Shear Wall Aspect Ratio AdjustmentsDefinitions of h and b are the same as in previous codes

ALL shear walls with 2:1 < aspect ratios <= 3.5:1 shall apply reduction factor known as the aspect ratio factor

Aspect Ratio Factor (WSP) = 1.25-0.125h/bs Formerly applied only to high seismic

15 SDPWS 4.3.4

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Shear Distribution to Shear Walls in Line Individual shear walls in line shall provide the same

calculated deflection. Exception: Nominal shear capacities of shear walls having 2:1<aspect

ratio<=3.5:1 are multiplied by 2bs/h for design. Aspect ratio factor (4.3.4.2) need not be applied.

15 SDPWS 4.3.3.4.1


h:b ratio PerforatedExcerpt Fig 4C

h:b ratio SegmentedExcerpt Fig 4D

1616

Perforated Shear Wall Aspect Ratios Full Height wall segments 2:1 < aspect ratio <= 3.5:1 Multiply those segments by 2bs/h to calculate Li and ΣLi

Sections 4.3.4.2 and 4.3.3.4.1 do not apply

L1 L2 L3 L4

L


15 SDPWS 4.3.4.3

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4. When designing shear walls with the NEW aspect ratio factor of 1.25-0.125h/bs, the deflection of each individual shear wall must be…A. < 1 inch

B. equal.

C. dependent on the wall material.

D. a parabola.

Audience Poll

4. When designing shear walls with the NEW aspect ratio factor of 1.25-0.125h/bs, the deflection of each individual shear wall must be…A. < 1 inch

B. equal.

C. dependent on the wall material.

D. a parabola.

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Typical FTAO Application Residential, Multifamily Single Opening Design assumes equal pier width

Commercial Strap continuous wall line above

and below openings Fully sheath wall

Field Survey 18+ sites fall 2010 (LA, Orange and San Diego Counties) Multi-Family 40-90% of all shear applications utilized FTAO

Single-Family 80% Minimum 1-application on front or back elevation 70% Multiple applications on front, back or both 25% Side wall application in addition to front or back application

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History of FTAO Research at APA

Joint Research Project APA - The Engineered Wood Association (Skaggs & Yeh)

University of British Columbia (Lam & Li),

USDA Forest Products Laboratory (Rammer & Wacker)

Study was initiated in 2009 to: Examine the variations of walls with code-allowable openings

Examines the internal forces generated during full-scale testing

Evaluate the effects of size of openings, size of full-height piers, and different construction techniques

Create analytical modeling to mimic testing data

2020

Study results will be used to:Support design methodologies in estimating the forces

around the openings Develop rational design methodologies for adoption in

the building codes and supporting standardsCreate new tools/methodology for designers to

facilitate use of FTAO


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L1 Lo L2

h

V

vp

v v

vp

v v

1

2


Prominent FTAO Techniques

Drag Strut Analogy Forces are collected

and concentrated into the areas above and below openings

Strap forces are a function of opening and pier widths

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ho/2F1

V1

L1

h1

ho/2F2

V2

L2

hU

1

2



Cantilever Beam Analogy Forces are treated as moment

couples

Segmented panels are piers at sides of openings

Strap forces are a function of height above and below opening and pier widths

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Diekmann Assumes wall behaves as

monolith

Internal forces resolved via principles of mechanics



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5. In which FTAO method are the forces determined by calculating moment couples?A. Drag Strut Analogy

B. Cantilever Beam Analogy

C. Diekmann (Thompson)

D. The Unicorn Method

Audience Poll

5. In which FTAO method are the forces determined by calculating moment couples?A. Drag Strut Analogy




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2.3' 4' 4'

8'4'

2'

2,000 lbf

2'

10.3'


FTAO Design Example Comparison

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Drag Strut Analogy F1 = 284 lbf

F2 = 493 lbf

Cantilever Beam Analogy F1 = 1,460 lbf

F2 = 2,540 lbf

Diekmann Technique F1 = 567 lbf

F2 = 986 lbf


FTAO Design Example Comparison

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Drag Strut Analogy Martin, Z.A. 2005. Design of wood structural panel shear walls with

openings: A comparison of methods. Wood Design Focus 15(1):18-20

Cantilever Beam Analogy Martin, Z.A. (see above)

Diekmann Method Diekmann, E. K. 2005. Discussion and Closure (Martin, above), Wood

Design Focus 15(3): 14-15 Breyer, D.E., K.J. Fridley, K.E. Cobeen and D. G. Pollock. 2014. Design

of Wood Structures ASD/LRFD, 7th ed. McGraw Hill, New York.

SEAOC/Thompson Method SEAOC. 2014. 2015 IBC Structural/Seismic Design Manual, Volume 2:

Examples for Light-frame, Tilt-up and Masonry Buildings. Structural Engineers Association of California, Sacramento, CA



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Advancements in FTAO

APA Testing w/ CUREE Basic Loading Protocol

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12 wall configurations tested Walls were tested with and without FTAO strapping

Wall nailing; 10d commons (0.148” x 3”) at 2” o.c.

Sheathing; 15/32 Perf Cat oriented strand board (OSB) APA STR I

All walls were 12 feet long and 8 feet tall

Cyclic loading protocol following ASTM E2126, Method C, CUREE Basic Loading Protocol


Test Plan

30

8'-0

"3'-0

"3

'-10

"


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31

5'-0

"1

'-10

"


32

4'-0

"

2'-4

"4'

-0"

5'-0

"

7'-0

"


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Information Obtained Through TestingCyclic hysteretic plots and various cyclic parameters

of the individual walls

Hold down force plots

Anchor bolt force plots

Hysteric plots of the applied load versus the displacement of the walls

Hysteric plots of the applied load versus strap forces


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Diekmann

Technique

Top Bottom Top Bottom Top Bottom Top/Bottom Top Bottom

Wall 4a 687 1,485 178% 82% 652% 183% 132% 406% 115%

Wall 4b 560 1,477 219% 83% 800% 184% 133% 499% 115%

Wall 4c (3)668 1,316 183% 93% 670% 207% 149% 418% 129%

Wall 4d 1,006 1,665 122% 73% 445% 164% 118% 278% 102%

Wall 5b 1,883 1,809 65% 68% 327% 256% 173% 204% 160%

Wall 5c (3)1,611 1,744 76% 70% 382% 265% 187% 238% 166%

Wall 5d 1,633 2,307 75% 53% 377% 201% 141% 235% 125%

Wall 6a 421 477 291% 256% 1063% 571% 410% 663% 357%

Wall 6b 609 614 201% 199% 735% 444% 319% 458% 277%

Wall 8a 985 1,347 118% 86% 808% 359% 138% 269% 120%

Wall 8b (4)1,493 1,079 78% 108% 533% 449% 124% 177% 150%

Wall 9a 1,675 1,653 69% 70% 475% 383% 185% 217% 166%

Wall 9b 1,671 1,594 69% 73% 476% 397% 185% 218% 172%

Wall 10a 1,580 n.a. (5) 73% n.a. (5) 496% n.a. (5) n.a. (5) n.a. (5) n.a. (5)

Wall 10b 2,002 n.a. (5)58% n.a. (5)

391% n.a. (5) n.a. (5) n.a. (5) n.a. (5)

Wall 11a 2,466 n.a. (5) 47% n.a. (5) 318% n.a. (5) n.a. (5) n.a. (5) n.a. (5)

Wall 11b 3,062 n.a. (5)38% n.a. (5)

256% n.a. (5) n.a. (5) n.a. (5) n.a. (5)

Wall 12a 807 1,163 81% 94% 593% 348% 128% n.a. (5) n.a. (5)

Wall 12b 1,083 1,002 60% 109% 442% 403% 138% n.a. (5) n.a. (5)

Error (2) For Predicted Strap Forces at ASD Capacity (%)

Wall ID

Measured Strap

Forces (lbf) (1)

Drag Strut Technique Cantilever Beam TechniqueSEAOC/Thompson

Technique


Measured vs Predicted Strap Forces

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Wall 13

Click to Play


Testing Observations

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12 assemblies tested, examining the three approaches to designing and detailing walls with openings Segmented

Perforated Shear Wall

Force Transfer Around Openings

Walls detailed for FTAO resulted in better global response


Testing Results

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Comparison of analytical methods with tested values for walls detailed as FTAO The drag strut technique was consistently un-conservative

The cantilever beam technique was consistently ultra-conservative

SEAOC/Thompson provides similar results as Diekmann

SEAOC/Thompson & Diekmann techniques provided reasonable agreement with measured strap forces

Better guidance to engineers will be developed by APA for FTAO Summary of findings for validation of techniques

New tools for IRC wall bracing


Conclusions of Tests

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6. Which FTAO method tested was found to be consistently un-conservative?A. Drag Strut Analogy




6. Which FTAO method tested was found to be consistently un-conservative?A. Drag Strut Analogy




Audience Poll

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www.apawood.org/publications

Report is 149 pages, 28.5 MB

Enter: “Force Transfer”

or “M410”


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SEAOC Convention 2015 Proceedings

Basis of APA FTAO Design Methodology

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Asymmetric Pier WidthsMartin, Diekmann (Wood Design Focus, 2005)


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Multiple OpeningsAPA FTAO Testing Wall 12 Two openings

Asymmetric pier widths

Diekmann Rational Analysis


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Conceptual Keys

The method assumes the following: The unit shear above and below the openings is equivalent.

The corner forces are based on the shear above and below the openings and only the piers adjacent to that unique opening.

The tributary length of the opening is the basis for calculating the shear to each pier. This tributary length is the ratio of the length of the pier multiplied by the length of the opening it is adjacent to, then divided by the sum of the length of the pier and the length of the pier on the other side of the opening.

For example, T1 = (L1*Lo1)/(L1+L2)

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Conceptual Keys

The method assumes the following: The shear of each pier is the total shear divided by the L of

the wall, multiplied by the sum of the length of the pier and its tributary length, divided by the length of the pier: v1 = (V/L)(L1+T1)/L1

The unit shear of the corner zones is equal to subtracting the corner forces from the panel resistance, (R). R is equal to the shear of the pier multiplied by the pier length: Va1 = (v1L1 – F1)/L1

L1 Lo1 L2 L3Lo2V

L

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Conceptual Keys

The method assumes the following:Once the entire segment shears have been calculated,

then the design is checked by summing the shears vertically along each line. The first and last line equal the hold-down force, and the rest should sum to zero.

4646

Audience Poll

7. Which lateral design method do you believe is the most economical?A. Segmented

B. Perforated

C. FTAO

D. Duct Tape

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Shear Wall Design Examples

Segmented Shear Wall Approach

Perforated Shear Wall Approach

Force Transfer Around Opening Approach

4848


3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”

2’-8” 2’-8”

8’-0

”

V

V = 3,750 lb

26’-0”

Standard Example Wall with 3 openings.

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4949

3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”

2’-8” 2’-8”

8’-0

”

V

Does not consider contribution of sheathing above and below openings

26’-0”

Segmented Approach

5050

4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”

2’-8” 2’-8”

8’-0

”

V

V = 3,750 lbsHeight/width Ratio = 8:3.5

2w/h = (2)(3.5)/8 = 0.875

vH HCode Limitation

3’-6” 3’-0”

vH H vH H vH H

15 SDPWS 4.3.3.4.1

Segmented Approach

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5151

1. Unit Shear

V = V/∑L = 3,750/15 = 250 lbs/ft

2. Allowable Shear 3’-6” wallsv allowable = 380 (0.875)=332 lbs/ft > 250 lbs/ft

3. Allowable Shear 4’ walls (2:1 h:w)

v allowable = 260lb/ft > 250 lbs/ft

4. Hold-down forcesH = vh = 250 x 8 = 2,000 lbs

15/32” Rated Sheathing 8d @ 4”o.c. at 3.5’ walls

Note: For simplicity Dead Load contributions and various footnote adjustments have been omitted

8 – hold downs @ 2000+ lb capacity

15/32” Rated Sheathing 8d @ 6”o.c. @ 4’ walls

Segmented Approach

5252


4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”2’-8” 2’-8”

8’-

0”

V

V = 3,750 lbsv = 250 lbs/ftH = 2,000 lbs

v v v vH H H H H H H H

3’-6” 3’-0”

15/32” Rated Sheathing 8d @ 6”o.c.


Summary

Segmented Approach

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5454

3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”

2’-8” 2’-8”

8’-0

”

V

V = 3,750 lb

v, tH H

26’-0”

Code LimitationHeight/width Ratio = 8:3.52w/h = (2)(3.5)/8 = 0.875

v, t v, tv, t

Perforated Approach

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5555

1. Unit shear in the wall

v = 3,750/15 = 250 lb/ft

2. Percent of Full-Height Sheathed

∑Li/L = 15/26 = 0.57 (57%)

3. Maximum opening heighth = 6’-8”

Perforated Approach

5656

57% 0.61

15 SDPWS Table 4.3.3.5

Perforated Approach

Shear Capacity Adjustment Factor, Co

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4. Co – Shear Resistance Adjustment Factor

Co = 0.612 say 0.61

5. Adjusted Shear Resistance 4’-0” Walls

v allowable = 490 x 0.61 = 299 lbs/ft > 250 lbs/ft

3’-6” WALLS

v allowable = 490 x 0.875 x 0.61 = 262 lbs/ft > 250 lbs/ft


15 SDPWS Table 4.3A

Perforated Approach

5858

6. Uplift at Perforated Shear Wall ends (hold downs)

R = (v*H)/Co = (250*8)/(0.61) = 3,280 lbs

7. In-plane Shear Anchorage

vmax = 250/0.61 = 410plf

8. Uplift anchorage between shear wall ends

t = 250/0.61 = 410 plf (at full segments only)

9. Deflection is calculated using the 4-term deflection

equation from Chapter 23 of the 2015 IBC

using our vmax value for v and the sum of

the full height segment lengths for b.

15 IBC Equation 23-2

Perforated Approach

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5959

3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

6’-8”

2’-8” 2’-8”

8’-0

”

V

V = 3,750 lbv = 250 lbs/ftH = 3,280 lbs

v, tH Hv, t v, tv, t

Summary

Vmax = t = 410 lbs/ft

(wall anchorage)


Perforated Approach

6060





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6161

3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

2’-8” 2’-8”

8’-

0”

V

V = 3,750 lbs

H H

26’-0”

Height/width Ratio = 2’-8” / 3’-6”

6’-8”

19’-6”6’-6”

FTAO Approach

6262

FTAO Approach

1. Calculate the hold-down forces:

H = Vh/L = (3750 x 8’)/19.5’ = 1538lbs

2. Solve for the unit shear above and below the openings:

va = vb = H/(ha+hb) = 1538/(1.33’+4’) = 289 plf

CK: The unit shear above and below the openings is equivalent.

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

L

6’-8”

hho

ha

hb

va

vb

va

vb

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FTAO Approach

3. Find the total boundary force above and below the openings

First opening: O1 = va x (Lo1) = 289 plf x 6’ = 1734lbs

Second opening: O2 = va x (Lo2) = 289 plf x 2’ = 578lbs

CK: The corner forces are based on the shear above and below the openings and only the piers adjacent to that unique opening.

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

L

6’-8”

hho

ha

hb

6464

FTAO Approach

4. Calculate the corner forces:

F1 = O1(L1)/(L1+L2) = 866# F2 = O1(L2)/(L1+L2) = 866#

F3 = O2(L2)/(L2+L3) = 308# F4 = O2(L3)/(L2+L3) = 269#

CK: Strap forces

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

L

6’-8”

hho

ha

hb

F1 F2 F3 F4

F1 F2 F3 F4

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FTAO Approach

5. Tributary length of openings (ft)

T1 = L1(Lo1)/(L1+L2) = 3’ T2 = L2(Lo1)/(L1+L2) = 3’

T3 = L2(Lo2)/(L2+L3) = 1.1’ T4 = L3(Lo2)/(L2+L3) = 0.9’

CK: Ratio of the length of the pier x length of the opening it is adjacent to, then / (length of the pier + length of the pier on the other side of the opening).

L1 Lo1 L2 L3Lo2V

H H

L

6’-8”

hho

ha

hb

T1 T2 T3 T4

6666

FTAO Approach

6. Unit shear beside the openingV1 = (V/L)(L1+T1)/L1 = 337 plf V2 = (V/L)(T2+L2+T3)/L2 = 388 plf

V3 = (V/L)(T4+L3)/L3 = 244 plf Check V1*L1 +V2*L2+V3*L3=V? YES

CK: The shear of each pier = the total shear / the L of the wall x (length of the pier + its tributary length)/ by the length of the pier

L1 Lo1 L2=4’ L3Lo2V

H H

L=19’-6”

6’-8”

hho

ha

hb

T1 T2

3’-0”

T3

1.1’

T4V1 V3V2

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FTAO Approach

7. Resistance to corner forces

R1=V1*L1 = 1346lbs

R2 = V2*L2 = 1551lbs

R3 = V3*L3 = 853lbs

8. Resistance – corner force

R1-F1 = 480lbs

R2-F2-F3 = 377lbs

R3-F4 = 583lbs

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

L

6’-8”

hho

ha

hb

6868

FTAO Approach

9. Unit shear in the corner zones

va1 = (R1-F1)/L1 = 120 plf

va2 = (R2-F2-F3)/L2 = 94 plf

va3 = (R3-F4)/L3 = 167 plfCK: The unit shear of the corner zones = panel resistance (R) -the corner forces . R = the shear of the pier x the pier length.

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

L

6’-8”

hho

ha

hb

va1 va2

vb1 vb2

va3

vb3

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FTAO Approach

L1 Lo1 L2 L3Lo2

2’-8” 2’-8”

V

H H

6’-8”

hho

ha

hb

10. Check your solution – YES to all

Line 1: va1(ha+hb)+v1(ho)=H?

Line 2: va(ha+hb)-va1(ha+hb)-V1(ho)=0?

Line 3: va2(ha+hb)+V2(ho)-va(ha+hb)=0?

Line 4 = Line 3

Line 5: va(ha+hb)-va3(ha+hb)-V3(ho)=0?

Line 6: va3(ha+hb)+V3(ho)=H?

1 2 43 5 6

CK: Once all segment shears are calculated, check the design by summing the shears vertically along each line. The 1st and last = hold-down force, and the rest should = zero.

va1 va2 va3

V1 V2 V3

7070

FTAO Approach

2-Horizontal straps rated at 866lbs

Summary

3’-6” 3’-0” 4’-0” 6’-0” 4’-0” 3’-6”2’-0”

2’-8” 2’-8”

8’-

0”

V

H H

26’-0”

6’-8”

19’-6”6’-6”

V = 3,750 lbv = 388 lbs/ftH = 1,538 lbs 15/32” Rated Sheathing 8d @ 4”o.c.

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7171

15/32” Rated sheathing

8d @ 4”o.c. (3’-6” walls)

8d @ 6” o.c. (4’ walls)


Segmented Approach

15/32” Rated Sheathing

8d @ 4”o.c.

2 – hold downs @ 1,538 lb capacity

2 Straps – 866 lb

Force Transfer

v, tH Hv, t v, t

15/32” Rated Sheathing

8d @ 3”o.c.

2 – hold downs @ 3280 lb capacity

extensive plateanchorage

Perforated

v, t

7272

2’-0” 3’-0” 3’-0” 8’-0” 3’-0” 2’-0”5’-0”

7’-0” 4’-0” 10’-

0”

V

H H

26’-0”

Segmented & Perforated use full height segments 3.5:1 for 10’-0” = 34”

FTAO uses heights adjacent to openings 3.5:1 for 7’-0” = 24” 2:1 for 4’-0” = 24”

6’-8”P2 P3 P4P1


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Deflection Calculations - Concept

V+

H Hh

2+

h1

+

h3

+

1+ 2

+ 3+

V-

H H

h2

-

h1

- h3

-

1- 2

- 3-

= average(1+2

+ 3+

1-2

-3-)

74

Deflection Calculations

Wall drift estimation when using FTAO

Historical 4-term deflection equation Average deflection, varying h

‐3,000

‐2,000

‐1,000

0

1,000

2,000

3,000

‐5 ‐4 ‐3 ‐2 ‐1 0 1 2 3 4 5

Applied Load (plf)

Deflection (in.)

Wall 12

12a

12b

4 term

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8. True or False: Wall sheathing can aid in FTAO tension force resistance?A. True

B. False

Audience Poll

8. True or False: Wall sheathing can aid in FTAO tension force resistance?A. True

B. False

76

APA FTAO Test Wall 6

Framing status quo

Reduce/eliminate strap force

C-shaped Panels

Benefits of FTAO with ContinuousWood Structural Panels

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For the Structural Engineer…Straightforward rational analysis

Easy to program: Excel, web based application, or other

Design check = confidence in calculations

7878


Value propositionReduction of more costly components

Continuous nail base + stiffer wall = fewer callbacks due to: Stucco cracking, water intrusion, wall buckling

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Learning Objectives

1. Participants will investigate past and current methods for determining force transfer around openings for wood shear walls through discussion of the joint research project of APA – The Engineered Wood Association, the University of British Columbia (UBC), and the USDA Forest Products Laboratory (FPL).

2. Participants will compare the effects of different opening sizes, full-height pier sizes, and their relationships to the three industry shear wall approaches by illustrating use of the segmented, perforated, and FTAO methods.

3. Participants will observe how the study examined internal forces generated during loading by reviewing full-scale wall test data as well as analytical modeling performed in determining statistical accuracy.

4. Participants will conclude that research results obtained from this study can be used to support different design methodologies in estimating forces around openings accurately.

80

Questions/ Comments?

Jared S. Hensley, [email protected] (253) 426-1224 www.apawood.org

This concludes The American Institute of Architects Continuing Education Systems Course

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