and Roof Design Structural CLT Floor - WoodWorks CSA O86-14, 2016 Supplement. Structural CLT Floor and Roof Construction Presenter: [email protected] 25 Shear Force Terminology

Structural CLT Floor and Roof Construction

Presenter: [email protected] 1

Structural CLT Floor and Roof Design

Scott Breneman, PhD, PE, SESenior Technical Director – Project Resources and Solutions DivisionWoodWorks – Wood Products Council Photo Ema Peter Photography

“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516.

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 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, distributing, or dealing in any material or product.______________________________

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



Course DescriptionThis presentation is intended for designers of building systems seeking to familiarize themselves with the category of products known as mass timber, and specifically cross laminated timber (CLT). Topics will include manufacturing and product performance standards, structural design standards, and recognition of CLT in the International Building Code. Specific attention will be given to the design of CLT in horizontal applications—i.e., as panels of floor and roof systems—and discussion will include how to address important serviceability requirements related to deflection and floor vibration design. Example projects and details will be presented to highlight possible applications of CLT in building structures.

Learning Objectives

1. Discuss product manufacturing and design standards relevant to cross laminated timber (CLT), and identify where these standards are recognized in the International Building Code.

2. Consider the structural design properties of CLT relevant to floor and roof applications.

3. Discover how to design CLT floors to achieve serviceability goals related to deflection and vibration.

4. Examine the use of CLT in example buildings and connection details.



Introduction

Wood Building Systems

Post and Beam Light Frame Mass Timber



Mass Timber Products

Nail Laminated Timber (NLT) Glue Laminated Timber (GLT)

Laminated Veneer Lumber (LVL)Massive Plywood Panels (MPP) Cross Laminated Timber (CLT)

Images Source: Structurecraft

Glulam Beams& Columns

Mass Timber ProductsCross-laminated timber (CLT)

8



Cooley Landing Education CenterEast Palo Alto, CA

Photo: Arbor Building Group Photos: WoodWorks

Cooley Landing Education Center

East Palo Alto, CA



Albina YardPortland, OR

Photo Credit: LEVER Architecture


Photo Credit: WoodWorks



ARCHITECT: Lever ArchitecturePhoto: Scott Breneman


4 stories16,000 sfGreen Roof

13

ARCHITECT: Lever ArchitecturePhoto: Scott Breneman


14



Redstone Arsenal HotelHuntsville, AL

Image Credit: Lend Lease

Photos: Lend Lease, IHG Hotels, & Schaefer

Redstone Arsenal Hotel62,600 sf, 4 story hotel, 92 private roomsCLT used for walls, roof panels, and floor panels

1,557 CLT Panels; Typical floor panel is 8’x50’

Completed Late 2015



ARCHITECT: Acton OstrayENGINEER: Fast & Epp

2 0 1 7TallWood House at Brock Commons

University of British ColumbiaVancouver, Canada

18 Stories (17+1) 174 Feet tallBeamless two-way CLT floor slab

Cross Laminated Timber

Considerations:

• Large light-weight panels

• Dimensionally stable

• Precise CNC machining available

• Recognized by IBC

• Dual Directional span capabilities

• Often architecturally exposed

• Fast on-site construction

Graphic Credit: StructureCraft



CLT History Timeline

1990 2000 2005 2010 2015

Significantly increased

use in Europe

• 2010 – 1st

Production• 2011- PRG320• 2011 -Canadian

Handbook• 2013 – US

Handbookinterest began

.3 million m3 of built

CLT projects

Recognized in 2015 IBC

Austria industry-academia

joint research

.6-1 million m3 of built

CLT projectsE

urop

eN

orth

A

mer

ica

SB31

CLT Product Standardization



Thickness3 to 20 inches*

Max Length24 to 60 feet* Max Width

8 to 10 feet*

3+ layers of laminationsTypically Solid Sawn LaminationsCross-Laminated Layup

What is CLT?

*All dimensions are approximate.Consult with manufacturers

First Tech Credit Union, Hillsboro, Oregon Photo Credit: Structurlam Products



North American CLT Product Standard

ANSI/APA PRG 320 Standard for Performance-Rated Cross-Laminated Timber

The Standard Covers:- U.S. and Canada Use- Panel Dimensions and Tolerances- Component Requirements- Structural Performance

Requirements- Panel and Manufacturing

Qualification- Marking (Stamping)- Quality Assurance

CLT Stress Grades

Stress Grade Major StrengthDirection

Minor Strength Direction

E1 1950f-1.7E MSR SPF #3 Spruce Pine FirE2 1650f-1.5E MSR DFL #3 Doug Fir LarchE3 1200f-1.2E MSR Misc #3 MiscE4 1950f-1.7E MSR SP #3 Southern PineV1 #2 Doug Fir Larch #3 Doug Fir LarchV2 #1/#2 Spruce Pine Fir #3 Spruce Pine FirV3 #2 Southern Pine #3 Southern Pine

Standard (Non-mandatory) CLT stress grade in PRG 320-2012.Other custom stress grades including structural composite lumber (SCL) permitted



Common CLT Layups

3-ply 3-layer

9-ply 9-layer

5-ply 5-layer

7-ply 7-layer 7-ply 5-layer

9-ply 7-layer

PRG 320 Defined Layups



3rd Party Product Certification of CLT

CLT Product ReportsStress Grade

(standard or custom)Layup

(standard or custom)Panel Properties



Structural Design Standardization

National Design Specification for Wood Construction2015 Edition

Model Building Code Acceptance

2015 International Building Code



CLT is Defined – 2015 IBCSB9

Highlights of CLT Provisions in IBC 2015

• CLT is generally available for use in Type III, IV and V construction.

• IBC 2015 Chapter 6 Defines Dimensions of CLT to qualify as Heavy Timber (Type IV Construction)

• 6” Walls• 4” Floors• 3” Roofs• Non Fire-Retardant Treated CLT allowed in Exterior Walls of Type

IV construction in many conditions. (IBC 2015 602.4)

The Heavy Timber construction size requirements only apply to Type IV Construction

SB16SB17



CLT Manufactures for use in the US to PRG-320

• DR Johnson Lumber, Oregon• KLH USA, Subsidiary of KLH Massivholz, Austria.• Nordic Structures, Quebec, Canada• SmartLam, Columbia Fall, Montana• Structurlam, British Columbia, Canada

Working with CLT: Know Your Supply Chain

• CLT Manufactures different CLT grades and maximum panel sizes• CLT Manufacturers have specific CNC capabilities• 3rd Party Fabricators can have additional CNC capabilities

Photo: DR Johnson Photo: Sauter Timber



Working with CLT: Communicate Your Requirements

Define the deliverables you need from the supplier:- Shop drawings- Shop drawings with Engineering Stamp- Engineered Drawings and Calculations (e.g. as a deferred submittal)

Structural Properties



Non-homogenous, anisotropic material

Structural Section Properties

FLATWISE Panel Loading

Span in MAJOR Strength Direction“Parallel” Direction

Span in MINOR Strength Direction“Perpendicular” Direction

Reference & Source: ANSI/APA PRG 320-2017



EDGEWISE Panel Loading

Span in MAJOR Strength Direction Span in MINOR Strength Direction


Design properties based on an Extreme Fiber Model:

Flexural Capacity Check:

Mb ≤ (FbSeff)′

Mb = applied bending moment

(FbSeff)′ = adjusted bending capacity

Seff = effective section modulus

Fb = reference bending design stress of outer lamination

Flatwise Flexural Strength

Mb

Bending Stress

Reference: NDS 2015



Flexural Capacity Check (ASD)

(FbSeff)′ = CD CM Ct CL (FbSeff)

Flatwise Flexural Strength

Mb

Bending Stress

Commonly1.0

Provided as combined value

Mb ≤ CD (1.0) (FbSeff)

perNDS

Reference: NDS 2015

Select acceptable CLT section

Given:

16 foot span floor

40 psf live load, 40 psf total dead load.

Assume:

one-way spanning action in major axis of CLT

Analysis of a 1 ft strip of panel as beam

Calculate ASD Dead + Live Applied Moment

Mb = w L2 / 8 = (40+40psf) (16ft)2 / 8 = 2560 lb-ft/ft

Flatwise Flexural Strength Design Example

16 foot span

40 psf DL, 40 psf LL



Look for Acceptable CLT Grade from PRG 320: FbSeff,0 > 2560 lb-ft/ft


Reference: ANSI/APA PRG 320-2012

4,800

Select 5-Ply 6 7/8” Thick V1 Panel with FbSeff,0 = 4800 lb-ft/ft

ASD Flexural Capacity:Dead + Live load, CD = 1.0

(FbSeff)′ = CD (1.0) (FbSeff)

= 1.0 (1.0) (4800 lb-ft/ft)= 4800 lb-ft/ft

Mb = 2560 lb-ft/ft ≤ (FbSeff)’ = 4800 lb-ft/ft

Flexural Strength OK


16 foot span

40 psf DL, 40 psf LL



Design Properties based on Extreme Fiber Model:

Shear Capacity Check:

Va ≤ Fs(Ib/Q)eff′Va = applied shear

Fs(IbQeff)′ = adjusted shear strength

Flatwise Shear Strength

Va

Shear Stress

Reference: NDS 2015

Jargon Alert! AKA “Planar Shear”, “Out-of-Plane Shear”, or “Rolling Shear” Strength

Wood Structural Panel Term

Structural Engineering Term

CLT Term

Design Properties based on Extreme Fiber Model:

Shear Capacity Check (ASD):

Fs(IbQ)eff′ = CM Ct (Fs(IbQ)eff) = CM Ct Vs

Vplanar ≤ (1.0) Vs


Vplanar

Shear Stress

Commonly1.0 From Manufacturer

Reference: NDS 2015 & Product Reports

Note: Duration of Load Effects (Cd and λ) NOT applicable to Flatwise Shear Strength in the NDS



Shear Force Terminology

Planar ShearRolling Shear

Shear-In-the-Plane?Out-of-plane forces?

FLATWISE Shear in PRG 320 2017

Source: ANSI/APA PRG 320-2017

NDS 2015: Fs(Ib/Q)effPRG 320 Product Reports: Vs,0 & Vs,90

Source: NDS 2015 Manual


Rolling Shear

Source: CSA O86-14, 2016 Supplement



Shear Force Terminology & Jargon

Through-the-Thickness ShearIn-plane Shear Forces

EDGEWISE Shear in PRG 320-2017


NDS 2015: Fv(tv)PRG 320-2017: Fv,e,0 tp & Fv,e,90 tp

Source: NDS 2015 Manual

Flatwise Flexural Stiffness

Bending Stress

EIeff

Shear Analogy Method

Reference: US CLT Handbook Chapter 3




EIeff

GAeff


EIeff

GAeff

Important to develop properties of new CLT Sections.

Not to use standard CLT Sections




EIeff

GAeff

Advanced Use: Calculating Structural Capacities under Fire

Conditions usingNDS 2015 Chapter 16

Flatwise CLT Panel Section Properties

Values in RED provided by CLT manufacturer

Flexural Strength: FbSeff,0

Flexural Stiffness: EIeff,0

Shear Strength: Vs,0

Shear Stiffness: GAeff,0

FbSeff,90

EIeff,90

Vs,90

GAeff,90

Reference: PRG 320 and CLT Product Reports



Using PRG 320 Standard Grades for Design?

PRG 320 includes pre-defined Stress Grades, Layups and related

Design Properties

Is doesn’t tell you what CLT grades and layups are available.

Coordinate your design with manufactures availability and

information

General Purpose: 1 Way, Beam ActionNeeded Stiffness: EIeff,0 GAeff,0

Deflection Calculations

Can model multiple spans, cantilevers, etc.



Example Calculation:Uniform loading on one way slab:

Beam Analysis using

Flexural Stiffness: EIeff,0

Shear Stiffness: 5/6 GAeff,0

Maximum Deflection @ Mid-Span

Example Deflection Calculations

16 foot span

5/6 GAeff

Design Example:

= 0.284 in + 0.034 in = 0.318 in

= L / 604

w = 80 psf

Deformation to Long Term Loads

Deflection Creep Factor

Δ" = $%&Δ(" + Δ*" NDS Eq 3.5-1

Δ*"Δ("$%&

Deflection due to short-term loading

Immediate deflection due to long term loading

2.0 for CLT in dry service conditions

Reference: NDS 2015

Design Example:

∆ST from 40psf = 0.159 in

∆LT from 40psf = 0.159 in

∆T = 2.0 (0.159) + 0.159 = 0.477 in

= L / 40316 foot span

w = 40 + 40 psf



Simplified Beam Deflections:Given load pattern and support conditions:


Span, L5/6 GAeff

Uniform load, w

Find Apparent Flexural Stiffness, EIapp, such that

EIapp

+,-.. =+,/00

1 +11.5+,/0045/0067Reference: US CLT Handbook

Simplified Beam DeflectionsFor single span, simple loading patterns, Apparent Flexural Stiffness, EIapp, to determine maximum (mid-span) deflection:


US CLT Handbook&

NDS 2015 Commentary

+,-.. =+,/00

1 +16$9,/005/0067+,-.. =

+,/001 + $9+,/0045/0067

NDS 2015

,/00 =+,/00

+:;

5/00= 45/00 4:⁄4: = +: 16⁄

For Major Axis Spans:

Reference: US CLT Handbook & NDS 2015



Simplified Beam DeflectionsFor single span, simple loading patterns, Apparent Flexural Stiffness, EIapp, to determine maximum (mid-span) deflection:


+,-.. =+,/00

1 +16$9,/005/0067+,-.. =

+,/001 + $9+,/0045/0067

Apparent Flexural Stiffness depends on Span Length

L1 = 20 foot+,-..= ≠ +,-..7

L2 = 16 foot

General Purpose, 2 Way, Plate ActionFlexural Stiffness

EIeff,0 EIeff,90

Shear Stiffness:5/6 GAeff,0 5/6 GAeff,90

5/6 from A′ = 5/6 A shape factor for rectangular sections




Occupant perception of vibration is a highly recommended design consideration.One approach: US CLT Handbook, Chapter 7 (FPI Method)

Calculated natural frequency of simple span of bare CLT:

? = 2.188267

+,-.."5

Where:

EIapp = apparent stiffness for 1 foot strip, pinned supported, uniformly loaded, simple span (Ks = 11.5) (lb-in2)

ρ = specific gravity of the CLT

A = the cross section area (thickness x 12 inches) (in2)

Floor Vibration

Reference: US CLT Handbook, Chapter 7

FPI Method Recommends Limiting CLT Floor Span such that

Floor Vibration

Span L


Frequency f > 9.0 Hz

Based on:- Un-topped CLT- Simple span - Bearing wall supports.

Does not account for:- Supporting beam flexibility- Multi-span conditions- Additional floor mass (topping slab, etc)

Recommend for preliminary sizing only



CLT Handbook, Chapter 7 Recommendations

Floor Vibration

Research by Lin Hu, et al. at

Experimental Verification – Results

0.04

0.03

0.02

0.01

0

0.05

0.06

0.07

0 5 10 15

Fundamental Natural Frequency (Hz)20

Stat

ic D

efle

ctio

n(in

ch)

Criterion ( f/d^0.7>125.1) UnacceptableMarginal Acceptable

FPI Method Recommends Limiting CLT Floor Span such that

Floor Vibration

Span L


Frequency f > 9.0 Hz Using spreadsheet & iterate:1) Estimate L2) Calculate EIapp3) Calculate L limit4) Repeat until converges

OR Values provided by Manufacturers, et al.Recall:



FPI Method Recommends Limiting CLT Floor Span such that:

Floor Vibration

Span L


Frequency f > 9.0 Hz16 Foot Simple Span Design Example:

5-Ply V1 CLT Layup previously selected:EIeff,0 = 415x106 lbf-in2/ft

Converged solution:EIapp,0 = 375.9x106 lbf-in2/ftf = 11.0 Hzmax L = 17.03 ft > 16 ft

Span meets recommended limit. Probably OK performance.

Grade Layup Thickness FPI Span LimitE1 3ply 4 1/8” 12’ 5”E1 5ply 6 7/8” 17’ 4”E1 7ply 9 5/8” 21’ 8”E2 3ply 4 1/8” 12’ 0”E2 5ply 6 7/8” 16’ 8”E2 7ply 9 5/8” 20’ 10”E3 3ply 4 1/8” 11’ 7”E3 5ply 6 7/8” 16’ 1”E3 7ply 9 5/8” 20’ 1”E4 3ply 4 1/8” 12’ 2”E4 5ply 6 7/8” 17’ 0”E4 7ply 9 5/8” 21’ 3”

FPI Span Limit for Standard Grades / Layups

Grade Layup Thickness FPI Span LimitV1 3ply 4 1/8” 12’ 2”V1 5ply 6 7/8” 17’ 0”V1 7ply 9 5/8” 21’ 3”V2 3ply 4 1/8” 11’ 11”V2 5ply 6 7/8” 16’ 8”V2 7ply 9 5/8” 20’ 10”V3 3ply 4 1/8” 12’ 0”V3 5ply 6 7/8” 16’ 9”V3 7ply 9 5/8” 21’ 0”

Approximate FPI Span Limits:- Not for final design:- Does not account for strength or deflections- Does not account for project specifics- Vibrations can be felt by the client.

Sharpen your pencil!

Approximate FPI Span Limits:3-ply: 11 to 12 ft5-ply: 16 to 17 ft7-ply: 20 to 21 ft



Alternative: Use acceptance criteria which address low frequency floors and alternative support configurations.

Calibration of dynamic modelingwith physical testing valuable

Alternative Vibration Criteria

AISC Design Guide 11, Velocity Criteria (Chapter 6 & 7)

Example Acceptance Criteria: (good performance)

≤ 16,000 µ-in/sec (mips) response to moderate walking in living areas

≤ 8,000 µ-in/sec (mips) response to slow walking pace in sleeping areas.

AISC DG 11 suggests approximate velocity limit of human perception

8,000 µ-in/sec at 8 Hz and above.

AISC Design Guide 11 not for dynamic modeling of CLT floors

Possible Alternative Vibration CriteriaSB10



A common European CLT Floor Design Method:

a) Static deflection to 1 kN point load > 0.25 mm

b) Keep fundamental frequency > 8 Hz

OR

Fundamental frequency > 4.5 Hz

+ additional acceleration investigation and limits

For more information see:

- “Floor Vibrations – New Results” Hamm, Richter & Winter, 2010

- Cross-Laminated Timber Structural Design. Basic design and engineering principles according to Eurocode. proHolz Austria, 2014

Possible Alternative Vibration CriteriaSB23

Edgewise Structural Properties




Span in MAJOR Strength Direction Span in MINOR Strength Direction


CLT Panels have a significant in-plane shear strength.

CLT in Lateral Force Resisting Systems

Source: ICC-ES ESR 3631

~75 to 195+ PSI Allowable Edgewise Shear

~900 to 2300 PLF per Inch of Thickness.

Consult with the Manufacturers for Details

Source: APA Product Report PR-L306

Standard test method defined using ASTM D198



ICC-ES Acceptance Criteria AC 455

Standardizes In-plane Panel Shear Strength for use in Floor and Roof Decks

Similar Tests in PRG 320 Standard 2017 Update


Span in MAJOR Strength Direction


Preview of PRG 320-2017 Update Nomenclature

Reference Shear CapacityFv,e,0 Wp tp

Shear StiffnessGe,0 Wp tp

Reference Flexural CapacityFb,e,0 Se,0 Se,0 = Wp

2 tp / 6

Flexural StiffnessEe,0 Ie,o Ie,0 = Wp

3 tp / 12

SB32



Connection Details

Panel to Panel at floors, roofs or walls

Connection Styles

Single Surface Spline Half Lap

SB7



An Efficient Panel to Panel Connection

Graphics: ASPECT Structural Engineers

5 ½” to 6” plywood strip ¾” or 1” Thick

Self-Tapping Screwsas “erection bolts”

~18” – 24” o.c

Nails at spacing required for shear

transfer

Connection Styles

Simple connections with:- Metal angles- Self taping Screws and

Nails

Source: US CLT Handbook



Mass Timber DesignConnections

Photo Credit: Alex Schreyer

Long self tapping screws Long self tapping screws Long self tapping screws Long self tapping screws used extensively used extensively used extensively used extensively throughout mass timber throughout mass timber throughout mass timber throughout mass timber constructionconstructionconstructionconstruction

87

Proprietary Products

Variety of Self Tapping Screws



Proprietary Products

Source: Simpson Strong-Tie Source: rothoblaas

SB24

Connectors for CLT in NDS 2015:

Dowel Type Fasteners, e.g. Lag Screws, Bolts and Nails

CLT in NDS 2015 - ConnectorsSB22



CLT in Lateral Force Resisting System

CLT in Lateral Force Resisting Systems

Source: A Ceccotti in the US CLT Handbook



Similar to Wood Structural Panel Shear Walls

Connections Determine Lateral Strength

Light frame shear wallstrength is dependent on perimeter (edge) nailing

Source: SDPWS 2008

Similar to Wood Structural Panel Shear Walls

Connections Determine Lateral Strength

CLT Shear Strength Depends on ConnectionsSource: US CLT Handbook



CLT Shear Wall Seismic Design Values

What R value can I use?

Photo: KLH Photo: FPI?

CLT Seismic Force Resisting Systems Not addressed In

CLT Seismic Design

ASCE/SEI 7-10 SDPWS 2015



Albina Yard – Portland OregonLEVER Architecture

KPFF Engineering4-story office

CLT floors and RoofGlulam Gravity Frame

Light-Frame Shear Walls

Photo: WoodWorks

The Bullitt CenterSeattle, WA

Architect: Miller Hull PartnershipPhotos © Nick Lehoux for the Bullitt Center



T3 MinneapolisCentral Core – concrete shearwalls

Photo Credit: Structurecraft99

FEMA P-695 Study for CLT Shear Walls

Project Lead: John van de Lindt, Colorado State University

Design Method

Modeling

-6 -4 -2 0 2 4 6

-4

-3

-2

-1

0

1

2

3

4

Displacement (in.)

Forc

e (k

ip)

TestFit

Testing

Non-Linear AnalysesDesign

Peer Review

Report



State of Oregon Statewide Alternative

State of Oregon Statewide Alternative

Y

Y

ASCE 7-10 Table 12.2-1 modified by Oregon Buildings Code Division



Mass timber designLateral framing systems

Central core – mass timber shearwalls

Photo Credit: alex schreyer

103

CLT Diaphragms

Strength of Connections covered by NDS 2015 and

Proprietary Fastener Evaluation Reports

Strength of CLT rarely (never?) governs. Capacity provided by

manufactures via ASTM standard testing. Standard to be included

in PRG 320 Update.



Panel In-Plane Strength:

• Panel strength generally does not govern diaphragm shear strength.

• Reference Design Values

• Not covered by APA PRG 320-12 product standard• Are covered by New ICC AC455 Acceptance Criteria• Ask for design values from the Manufacturers

Connection Strength:

• Commodity connectors (e.g. Nails) per NDS 2015

• Proprietary Connectors (Self-Tapping Screws) per Evaluation Reports, Manufacturer’s Information and Engineering Mechanics.

• For seismic design, select connection details so ductile limit states govern capacities.

CLT Floors as Diaphragms

CLT Diaphragm Design Example PaperSB26



CLT Diaphragm Design Example Paper

Lateral load, w =1 kip/ft

Shear Wall

CLT Panels

SB27

CLT Diaphragms

Is the Diaphragm Rigid or Flexible?.

SB28



Calculated Diaphragm DeflectionsOR

Enveloped Diaphragm Design(check for both flexible and rigid diaphragm behavior)

(check for conservatively flexible and conservatively stiff semi-rigid behavior)

CLT Diaphragms in US Seismic Applications

#$%& ='()*+,-.+ ()

/0(1(+ 2)34 +

∑ 6789.


• Detailed design example for simple diaphragm following NDS 2015, US CLT Handbook

• Includes approximate deflection equation:• Modified 4-term wood panel sheathed diaphragm

equation in SDWPS 15

2 = :9

:;)

+ :;.

PL is panel lengthPW is panel widthen is connector slip at diaphragm edge

ChordFlexure

PanelShear

ChordSlip

ConnectorSlip




0.283 in + 0.300 in + 0.568 in + 0.199 in = 1.35 in

Seismic Detailing: An European Approach

Yielding Connections

Non Yielding Connections

Designed to Overstrengthfactor of 1.3 to 1.6 of yielding connection strength

Fragiacomo, Vasallo et al.

Typical Assumption of Rigid Diaphragm Behavior for CLT wall

and floor systems



Seismic Detailing: US CLT Handbook Approach

Yielding Connections

Non Yielding ConnectionsChords and Anchorage

• NDS Yield Modes III and IV govern.• Strength of other (non-yielding) limit

states at connection designed to nominal yielding connection capacity. 1/ϕ = 1/0.65 = 1.54 overstrengthfactor

Possible routes for near term seismic project designs under Alternative Means and Methods include:

1) Elastic Design Method• Based on lower-bound strength of components• Following new ASCE 7-16 alternative diaphragm method to determine

elastic seismic diaphragm force demands

2) Capacity-Based Design Method

• Using designated yielding connections with overstrengthdesign of non-desirable limit states.

• Based on yielding connection technologies of proven cyclic behavior! Relatively equivalent to Wood Structural Panel diaphragm

behavior OR! Advanced Engineering with supporting testing to justify design

Routes for Seismic Diaphragms



WoodWorks Solutions Paper on CLT Modeling

http://www.woodworks.org/wp-content/uploads/Approach-to-CLT-Diaphragm-Modeling-for-Seismic-WoodWorks-Jan-2017.pdf

SB6

Additional Resources



June 2016 Structures Magazine Article

http://www.structuremag.org/wp-content/uploads/2016/05/C-StrucDesign-Breneman-Jun161.pdf

SB6

US CLT Handbook

1. Introduction2. Manufacturing3. Structural4. Lateral5. Connections6. DOL and Creep7. Vibration8. Fire

9. Sound 10.Enclosure11.Environmental12.Lifting

SB15



Source of CLT Handbook

www.rethinkwood.com/masstimber

Questions?This concludes The American Institute of Architects Continuing Education Systems Course Scott Breneman

[email protected]

144



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