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CLT Design: Using CWC’s 2017 Wood Design Manual and WoodWorks®
Sizer Software
Kevin Rocchi, MASc, P.Eng.
The Canadian Wood Council represents the Canadian wood products industry through a
national federation of Associations:
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CWC produces and communicates technical information to architects, engineers, builders, and
other designers on how to use wood in buildings from a structural, fire, and sustainability design perspective.
www.cwc.ca
Presentation Outline
1. CSA O86‐14 Overview
2. Where are we with CLT Design in Canadian Codes?
3. How are wood structures Taller than 6 Storeys being built?
4. CWC CLT Design Tools? Wood Design Manual 2017 Woodworks® Sizer
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CSA O86-14 Update 1 Overview
• Published in June 2016
• Clause 8 (Gravity load Design of CLT)
• Clause 11.9 (Lateral Load Design of CLT)
• Clause 12 (CLT Connection Design)
• Provides Guidance for CLT Platform framed LFRS up to 6 Storeys KR1
Where are we with CLT Design in Canadian Codes?
Provincial or
National Code
Part 4 Based
on
Referenced
CSA O86
Number
of Storeys
NBC 2010 CSA O86‐09 4
BCBC 2012 NBC 2010 CSA O86‐09 6
ABC 2014 NBC 2010 CSA O86‐09 6
OBC 2012 NBC 2010 CSA O86‐09 6*
RBQ 2010 NBC 2010 CSA O86‐14* 6*
NBC 2015 CSA O86‐14 6
*Provincial Code Amended to allow more storeys or updated standard
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How are wood structures taller than 6 storeys being built?
Alternative SolutionsNBC 2015 Clause 1.2.1.1.1)b)
CSA O86‐14 Clause 4.3.2
Typically more expensive to achieve alternative solutions
How are wood structures taller than 6 storeys being built?
18 Storey Brock Commons Demonstration Project (Vancouver)
o Gravity: 2‐way CLT Floors and SCL/Glulam Columns
o LFRS: Concrete Shearwalls
o Utilized Site SpecificCode Amendment to allow for an 18 StoreyWood Structure
o UBC Campus has its own Building Department
Photos Courtesy of Acton Ostry Architect Inc. (website)
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How are wood structures taller than 6 storeys being built?
12+1 Storey OrigineDemonstration Project (Quebec City)
o Gravity: Glulam post and beam, CLT Walls and Floors
o LFRS: CLT Shearwallsand Diaphragms
o Alternative Solution
Origine (from the package NORDIC‐CWC‐2017.zip): Nordic Structures © Stéphane Groleau
How are wood structures taller than 6 storeys being built?
8 Storey Abora Condos (Montreal)o Gravity: Glulam post and beam, CLT Walls
and Floors o LFRS: CLT Shearwalls and Diaphragmso Alternative Solution using Quebec Guide
Arbora (from the package NORDIC‐CWC‐2017.zip): Nordic Structures © Adrien Williams
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How are wood structures taller than 6 storeys being built?
Quebec Guide for Mass Timber Construction up to 12 Storeys• Pre‐approved
Alternative Solution for Mass Timber including CLT for up to 12 Storeys
• RBQ is the only body which reviews and accepts alternative solutions in Quebec
• Other Provinces ‐required to prove Alternative Solutions with local AHD
How are wood structures taller than 6 storeys being built?
Why is the Tall Wall Guide Limited to 12 Storeys?
Most cities don’t build taller than 12 Wood Compression Perpendicular to Grain
Failure
Photo Courtesy of Acton OstryArchitect Inc. (website)
The Case for Tall Wood Buildings (2012) By MGB Architects + Design, Equilibrium Consulting, LMDG Lft. And BTY Group
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How are wood structures taller than 6 storeys being built?
What options do I have outside Quebec?
• Wait for Possible Code Changes to the NBC (2020?)
• Ontario Ministry of Natural Resources and Forestry Ontario Tall Wood Building
Reference: A Technical Resource for Developing Alternative Solutions under Ontario’s Building Code
November 2017
How are wood structures taller than 6 storeys being built?
New NRCan Demonstration Project Funding: Facilitate revisions to the 2020 and 2025 NBC to
allow wood buildings up to 12 stories. A Call for Expressions of Interest closes in
December 2017 Visit gcwood.ca
ON specific projects received MIGHT be evaluated concurrently by MNRF and NRCan
Based on updated climatic models, Climatic and Seismic Data is likely to change in NBC 2020
Why stop at 12 Storeys when wood components work within an 18 Storey Building?
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Wood Design Manual 2017
CSA O86‐14 Update 1 and 2 O86 Structural Commentary
Wood Design Manual 2017Chapter 2 Bending Members
• Several orthogonal layers of lumber, laid flatwise and glued (Typical 3 to 9 alternating layers).
• Thickness usually ranges between 100 mm and 300 mm (as thick as 500 mm can be produced).
• Width usually ranges from 1.2 to 3 m, Length can range from 5 to 19.5 m
• Panel Size limited by manufacturers’ press and transportation regulations.
Photos Courtesy of FPI CLT HandBook
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Wood Design Manual 2017Chapter 2 Bending Members
• CSA O86 includes 5 Stress Grades (E1, E2, E3, V1 and V2). o E – MSR, V‐ visually graded lumber (Refers to grade of
Longitudinal layers)o Transverse layers consist of lower grade visually graded
lumber
Longitudinal Layers
Transverse Layers
Wood Design Manual 2017Chapter 2 Bending Members
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Wood Design Manual 2017Chapter 2 Bending Members
Manufacturer CLT Layups and Properties
• British Columbia• Engineers Responsible for Design
• Grades – E1, V2 • SPF MSR and visual grade D.Fir‐L
Crosslam CLT Technical Design Guide (www.structurlam.com)
Wood Design Manual 2017Chapter 2 Bending Members
Manufacturer CLT Layups and Properties
• Quebec• Nordic Engineers Complete Design (Exceptions)
• Grades – E1• Black Spruce MSR
Nordic Structures Design Properties, Nordic X‐lam(www.Nordic.ca)
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Wood Design Manual 2017Chapter 2 Bending Members
*Similar Equations for Minor Strength Axis
Wood Design Manual 2017Effective Bending Stiffness and in‐plane shear rigidity
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Wood Design Manual 2017Chapter 2 Bending Members
Wood Design Manual 2017Chapter 2 Bending Members
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Wood Design Manual 2017Chapter 2 Bending Members
Wood Design Manual 2017Chapter 2 Bending Members
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Wood Design Manual 2017
Wood Design Manual 2017Chapter 2 Bending Members
5‐ply, V1 stress grade (h=175 mm):
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Wood Design Manual 2017Chapter 2 Bending Members
Wood Design Manual 2017Chapter 2 Bending Members
CLT Stiffness
= Elastic deflection due to Short and Standard term loads
= Elastic deflection due to long term loads
= Creep Adjustment factor (=2.0)
Uniform Loads: Concentrated Loads:
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Wood Design Manual 2017Panel Selection Tables
Wood Design Manual 2017Chapter 2 Bending Members
From the floor panel selection table D=1.5 kPa and L=2.4 kPa:For V1, 5‐plyAllowable span = 6.63 m > 6 m
What if the floor is sensitive to vibration? (e.g. Residential Floor)
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Wood Design Manual 2017Chapter 2 Bending Members
CLT Vibration Design
Wood Design Manual 2017Panel Selection Tables
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Wood Design Manual 2017Chapter 2 Bending Members
From the vibration selection table:For V1, 5‐plyAllowable span = 5.27 m < 6 m X
Use 7‐ply V1 ‐ 6.58 m
What if the floor is sensitive to vibration? (e.g. Residential Floor)
Wood Design Manual 2017Chapter 2 Bending Members
Nail‐Laminated Timber Panels (NLT)
• Consists of lumber members stacked on edge and spiked together
• CSA O86‐14 Clause 6.5.11.1 Nail‐Laminated Decking
• Treated similarly to Plank Decking in CSA O86
Photo Courtesy of Structurcraft
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Wood Design Manual 2017Chapter 2 Bending Members
Nail Laminated Timber Panels (NLT)• “Mill construction” • Over 43 buildings (5 storey and greater in height) exist in Toronto
• NLMA published the Heavy Timber Mill Construction Buildings (1916)
• Guidance on the Design of NLT existed in first NBC (1941) and the first CSA O86 (1959)
Photo Courtesy of FPI
Wood Design Manual 2017Chapter 2 Bending Members
Nail Laminated Timber Panels (NLT)
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Wood Design Manual 2017Chapter 2 Bending Members
Nail Laminated Timber Panels (NLT)
Wood Design Manual 2017Chapter 2 Bending Members
Glued‐Laminated Timber Panels (GLT)
Treat the system as a built‐up beam consisting of No.2 grade lumber No increased strength for higher grades of Glulam
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Wood Design Manual 2017Chapter 2 Bending Members
Glued Laminated Timber Panels (GLT)
Wood Design Manual 2017Chapter 3 Compression Members
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Wood Design Manual 2017Chapter 3 Compression Members
< 43
Wood Design Manual 2017Chapter 3 Compression Members
Ieff, Aeff and reff for CLT Panels Major and Minor Strength Axis
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Wood Design Manual 2017Chapter 3 Compression Members
Wood Design Manual 2017Chapter 5 Combined Bending and Compression Members
PΔ
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Wood Design Manual 2017Chapter 5 Combined Bending and Compression Members
0
100
200
300
400
500
600
700
0 10 20 30 40
Pf (kN)
Mf (kNm)
(Pf/Pr) + (Mf/Mr)PΔ = 1.0 Selection Tables:• Based on various levels Pr (10 –80%)
• Provides factored uniform area loads, w’r (kPa) which result when
(Pf/Pr) + (Mf/Mr)PΔ= 1.0
0.4Pr
Determinew’r based on Mf
Wood Design Manual 2017Chapter 5 Combined Bending and Compression Members
e = 0 e = d/2e = d/6
w’r w’r w’r
Pf Pf Pf
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Wood Design Manual 2017Chapter 5 Combined Bending and Compression Members
Wood Design Manual 2017Chapter 6 Bearing Design
General Bearing Check
Critical Bearing Check
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Wood Design Manual 2017Chapter 6 Bearing Design
Wood Design Manual 2017Chapter 6 Bearing Design
General Bearing Check
Critical Bearing Check
*Load on floor panel adds 15 kN
Critical Bearing Governs
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Wood Design Manual 2017Chapter 7 Connection Design
Cross Lamination Effect
F • Different layers are loaded at different angles due to cross lamination
• Causes decrease in strength compared with common wood‐to‐wood connections (observed through testing)
• Adjustment factor for CLT (Jx = 0.9)
• O86 covers, nails, wood screws, bolts and lag screws
Longitudinal Layers
Transverse Layers
Wood Design Manual 2017Chapter 7 Connection Design ‐ Bolts
o Load perp. to major strength direction
o Load // to major strength direction (i.e., outer layer)
50 1 0.01
22 1 0.01
Check Brittle Failure Modes for uncommon bolt configurations
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Wood Design Manual 2017Chapter 7 Connection Design ‐ Bolts
Check Brittle Failure Modes for uncommon bolt configurationsSee O86 for guidance
Wood Design Manual 2017Chapter 7 Connection Design – Bolts
How Many ¾” bolts per along a 1 m wide panel when the factored load is 30.9 kN?
105 mm thick V2 stress grade CLT
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Wood Design Manual 2017Chapter 7 Connection Design – Bolts
30.9 kN / 16.2 kN = 1.91Therefore use 2 – 3/4” Bolts per m
Wood Design Manual 2017Chapter 7 Connection Design – Nails and Wood Screws
2 50 1 0.01
Lateral resistance
110 . 1 0.01
16.4 . . nails
0.9forCLT
59 . . screws
0.67fornailingintoendgrain,ormakesuresidegrainpenetrationoccurs
Withdrawal resistance
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Wood Design Manual 2017Chapter 7 Connection Design – Nails and Wood Screws
Wood Design Manual 2017Chapter 7 Connection Design – Nails and Wood Screws
Notes:4. Table based on Jx = 1.0, applicable to all wood products except CLT. For CLT multiply the values in the Table by 0.9.
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Wood Design Manual 2017Chapter 8 Lateral Load Design
• Structure type Platform construction
• Design ConsiderationsRely on capacity design procedures moderate or high ductility connections for
energy dissipation at specified locations other connections are designed with sufficient
over-strength to be non-dissipative connections • Rd <= 2.0, Ro = 1.5• CLT Panels Act as rigid bodies
O86 does not provide guidance on in-plane bending and shear strength and stiffness
Research has shown it is unlikely to govern Prudent to check (Manufacturer)
Wood Design Manual 2017Chapter 8 Lateral Load Design
• Intended rigid body motionRocking or rocking and
sliding in combination If sliding only RdRo=1.3
• Aspect Ratio 1:1 to 1:4 If less than 1:1 use RdRo=1.3
• Height limit In high seismic zones, <=20 m; other seismic
zones, <=30 mSame as nailed wood-based shearwall
• Irregularity restrictionType 4 or 5 irregularities not allowed
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Wood Design Manual 2017Chapter 8 Lateral Load Design
• Energy-dissipative connections (Fuse): connections joining the walls to the foundation or the floor
panels below, vertical joints between the wall panels discrete hold-downs
• Non-dissipative connections (Over-Strength): continuous steel rods floor to supporting wall joints connections between perpendicular walls
• Factored resistance of non-dissipative connections required to be higher than the strength demand that is induced on them when the energy-dissipative connections reach their 95th percentile of ultimate resistance under cyclic loading.
Wood Design Manual 2017Chapter 8 Lateral Load Design
• In the case of a monolithic CLT wall, the analytical procedure is simple and only based on equilibrium
Non‐dissipative connections: Angle Brackets
Energy‐dissipative connections:Hold‐downs
F
Photo Courtesy of FPI
Kinematic Mode –Rocking (Rd=2.0,Ro=1.5)
For Simplicity – No Dead Load
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Wood Design Manual 2017Chapter 8 Lateral Load Design
F = 16 kN
Photo Courtesy of FPI
HDF
H=3m
L=3m
HDF = F x H / L16 kN x 3m/3m =HDF = 16 kN
Wood Design Manual 2017Chapter 8 Lateral Load Design
F = 16 kN
Photo Courtesy of FPI
HDcap
HDF = 16 kNCustom HD¾” bolt, single 6 mm steel plate,105 mm thick panelHDcap = 16.2 kN> 16 kN
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Wood Design Manual 2017Chapter 8 Lateral Load Design
HDcap
HDcap = 16.2 kN Based on 5th%ile
Capacity (CSA O86) Need 95th%ile
capacity to design non‐dissipative connections
Connector ManufacturerNon‐dissipative connections:
Angle Brackets
Energy‐dissipative connections:Hold‐downs
Wood Design Manual 2017Chapter 8 Lateral Load Design
• Two Panel CLT wall no established analytical procedures in O86 no specific guidance on the actual kinematic mode the
wall will experience (Rocking, sliding, combo) further complicated by the presence of gravity loads
• Two Panel CLT wall example - “Analytical Approach to Establish the Elastic Behaviour of Multi-Panel CLT Shear-Walls Subjected to Lateral Loads”
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Wood Design Manual 2017Chapter 8 Lateral Load Design
Design CLT Shearwalls beyond the Code and Standard?
Detailed Finite Element Models
Application of Analysis Tools from NEWBuildSResearch Network in Design of a High‐Rise Wood Building
Available at:Newbuildscanada.ca
Wood Design Manual 2017Chapter 10 Fire Design
CSA O86-14 Annex B – Alternative Solution for Determining Fire Resistance of large cross sectional wood members
Steps:1. Determine Specified
Loads (Mf)2. Determine reduced
cross section based on charring
3. Determine Mr for reduced cross section with additional adjustment factors
4. Check Mr > Mf
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Wood Design Manual 2017Chapter 10 Fire Design