clt design: using cwc’s 2017 wood design manual and woodworks® sizer software · quebec guide...

2017‐11‐10

Kevin Rocchi, MASc, P.Eng. 1

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


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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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


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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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


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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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


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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• 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


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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)


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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*Similar Equations for Minor Strength Axis

Wood Design Manual 2017Effective Bending Stiffness and in‐plane shear rigidity

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Wood Design Manual 2017


5‐ply, V1 stress grade (h=175 mm):

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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


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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CLT Vibration Design

Wood Design Manual 2017Panel Selection Tables

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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)


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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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


Nail Laminated Timber Panels (NLT)

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Nail Laminated Timber Panels (NLT)


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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Glued Laminated Timber Panels (GLT)

Wood Design Manual 2017Chapter 3 Compression Members

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< 43


Ieff, Aeff and reff for CLT Panels Major and Minor Strength Axis

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Wood Design Manual 2017Chapter 5 Combined Bending and Compression Members

PΔ

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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


e = 0 e = d/2e = d/6

w’r w’r w’r

Pf Pf Pf

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Wood Design Manual 2017Chapter 6 Bearing Design

General Bearing Check

Critical Bearing Check

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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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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)


• 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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• 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.


• 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


Kinematic Mode –Rocking (Rd=2.0,Ro=1.5)

For Simplicity – No Dead Load

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F = 16 kN


HDF

H=3m

L=3m

HDF = F x H / L16 kN x 3m/3m =HDF = 16 kN


F = 16 kN


HDcap

HDF = 16 kNCustom HD¾” bolt, single 6 mm steel plate,105 mm thick panelHDcap = 16.2 kN> 16 kN

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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


• 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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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

clt design: using cwc’s 2017 wood design manual and woodworks® sizer software · quebec guide...

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