Copyright Materialswood-works.ca/wp-content/uploads/Overview-of-Changes-to-CSA-O86...Current equation in CSA O86-09 applies to single-storey shearwall segments

05/12/2014

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Overview of Changes to CSA O86-2014 &

Structural Design Provisions for Mid-Rise in OBC

Wood Solutions Fair, 2014, Toronto

Jasmine Wang, Ph.D., P.Eng.

Canadian Wood Council

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Program Education Credit Information

The Canadian Wood Council is a Registered Provider with the American Institute of Architects. This course meets Continuing Education System requirements for one Learning Unit. Credit earned on completion of this program will be reported to CES Records for AIA members who provided their member number during the online registration. This course also qualifies as Structured Learning with OAA. Certificates of Completion for OAA members, and all other delegates, will be emailed after the event. We will also report participation to the Engineering Institute of Canada on behalf of any engineers who requested their participation be recorded. This program is registered with the 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. The same is true for the OAA and EIC. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Outline

Mid-rise Related Changes in Building Codes

Overview of Changes to CSA O86-2014

Technical Resources for Engineering Design for Mid-Rise

Photo credit: Steven Street, WoodWORKS!ON

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National (proposed) and Provincial building codes allow wood construction of up to 6 storeys

Firstly adopted in amendment to 2006 BCBC in 2009

Proposed for 2015 NBCC

Different fire provisions

Essentially the same structural/seismic provisions but with broader scope

Recently adopted by OBC

Different fire requirements

The same structural/seismic provisions as NBCC 2015

Mid-rise Related Changes in NBCC 2015 & OBC - Structural/Seismic Design Aspects

Restrictions on irregularities (Sentence 4.1.8.10.(4))

For medium and high seismic zones (IEFaSa(0.2)>=0.35), Type 4 or 5 Irregularities are not allowed in 5 or 6 storeys of continuous wood construction

(a) offset: Shear wall location moves (b) lateral stiffness: Shear wall has more openings in a storey below

(a) (b)

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Increased static design force level (Sentence 4.1.8.11.(11))

Only for seismic design;

If the empirical code period is used, no need to increase the base shear

When the fundamental period is determined using established methods of mechanics other than the empirical code period, the static base shear shall be increased by 20%, but need not exceed the maximum.

Increased dynamic design force level (Sentence 4.1.8.12.(12))

Only for seismic design;

Having a fundamental period as determined using established methods of mechanics other than the empirical code period, the base shear shall be the larger of dynamic design force and 100% of static design force.

Mid-rise Related Changes in NBCC 2015 & OBC

- Structural/Seismic Design Aspects

Outline




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Overview of CSA O86-2014 Changes

Published in July 2014 (PDF format)

Mid-rise related changes

Shear resistance of shearwalls and diaphragms

Shear and bending moment resistance of glulam

Withdrawal resistance of lag screws

Other changes

Mid-Rise Related Changes in CSA O86-2014

Requirements for Anticipated Building Movements due to Moisture

Content Change

Requirements for Calculation of Deflection for Multi-Storey Shearwalls

Requirements for Shearwalls Using Gypsum Wallboard

Shear Resistance of High Capacity Shearwalls and Diaphragms

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Requirements for Anticipated Building Movements due to

Moisture Content Change

O86-2014 Clause 5.4.6 Building movements due to moisture content change

O86-2014 Clause A.5.4.6 Shrinkage and swelling of wood members

Information on the effect of shrinkage on differential movements and overall lateral drift calculations &

how to mitigate shrinkage

Information on areas that should be paid attention to:

Information on how to estimate shrinkage

Requirements for Anticipated Building Movements due to MC Change

Estimate of shrinkage

In multi-storey wood frame buildings

Shrinkage occurs mainly in horizontal members

Cumulative shrinkage in studs (parallel to grain) may be considerable in 5 & 6-storey buildings

Table 1: Estimated vertical movement in a 4-storey building (mm)

Table 2: Estimated vertical movement in a 5-storey building (mm) Examples:

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Shrinkage in multi-storey wood buildings

Shrinkage can contribute to overall lateral drift

Interstorey drift ratio may become the governing

factor

2.5% for earthquake design (normal occupancy)

0.2% for wind design

Can be mitigated by

Using shrinkage compensators, and

Using material subjected to less dimensional

change

Shrinkage Take-Up Devices

(Source: Simpson Strong-Tie)

TUD

CTUD

Requirements for Calculation of Deflection for Multi-

Storey Shearwalls

Current equation in CSA O86-09 applies to single-storey shearwall segments

Clause 11.7.1 (CSA O86-2014) Deflections of shearwalls

In the calculation of deflection for multi-storey shearwalls, multi-storey effects shall be considered

Note: See Clause A.11.7.1 for additional information on multi-storey effects

Clause A.11.7.1 Deflection of shearwalls in multi-storey buildings

A purely mechanics-based approach;

Appropriate for a typical shearwall cantilevered from its base and stacked for the full height;

Comprised of interstorey drift due to bending, panel shear, nail slip and vertical elongation of the wall anchorage system;

Takes into account the cumulative rotational effects from the storeys below;

The methodology is the same as the one given in APEGBC Bulletin.

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v = maximum shear force per unit length due to specified lateral loads Hs = shearwall segment height A = cross-sectional area of chord members E = modulus of elasticity of chords Ls = length of shearwall segment

v = maximum shear force per unit length due to specified lateral loads Hs = shearwall segment height

Bv = shear-through-thickness rigidity (Tables 7.3 A~C of CSA O86)

en = nail deformation for a particular load per nail (Table 8.2 of WDM) Hs = shearwall segment height

Hs = shearwall segment height Ls = length of shearwall segment

da = total vertical elongation of the wall anchorage system

Deflection of single-storey shearwalls

Deflection of shearwalls in multi-storey buildings

Bending Anchorage system elongation

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Deflection of shearwalls in multi-storey buildings

Fastener slip, en, for shearwall and diagram deflection calculation (Clause A.11.7 O86-2014)

en table was replaced with one equation

1. For nails used in wood-based

sheathing with dry lumber:

2. Multiply by 2 for green

lumber

3. en may be taken as 0.76

mm for GWB with dry lumber

Requirements for Shearwalls Using Gypsum Wallboard

O86-2014 Clause 11.8.8 Seismic design requirements for shearwalls using

gypsum wallboard

Gypsum wallboard shall not be considered to provide lateral resistance when the

interstorey drift ratio exceeds 1%.

For buildings higher than 4 storeys the contribution of the gypsum wallboard shall not

be accounted for in seismic resistance.

Different from APEGBC Bulletin

O86-2014 Clause 11.8.9 Load bearing walls constructed with gypsum

wallboard only

When interstorey drift exceeds 1% the design should be based on the assumption that

GWB provides no lateral support to studs.

Alternatively a secondary blocking system shall be used

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Shear Resistance of Shear Resistance of High Capacity

Shearwalls and Diaphragms

Clause 11.5.1, 11.5.2 & 11.5.3.4 of CSA O86-2014:

A mechanics-based approach was adopted to calculate the shear

resistance of shearwalls and diaphragms

Makes it possible for designers to design for high capacity shearwalls

& diaphragms

Mid-panel shearwalls

Diaphragms with multiple rows of fasteners







Other changes

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Tabulated values in CSA O86-09

Based on test data

Limited to assemblies constructed with dimension lumber, common nail and sheathing of discrete thicknesses

A mechanics based approach was adopted in CSA O86-2014

Shear resistance of shearwall/diaphragm sheathed with wood-based structural panels governed by the smaller of:

Sheathing-to-framing connection

For seismic design nail shall be designed to fail in the modes where plastic hinge(s) form to ensure sufficient ductility

Sheathing panel buckling

Advantages

More engineering sense

More flexibility in terms of the assemblies

High capacity shearwalls and diaphragms: mid-panel shearwalls and diaphragms with multiple rows of fasteners


Sheathing-to-framing connection

Sheathing panel buckling

Selection tables will be provided in

WDM 2015

Seismic

design

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High capacity shearwalls and diaphragms

Mid-panel shearwalls – double shear

Diaphragms with multiple rows of fasteners

Nail in single shear

Nail in double shear

Sheathing Stud or

Plate

Grain direction

89 mm

Stud or Plate

38 mm 38 mm

ns = 2







Other changes

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Bending Moment Resistance of Glulam

Design provisions in CSA O86-09

Design provisions in CSA O86-2014

Shear resistance of glulam with tension side notch at supports

Design provisions in CSA O86-09 (Clause 6.5.7.2.1)

Design provisions in CSA O86-2014 (Clause 7.5.7.4)

Longitudinal shear resistance of residual member above notch

Tension side notch not exceeding 0.25d

Within a distance “d” from the inner edge of the closest support to the furthest edge of the notch

Fracture shear resistance at notch

No reduction in shear resistance calculated using gross cross sectional area

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Other changes


Design provisions in O86-09 (Clause 10.6.5)

Design provisions in O86-14 (Clause 12.6.5)

• Based on the density of various wood products

• Apply not only to lag screws but also self-drilling

fasteners compliant to appropriate product

standards or product evaluation reports

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Other changes

Other changes

Reduction in the concentrated loaded area on roof deck

Commentary information on plank decking and structural sheathing

Requirements for lateral brace forces for metal-plate-connected wood

truss compression webs (Clause 5.5)

1.25% of the axial compressive force in the member

Newly added finger-joined lumber grade (Clause 6.2.3)

NLGA SPS 4 “Dry Use Only” lumber

Metal-plate-connected trusses application

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Other changes

Reaction resistance for I-Joist (Clause 15.2.3.5 & 16.2.3.5)

Strength resistance of truss plates (Clause 16.4)

Revised ultimate lateral resistance of teeth, tensile, shear and lateral slip resistance

Allowed in SCL to SCL connections or sawn lumber to SCL connections

Allowing lag screws and wood screws for joist hanger connections (Clause

12.10)

Annex B: Fire resistance of large cross-section wood elements

Outline




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Wood Design Manual 2015 (to be published in late 2015)

Mid-Rise Wood Frame Construction Handbook (in process)

APEGBC Bulletin

NBC Structural Commentary


Fact Sheets -

Vertical Movement in Wood Platform Frame Structures

Basics

Movement Prediction

Design and Detailing Solutions

Diaphragm Design

Diaphragm Flexibility

Design Example: Wood Diaphragm on Reinforced CMU Shearwalls

Design Example: Design for Openings in Wood Diaphragm

Design Example: Wood Diaphragm Using Envelope Method

Design of Multi-Storey Wood-Based Shearwalls: Linear Dynamic Analysis & Mechanics-Based Approach

Linear Dynamic Analysis for Wood-Based Shearwalls and Podium Structures

A Mechanics-Based Approach for Determining Deflections of Stacked Multi-Storey Wood-Based Shearwalls

Design Example: Design of Stacked Multi-Storey Wood-Based Shearwalls Using a Mechanics-Based Approach

Design of Wood Frame and Podium Structures Using Linear Dynamic Analysis (WCTE 2014 Proceedings)

http://cwc.ca/publications/



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Shrinkage Compensator Video

Source: Brent Bunting, Simpson Strong-Tie

This concludes the:

American Institute of Architects

Ontario Association of Architects

Engineering Institute of Canada

Continuing Education Systems Program

Overview of Changes to CSA O86-2014 & Mid-Rise Related Changes in OBC

Canadian Wood Council

http://cwc.ca

Questions/ Comments?

http://cwc.ca/

Documents

Copyright Materialswood-works.ca/wp-content/uploads/Overview-of-Changes-to-CSA-O86...Current equation in CSA O86-09 applies to single-storey shearwall segments