A MULTI-DISCIPLINARY CANADIAN RESEARCH NETWORK
TO SUPPORT USE OF TIMBER IN MULTI-STOREY AND NONRESIDENTIAL CONSTRUCTION
Ying-Hei Chui1, Erol Karacabeyli2, Kenneth Koo3
ABSTRACT: A five-year multi-disciplinary research network was established under the Natural Sciences and
Engineering Research Council’s (NSERC) Forest Sector R&D Initiative in 2010 in Canada to support the development
of innovative construction technologies and advanced design methodologies, and to review some of the building code
barriers, with the ultimate goal of increasing the use of structural wood products in mid-rise and non-residential
construction. The network, referred to as NEWBuildS, consists of researchers from 11 Canadian universities,
FPInnovations, National Research Council and the Canadian Wood Council. Because a building is required to be
designed to meet the requirements of a number of performance attributes, including structural, fire, serviceability,
acoustic and durability, a multi-disciplinary team of researchers with these backgrounds have been assembled to
conduct collaborative research projects in this Network. This will ensure that any proposed solutions will meet the key
objectives of the National Building Code of Canada. This paper provides an overview of the structure of the research
network and its research program, the logics behind the various research clusters, expected key results and outreach
structure.
KEYWORDS: Research network, hybrid building system, mid-rise light wood frame building, cross laminated timber,
building code
1 INTRODUCTION
123
Timber is one of the most common and oldest structural
materials. It was used to build tall structures centuries
ago in Europe and Asia. Some of these structures are still
standing today. Nowadays, the use of timber is limited
mostly in low-rise (four storeys or lower) residential
buildings in Canada mainly because of restrictions
imposed by the building codes developed during the 20th
century. Increased emphasis on sustainable building
designs and the emergence of engineered wood products
and systems have led to renewed interest in using
construction with wood products beyond the current
low-rise residential market. Coincide with renewed
interested in timber was the timely transformation of the
building codes to a performance-based format in a
1
Wood Science and Technology Centre, Faculty of Forestry
and Environmental Management, University of New
Brunswick, 28 Dineen Drive, Fredericton, NB, Canada.
Email: [email protected]
2
Building Systems, FPInnovations, 2665 East Mall,
Vancouver, BC, Canada. Email:
[email protected]
3
Building Systems, FPInnovations, 319, rue Franquet, St-Foy,
Quebec, Canada. Email: [email protected]
number of countries. Under the new performance-based
format, designers are offered the opportunity to apply
advanced design methods and construction technologies
to demonstrate that non-traditional building solutions can
meet and exceed the performance requirements of the
building codes. In Canada, the alternative solution
provisions in the objective-based building codes
facilitated the construction of a 6-storey wood building
in 2009. Earlier, a similar approach has led to the design
and construction of a 9-storey building constructed
entirely of cross laminated timber (CLT) in the top 8
storeys in London, UK. Construction companies and
building designers are exploring various design concepts
of buildings taller than 9 storeys with timber alone or in
hybridized systems consisting of timber in conjunction
with other materials. If these concepts are to be realized
in practice, continued research to develop new
technologies, including innovative products, systems,
design tools and construction techniques, and to remove
unjustified building code barriers, is required.
2 RESEARCH NETWORK
In Canada, under the Natural Sciences and Engineering
Research Council’s (NSERC) Forest Sector R&D
Initiative, a five-year multi-disciplinary strategic
research network, known as NEWBuildS, was
established in 2010 to support the development of such
technologies and advanced design methodologies, and
the review of some of the key building code barriers.
The vision of the Network is to increase the use of wood
products in mid-rise buildings for residential and nonresidential purposes in Canada and other markets.
The research program was established in collaboration
with FPInnovations, wood industry and design
community. The research network consists of about 40
researchers
from
11
Canadian
universities,
FPInnovations, National Research Council of Canada
(NRC) and the Canadian Wood Council (CWC).
University of New Brunswick is the host university.
The research activities are organized into four linked
research Themes:
• Theme 1: Cross laminated timber (CLT) – material
characterization and structural performance
• Theme 2: Hybrid building systems – structural
performance
• Theme 3: Building systems – fire performance,
acoustic and vibration serviceability
• Theme 4: Building systems – durability,
sustainability and enhanced products
Each theme is led by a university-based leader and a coleader from FPInnovations. At the outset, 36 research
projects were planned, with the intention that more
projects would be added as the network progresses. An
estimated 60 highly qualified personnel (HQP) will be
trained within the 5-year duration of the network.
NEWBuildS has established an International Expert
Panel. Members of the Panel not involved in conducting
research within the NEWBuildS network, to provide an
impartial review of research proposals and, when
necessary, the direction and progress of existing projects
3 RESEARCH PROGRAM
NEWBuildS is investigating the use of traditional light
wood frame in mid-rise residential construction, as well
as heavy systems built with timber products or with an
innovative approach to combine timber with different
materials (hybrid system). Because a building is required
to be designed to meet the requirements of a number of
performance attributes, including structural, fire,
serviceability, acoustic and durability, a multidisciplinary team of researchers with these backgrounds
have been assembled to conduct collaborative research
projects in this network. This will ensure that any
proposed solutions will meet the key objectives of the
National Building Code of Canada [1].
3.1 THEME 1: CROSS LAMINATED TIMBER
This theme focuses on material characterization of CLT
and structural performance of CLT building assemblies.
It will generate technical information, such as design
properties, product evaluation procedures and systembased uses, in support of the development of a national
manufacturing industry for CLT and building
applications in Canada. This research will also develop
CLT product designs that utilize Canadian forest
resources in a sustainable manner.
CLT was developed and used in Europe for over a
decade. Each producer has developed its proprietary
approach to manufacture the product according to an
European Technical Approval (ETA) report. Currently,
efforts are underway to develop a European (EN) CLT
standard. CLT is attracting considerable attention in
North America as this engineered wood product can be
an alternative to concrete and steel in non-residential
construction as well as non-traditional high-rise wood
construction.
With support from FPInnovations, APA – The
Engineered Wood Association established a bi-national
(U.S. and Canada) CLT Standard Committee. The
American National Standards Institute (ANSI) approved
the ANSI/APA PRG 320-2011 Standard [2] in
December 2011. ANSI/APA PRG 320 provides
requirements and test methods for qualification and
quality assurance of CLT. This standard lists seven stress
classes covering major wood species in North America.
Under NEWBuildS, complementary work is being
undertaken for further expanding the use of CLT in midrise and non-residential construction, where the
structural, fire and moisture loads can have different
characteristics compared with the traditional low-rise
timber frame construction. There have been substantial
interactions between Canadian and European researchers
who have conducted research on CLT for the past few
years. FPInnovations [3] published a CLT Handbook to
assist architects and engineers to design buildings with
CLT. Based on these interactions and earlier research
findings from FPInnovations, and Canadian universities,
research topics related to material property
characteristics and structural performance of CLT
building systems or sub-systems in the Canadian context
are identified as priority. Canadian design community is
familiar with traditional post-and-beam and stick-frame
construction. CLT presents a different type of structural
form based on connecting plate-like sub-systems to form
a complete building. There is a need to implement
engineering design specifications and procedures in the
Canadian material design standards and in the National
Building Code of Canada [1], and investigate connection
behaviours, in-plane stiffness and strength of floor and
roof diaphragms, stability of wall systems and dynamic
response of buildings under wind and seismic excitation.
The material characterization research focuses on several
subjects:
• A test method and calculation procedures will be
developed as part of the evaluation procedures for
rolling shear and modulus of CLT.
• An experimental study on the use of self-tapping
screws as localized rolling shear reinforcement will
be performed and validated with full scale tests to
develop provisions and guidelines.
• The adoption of a vibration-based Non-destructive
Testing (NDT) method for an orthotropic plate, such
as CLT, can lead to the development of a tool for
grading and quality control of CLT panels.
• Understanding the influence of manufacturing
parameters, such as layup, properties and
connections, on CLT plate to resist out-of-plane
short and long term loading.
To design CLT building systems, research is required to
address structural performance in specific areas of
concern. These issues are investigated within a number
of Theme 1 projects.
• Design approach based on advanced plate theories
will be required if the benefits of the two-way
bending action of CLT panels are to be realized.
• Structural model for the evaluation of seismic
performance of mid-rise CLT buildings will be
developed. This model should be capable of
modelling the hysteretic behaviour of the CLT
connections that connect CLT panels together to
form structural systems.
• Study of the in-plane stiffness and strength of CLT
floor diaphragms using a non-linear floor diaphragm
model which will be calibrated by a material
property database and full-scale tests.
• Study of the force transfer around openings in CLT
walls to develop a rational design method.
• The stability of CLT wall panels under in-plane
gravity loading will be investigated with the aim to
develop design guidelines.
• The use of post-tensioned and self-centring
connection can be adopted to improve seismic
performance of CLT walls. This subject will be
investigated using scaled specimens.
• Design properties for connections in CLT building
systems will be required for implementation in
design standards. The research will cover CLT-toCLT,
CLT-to-steel
and
CLT-to-concrete
connections.
3.2 THEME 2: HYBRID BUILDING SYSTEMS
This theme focuses on structural performance of midrise wood frame buildings and buildings using hybrid
construction systems such as heavy timber and
innovative approaches that combine wood with concrete
or wood with steel.
In April 2009, the province of British Columbia
modified its building code to permit the construction of
5- and 6-storey light wood-frame, multi-unit residential
buildings based on utilization of ‘conventional’
construction materials and methods. Figure 1 shows the
first 6-storey building constructed in B.C. The wood
industry and engineering professionals have identified
research topics that need to be addressed to improve the
design and construction of mid-rise, light wood-frame
buildings in Canada. They are design guidance on floor
diaphragms to transfer design loads on buildings to
walls, cumulative shrinkage due to changes in moisture
content of wood, reliable design models for predicting
inter-storey drift and fundamental natural frequency of
multi-storey wood frame buildings under lateral load and
the role played by non-structural components and
interaction between wood and other substructures.
Figure 1 - First
6-storey light
wood frame
residential
building,
Richmond, B.C.
Design for mid-rise heavy frame timber systems in
Canada is possible but will require special structural
engineering design skills on the engineers as there are no
guidelines in current design standards. Figure 2 shows a
6-storey glulam structure designed using the alternative
solution path in the building code. The challenge can be
the design of lateral bracing systems and the interface
with reinforced concrete shear walls and connections
between members and between frameworks and
diaphragms.
Figure 2 – 6-storey
glulam office building in
Quebec City, Quebec
The innovative approach is to combine the use of wood
with other structural materials such as steel and
reinforced concrete to form an efficient hybrid structural
system that utilizes the strengths of one material to
address the weaknesses of other materials employed.
Buildings can be designed with lower weight of wood
and with stability and lateral resistance of a steel and
concrete frame. An example of such a hybrid structure is
shown in Figure 3.
•
Study of diaphragm action in heavy-frame ribbedplated floor systems consisting of thick wood plate
on timber, steel and RC beams through the use of
finite element modelling and laboratory tests.
3.3 THEME 3: BUILDING SYSTEMS – FIRE
PERFORMANCE, ACOUSTIC AND
VIBRATION SERVEABILITY
Figure 3 - A
hybrid structure
under construction at
the University of
New Brunswick.
Research projects under Theme 2 are as follows;
• Development of techniques for multi-functional
construction interfaces will identify and investigate
interfacing material and system combinations in
hybrid-buildings through literature study and
laboratory tests.
• Field measurements of mid-rise wood frame
buildings will be conducted to measure ambient
building vibration and to develop empirical models
to predict natural period of mid-rise wood buildings.
Rational mechanics-based approach will be
developed to calculate lateral drift of wood frame
buildings.
• Influence of diaphragm action in light wood frame
platform construction on failure and transfer of
lateral load to supporting wall elements will be
studied using a computer model.
• Design guidelines will be developed for hybrid
bracing systems consisting of conventional shear
wall and portal frames and of shear walls containing
wood-based panels and gypsum wallboard under
lateral loads.
• Seismic performance of hybrid building consisting
of a light wood-frame sub-system and a rigid
elevator core with varying degrees of connectivity
between the core and wood frame will be studied
using a computer model.
• Moisture-related movements and stresses in
components in buildings consisting of a heavy
timber frame and reinforced concrete core will be
studied using a combination of laboratory testing of
scaled model, field measurement and computer
modelling.
• Study to develop construction details for
implementing wood in-fill wall panels into a
reinforced concrete frame through laboratory
testing.
• Study to develop design guidelines for
implementing wood structural sub-systems such as
wall and floor in mid-rise heavy steel frame building
through the use of computer models and component
testing.
• Development of a composite long-span floor system
consisting of an innovative post-tension glulam
beam and reinforced concrete slab.
This theme focuses mainly on fire performance of midrise and non-residential buildings. It also covers projects
addressing vibrational serviceability and acoustic
performance of building systems since construction
details affect fire performance often have an impact on
sound
and
vibration
transmission
between
compartments.
The objective-based format was introduced in the
National Fire Code [4] in 2005 as part of the overhaul of
the Canadian building code system. Objectives of each
provision in the National Fire Code are specified which
facilitate the application of scientific principles and
engineering tools to develop alternative solutions that
meet the performance objectives and ensure that these
alternative solutions provide an acceptable level of fire
safety to building occupants. This engineering-based
approach allows the selection of building assemblies to
be based on actual performance and predicted impact on
life safety. To fully capitalize on such an opportunity,
there is a need for engineering tools, data, design
guidelines and highly trained professionals to be
developed.
Canadian researchers have been conducting leading
research on vibrational serviceability of wood floor
systems for many years and the development of design
procedures against excessive vibration in traditional
ribbed-plate type wood floor assemblies. There is a need
to transfer that knowledge to study the vibrational
performance of floor systems built with new engineered
wood products such as CLT. Projects to study the
acoustic performance of building systems in mid-rise
light wood frame and innovative systems will need to
consider the construction details developed for fire
resistance and structural details in other projects.
Researchers working within this theme will interact
regularly to ensure that recommended engineering
practices and construction details will not be in conflict
with each other.
Figure 4 - Carleton
University fire research
facility, Ottawa, Ontario
Research projects are as follows;
• Further development of a previously developed fire
risk model, CUrisk, will be necessary to analyse the
•
•
•
•
•
fire performance of mid-rise buildings. The research
will include the development of sub-models to
predict fire and smoke development and the loadcarrying capacity of CLT building assemblies
during a fire event.
Rationalization of life safety objectives and
provisions in building and fire codes. The focus will
be on analysing code requirements related to fire
resistance and sprinklers for mid-rise buildings built
with combustible or non-combustible construction
and determining the level of safety through the use
of the CUrisk model.
A model previously developed to predict loadcarrying capacity of traditional wood floor system
during a fire event will be modified to predict the
same for CLT floor system. Full-scale test data at
the National Research Council will be used to
validate the model predictions.
Fire performance of timber connections used in
heavy frame and CLT construction will be studied
using the fire testing facility at Carleton University
(Figure 4) and computer modelling. This will
develop design rules to predict load-carrying
capacity of connection during a fire event.
Influence of support characteristics, such as doublespan, support flexibility, and wall flexibility on
vibrational performance of CLT floor systems will
be studied using a combination laboratory and field
testing, and computer modelling.
Acoustic performance of traditional and innovative
wood constructions will be studied to develop
appropriate construction details for mid-rise
buildings.
3.4 THEME 4: BUILDING SYSTEMS –
DURABILITY, SUSTAINABILITY AND
ENHANCED PRODUCTS
This theme studies durability and moisture related issues
for wood construction in mid-rise and non-residential
buildings. It also covers sustainability and enhanced
wood products with coating and treatment.
In recent years, considerable interests have been shown
by environmentally-conscious design professionals to
consider the environmental footprint of a building which
can only be assessed through detailed life cycle
assessment (LCA) of the building with focus on
innovative components of the buildings such as CLT,
hybrid wood-steel and wood-concrete structures.
Moisture has an impact on wood such as dimensional
stability, decay and mould and is affected by design of
building envelope and integrity for moisture ingress and
accumulation. The extension of wood construction to 6
storeys and taller, whether using platform-frame, heavy
timber, CLT or hybrids, requires attention to building
envelope details on moisture management. Furthermore,
the moisture load from wind-driven rain and stack effect
pressures will be higher due to increase of building
height.
Enhanced product performance can be achieved by new
finish and treatment. Intumescent coating may be a
solution that can address the rapid flame spread on
interior finish and rapid strength loss in fire situations.
Borate treatment technology is a safe and low
environment impact wood preservative that can ensure
wood structure will not decay if exclusion of water
cannot be assured.
Figure 5 –
Environmental
test hut,
University of
Waterloo,
Ontario
Research projects are as follows;
• The environmental performance of innovative wood
building systems using life-cycle assessment
programs will be conducted using different
databases and impact assessment methods. Various
building systems, such as wood and steel
construction, massive wood walls (CLT), and the
integration of light-frame wood walls in hybrid
construction will be assessed.
• Instrumentation and field measurement of several
mid-rise buildings will lead to characterization of
wind-driven rain load and the effectiveness of
overhang on wind-driven rain wetting for mid-rise
buildings. The end result is the development of
specific recommendations on rain loading and
corresponding overhang designs.
• A computational fluid dynamics (CFD) model will
be developed to characterize wind-driven rain load
on mid-rise buildings and predict the loads on
building surfaces with different building geometries
and overhang configurations.
• Hygrothermal
performance
of
CLT
wall
construction in various geographic locations in
Canada is investigated through experimental field
study at instrumented field exposure facility (Figure
5) and validated by advanced hygrothermal model,
e.g. HAMFit.
• Collaborating with FPInnovations and coating
industry specialists, the use of intumescent coating
to protect engineered wood products from fire
damage will be investigated.
• Borate pre-treatment procedure will be developed
for CLT and engineered wood-based composites
used in mid-rise buildings in areas vulnerable to
water ingress or condensation.
• The durability of traditional stud wall construction
with various enhanced insulation systems, in
accordance with the new energy performance code
requirements in Canada will be studied using the
test hut shown in Figure 5.
4 EXPECTED OUTCOME
NEWBuildS is divided into the four themes outlined
above for administrative purposes. However, it is more
effective and efficient to organize research activities by
clusters. Each cluster consists of a number of projects
that may deal with an issue from a single theme or
multiple theme perspective. This is intended to ensure
close
interaction
between
researchers
with
complementary skills at the early stage of project
development and technology transfer by or with
FPInnovations. Examples of technology transfer will be
submission of code change proposals and preparation of
design guidelines and best practice codes. For most of
the clusters, there are parallel, usually applied, research
or technology transfer projects undertaken at
FPInnovations. This formal link will ensure that the
university research funded via the Network is
complementary to the parallel FPInnovations projects,
and to ensure that some of the specific theme objectives
are achievable within the 5-year term of the Network.
The anticipated outcomes and achievements of the
NEWBuildS research program are:
•
To strengthen the national innovation capacity in
support of the wood industry and lay the foundation
for future technical activities that lead to the
expansion of wood use in non-traditional building
construction.
•
To develop tools for the technical evaluation of
CLT, and for predicting responses of selected CLT
and hybrid building systems to structural strength
and serviceability, fire and moisture loads. (Figure 6)
•
To develop technical information in support of the
use of wood-based products in mid-rise and nonresidential construction for building codes, material
design standards and product standards. (Figure 6)
•
5 CONCLUSIONS
The Canadian research community in wood building
systems organized itself under the NSERC Forest Sector
R&D Initiative. The research undertaken by NEWBuildS
network is well aligned with the research undertaken by
FPInnovations, and ambitious but scientifically and
technically feasible. It brings together a world-class team
of researchers, using a multi-disciplinary approach to
address critical issues for the Canadian wood and
building industries. There are challenges for the
management of this complex network and the
implementation of its outcomes such as addressing
current building code limitations which prevent the use
of wood in mid- and high-rise structures.
NEWBuildS will reach out for collaborations with other
international centres of expertise, create a virtual
knowledge gateway and repository for the generated
data, and maintain the momentum and synergy among
the Network participants beyond the 5-year window of
funding.
ACKNOWLEDGEMENT
Financial supports by Natural Sciences and Engineering
Research Council (NSERC) of Canada, Canada
Mortgage and Housing Corporation (CMHC) and
FPInnovations are gratefully acknowledged. In-kind
support provided by Canadian Wood Council (CWC)
and National Research Council – Institute for Research
in Construction, is greatly appreciated.
REFERENCES
[1]
[2]
[3]
[4]
Figure 6 – Technical outcome of NEWBuildS research.
NEWBuildS establishes an Outreach Committee with a
strategy and planned activities to ensure transfer of the
outcome and research results to the appropriate
stakeholder groups. These activities include:
• Annual Workshop – research findings are presented
to researchers, design professionals, wood industry
representatives and government officials.
• Ad hoc outreach workshops
• Bi-annual Network newsletters
Web site: www.newbuildscanada.ca
NRC. 2010. National Building Code of Canada.
National Research Council, Ottawa, ON.
APA. 2011 Standard for performance-rated crosslaminated timber. ANSI/APA PRG320-2011.
APA – The Engineered Wood Association.
Tacoma, WA.
FPInnovations.
2011.
CLT
Handbook.
FPInnovations, Vancouver, BC.
NRC. 2005. National Fire Code. National
Research Council, Ottawa, ON.