The acceptable solutions in Division B of the anticipated 2020 NBCC limit the height of Groups C and D buildings of sprinklered encapsulated mass timber construction (EMTC) to 12 storeys in building height, and a measured building height of 42m. The recently published 2021 IBC contains provisions to permit buildings of mass timber construction under the IBC Type IV construction, surpassing the NBCC provisions by maximum building height, building area, occupancy groups, and interior exposed timber. The IBC mass timber buildings are permitted to have a building height of maximum 18 storeys, depending on the occupancy group. Within Type IV construction, four subdivisions are described to have varying maximum permissible building height, area, fire resistance rating (FRR), and interior exposed timber.
Through a comparison of mass timber provisions of both Codes, relevant research reports, test reports, industry standards, this report documents the consequential and inconsequential differences and developed conclusions on whether the NBCC can adopt the IBC provisions, and with what modifications so that the new provisions may fit the NBCC context.
The Italian building heritage is aged and inadequate to the high-performance levels required nowadays in terms of energy efficiency and seismic response. Innovative techniques are generating a strong interest, especially in terms of multi-level approaches and solution optimizations. Among these, Nested Buildings, an integrated intervention approach which preserves the external existing structure and provides a new structural system inside, aim at improving both energy and structural performances. The research presented hereinafter focuses on the strengthening of unreinforced masonry (URM) buildings with cross-laminated timber (CLT) panels, thanks to their lightweight, high stiffness, and good hygrothermal characteristics. The improvement of the hygrothermal performance was investigated through a 2D-model analyzed in the dynamic regime, which showed a general decreasing in the overall thermal transmittance for the retrofitted configurations. Then, to evaluate the seismic behavior of the coupled system, a parametric linear static analysis was implemented for both in-plane and out-of-plane directions, considering various masonry types and connector spacings. Results showed the efficiency of the intervention to improve the in-plane response of walls, thus validating possible applications to existing URM buildings, where local overturning mechanisms are prevented by either sufficient construction details or specific solutions. View Full-Text
Technical Guide for Evaluation of Seismic Force Resisting Systems and Their Force Modification Factors for Use in the National Building Code of Canada with Concepts Illustrated Using a Cantilevered Wood CLT Shear Wall Example
The objective of this guideline is to provide a simple, systematic, and sufficient procedure for evaluating the performance of Seismic Force Resisting Systems (SFRSs) and to determine the appropriate ductilityrelated (Rd) and over-strength related (Ro) force modification factors for implementation in the National Building Code of Canada (NBC). The procedure relies on the application of non-linear dynamic analysis for quantification of the seismic performance of the SFRS. Note that the procedure is also suitable for assessing force modification factors (RdRo values) of systems already implemented in the NBC.
The audience for this guideline are those (called the “project study team” in this document) who submit proposals for new SFRSs with defined RdRo values to the NBC for inclusion in Subsection 4.1.8., Earthquake Loads and Effects, of Division B of the NBC. This guideline can also be used by a team performing an alternative design solution for a specific project and seeking acceptance from authority having jurisdiction. In such cases, not all aspects of this guideline (e.g., having different archetypes) will be needed.
The current study uses knowledge from digital architecture, computer science, engineering informatics, and structural engineering to formulate an algorithmic framework for integrated Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE) of Integrally-Attached Timber Plate (IATP) structures. The algorithm is designed to take the CAD 3D geometry of an IATP structure as input and automates the construction and analysis of the corresponding CAE model using a macroscopic element, which is an alternative to continuum Finite Element (FE) models. Each component of the macro model is assigned a unique tag that is linked to the relevant geometric and structural parameters. The CAE model integrity is maintained through the use of the common data model (CDM) concept and object-oriented programming. The relevant algorithms are implemented in Rhinoceros 3D using RhinoCommon, a .NET software development kit. Once the CAE macro model is generated, it is introduced to the OpenSees computational platform for structural analysis. The algorithmic framework is demonstrated using two case structures: a prefabricated timber beam with standard geometry and a free-form timber plate arch. The results are verified with measurements from physical experiments and FE models, where the time needed to convert thousands of CAD assemblies to the corresponding CAE models for response simulation is considerably reduced.
The development of this primer commenced shortly after the 2018 launch of the Mass Timber Institute (MTI) centered at the University of Toronto. Funding for this publication was generously provided by the Ontario Ministry of Natural Resources and Forestry. Although numerous jurisdictions have established design guides for tall mass timber buildings, architects and engineers often do not have access to the specialized building science knowledge required to deliver well performing mass timber buildings. MTI worked collaboratively with industry, design professionals, academia, researchers and code experts to develop the scope and content of this mass timber building science primer. Although provincially funded, the broader Canadian context underlying this publication was viewed as the most appropriate means of advancing Ontario’s nascent mass timber building industry. This publication also extends beyond Canada and is based on universally applicable principles of building science and how these principles may be used anywhere in all aspects of mass timber building technology. Specifically, these guidelines were developed to guide stakeholders in selecting and implementing appropriate building science practices and protocols to ensure the acceptable life cycle performance of mass timber buildings. It is essential that each representative stakeholder, developer/owner, architect/engineer, supplier, constructor, wood erector, building official, insurer, and facility manager, understand these principles and how to apply them during the design, procurement, construction and in-service phases before embarking on a mass timber building project.
When mass timber building technology has enjoyed the same degree of penetration as steel and concrete, this primer will be long outdated and its constituent concepts will have been baked into the training and education of design professionals and all those who fabricate, construct, maintain and manage mass timber buildings.
One of the most important reasons this publication was developed was to identify gaps in building science knowledge related to mass timber buildings and hopefully to address these gaps with appropriate research, development and demonstration programs. The mass timber building industry in Canada is still a collection of seedlings that continue to grow and as such they deserve the stewardship of the best available building science knowledge to sustain them until such time as they become a forest that can fend for itself.
Cross-laminated timber (CLT) is a large prefabricated solid engineering plank made of multiple layers of planks glued together and it is primarily used in structures such as the floors, walls, and roofs of buildings. ANSI/APA PRG 320 is the world recognized CLT lumber production standard, and the main raw material of CLT has always been softwood rather than hardwood. However, the bending strength, compressive strength, and shear strength of hardwood CLT lumber are stronger than softwood CLT lumber. The large and underutilized hardwood resources in central and southern Ontario provide a huge resource advantage for the hardwood CLT project. This article uses the Cost-Benefit Assessments model to assess the feasibility of investing in hardwood CLT plants in central and southern Ontario. The results show that the payback period of the hardwood CLT factory is 5 years, and the rate of return on investment of 10 years, 15 years, and 20 years are all-around 11%. This study could strengthen investor confidence and it also identifies the direction for the development of hardwood CLT plants in central and southern Ontario.
This paper presents an innovative and sustainable timber constructive system that could be used as an alternative to traditional emergency housing facilities. The system proposed in this study is composed of prefabricated modular elements that are characterized by limited weight and simple assembly procedures, which represent strategic advantages when it comes facing a strong environmental disaster (e.g. an earthquake). The complete dismantling of structural elements and foundations is granted thanks to specific details and an innovative connection system called X-Mini, capable of replacing traditional anchoring devices (i.e. hold downs and angle brackets) by resisting both shear and tension loads. This constructive system, denoted as Hybrid Timber Frame (HTF), takes advantage of the strong prefabrication, reduced weight of light-frame timber systems, and of the excellent strength properties of the Cross Laminated Timber (CLT) panels. Specifically, the solid-timber members typically used in the structural elements of light-frame systems are replaced by CLT linear elements. The results of experimental tests and numerical simulations are critically presented and discussed, giving a detailed insight into the performance of the HTF under seismic conditions.
This project proposes a timber-based composite floor that can span 12 m and be used in the construction of 40+ story office buildings. This floor system integrates timber panels and timber beams to form a continuous box girder structure. The timber panels function as the flanges and the timber beams as the web. The beams are spaced and connected to the flange panels so that sufficient bending stiffness of a 12 m span can be achieved via the development of composite action.
The current phase of this project studied the performance of the connections between timber elements in the proposed composite member. Six types of connections using different flange material and connection techniques were tested: Cross Laminated Timber (CLT), Laminated Strand Lumber (LSL), Laminated Veneer Lumber (LVL), and Post Laminated Veneer Lumber (PLVL). Glulam was used as the web. The majority of the connections used self-tapping wood screws except one had notches. The load-carrying capacity, stiffness, and ductility of the connections were measured. The stiffness of CLT, LSL, and PLVL connections was in the same range, 19-20 kN/mm per screw. Amongst the three, LSL had the highest peak load and PLVL had the highest proportional limit. The stiffness of the two LVL screw connections was around 13 kN/mm. The notched LVL connection had significantly higher stiffness than the rest, and its peak load was in the same range as LSL, but the failure was brittle.
LVL was used to manufacture the full scale timber composite floor element. With a spacing of 400 mm, the overall stiffness reached 33689 N
mm2×109, which was 2.5 times the combined stiffness of two Glulam beams. The predicted overall stiffness based on Gamma method was within 5% of the tested value, and the estimated degree of composite action was 68%. From both the test results and analytical modeling, the number of screws may be further reduced to 50% or less of the current amount, while maintaining a high level of stiffness.
Future work includes testing the composite floor under different screw spacings,
investigating the effect of concrete topping, and the connections between floor members
and other structural elements.
This manual is helpful for experts and novices alike. Whether you’re new to mass timber
or an early adopter you’ll benefit from its comprehensive summary of the most up to date
resources on topics from mass timber products and applications to tall wood construction
The manual’s content includes WoodWorks technical papers, Think Wood continuing
education articles, case studies, expert Q&As, technical guides and other helpful tools.
Click through to view each individual resource or download the master resource folder for
all files in one handy location. For your convenience, this book will be updated annually as
mass timber product development and the market are quickly evolving.
An advanced modelling tool, WoodST, has been developed for fire safety analysis of timber structures. It is demonstrated that this advanced modelling tool can predict the structural response of LVL beams, glulam bolted connections, OSB-web I-joist and wood-frame floors under forces and fire conditions with an accuracy acceptable to design practitioners (i.e., within 10% of test data). The developed modelling tool can:
Fill the gap in terms of suitable models for timber connections, which is an impediment for the design and construction of tall wood buildings;
Provide a cost-effective simulation solution compared to costly experimental solutions; and
Significantly reduce the cost and shorten the time for the development and/or optimization of new wood-based products and connections.