It is not surprising to see a rapid growth in the demand for mid- to high-rise buildings. Traditionally, these types of buildings have been dominated by steel and concrete. This trend creates a great opportunity for wood to expand its traditional single and low-rise multi-family building market to the growing mid- to high-rise building market. The significance and importance of wood construction to environmental conservation and the Canadian economy has been recognized by governments, the building industry, architects, design engineers, builders, and clients. It is expected that more and more tall wood frame buildings of 6- to 8-storeys (or taller) will be constructed in Canada. Before we can push for use of wood in such applications, however, several barriers to wood’s success in its traditional and potential market places have to be removed. Lack of knowledge of the dynamic properties of mid- to high-rise wood and hybrid wood buildings and their responses to wind, and absence of current guidelines for wind vibration design of mid- to high-rise wood and hybrid wood buildings are examples of such barriers.
This pilot study was conducted to build a framework for the development of design and construction solutions for controlling wind-induced vibration of mid- to high-rise wood and hybrid wood frame buildings, to ensure satisfactory vibration performance during high winds.
A literature review and ambient vibration tests (AVT) on existing two- to six-storey wood frame buildings were conducted to establish a database of the vibration properties of wood frame buildings. Monitoring the vibration response to wind of a six-storey wood frame building was initiated. Collaboration with McGill University was also established to verify the AVT results. The measured fundamental natural frequencies of the wood-frame building were used to verify the NBCC equations to estimate the building’s fundamental natural frequencies. Collaboration with Tongji University was established to explore the potential use of the finite element commercial software Ansys, for simulation of vibration performance of wood frame buildings.
It is concluded that this project achieved its objectives, i.e. built a framework for the development of a design guide for controlling wind-induced vibrations of mid- to high-rise wood frame buildings. The framework includes the AVT system, software and protocol, a building vibration monitoring system and protocol, computer simulation tool, a database of natural frequencies and damping ratios of wood frame buildings, and the expertise for conducting AVT, building monitoring, and computer simulation. Pilot study results confirmed that AVT and computer simulation are useful, and appropriate tools for the development of techniques and a design guide for controlling wood frame building vibrations in wind.
It is recommended that current NBCC equations using building height as a variable to estimate the building’s fundamental natural frequency be used to predict the fundamental natural frequencies of wood-frame buildings, until a better calculation methodology is developed. More field data of the fundamental natural frequencies measured on mid- to high-rise wood frame or hybrid wood buildings are needed to further verify the NBCC equations, or to develop more suitable equations for wood buildings.
Evaluating a selective harvest operation as a forest fuel treatment as a forest fuel treatment. A case study in a mature douglas-fir forest in central interior British Columbia
The City of Quesnel, B.C. has applied an innovative selective harvesting technique in a mature Douglas-fir forest stand with the objectives of maintaining biodiversity and reducing fuel-load buildup and consequent wildfire threat. FPInnovations researchers monitored and documented the harvesting operations and measured machine productivity to evaluate the cost-effectiveness of the operation.
To support the assessment of fuel-load reduction, FPInnovations’ Wildfire Operations group conducted pre- and post-harvest fuel-sampling activities to evaluate changes in forest fuel components.
Forest fuels engineering is one of the primary wildfire mitigation strategies advocated by FireSmart™ Canada and applied by partnering wildfire management agencies and industry operators. Fuel treatments have been extensively applied in and around communities in the wildland-urban interface, through a broad range of fuel modification techniques. A primary objective of fuel treatments is to modify fire behaviour to a ‘less difficult, disruptive, and destructive’ state (Reinhardt et al. 2008) which can allow for safer, more effective fire suppression operations (Moghaddas and Craggs 2007).
Black spruce is one of the most prevalent fuel types surrounding communities in central and northern Alberta, as well as other parts of boreal Canada. The densely stocked black spruce forest stands in the Red Earth Creek FireSmart research area exhibit typical crown fuel properties of black spruce: high crown bulk density and low crown base height, which contribute to crown fire initiation (Van Wagner 1977). These fuel characteristics, combined with low fuel moisture contents and strong winds, create ideal conditions for high-intensity, rapidly-spreading catastrophic wildfire (Flat Top Complex Wildfire Review Committee 2012).
Mulch fuel treatments use various types of equipment to masticate forest vegetation resulting in a reduction in crown bulk density and the conversion of canopy and ladder fuels to a more compacted and less available fuel source in the surface layer (Battaglia et al. 2010). Mulch thinning and strip mulch treatments create a more open surface fuel environment with both negative and positive impacts. Due to increased exposure to sun and wind flow, the chipped debris and other surface fuels in the open areas of the treatments dry more quickly than fine fuels in enclosed stands (Schiks and Wotton 2015). From a control perspective, the open thinned areas of the treatments allow more effective penetration of water/suppressant through canopy fuels to surface fuels (Hsieh in progress). Additionally, fine fuels at the surface of openings respond more quickly to water and suppressant application. Open areas of the treatments that have been wetted by sprinkler systems or aerial water delivery should reduce the potential for ignition and sustained burning, providing a potential barrier to fire spread.
Experimental crown fires have been conducted to challenge fuels treatments in other forest fuel types (Schroeder 2010, Mooney 2013) to evaluate the efficacy of these treatments in moderating fire behaviour. Mechanical (shearblading) fuel treatments in black spruce fuels (Butler et al. 2013) have been shown to reduce fire intensity. However, documentation of crown fire challenging mulch fuel treatments in black spruce fuels is limited. Fire and fuels managers would like to evaluate the effectiveness of mulch fuel treatments in reducing fire intensity and rate of spread and, ultimately, their ability to mitigate wildfire risk to communities surrounding these hazardous fuels.
Alberta Agriculture and Forestry (AAF) Wildfire Management Branch fuels managers designed the Red Earth Creek FireSmart research area with the objective of conducting research that will lead to a better understanding of mulch fuel treatments and how these changes in the black spruce fuel environment affect fire behaviour. On May 14, 2015, Slave Lake Forest Area personnel conducted an experimental fire at this site; FPInnovations and research partners collected data to document changes in fire behaviour.
This study investigated the effects of applying three mulch treatment intensities on fuel bed characteristics and the resultant fire behaviour. This is a companion report to a previously published report titled Mulching productivity in black spruce fuels: Productivity as a function of treatment intensity. The findings of these fire behaviour trials, in conjunction with productivity results, can assist fuel management practitioners in developing appropriate cost-effective mulching prescriptions.
It is not surprising to see a rapid growth in the demand for mid- to high-rise buildings. Traditionally, these types of buildings have been dominated by steel and concrete. This trend creates a great opportunity for wood to expand its traditional single and low-rise multi-family building market to the growing mid- to high-rise building market. The significance and importance of wood construction to environmental conservation and the Canadian economy has been recognized by governments, the building industry, architects, design engineers, builders, and clients. It is expected that more and more tall wood frame buildings of 6- to 8-storeys (or taller) will be constructed in Canada. Before we can push for use of wood in such applications, however, several barriers to wood success in its traditional and potential market places have to be removed. Lack of knowledge of the dynamic properties of mid- to high-rise wood and hybrid wood buildings and their responses to wind, and absence of current guidelines for wind vibration design of mid- to high-rise wood and hybrid wood buildings are examples of such barriers.
This report summarises results from the first year study of this project and from other two one-year related projects. The main objective of the study was to build a framework for the development of design guide for controlling wind-induced vibration of mid- to high-rise wood and hybrid wood frame buildings, to ensure satisfactory vibration performance during high winds.
A literature review of the existing database of the dynamic properties of 1- to 3-storey wood platform buildings was conducted. The test system and protocols of ambient vibration tests (AVT) was developed. Collaboration with McGill University was also established to verify the AVT system and the test protocols. AVT tests were conducted on two 2-storey non-residential hybrid heavy timber platform buildings, three new heavy timber (glulam) non-residential buildings of 4-6 storeys and on two cross-laminated timber (CLT) condominium buildings of 3 and 4 storeys. The monitoring system to determine the vibration response in wind of mid-to high-rise wood frame building was developed. The database consisting of the data in the literature and our measured fundamental natural frequencies of the wood frame building were used to verify the NBCC equations to estimate building fundamental natural frequencies. Collaboration with Tongji University was established to explore the potential use of the finite element commercial software Ansys, for simulation of vibration performance of wood frame buildings.
It is concluded that the project was on the right track towards the development of a design guide for controlling wind-induced vibrations of mid- to high-rise wood frame buildings. The results from this study and other two relevant projects confirmed that AVT and computer simulation are useful, and appropriate tools for the development of solutions and a design guide for controlling wood frame building vibrations in wind.
It is recommended that current NBCC equations using building height as a variable to estimate the building fundamental natural frequency can be used to predict the fundamental natural frequencies of wood frame buildings, until a better calculation methodology is developed. More field data of the fundamental natural frequencies measured on mid- to high-rise wood frame or hybrid wood buildings are needed to further verify the NBCC equations, or to develop more suitable equations for wood buildings.
This report focusses on progress towards supporting industry to expand its markets for wood and wood products by providing the designers and specifiers with design provisions and practical design solutions for wood-based lateral load resisting systems in engineered wood construction. This four-year project will particularly address two main issues:
Develop and compile the fundamental information needed to establish a Lateral Load Resisting Systems Design Section in CSA O86, which will be consistent with the 2005 edition of the National Building Code of Canada (NBCC 2005).
Develop and compile the information needed to link the new Lateral Load Resisting Systems Design Section in CSA O86 with the Fastenings Section in terms of connection behaviour required to satisfy the specified system response to lateral loading.
The purpose of this project is to support industry to expand its markets for wood and wood products by providing designers and specifiers with design provisions and practical design solutions for wood-based lateral load resisting systems in engineered wood construction. This four-year project will address two main issues:
1) Develop and compile the fundamental information needed to establish a Lateral Load Resisting Systems Design Section in CSA O86, which will be consistent with the 2005 edition of the National Building Code of Canada (NBCC 2005).
2) Develop and compile the information needed to link the new Lateral Load Resisting Systems Design Section in CSA O86 with the Fastenings Section in terms of connection behaviour required to satisfy the specified system response to lateral loading.
Support industry to expand its markets for wood and wood products by providing designers and specifiers with design provisions and practical design solutions for wood-based lateral load resisting systems in engineered wood construction. This four-year project will address two main issues:
Develop and compile the fundamental information needed to establish a Lateral Load Resisting Systems Design Section in CSA O86, which will be consistent with the 2005 edition of the National Building Code of Canada (NBCC 2005).
Develop and compile the information needed to link the new Lateral Load Resisting Systems Design Section in CSA O86 with the Fastenings Section in terms of connection behaviour required to satisfy the specified system response to lateral loading.
The main sources of lateral loads on buildings are either strong winds or earthquakes. These lateral forces are resisted by the buildings’ Lateral Load Resisting Systems (LLRSs). Adequate design of these systems is of paramount importance for the structural behaviour in general. Basic procedures for design of buildings subjected to lateral loads are provided in national and international model building codes. Additional lateral load design provisions can be found in national and international material design standards. The seismic and wind design provisions for engineered wood structures in Canada need to be enhanced to be compatible with those available for other materials such as steel and concrete. Such design provisions are of vital importance for ensuring a competitive position of timber structures relative to reinforced concrete and steel structures.
In this project a new design Section on Lateral Load Resisting Systems was drafted and prepared for future implementation in CSA O86, the Canadian Standard for Engineering Design in Wood. The new Section was prepared based on gathering existing research information on the behaviour of various structural systems used in engineered wood construction around the world as well as developing in-house research information by conducting experimental tests and analytical studies on structural systems subjected to lateral loads. This section for the first time tried to link the system behaviour to that of the connections in the system. Although the developed Section could not have been implemented in CSA O86 in its entirety during the latest code cycle that ended in 2008, the information it contains will form the foundation for future development of technical polls for implementation in the upcoming editions of CSA O86.
Some parts of the developed Section were implemented in the 2009 edition of CSA O86 as five separate technical polls. The most important technical poll was the one on Special Seismic Design Considerations for Shearwalls and Diaphragms. This technical poll for the first time in North America includes partial capacity design procedures for wood buildings, and represents a significant step forward towards implementing full capacity-based seismic design procedures for wood structures. Implementation of these design procedures also eliminated most of the confusion and hurdles related to the design of wood-based diaphragms according to 2005 National Building Code of Canada. In other polls, the limit for use of unblocked shearwalls in CSA O86 was raised to 4.8 m, and based on the test results conducted during the project, the NLGA SPS3 fingerjoined studs were allowed to be used as substitutes for regular dimension lumber studs in shearwall applications in engineered buildings in Canada.
With the US being the largest export market for the Canadian forest products industry, participation at code development committees in the field of structural and wood engineering in the US is of paramount importance. As a result of extensive activities during this project, for the first time one of the AF&PA Special Design Provisions for Wind and Seismic includes design values for unblocked shearwalls that were implemented based on FPInnovations’ research results. In addition, the project leader was involved in various aspects related to the NEESWood project in the US, in part of which a full scale six-storey wood-frame building will be tested at the E-Defense shake table in Miki, Japan in July 2009. Apart from being built from lumber and glued-laminated timber provided from Canada, the building will also feature the innovative Midply wood wall system that was also invented in Canada. The tests are expected to provide further technical evidence for increasing the height limits for platform frame construction in North America.
The goals of the project are to expand the use of wood and wood products in structural applications by enhancing seismic and wind design provisions for engineered wood-based structural systems. The project will develop new research information, as well as compile the existing research information necessary for development of new Lateral Load Design Provisions for engineered wood-based structural systems in the Canadian Standard for Engineering Design in Wood (CSA O86). When the appropriate code committees and industry associations implement these design provisions into the next edition of CSA O86, they will provide designers and specifiers more structural options for wood-based lateral load resisting systems, similar to those offered in other material codes.
