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.
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.
To assure the appropriate use of wood in large residential and non-residential buildings, it is necessary to carry out a comprehensive study of the resistance provided by these wood structures to lateral loads due to wind and earthquakes. Given that this is a topic of international interest, and there is a strong movement towards worldwide harmonisation of codes and standards, the proposed work requires the cooperation of a number of specialists in Canada and abroad. As a first step in creating a coordinated program of research, a consultation on the seismic resistance of timber structures has been carried out. A group of six seismic experts from Japan, New Zealand, USA, Germany, Italy and Greece were brought together in Vancouver, B.C. for two days in May, 1993. This consultation was joined by six Canadian experts on seismic analysis and timber engineering research. Following this meeting, a five-year research program on the lateral resistance of engineered wood structures to seismic and wind loads was launched. The objective of the program is to provide designers and code writers with the test data and analytical tools needed to design large timber buildings for wind and earthquake forces. The program includes wood-framed and sheathed walls and diaphragms, braced timber structures, structural wood frames and arches. In the first year of the program, in cooperation with Dr. M. Yasumura, a visiting scientist from the Building Research Institute, Tsukuba, Japan, and Mr. D. Kishi, a structural engineering consultant from British Columbia, a total of 21 16' x 8' (4.8 m by 2.4 m) wood shear walls have been tested at Forintek under static and reversed cyclic loading. In these walls, three types of sheathing material (plywood, Oriented Strand Board, and Gypsum Wall Board (GWB) were used to investigate the effects of sheathing position (vertical or horizontal), blocking, nail spacing, and taping (in the case of GWB). The structural behaviour of elements such as shear walls is dependent on the behaviour of individual connections. Research alliances are currently being formed with the University of New Brunswick and the University of British Columbia for the development of test data and analytical models on the behaviour of connections.
The progress in the second year of the 5 year research program entitled "Lateral Resistance of Engineered Wood Structures to Seismic Loads" is presented. Because of the international scope of the problem, the work is being carried out in cooperation with scientists from several universities and research institutes. A procedure for determining force modification factors for timber structures is presented using the experimental data collected on nailed shear walls.
Low-rise buildings constructed using wood are vulnerable to extreme wind storms and earthquakes. While several experimental measurements of the environmental loads (mostly wind) on the building envelope have been made at full scale, none of these studies directly linked these external loads with the internal forces and displacements of the structure.
This report presents the experimental and analytical work on two light-frame wooden structures, with one that already existed (Forintek shed in Québec City) and the other (UNB house) that was built specifically for the research project on the University of New Brunswick campus in Fredericton. The research goal was to devise and demonstrate methods of identifying load paths in light-frame wood buildings subject to environmental loads. This goal was achieved by carrying out experiments at the element level (studs, sheathings), subsystem level (shear walls) and on the whole-building level (finished and “realistic” light-frame timber buildings). The responses of these buildings to controlled static tests as well as natural environmental loads were observed and compared with a wind tunnel study and with detailed finite element models with good agreement.
Shear walls were tested in isolation and as a part of the whole structure. The tests indicated that neither the strength nor the stiffness decreased by the same magnitude as the wall effective length is reduced. For the Forintek shed, the structural monitoring was based on measurements of deformations within a representative segment of the wall and roof surfaces and a matching grid of wall and roof wind pressure taps supplemented with a wind tunnel study at Concordia University. In general, it was shown that the building surroundings had a great effect on the pressure distribution of the surface on the structure and that these effects cannot always be determined intuitively. Both mean and peak pressure coefficient were measured and they compared well with corresponding values obtained in the wind tunnel tests.
Results from controlled static loads on the UNB house indicated that the load was distributed to all walls, and significant load sharing was observed. The stiffness of the roof was sufficient to distribute load to walls farthest away from the load application point. It was also found that the internal forces are concentrated near the corners of the building. Under vertical loading on the roof, the load at the roof-to-wall interface was concentrated in a small region of the building plan around the application point. The test results also showed that the load was transferred to the transverse walls, even though there were only nominal connection between the wall and the roof trusses.
Analytical modeling results showed good agreement with the full-scale test results for shear walls as well as for the whole building. The 3-D model was able to simulate the sharing of racking forces between shear walls, based on experiments reported in the literature. In general, the errors in the numerical prediction were small. The model was able to predict the interaction between the roof system and the walls and the interactions amongst walls.
