Timber construction has become completely modernized. It has gained considerably in market share with respect to competing building materials and is dominated by systems such as frame and solid timber construction.
Every timber construction is determined by its structure. Hence it is essential to know the connections and relationships from the design stage right through to the construction phase. Systems in Timber Engineering takes a whole new approach to this subject. It is a comprehensive, analytical, and visually organized treatment, from the simple single-family house to the large-scale multistore structure. It includes the building envelope, which is so important for saving energy, and systems for ceilings and interior dividing walls, which are so essential from the vantage point of construction.
This work uses plans, schematic drawings, and pictures to show the current and forward-looking state of the technology as applied in Switzerland, a leading country in the field of timber construction.
Most of the timber used in the Australian built environment is presently for low-rise residential construction. This market share is under constant erosion from competitive systems; therefore, entry into non-traditional sectors would benefit the industry through a wider market portfolio of building type applications, and a higher value product system development.
The project analysed building designs in order to estimate the size and value of the market sector in commercial and high-rise residential buildings; established the major building systems used in these sectors, and why these systems are popular (major attractiveness of current systems) and scoped two current timber systems (Cassette Flooring and Access floors) that have the opportunity to increase timber volumes in these markets.
spIn this report, the seismic performance of 6-storey wood frame residential buildings is studied. Two building configurations, a typical wood-frame residential building and a building to be tested under the NEESWood project, were studied. For each building configuration, a four-storey building and a six-storey building were designed to the current (pre-April 6, 2009) 2006 BC Building Code (BCBC) and to the anticipated new requirements in the 2010 National Building Code of Canada (NBCC), resulting in four buildings with different designs. The four-storey building designed to the current 2006 BC Building Code served as the benchmark building representing the performance of current permissible structures with common architectural layouts.
In the design of both four-storey and six-storey buildings, it was assumed that the buildings are located in Vancouver on a site with soil class C. Instead of using the code formula, the fundamental natural period of the buildings was determined based on the actual mass and stiffness of wood-based shearwalls. The base shear and inter-storey drift are determined in accordance with Clauses 22.214.171.124.(3)(d)(iii) and 126.96.36.199.(3)(d)(iv) of BCBC, respectively.
Computer programs DRAIN 3-D and SAPWood were used to evaluate the seismic performance of the buildings. A series of 20 different earthquake records, 14 of the crustal type and 6 of the subcrustal type, were provided by the Earthquake Engineering Research Facility of the University of British Columbia and used in the evaluation. The records were chosen to fit the 2005 NBCC mean PSA and PSV spectra for the city of Vancouver.
For representative buildings designed in accordance with 2006 BCBC, seismic performance with and without gypsum wall board (GWB) is studied. For representative buildings designed in accordance with the 2010 NBCC, the seismic performance with GWB is studied. For the NEESWood building redesigned in accordance with 2010 NBCC, seismic performance without GWB is studied. Ignoring the contribution of GWB would result in a conservative estimate of the seismic performance of the building.
In the 2006 BCBC and 2010 NBCC, the inter-storey drift limit is set at 2.5 % of the storey height for the very rare earthquake event (1 in 2475 year return period). Limiting inter-storey drift is a key parameter for meeting the objective of life safety under a seismic event.
For 4-storey and 6-storey representative wood-frame buildings where only wood-based shearwalls are considered, results from both DRAIN-3D and SAPWood show that none of the maximum inter-storey drifts at any storey under any individual earthquake exceed the 2.5% inter-storey drift limit given in the building code. With DRAIN-3D, the average maximum inter-storey drifts are approximately 1.2% and 1.5% for 4-storey and 6-storey buildings designed with 2006 BCBC, respectively.
For the NEESWood wood-frame building, none of the maximum inter-storey drifts at any storey under any individual earthquake exceed the 2.5% inter-storey drift limit for 4-storey building obtained from SAPWood and 6-storey building obtained from DRAIN-3D and SAPWood. For any 4-storey building analysed with DRAIN-3D, approximately half of the earthquakes resulted in the maximum inter-storey drifts greater than 2.5% inter-storey limit. This is partly due to the assumptions used in Drain-3D model in which the lumped mass at each storey is equally distributed to all the nodes of the floor. As a result, the total weight to counteract the uplift force at the ends of a wall would be much smaller than that anticipated in the design, thus causing hold-downs to yield and large uplift deformations to occur.
Based on the analyses of a representative building and a redesigned NEESWood building situated in the city of Vancouver that subjected the structures to 20 earthquake records, 6-storey wood-frame building is expected to show similar or smaller inter-storey drift than a 4-storey wood-frame building, which is currently deemed acceptable under the current building code.
Building construction - Design
Building construction - Specfications
Earthquakes, Effect on building construction
This report summarizes the existing knowledge on building movement related to wood-frame construction. This knowledge includes fundamental causes and characteristics of wood shrinkage, instantaneous and time-dependent deformations under load, major wood-based materials used for construction and their shrinkage characteristics, movement amounts in publications based on limited field measurement, and movement estimations by construction practitioners based on their experience with wood-frame construction. Movement analysis and calculations were also demonstrated by focusing on wood shrinkage based on common engineering design assumptions, using six-storey platform buildings as examples. The report then provides engineering solutions for key building locations where differential movement could occur, based on the literature review as well as a small-scale survey of the construction industry.
The report emphasizes the importance of comprehensive analysis during design and construction to accommodate differential movement. Most building materials move when subjected to loading or when environmental conditions change. It is always good practice to detail buildings so that they can accommodate a certain range of movement, whether due to structural loading, moisture or temperature changes. For wood-frame buildings, movement can be reduced by specifying materials with lower shrinkage rates, such as engineered wood products and drier lumber. However, this may add considerable costs to building projects, especially when specifications have to be met through customized orders. Producing lumber with a lower moisture content adds significant costs, given the additional energy consumption, lumber degrade and sorting requirements during kiln drying. Specifying materials with lower moisture content at time of delivery to job site does not guarantee that wood will not get wet during construction, and excessive shrinkage could still be caused by excessively long time of exposure to rain during construction. On the other hand, effective drying can occur during the period between lumber delivery and lumber closed into building assemblies. Appropriate measures should be taken to ensure lumber protection against wetting, protected panel fabrication on site, good construction sequence to facilitate air drying, and supplementary heating before closing in to improve wood drying.
This report also provides recommendations for future work, including field measurement of movement and construction sequencing optimization, in order to provide better information for the design and construction of wood buildings, five- and six-storey platform frame buildings in particular.
Ease of construction and favorable overall costs relative to other construction types are making high-rise (i.e., 4- and 5-story) wood frame construction increasingly popular. With these buildings increasing in height, there is a greater impetus on designers to address frame and finishes movement in such construction. As we all know, buildings are dynamic creatures experiencing a variety of movements during construction and over their service life. In wood frame construction, it is important to consider not only absolute movement but also differential movement between dissimilar materials.
This article focuses on differential movement issues and how to recognize their potential and avoid problems by effective detailing.
The research is aimed at developing seismic methods for the design and evaluation of the seismic vulnerability of wooden structures, using a displacement-based approach. After a brief introduction on the seismic behaviour of timber structures, the general Direct Displacement-Based Design (Direct-DBD) procedure and the state-of-the-art are presented, with clear reference to the application of the Direct-DBD method to wooden buildings. The strength of the Direct-DBD method is its ability to design structures in a manner consistent with the level of damage expected, by directly relating the response and the expected performance of the structure. The research begins with a description of the procedural aspects of the Direct-DBD method and the parameters required for its application. The research presented focuses on the formulation of a displacement-based seismic design procedure, applicable to one-storey wooden structures made with a portal system. This typology is very common in Europe and particularly in Italy. A series of analytical expressions have been developed to calculate design parameters. The required analytical Direct-DBD parameters are implemented based on the mechanical behaviour of the connections, made with metal dowel-type fasteners. The calibration and subsequent validation of design parameters use a Monte Carlo numerical simulation and outcomes obtained by tests in full-scale. After the description of the Displacement-Based method for one-storey wooden structures, a series of guidelines to extend the Direct-DBD methodology to other types and categories of timber systems are proposed. The thesis presents the case of a multi-storey wood frame construction, which is a simple extension of the glulam portal frame system. Part of this work has been done within the RELUIS Project, (REte dei Laboratori Universitari di Ingegneria Sismica), Research Line IV, which in the years between 2005 and 2008 involved several Italian universities and Italian institutes of research in the development of new seismic design methods. The Project produced the first draft of model code for the seismic design of structures based on displacement (Direct-DBD). This thesis is the background to the section of the model code developed for timber structures.
This report explores the potential increased use of timber and wood products in building construction, particularly in the growing multi-residential (i.e. units, hotels, etc.), commercial (i.e. shops, offices, etc.), and public building sectors (i.e. hospitals, schools, theatres, etc.).
Many technical solutions already exist to economically and successfully include more timber in multi-storey buildings; however, the timber and wood products industry do not have sufficient staff with the skill and expertise necessary to engage the building industry regularly and effectively. The building products industry is highly competitive and unsupported systems can quickly be overshadowed.
This report recommends the timber and wood products industry develop its own capacity in timber design and construction, and support increased capacity in these areas in the building design professions and the general building industry. Timber industry staff may need further training and education to create and sell timber-based technical solutions for projects, rather than just products.
This report was produced by the University of Canterbury for the Ministry of Agriculture and Forestry under Expression of Interest MAF POL 0910-11665. The report covers extensive research carried out on the construction of the new Arts and Media building at Nelson Marlborough Institute of Technology in Nelson, New Zealand, between March 2010 and June 2011. The collaborative research programme was directed by the Department of Civil and Natural Resources Engineering at the University of Canterbury (UC), Christchurch. Major contributions to the research programme were made by third-party industry consultants and reported in separate documents – a copy of all the original reports is included in the Appendices.
Wind-induced vibration is an important design consideration in tall buildings in any structural material. The two main forms of wind-induced vibration - across-wind vibration due to vortex shedding and along-wind vibration due to turbulence - were taken into consideration when undertaking this study. Both types are addressed in Eurocode 1.
This research summary discusses a study which, following a sensitivity study into the effect of stiffness and damping on wind-induced vibration, addresses a shortfall in current knowledge of stiffness in dowel-type connections. This type of connection is found in the glulam frame and CLT structures currently at the forefront of tall timber construction, and its behaviour was investigated by measuring and analysing stiffness and damping under oscillating loads representative of wind-induced vibration.
This research summary covers a number of factors relating to wind-induced vibration which must be considered when constructing a tall timber building, such as how to assess connection stiffness under in-service vibration. The various conditions were then applied to a case study - the proposed Barentshaus building.