The following topics in the field of seismic analysis and design of mid-rise (5- and 6-storey) wood-frame buildings are included in this paper: Determination of the building period, linear dynamic analysis of wood-frame structures, deflections of stacked multi-storey shearwalls, diaphragm classification, capacity-based design for woodframe...
FPInnovations carried out a survey with consultants and researchers on the use of analytical models and software packages related to the analysis and design of mass timber buildings. The responses confirmed that a lack of suitable models and related information for material properties of timber connections was creating an impediment to the design and construction of this type of buildings. Furthermore, there is currently a lack of computer models and expertise for carrying out performance-based design for wood buildings, in particular seismic and/or fire performance design.
In this study, a sophisticated constitutive model for wood-based composite material under stress and temperature was developed. This constitutive model was programmed into a user-subroutine which can be added to most general-purpose finite element software. The developed model was validated with test results of a laminated veneer lumber (LVL) beam and glulam bolted connection under force and/or fire.
Figure 1 shows a floor plan and elevation along with the preliminary shear wall locations for a sixstorey wood-frame building. It is assumed some preliminary calculations have been provided to determine the approximate length of wall required to resist t...
Wood-concrete composite slab floors provide a promising solution for achieving long spans and shallow wood-based floor systems for large and tall wood buildings. In comparison with conventional wood floor systems, such long span and heavy floors have a lower fundamental natural frequency...
Utilizing Linear Dynamic Analysis (LDA) for designing steel and concrete structures has been common practice over the last 25 years. Once preliminary member sizes have been determined for either steel or concrete, building a model for LDA is generally easy as the member sizes and appropriate stiffness...
Nail-Laminated Timber (NLT) and box beam are efficient and economical engineered wood products. Although NLT has been used in North America for more than a century, only in recent years it has gained renewed interests as they have been seen as the most economical panel products used in mass timber buildings. Box beams, on the other hand, are lightweight and generally possess higher strength and stiffness than comparable-sized solid timber and are more efficient than solid timber large spans and loads.
In this report, existing design provisions and their limitations for the design and construction of NLT in box beam in Canadian standards are reviewed. For NLT, there is a general lack of information related to manufacturing, design and construction to ensure consistent manufacturing and installation practices. Therefore, it is difficult to research and document with confidence the full range of performance that can be achieved with NLT. It is therefore recommended that a North American product standard and design information on structural performance, floor vibration, fire resistance, acoustic performance, and construction risk mitigation measures (e.g. moisture and fire) be developed.
In CSA 086, design methods are limited to box beams with flanges and webs bonded with glue. As the flanges and webs of a box beam can be assembled by either glue or mechanical fasteners, it is recommended that design provisions for box beam with mechanical joints be also developed. With the information in Eurocode 5 and relevant supporting research papers, it is ready to be implemented.
The 2009 edition of CSA Standard O86, Engineering Design in Wood (CSA 2009), provides an equation for determining the deflection of shear walls. It is important to note that this equation only works for a single-storey shear wall with load applied at the...
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.
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 126.96.36.199.(3)(d)(iii) and 188.8.131.52.(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