The objective of this work is to generate fire performance data for NLT assemblies to address gaps in technical knowledge. This project aims to study how the size of gaps between NLT boards might affect charring of an assembly and its overall fire performance. This research will support designers and builders in the use of mass timber assemblies in larger and taller buildings, by ensuring fire safe designs.
FPInnovations initiated this project to demonstrate the ability of wood exit stairs in mid-rise buildings to perform adequately in a fire when NBCC requirements are followed, with the intent of changing perceptions of the fire safety of wood construction. The objective of this research is to investigate further the fire safety afforded by exit stair shafts of combustible construction, with the ultimate objective of better consistency between the provincial and national building codes with respect to fire requirements for exit stair shafts in mid-rise wood-frame construction.
Mass timber is a family of Solid Laminate Timber Systems (SLTS) formed from smaller sections of timber connected by glue, mechanical fixings, moisture movement or a combination of methods. These products, which include Structural Composite Lumber, GluLam, Cross Lam, Nail Lam and Dowel Lam (or Brettstapel), have over the past two decades seen an extraordinary upsurge in use internationally. This global phenomenon has been driven by a greater emphasis on the sustainable use of renewable resources and by significant technological developments in the manufacture of SLTS. This research paper considers the merits of each of these products, their manufacturing processes and the corresponding quality assurance requirements necessary for successful project delivery. The paper describes the advantages and barriers to the use of the mass timber and provides an overview of the various aspects to be considered during design for offsite and modular construction. The work presented also provides case studies of how these products have been researched and utilised into live projects in the UK utilising local resource resulting in the formation of new supply chain arrangements. The work further explains the advantages of the respective systems for the given application including information on species selection, connection systems employed and the necessary onsite and offsite management approaches deployed.
Following on from the author’s recently completed doctorial research investigating Scandinavian industrially produced engineered construction methodologies and their potential application in Australia, this paper reports on the research and development of a hybridised nail laminated 3 ply CLT and OSB wall panel with a cavity through the design and construction of a prototype commercial building for Western Australia’s largest soft wood timber processor, Wespine.
Findings resulting from the author’s doctorial research and research undertaken for New Zealand research consortium, Solid Wood Innovation, demonstrated the potential for rough sawn multi-grade Radiata pine to be used as a structural material with the capacity to be used in developments of five and six storeys when laminated via a simple gun nailing lamination process. This paper introduces new developments on this concept through the hybridisation of a two ply cross laminated panel with OSB bracing to create a rigid modular wall element suitable for a range of building types.
As 6-storey wood-frame, massive-timber and hybrid wood buildings are increasingly accepted by more jurisdictions across Canada, there is a need to develop reliable elevator shaft designs that meet the minimum structural, fire, and sound requirements in building codes. Elevator shaft walls constructed with wood-based materials have the advantages of material compatibility, use of sustainable materials, and ease of construction.
In this exploratory study, selected elevator shaft wall designs built with nail-laminated-timber (NLT) structural elements were tested to investigate their sound insulation performance because little is known about the sound insulation performance of such wall assemblies. The tests were carried out in an acoustic mock-up facility in accordance to standard requirements, and provide preliminary data on the sound insulation performance of elevator shaft walls built with NLT panels.
Four different elevator shaft walls built with NLT panels were tested and their measured apparent sound insulation class (ASTC) ratings ranged from 18 to 39 depending on their construction details. Some of the reasons that may have contributed to the ASTC ratings obtained for the elevator shaft walls described in this report as well as recommendations for future designs were provided.
It is recommended to continue improving the sound insulation of elevator shaft walls built with NLT panels to meet or exceed the minimum requirements in building codes.
With the trend towards sustainable building design, timber-concrete composite floor systems attract great interest among building designers and developers as an alternative to the profiled steel-concrete deck that are commonly used in commercial construction. The proposed 2-layer composite floor deck consists of a profiled nail laminated timber (NLT) mainly designed in tension and concrete slab in compression. A numerical modelling approach was developed via commercial software ABAQUS to simulate the composite action of wood-concrete floors under four-point bending. The effects of NLT profile, thickness of concrete slab topping, fastening details, and shear span on composite action were analysed through a comparison of stress-strain development in both concrete and timber layers and the loaddeformation responses in shear connections of composite floors. Initial construction details of this composite floor system were therefore defined based on the preliminary analysis and will be examined further in the experimental phase of the project.
Currently the massive timber shear walls are mainly made from Cross Laminated Timber (CLT), which possesses a high in-plane shear strength and rigidity. But only part of its elements (mainly the vertically aligned laminae) are engaged in carrying the vertical load and that could be a limitation when designing taller timber structures or wherever higher vertical load is present. This project studied alternative solutions to massive timber shear wall system, based on Nailed Laminated Timber (NLT) and post laminated LVL (Laminated Veneer Lumber).
The test was conducted on three levels: shear test on glue/nail line, bending-shear test on a small element, and full size wall test under lateral loading. The former two tests investigated the properties of basic elements in NLT and post laminated LVL. The results were used to design and predict the performance of full size shear walls.
The NLT walls were tested under two conditions: without sheathing and with plywood sheathing. The wall without sheathing had the lowest load-carrying capacity and lowest stiffness. Adding plywood sheathing significantly increased its strength and stiffness. The failure in the wall with sheathing was at the sheathing connections, in the forms of nail withdrawal, nail head pull through, and nail breakage. The NLT wall with sheathing had a peak load up to 60% higher than the comparable light wood frame wall, also with a higher stiffness and better ductility. NLT shear walls have an internal energy dissipating capacity which CLT and post laminated LVL walls lack. The post laminated LVL walls behaved as a rigid plate under lateral loading, with little internal deformation. The failure occurred at the holdowns not within the wall. The size effect of its shear strength was studied and an equation was developed to calculate the shear strength of a large size wall plate.
Both products have efficient vertical load bearing mechanism by arranging all elements in the vertical direction. They may serve as alternative to light wood frame walls or CLT walls. Some guidelines for the application and design of NLT shear walls and post laminated LVL shear walls were proposed.
Many of the 1,400 timber bridges in Minnesota do not meet present day standards. Some of these bridges can be improved rather than replaced. When the desired service level can be attained by widening a bridge six feet or less, the bridge can be retrofitted by placing a second, wider, transverse deck onto the existing deck and substructure. Bridge components must be carefully inspected prior to a retrofit project. The retrofit of Bridge #6641 in Sibley County is a good example. First, the bituminous surface was removed. A longitudinal beam supported the extended deck. Grout was poured and leveled and then nail-laminated panels were laid transversely. A bituminous surface was laid over the full width of the new deck. The cost of the project was $51,632. (Replacing the bridge was estimated to take 2-3 years and cost $215,000.) The county quantified the strength change and load distribution characteristics by performing static and dynamic load tests before and after the retrofit. Adding a second deck effectively decreased the static deflections and improved the transverse load distribution. Nail-laminated timber bridge #2642, also in Sibley County, was retrofitted in 1992 and load-tested again in 1995. All dynamic deflections were lower than those of the post-retrofit tests in 1992. This improvement can be explained in part by the drying of the moisture that was introduced into the bridge deck during grouting. A retrofitted timber bridge is expected to last an additional 20-40 years.