Mass timber products, together with careful forestry management, could help decarbonize the construction industry. These products must be long-lasting, to safely store atmospheric carbon for decades or centuries, and multi-functional, to displace materials and equipment that are emissions-intensive. This paper shows how to optimize mass timber panels as heat-exchangers, suggesting how to eliminate insulation while simplifying HVAC systems. Test panels measured the heat-exchange in steady and transient conditions, when the ventilation was driven by a fan or by thermal buoyancy. The total heat transfer was predicted accurately by theory in all cases. Further investigation is needed to understand the possible heat-recovery effects at the exterior surface.
Wood has been gaining popularity as a building material over the last few decades. There has been significant progress in technology during this period to push the limits of wood construction. At the same time, it has become more economically competitive to build with wood beyond low-rises. As a result, there has been a noteworthy shift in public perception in terms of acceptance of wood as a material for high-rise buildings. There is a growing list of tall wood buildings that have been constructed in different continents over the last decade. With worldwide population growth and increased urbanization, the trend is expected to continue. Considerable urgency for using sustainable resources to tackle the threat of climate change has resulted in a surge in demand as well as applications in recent decades. This paper reviews the significant technical advances that have contributed to those achievements and are expected to facilitate further developments.
The main objective of this study is to evaluate the heat release rate and fire growth contribution due to heat delamination characteristics of CLT manufactured with four types of adhesives used for face bonding, when exposed to a constant radiant heat flux. The evaluation is performed using the principles of ISO 5660-1 “Reaction-to-fire tests - Heat release, smoke production and mass loss rate – Part 1: Heat release rate (cone calorimeter method)”. The American version of this test method is ASTM E1354 « Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter ».
The long-term objective is to determine which currently accepted test methods allow for the most suitable evaluation of heat delamination characteristics of adhesives used in structural engineered wood products, based on their actual end-use applications (e.g. bending, compression, combined stress, cross-plies, etc.).
Timber-concrete composite slabs are more and more in use: the combination of timber and concrete combines the advantages of both materials and offer a valid solution for the increasing demand for sustainable construction. The connection between timber and concrete is the crucial element, yet its potential regarding material and time expenses is not exploited. This paper presents the novel connection system micro-notches, an interlocking concept between timber and concrete with indentations in the millimetre range. Micro-notches provide a continuous shear transfer without additional steel fasteners such as screws or dowels. The paper presents the development of the micro-notch concept in an extensive experimental program supplemented with analytical and numerical models, a calculation model, and practice-relevant guidelines. The results of the investigations show that micro-notches feature an approximately rigid composite action between timber and concrete and a sufficient shear strength for the use in office and residential buildings.
The excessive use of steel and concrete as energy- and carbon-intensive construction materials have led to a great deal of research on environmentally friendly alternatives to replace conventional construction materials and methods that can reduce the negative environmental impact of the building industry. Application of timber as an environmentally sustainable and light-weight construction material has been highlighted in many studies, but, the widespread use of structural timber has been hindered by significantly different mechanical properties in longitudinal and transverse directions and its variability due to environmental conditions. The recent advancements in manufacturing engineered wood products such as cross-laminated timbers (CLT) with enhanced dimensional stability and similar mechanical properties in both directions have largely addressed the former drawbacks. Accordingly, it has been seen growing interest in mass CLT constructions and/or combining the light-weight CLT panels with steel and reinforced concrete to develop environmentally sustainable structural systems. One such system is steel-timber composite (STC) which comprises prefabricated CLT slabs connected to steel girders using mechanical connectors (e.g. screws and bolts). The adoption of STC floors in practice is however affected by lack of knowledge on the amount of achievable environmental benefit by the trade-off between embodied and operation energy consumption due to the lesser thermal mass of the timber compared to concrete. Furthermore, the long-term behaviour and vibration performance of the steel-CLT composite beams under service loads remains largely unexplored. This study demonstrates the environmental benefits (lower carbon footprint and energy consumption saving) of the STC system in the first step. Then, the hygro-mechanical properties of CLT are measured experimentally as input for numerical simulations. The acceptable long-term performance of the STC connections and beams under sustained service loads are demonstrated by long-term push-out and six-point bending tests in the following part. A simplified numerical model that takes advantage of fibre element is developed and validated against experimental data to predict the long-term creep induced deflections for a service life of 50 years. In the last part of this study, the vibration performance of the STC floors as a governing factor in the design of light-weight low-damping STC systems is studied experimentally and numerically.
Across B.C. and Canada, communities are under pressure to create better-performing buildings that meet stringent code requirements while reducing construction waste. Meanwhile, consumers are demanding high-quality structures that are delivered quickly and at a reasonable price. Modern methods of construction that include prefabrication can help construction professionals create buildings that meet all these criteria.
Furthermore, prefabrication provides steady employment and is good for the economy. The market opportunities are present across Canada and in the U.S., but prefabrication is not being used to its potential due to several barriers:
Negative perception of quality
Fear of innovation
Lack of information and understanding
Unclear economic benefits
Limited industry capacity
Planning and regulatory complications
A concerted effort to address these barriers includes:
Improving products through research and development
Researching, documenting, and promoting best practices
Developing guidance documents so prefabrication is easier to incorporate
Providing national-level leadership and resources to promote innovation
Successfully implementing these recommendations will require a broad and deep national perspective, an understanding of all stages and aspects of wood construction, and the vision and skills to bring together diverse experts and stakeholders.
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