Sustainability and innovation are key components in the fight against climate change. Mass timber buildings have been gaining popularity due to the renewable nature of timber. Although research comparing mass timber buildings to more mainstream buildings such as steel is still in the early stages and therefore, limited. We are looking to determine the difference between carbon footprints of mass timber and traditional steel and concrete buildings. This is done with the intention of determining the sustainability and practicality of mass timber buildings.
DOI link: http://dx.doi.org/10.1080/15732479.2018.1456553
This paper investigates the structural behaviour of a twelve-storey Cross-Laminated Timber (CLT) building subjected to sudden removal of internal and external ground floor load-bearing walls, and computes the probability of disproportionate collapse. Analyses are carried out at three different structural idealisations, accounting for feasibility and complexity of finite elements models to understand their performance at: i) the global, ii) the component, and iii) the connection level. Focus is devoted on force and deformation-demands obtained from nonlinear dynamic analyses of the building. The demands are compared against the supply from common CLT panel sizes and the rotational stiffness (k) of the joints, detailed with off-the-shelf angle brackets and self-tapping screws. The study demonstrates that the applied forces and deformations required to develop resistance mechanisms are too large to be supplied by the proposed element and connection designs, if an internal ground floor wall is removed. The considered building has a probability of failure as high as 32% if designed without considerations of the complexities associated with disproportionate collapse. Consequently, to resist the effects of internal wall removal, the floors need to be redesigned and improved structural detailing with sufficient strength, stiffness, and ductility is necessary to trigger collapse resistance mechanisms.
Climate change, environmental degradation, and limited resources are motivations for sustainable forest management. Forests, the most abundant renewable resource on earth, used to make a wide variety of forest-based products for human consumption. To provide a scientific measure of a product’s sustainability and environmental performance, the life cycle assessment (LCA) method is used. This article provides a comprehensive review of environmental performances of forest-based products including traditional building products, emerging (mass-timber) building products and nanomaterials using attributional LCA. Across the supply chain, the product manufacturing life-cycle stage tends to have the largest environmental impacts. However, forest management activities and logistics tend to have the greatest economic impact. In addition, environmental trade-offs exist when regulating emissions as indicated by the latest traditional wood building product LCAs. Interpretation of these LCA results can guide new product development using biomaterials, future (mass) building systems and policy-making on mitigating climate change. Key challenges include handling of uncertainties in the supply chain and complex interactions of environment, material conversion, resource use for product production and quantifying the emissions released.
Raw materials for buildings and construction account for more than 35% of global primary energy use and nearly 40% of energy-related CO2 emissions. The Intergovernmental Panel on Climate Change (IPCC) emphasized the drastic reduction in GHG emissions and thus, wood products with very low or negative carbon footprint materials can play an important role. In this study, a cradle-to-grave life cycle assessment (LCA) approach was followed to quantify the environmental impacts of laminated strand lumber (LSL). The inventory data represented North American LSL production in terms of input materials, including wood and resin, electricity and fuel use, and production facility emissions for the 2019 production year. The contribution of cradle-to-gate life cycle stages was substantial (>70%) towards the total (cradle-to-grave) environmental impacts of LSL. The cradle-to-gate LCA results per m³ LSL were estimated to be 275 kg CO2 eq global warming, 39.5 kg O3eq smog formation, 1.7 kg SO2 eq acidification, 0.2 kg N eq eutrophication, and 598 MJ fossil fuel depletion. Resin production as a part of resource extraction contributed 124 kg CO2 eq (45%). The most relevant unit processes in their decreasing contribution to their cradle-to-grave GW impacts were resource extraction, end-of-life (EoL), transportation (resources and product), and LSL manufacturing. Results of sensitivity analysis showed that the use of adhesive, consumption of electricity, and transport distance had the greatest influences on the LCA results. Considering the whole life cycle of the LSL, the final product stored 1,010 kg CO2 eq/m³ of LSL, roughly two times more greenhouse gas emissions over than what was released (493 kg CO2 eq/m³ of LSL) from cradle-to-grave. Overall, LSL has a negative GW impact and acts as a carbon sink if used in the construction sector. The study results are intended to be important for future studies, including waste disposal and recycling strategies to optimize environmental trade-offs.
The Petawawa Research Forest (PRF) was established in 1918 and is the oldest research forest in Canada. It is located along Highway 17, east of Chalk River, Ontario, and is part of Garrison Petawawa under the jurisdiction of the Department of National Defence. By special agreement, it is managed by the Canadian Wood Fibre Centre, under the Canadian Forest Service, Natural Resources Canada. The research undertaken at the PRF influences forest policy, industry, silvicultural practices, and private forest management practices across the country. Operational commercial harvests also occur at the PRF.
Meridian Road is an access road at the PRF and leads to research, forest management, and recreational sites. A multi-cell culvert system at Young’s Creek recently failed (bottom left), and the crossing needed large-scale maintenance to allow the continued movement of logging trucks, vehicles, and research teams. The culvert failure negatively impacted water flow and habitat. To rectify these issues, a modern, single-lane engineered wood product (EWP) bridge, named Centennial Bridge (bottom right), was installed and built by Corington Engineering Inc., of Renfrew, Ontario. The experience at the PRF is of interest to sustainable forest licence (SFL) holders (and municipalities) looking to gain more knowledge about the construction and design of EWP access road bridges. The goal of this case study was to highlight the main construction and design details of Centennial Bridge and draw some comparisons to conventional steel-logging road bridges.