Environmental and Economic Evaluation of Small-Scale Bridge Repair Using Cross-Laminated Timber Floor Slabs

This paper analyses and compares the embodied and operational greenhouse gas (GHG) emissions of two nearly Zero Energy Buildings, a student housing building in Trondheim, Norway, and a residential building in Växjö, Sweden. The student housing in Trondheim, Moholt Allmenning Tower B, is a 9-storey tower composed of cross laminated timber (CLT) panels and concrete floor slabs with a total heated floor area of 3801 m2. The apartment building in Växjö, House A, consists of 8 floors composed of glued laminated timber (glulam) beams with a wood-cassette floor, and concrete slabs with a total heated floor area of 3483 m2. The results show that the use of CLT has the largest reduction of total GHG emissions due to substituting concrete elements in the structural frame. The comparative assessment of the external wall and the internal floor constructions shows that the use of CLT adds marginal GHG emissions per unit of area of component. The calculation of operational GHG emissions shows that the use of the Nordic electricity mix disfavours the full-electric energy system of Moholt Allmenning Tower B, in contrast to the district heating used in Norra Vallen Building A.

Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

The Cross-Laminated Timber (CLT) has been receiving special attention in recent research as an alternative for climate change mitigation since it is a renewable source and can remove and stock high amounts of CO2 from the atmosphere. Some countries, such as Brazil, still do not have mature and large CLT industry. However, the development of this industry in other countries is expected since the CLT is considered the main wood material to be used in high-rise mass timber buildings. It is particularly important to have environmental information, especially concerning the climate change impacts, in terms of life cycle greenhouse gas (GHG) emissions, for this product to increase its competitiveness in a new market. In this context, this research aimed to evaluate three different Life cycle inventories (LCIs) for CLT production of studies from Japan and the United States. Based on the first findings, we summarized the critical items in the LCI of CLT production and listed some actions for the reduction of GHG emissions that occur in this process. The LCIs are adapted considering the context of Brazil (a country with a cleaner electricity matrix) and China (a country with the highest share of fossil fuels). The main inconsistencies present in the LCIs are presented and discussed. The GHG emissions are concentrated in the following hotspots: (1) Roundwood production; (2) electricity consumption; and (3) adhesives production for CLT production. Therefore, the reduction of the consumption of these materials and activities should be encouraged for the decrease of GHG emissions. The data of Roundwood used in the modelling severely affects the final results. Their GHG emissions are related to the consumption of diesel in forestry activities. This research brings insights into the evaluation of the life cycle GHG emissions from the production of CLT.

The use of cross-laminated timber (CLT) in multi-story buildings is increasing due to the potential of wood to reduce green house gas emissions and the high load-bearing capacity of CLT. Compression perpendicular to the grain (CPG) in CLT is an important design aspect, especially in multi-storied platform-type CLT buildings, where CPG stress develops in CLT floors due to loads from the roof or from upper floors. Here, CPG of CLT wall-to-floor connections are studied by means of finite element modeling with elasto-plastic material behavior based on a previously validated Quadratic multi-surface (QMS) failure criterion. Model predictions were first compared with experiments on CLT connections, before the model was used in a parameter study, to investigate the influence of wall and floor thicknesses, the annual ring pattern of the boards and the number of layers in the CLT elements. The finite element model agreed well with experimental findings. Connection stiffness was overestimated, while the strength was only slightly underestimated. The parameter study revealed that the wall thickness effect on the stiffness and strength of the connection was strongest for the practically most relevant wall thicknesses between 80 and about 160 mm. It also showed that an increasing floor thickness leads to higher stiffness and strength, due to the load dispersion effect. The increase was found to be stronger for smaller wall thicknesses. The influence of the annual ring orientation, or the pith location, was assessed as well and showed that boards cut closer to the pith yielded lower stiffness and strength. The findings of the parameter study were fitted with regression equations. Finally, a dimensionless ratio of the wall-to-floor thickness was used for deriving regression equations for stiffness and strength, as well as for load and stiffness increase factors, which could be used for the engineering design of CLT connections.

The study on the mechanical properties of cross laminated timber (CLT) panels made from tropical hardwood species is essential in order to promote the use of CLT as buildings material in Malaysia. The objective of this study were to evaluate the mechanical performance and failure characteristics of CLT fabricated from tropical timbers species, namely, batai (Paraserianthes falcataria), sesendok (Endospermum malacensis), rubberwood (Hevea brasiliensis) and kedondong (family Burceraceae). The modulus of rupture (MOR), modulus of elasticity (MOE), and compressive strength were determined. The failure characteristics of each samples were visually examined and recorded. The results indicated that CLT made from kedondong (KKK) had the highest value of MOR (82.63 N/mm2) and MOE (11,371.33 N/mm2) compared to other species. For compressive strength, CLT made from kedondong (KKK) and rubberwood (RRR) were not significantly different. The failure characteristics observed from bending test were tension, rolling shear and glue line failure while the crushing, shearing and splitting failure were found during compression test. Based on the results obtained, it showed that, the tropical hardwood is suitable to be used as raw material to produce CLT. However, more study should be conducted to observe the performance of CLT on durability and outdoor weathering.

The use of CLT has been increasing the last decade, and a subsequently focus on documentation of the accompanying indoor climate and exposed wooden surfaces on human well-being. This study presents the results of a measurement campaign conducted over one year of a CLT apartment building in Grimstad, Norway. The apartment building consists of three floors with 35 apartments and comply with the Norwegian passive house standard and energy grade A. Measurements of the relative humidity (RH), indoor air temperature and wood moisture content (MC) were performed in the exposed CLT spruce panels in three apartments in two different floors. The results from the three apartments show a relatively small variation in the MC values regardless the residents behavior measured as RH variation through a complete year. Selected periods from a cold period (winter) and a warm period (summer) show the variation in relative humidity (RH) and moisture content in the CLT element. However, results from control measurements showed higher MC values. The gap between the measurements and methods are discussed.

The effects of wood species and panel connections on the vibration and heavy-weight impact sound insulation performance of cross-laminated timber (CLT) slabs were investigated. CLT panels (5-ply, 150 mm thick, 1 m wide, and 4.2 m long) made of larch (Larix kaempferi) and pine (Pinus densiflora) were manufactured with 30 mm thick laminae, considering three types of joints. Three CLT panels of the same species and joint type were connected using spline joints, butt joints, or half-lap joints to form 3 m wide and 4.2 m long slabs for testing. The floor impact sound insulation performance of the CLT slabs was measured according to KS F ISO 10140-3, using the standard heavy-weight impact source, a rubber ball. Additionally, four accelerometers were installed at 400 mm intervals beneath the CLT slabs to analyze the deflections and natural frequencies of the slabs. The results of the experiment indicated that there were no significant differences depending on the wood species and the CLT panel joints. These findings suggest that wood species and joint methods can be flexibly applied in the design of CLT slabs.

Problem statement. Cross-laminated timber (CLT) is a modern building material that can be used in the construction of buildings for various purposes. Despite its popularity abroad, CLT is still a relatively new material in Ukraine, and the current standards for designing timber structures do not include recommendations for the calculation of structures made from CLT panels. To promote the use of CLT in domestic practice, it is necessary to conduct studies on its strength characteristics in accordance with international standards. The purpose of the article is to investigate the characteristics of bending and compressive strength of domestically produced CLT through tests according to European standards. Methods. For experimental studies, samples of elements from the CLT-Result domestic manufacturer were used. The samples consisted of coniferous lumber (pine Pinus sylvestris I.) in a configuration of 3 layers 30 mm thick (CLT thickness 90 mm) and 5 layers 20 mm thick (CLT thickness 100 mm). Bending and compression tests were performed parallel and perpendicular to the plane of the longitudinal layers in accordance with the requirements of EN 16351:2021 and EN 408:2012. Conclusion. The bending strength of CLT samples is determined by the strength of the timber of the outer, most stretched layer. The destruction of the samples during bending began with the formation of cracks along the annual rings of the wood of the outer lower layer, followed by the rupture of the stretched fibers. CLT samples, when tested for compression parallel to the plane of the layers, collapsed due to the exhaustion of the bearing capacity of the timber of the longitudinal layers, which was accompanied by shearing along the inclined areas. The destruction of the CLT compressed perpendicular to the plane of the layers occurred as a result of significant compression of the wood. The following characteristics were determined: the bending strength of the 3-layer CLT panel was 15.3 MPa, and the 5-layer panel had a bending strength of 20.1 MPa; the compressive strength of the 5-layer CLT panel parallel to the plane of the layers fc,0 = 26.88…29.15 MPa, and perpendicular to the plane of the layers fc,90 = 11.16...12.13 MPa.

BackgroundThe availability of feedstock options is a key to meeting the volumetric requirement of 136.3 billion liters of renewable fuels per year beginning in 2022, as required in the US 2007 Energy Independence and Security Act. Life-cycle greenhouse gas (GHG) emissions of sorghum-based ethanol need to be assessed for sorghum to play a role in meeting that requirement.ResultsMultiple sorghum-based ethanol production pathways show diverse well-to-wheels (WTW) energy use and GHG emissions due to differences in energy use and fertilizer use intensity associated with sorghum growth and differences in the ethanol conversion processes. All sorghum-based ethanol pathways can achieve significant fossil energy savings. Relative to GHG emissions from conventional gasoline, grain sorghum-based ethanol can reduce WTW GHG emissions by 35% or 23%, respectively, when wet or dried distillers grains with solubles (DGS) is the co-product and fossil natural gas (FNG) is consumed as the process fuel. The reduction increased to 56% or 55%, respectively, for wet or dried DGS co-production when renewable natural gas (RNG) from anaerobic digestion of animal waste is used as the process fuel. These results do not include land-use change (LUC) GHG emissions, which we take as negligible. If LUC GHG emissions for grain sorghum ethanol as estimated by the US Environmental Protection Agency (EPA) are included (26 g CO2e/MJ), these reductions when wet DGS is co-produced decrease to 7% or 29% when FNG or RNG is used as the process fuel. Sweet sorghum-based ethanol can reduce GHG emissions by 71% or 72% without or with use of co-produced vinasse as farm fertilizer, respectively, in ethanol plants using only sugar juice to produce ethanol. If both sugar and cellulosic bagasse were used in the future for ethanol production, an ethanol plant with a combined heat and power (CHP) system that supplies all process energy can achieve a GHG emission reduction of 70% or 72%, respectively, without or with vinasse fertigation. Forage sorghum-based ethanol can achieve a 49% WTW GHG emission reduction when ethanol plants meet process energy demands with CHP. In the case of forage sorghum and an integrated sweet sorghum pathway, the use of a portion of feedstock to fuel CHP systems significantly reduces fossil fuel consumption and GHG emissions.ConclusionsThis study provides new insight into life-cycle energy use and GHG emissions of multiple sorghum-based ethanol production pathways in the US. Our results show that adding sorghum feedstocks to the existing options for ethanol production could help in meeting the requirements for volumes of renewable, advanced and cellulosic bioethanol production in the US required by the EPA’s Renewable Fuel Standard program.

Cross laminated timber (CLT) has recently increased in use as a building material for low carbon design and is often applied in small and multi-story buildings. Several studies have shown lower fossil related greenhouse gas emission than alternatives, but the life cycle emissions vary substantially between different CLT producers. These emissions are mainly indirect and thus climate change mitigation could reduce these emissions. Previous research shows that that biofuels and carbon capture and storage (CCS) are technologies that have the potential to reduce the climate impacts of the CLT life cycle. This study assesses the impacts on climate change from CLT with these technologies within the framework of environmental product declarations (EPD). In the short run, switching to fossil free fuels provides a reduction in the carbon footprint of CLT. In the long run, CCS at the end-of-life of CLT buildings can provide a net negative carbon footprint over the life cycle. This assessment on the use of CLT is mainly related to the Sustainable Development Goal SDG9 Industries, innovation and infrastructure and the indicator for CO2 emissions per value added, so the assessment in this paper is mainly focused on this goal. SDG7 on affordable and clean energy and SDG15 Life on land are also relevant.

In the 20 years since its invention in Europe, cross-laminated timber (CLT) has become a widely used construction material in parts of the old continent and has started to attract global attention. CLT possesses numerous advantages as a construction material, including its superior structural and environmental performance, as well as the speed and efficiency with which CLT buildings can be erected. In this study, European engineers were surveyed to learn about their current level of awareness of CLT, the major barriers to CLT adoption, and about the most pressing research needs to advance the use of CLT as a construction material. The study used a web-based survey with a convenience sample of 93 different kinds of timber and civil engineers and/or researchers, most of which belong to a European CLT research network. Results showed that participants think that, in general, the level of awareness about CLT among developers, construction managers, engineers, architects, and construction managers, is low. The majority of perceived barriers for CLT adoption involved its building code compatibility and the availability of technical information. The most pressing research needs for CLT development, according to respondents, are in the areas of structural performance and connections, moisture performance, and market research.

Estimation of energy demand and greenhouse gas emission reduction effect of cross-laminated timber (CLT) hybrid wall using life cycle assessment for urban residential planning

Aluminum production is a major energy consumer and important source of greenhouse gas (GHG) emissions globally. Estimation of the energy consumption and GHG emissions caused by aluminum production in China has attracted widespread attention because China produces more than half of the global aluminum. This paper conducted life cycle (LC) energy consumption and GHG emissions analysis of primary and recycled aluminum in China for the year 2020, considering the provincial differences on both the scale of self-generated electricity consumed in primary aluminum production and the generation source of grid electricity. Potentials for energy saving and GHG emissions reductions were also investigated. The results indicate that there are 157,207 MJ of primary fossil energy (PE) consumption and 15,947 kg CO2-eq of GHG emissions per ton of primary aluminum ingot production in China, with the LC GHG emissions as high as 1.5–3.5 times that of developed economies. The LC PE consumption and GHG emissions of recycled aluminum are very low, only 7.5% and 5.3% that of primary aluminum, respectively. Provincial-level results indicate that the LC PE and GHG emissions intensities of primary aluminum in the main production areas are generally higher while those of recycled aluminum are lower in the main production areas. LC PE consumption and GHG emissions can be significantly reduced by decreasing electricity consumption, self-generated electricity management, low-carbon grid electricity development, and industrial relocation. Based on this study, policy suggestions for China’s aluminum industry are proposed. Recycled aluminum industry development, restriction of self-generated electricity, low-carbon electricity utilization, and industrial relocation should be promoted as they are highly helpful for reducing the LC PE consumption and GHG emissions of the aluminum industry. In addition, it is recommended that the central government considers the differences among provinces when designing and implementing policies.

<p>Ultra-lightweight products like Cross-Laminated-Timber (CLT) have entered the marketplace as alternatives to cast in-situ or precast reinforced concrete (RC) for construction of floor slabs. The primary advantage of using lightweight materials is that they reduce structural demands on supporting elements. However, lightweight slabs tend to exhibit higher levels of acceleration than RC slabs when subjected to dynamic loads, making it prudent to pay close attention to vibration serviceability when designing CLT slabs. Discussion here addresses a detailed finite element (FE) analysis approach as the reference point for defining accuracy capabilities of simple dynamic analysis formulas. It is concluded CLT floor slabs embody complexities in their modal responses that are beyond abilities of simple engineering formulas to predict.</p>