130,597 research outputs found
Effect of Weathering on The Dimensional Properties of Particleboard Decking
No full textThe effect of outdoor weathering on the dimensional properties of phenolic-bonded particleboard manufactured as decking for factory-built housing was evaluated. Results were compared to those for urea-bonded particle board made with a similar southern pine furnish. Results indicate that in terms of linear expansion, thickness swelling and swelling recovery, and resistance to buckling, weathering did not severely affect the performance of the phenolic-bonded decking material. Weathering significantly affected the performance of urea-bonded material
Life Cycle Impacts of Manufacturing Redwood Decking in Northern California
No full textAwareness of the environmental footprint of building construction and use has led to increasing interest in green building. Defining a green building is an evolving process with life cycle inventory and life cycle impact assessment (LCIA) emerging as key tools in that evolution and definition process. This study used LCIA to determine the environmental footprint associated with manufacturing 38- x 138-mm redwood (Sequoia sempervirens) decking from sustainably managed northern California redwood forests. Primary survey data were collected from four redwood mills that represent 90% of redwood lumber production. The primary data were then weight-averaged on a per-unit basis of 1 m3 of planed redwood decking (380 oven-dry kg/m3) to calculate material flows and energy use. All of the raw material consumption and environmental outputs were assigned to dry planed redwood decking and none to coproducts. The gate-to-gate, cumulative energy consumption associated with manufacturing 1 m3 of planed redwood decking from 1.8 m3 of incoming logs was 1.36 GJ/m3 with 19% of the energy provided by burning wood residues. Emission data produced through modeling the production process found that the estimated biomass and fossil CO2 emissions were 20.9 and 52.9 kg/m3, respectively. Based on the carbon content of redwood of 53%, a cubic meter of 38- x 138-mm redwood decking product stores 201 kg of carbon and if released into the atmosphere would emit 738 kg of CO2. The amount of carbon stored in redwood decking is equivalent to about 10 times the total CO2 emissions released during the manufacturing process. Low carbon emissions during the manufacturing process and carbon storage during the service life of a redwood deck are positive environmental attributes that should be considered when selecting a decking product
Lightweighting road freight semi-trailers through the application of composites in trailer decking
No full textIn road haulage the empty weight of a vehicle is a significant contributor to fuel consumption and resulting CO2 emissions. Therefore, the application of lightweight materials in semi-trailer design is one avenue that needs to be explored in reducing the carbon footprint of road freight vehicles. Preliminary work has identified conventional hardwood-based trailer decking as a sub-component that is particularly suited to lightweighting. This paper investigates the potential application of different composite materials for use as lightweight replacements to conventional decks. Two different E-glass fibre/polyester (GFRP) pultrusions and a sandwich panel comprised of woven GFRP face sheets and a balsa core are tested in three point bending and then compared to hardwood decking through a material selection index. Mechanical testing has shown that the lightweight composite deck materials have superior flexural strength and stiffness compared to hardwood decking. The sandwich panel decking and pultruded decking are calculated to be approximately 40% and 12% lighter than existing hardwood based decking respectively. However, the highly cost-driven nature of the trailer industry could dictate that the use of pultruded GFRP decking is the most reasonable first step to introducing composites into trailer decks. The effect of indentation and water damage to the flexural strength and stiffness of hardwood decking is also examined to give an insight into the mechanical performance criteria required of lightweight decking in-service. Water damage is found to be the most severe form of in-service damage and can reduce the strength and stiffness of hardwood decking by approximately 40% and 30% respectively. This is encouraging for the potential application of a GFRP deck which would be less susceptible to water damage
The performance of wood decking after five years of exposure
No full textWood is one of the most important construction materials, and its use in building applications has increased in recent decades. In order to enable even more extensive and reliable use of wood, we need to understand the factors affecting woodʹs service life. A new concept for characterizing the durability of wood-based materials and for predicting the service life of wood has recently been proposed, based on material-inherent protective properties, moisture performance, and the climate- and design-induced exposure dose of wooden structures. This approach was validated on the decking of a model house in Ljubljana that was constructed in October 2013. The decay and moisture content of decking elements were regularly monitored. In addition, the resistance dose D, as the product of the critical dose D, and two factors taking into account the wetting ability of wood (k) and its inherent durability (k), were determined in the laboratory. D correlated well with the decay rates of the decking of the model house. Furthermore, the positive effect of thermal modification and water-repellent treatments on the outdoor performance of the examined materials was evident, as well as the synergistic effects between moisture performance and inherent durability
EXPERIMENTAL INVESTIGATION INTO THE FATIGUE RESPONSE AND ULTIMATE STRENGTH PERFORMANCE OF CONCRETE FILLED GRID BRIDGE DECKS
No full textMost bridges located in major cities experience large traffic volumes, which require bridge decks to be extremely durable under this constant loading. Concrete filled steel grid bridge decks have exhibited extended service lives under severe urban traffic conditions, and in some instances, have been in use for more than 60 years. Concrete filled steel grid decking can be a viable option for both decking and re-decking operations since it can be installed quickly, and because it can be equipped with stay-in-place form pans. The current PennDOT BD-604 design standard appears to be conservative in its specification of allowable span lengths. The present research will investigate the use of concrete filled steel grid deck on greater span lengths. The BD-604 is based on the performance of older grid deck installations, and does not take advantage of modern materials, or more advanced analysis and design techniques. An experimental evaluation of the fatigue and ultimate strength performance of a series of full-depth, overfilled, two span continuous grid deck panels on a simulated 10' stringer spacing is carried out. The testing was conducted at the University of Pittsburgh Main Campus in the Watkins-Haggart Structural Testing Laboratory in Benedum Hall. Based on the results from this testing it appears that the span lengths in the BD-604 may be increased by a factor of 1.67
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mechanical model to predict the resistance of the shear connection in composite beams with deep steel decking. (LAC17.D)
No full textpeer reviewedThe resistance of a typical shear connection with headed shear studs in a composite beam is analysed for the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking to the ultimate loadbearing capacity is considered with empirically derived reduction factors and equations that were developed between the late 1970s and early 1980s. The RFCS research project ”DISCCO“ investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance predicted by EN 1994-1-1 was not reached in tests.
In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the loadbearing capacity of the shear stud, which formed one or two plastic hinges in the shaft depending on the actual geometry.
Based on these observations, new equations have been developed to predict the shear connection's resistance with more accuracy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen, was extended by the aforementioned loadbearing component ”concrete cone“. The formulae consider the geometry of the stud and the steel decking and the material strength of the stud and the concrete. The statistical evaluation of the equations developed demonstrates good agreement with test results
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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