Published Date
Construction and Building Materials 15 August 2016, Vol.118:262–267,doi:10.1016/j.conbuildmat.2016.05.038
Author
Thomas Tannert
Wood Science and Civil Engineering, The University of British Columbia, 2424 Main Mall, Vancouver BC V6T1Z4, Canada
Received 12 February 2016. Revised 2 May 2016. Accepted 3 May 2016. Available online 14 May 2016.
Highlights
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Rounded Dovetail Joints (RDJ) are a viable option to connect timber members.
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Structural performance of hand- and machine routed joints is similar.
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Design equation for RDJ yields conservative predictions.
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RDJ performance can be improved through reinforcements.
Abstract
The paper presents experimental investigations on different methods to increase the stiffness of Rounded Dovetail Joints (RDJs). Departing from a reference geometry, the specific methods were (i) oversizing the dovetail tenon part for a tighter fit; (ii) reinforcement with self-tapping screws; (iii) reinforcement with an adhesive layer; and (iv) a combination of adhesive layer and self-tapping screws. The specimens from the reinforced test series were compared to regular RDJ specimens and to beam to joist connections by means of self-tapping screws only. It was demonstrated that all methods significantly increased the joint stiffness of RDJs. Furthermore, the research showed that there is no difference in structural performance between hand-routed joints and CNC-routed joints, and that a previously suggested design equation for RDJs yields conservative predictions when compared to the experimentally obtained 5th percentile values.
Paiva, D. & Magalhães, F.D. Eur. J. Wood Prod. (2017). doi:10.1007/s00107-017-1158-y
Abstract
The mechanical behavior of agglomerated cork, made of cork granules bound with polyurethane moisture-cured adhesive is investigated and compared to natural cork in the small strain regime (strain <5%). Dynamic mechanical analysis (DMA) of the agglomerated material revealed two distinct thermal transitions, one at −45 °C, related to the glass transition of polyurethane, and one at 3 °C, associated with melting of suberin, a natural polyester that is the main component of cork’s cell walls. Natural cork showed the latter transition to occur at a higher temperature range, between 10 and 25 °C, probably due to a different crystalline arrangement being formed upon cooling the cork granules under pressure in the mold. The storage modulus of agglomerated cork was found to be similar to that of natural cork. Creep and recovery experiments were well described by Burgers model and Weibull distribution function, respectively. Agglomerated cork showed higher instantaneous creep strain and viscous flow than natural cork, probably due to relative displacement and slippage of the granules being allowed by the binder. In all cork materials, not all the instantaneous creep strain was instantaneously recovered. A fraction underwent delayed recovery and another turned into permanent strain. This behavior was associated with the deformation of corrugations in the cork cell walls. Cyclic creep-recovery tests showed for all cork materials recoveries above 90%, except for the first cycle. References
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http://link.springer.com/article/10.1007/s00107-017-1158-y
Abstract:Biomass based energy production has attained a significant market share within the developing renewable energy market. In comparison to alternative renewable energy sources, biomass has several special features: it is not inexhaustible in the short term (limitation of arable land) and it is not only an energy source. Other usages like food or feed compete with energy production for this resource. A number of problems arise which have a direct impact on the fulfillment of policy objectives which are connected with its promotion. Primarily, the production of bioenergy has significant impacts on coupled biomassmarkets. Further, a change in production intensity or arable land use increases the use of nutrient loads and agro - chemicals. When evaluating renewable energy production, the wide range of political objectives has to be considered. Therefore, the focus of the overall study will be on three objective areas: promotion of the agricultural sector, environmental protection (reduction of GHG emissions) and maintenance of food supply security. The objective of this study is to combine an analysis of selected economic and ecological impacts of an increased biomass based energy production (primarily biofuels) under the assumption of European and international quantity targets by adjusting and applying the agricultural sector model CAPRI (Common Agricultural Policy Regional Impact Analysis). This poster intends to display the methodical approach of the intended analysis.
Abstract: Forty five accessions of dhaincha germplasms were collected from different parts of Bangladesh and characterized on the basis of morphological descriptors and biomassproduction ability. Thirty eight accessions were identified as Sesbania bispinosa, four as S. cannabina and two as unidentified Sesbania spp. One accession as S. rostrata was included for comparison. Both at seedling and maturity stages, wide and significant differences were observed among the accessions of different dhaincha germplasms for their biomassproduction capability and other morphological descriptors. At the seedling stage, total dry mass (TDM) production varied from 10.2 to 41.6g 30-plants–1. At the maturity stage, plant height, total number of branches and base diameter of dhaincha germplasms varied from 347.5–474.7cm, 10.4–23.7, and 1.9–4.9cm, respectively. The highest amount (4.10kg 10-plants–1) of above-ground TDM was produced in one accession of unidentified Sesbania sp. followed by S. rostrata and one accession of S. cannabina (3.85kg 10-plants–1), and the lowest TDM (0.9kg 10-plants–1) was measured in two accessions of S. bispinosa. It may be concluded that the biomassproduction capability of at least two accessions of local Sesbania germplasms were higher/comparable to that of exotic S. rostrata. It will be too early to make a conclusive remark based on only a few dhaincha germplasms. A detailed study with a large number of germplasms collected from whole Bangladesh is obviously needed to reach in a precise conclusion.
