Browsing by Author "Wessels, C. Brand"
Now showing 1 - 4 of 4
Results Per Page
- ItemInvestigating the potential of strength grading green Eucalyptus grandis lumber using multi-sensor technology(North Carolina State University, 2017-11) Nocetti, Michela; Proller, Marco; Brunetti, Michele; Dowse, George P.; Wessels, C. BrandThe exploitation of Eucalyptus grandis lumber as structural material may take advantage of the finger-joint and edge-gluing of the boards while they are still wet, so as to reduce the natural susceptibility of the species to warp and split during drying. But the strength grading needed for structural uses, usually performed on dried lumber, should be done before any gluing process, then already in wet condition. Thus, detection and assessment of selected properties of the wet lumber were evaluated. Eucalyptus grandis boards were measured by a multi-sensor machine soon after sawing, then dried and measured again. Destructive bending tests were then performed to determine the mechanical properties of the lumber and several predictive models were compared. The determination on non-destructive parameters by the machine was as effective on fresh as on dry lumber. The dynamic modulus of elasticity was the best single predictor of mechanical properties. In contrast, the know parameter did not show a correlation between strength and stiffness robust enough to justify the efforts to measure it. Wet grading proved to be as effective as dry grading. Therefore, the study suggests that measuring only dynamic modulus of elasticity on fresh lumber is the best approach for the mechanical grading in Eucalyptus grandis.
- ItemMixed visual and machine grading to select Eucalyptus grandis poles into high-strength classes(MDPI, 2021) Brunetti, Michele; Aminti, Giovanni; Wessels, C. Brand; Nocetti, MichelaENGLISH ABSTRACT: Before round timber can be profitably used in construction, it needs structural characterization. The visual grading of Eucalyptus grandis poles was integrated with additional parameters developed by multivariate regression analysis. Acoustic velocity and dynamic modulus of elasticity were combined with density and pole diameter in the estimation of bending strength and stiffness. The best models achieved were used to group the visually graded material into qualitative structural classes. Overall, dynamic modulus of elasticity was the best single predictor; and adding density and diameter to the model improved the estimation of strength but not of stiffness. The developed parameters separated the material into two classes with very distinct mechanical properties. The models including velocity as a parameter did not perform as well. The strength grading of Eucalyptus grandis poles can be effectively improved by combining visual parameters and nondestructive measurements. The determination of the dynamic modulus of elasticity as a grading parameter should be preferred over that of acoustic velocity
- ItemThe potential of South African timber products to reduce the environmental impact of buildings(Academy of Science of South Africa, 2017) Crafford, Philip L.; Blumentritt, Melanie; Wessels, C. BrandSouth Africa was the first country in Africa to implement a locally developed green building rating tool and has a growing number of rated green building projects. The method of life-cycle assessment can help to compare and assess the environmental performance of building products. At present, more than 70% of all sawn timber in South Africa is used in buildings, mainly in roof structures. Light gauge steel trusses have recently also been gaining market share. However, to date, no studies have been conducted that quantify and compare the environmental impacts of the different roof truss systems in South Africa. We thus compared several roof truss systems (South African pine, Biligom and light gauge steel) found in low- and medium-income house designs in South Africa using a simplified life-cycle assessment approach. Our results show that the two timber systems had overall the lowest environmental impact. Although the difference between the timber systems was small, light gauge steel had a 40% higher normalised impact over all assessed environmental impact categories. The benefit of biogenic carbon dioxide present in timber proved to play a significant positive role in the global warming potential impact and could even be further reduced if wood were used to generate energy at its end-of-life. This study demonstrates the potential advantage of using local timber products to reduce the environmental impact of the truss and building industry in South Africa.
- ItemSouth African log resource availability and potential environmental impact of timber construction(ASSAf, 2020-07-29) Crafford, Philip L.; Wessels, C. BrandENGLISH ABSTRACT: We investigated the South African log resource availability and the potential global warming impact of an increasing wood-based residential building market. We have shown that, with the use of wood resources currently exported as chips, as well as planting trees in areas that have been earmarked for afforestation, a sustainable residential building market, where all constructions are wood-based, is possible. However, in the short term, imports of wooden building components might be necessary if rapid growth in woodbased building occurs. Basic modelling analyses show that if the market share of wood-based buildings increases to 20% of new constructions, the embodied energy and global warming potential of the residential building sector could decrease by 4.9%. If all new constructions were wood based, the total embodied energy and global warming potential of the residential building sector could decrease by up to 30%.