Browsing by Author "Crafford, Philippus Lodewicus"
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- ItemAn investigation into the environmental sustainability of buildings in South Africa with a focus on timber building systems(Stellenbosch : Stellenbosch University, 2019-04) Crafford, Philippus Lodewicus; Wessels, C. B.; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.ENGLISH ABSTRACT: Buildings are responsible for about 33% of global anthropogenic carbon dioxide emissions, high-energy consumption and other environmental resource uses. Numerous studies over the past 20 years showed that wood-based constructions have lower environmental impacts in terms of energy use, global warming potential, air pollution, water pollution and solid waste production than steel and cement-based systems. However, there are still questions about the accuracy of green building rating tools. The objectives of this research were to (1)critically examine established international green building rating tools and methods to measureenvironmental impacts of buildings, (2)to investigate and quantify the environmental impact of selected building systems, components,and processes (including transport) relevant to the South African context, and (3)to develop a local environmental impact base and comparison models for timber-based buildingand future resource demand in South Africa. A review of green building rating tools indicated that the well documented environmental benefits of using wood was not sufficiently reflected in these rating systems. Life cycle-assessment is recognized as the best way to holistically evaluate the environmental impacts of a building. However, there is a critical need for local life cycle assessment based research in South Africa and other developing countries on building products and processes. At present, more than 70% of all sawn timber in South Africa is used in buildings, mainly in roof structures. A comparison between several roof truss systems (South African pine, Biligom and light gauge steel) using the life cycle assessment method showed 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. In a modelling analyses where different future building market scenarios in South Africa were compared, it was shown that if wood based residential buildings increase its market share to 20%, the embodied energy and global warming potential of the sector decrease by 4.9% from the current levels. If all new constructions is wood based, the total embodied energy and global warming potential of the residential building sector will decrease by 30.4%. It was 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, it will be possible (in the long term) to sustain a future residential building market where all constructions are wood based. A decision support tool was developed to compare the environmental impact of timber transport in and to South Africa. Transport linked to local and international timber sources and markets were modelled for global warming potential and primary energy impacts. It was shown that the Johannesburg, Nelspruit and Durban markets were well located within current local truck networks and showed lower global warming potential (GWP) values per ton kilometre compared to Cape Town and Port Elizabeth markets. Results also illustrated that importing timber from regions such as Cacador, Brazil to the Cape Town and Port Elizabeth areas using container shipping will have a lower global warming potential impact than using timber from the Nelspruit area with truck transport.
- ItemAn investigation of selected mechanical and physical properties of young, unseasoned and finger-jointed Eucalyptus grandis timber(Stellenbosch : Stellenbosch University, 2013-03) Crafford, Philippus Lodewicus; Wessels, Brand; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.ENGLISH ABSTRACT: South Africa is a timber scarce country that will most probably experience a shortage of structural timber in the near future. In this study the concept of using young finger‐jointed Eucalyptus grandis timber was evaluated for possible application in roof truss structures while the timber is still in the green, unseasoned state. 220 finger‐jointed boards of cross‐sectional dimension 48 x 73 mm and 36 x 111 mm timber, cut from 5‐18 year old Eucalyptus grandis trees were obtained from Limpopo province, South Africa. The boards were manufactured using a polyurethane (PU) adhesive at moisture content levels above fibre saturation point and no drying was performed. The objectives of this study were to determine various mechanical and physical properties of this finger‐jointed product. More specifically (1) to determine the strength and stiffness potential of the product in the wet and the dry condition, (2) to evaluate physical properties such as density, warp, checking and splitting, (3) to evaluate potential indicator properties to be used as structural grading parameters, and (4) to compare the flexural properties to the current SA pine resource and SANS structural grade requirements. The boards were divided into two groups of the same size, which constituted the wet and the dry samples. Each sample was further separated into six different groups for testing the different strength and stiffness properties. The dry group was stacked in a green‐house for nine weeks until equilibrium moisture content was reached. Afterwards selected physical properties such as warp, checking and splitting were assessed. Destructive testing was conducted on the boards and the results were used to determine various mechanical properties. Finally, each board was assessed for density and moisture content (MC) values. The study showed that the young finger‐jointed Eucalyptus grandis timber had very good flexural properties. Both mean modulus of elasticity (MOE) and modulus of rupture (MOR) 5th percentile strength values for wet and dry boards complied with the current SANS 10163‐1 (2003) requirements for grade S7.The values of tensile perpendicular to grain and compression perpendicular to grain strength did not conform to SANS requirements for grade S5. The other strength properties for the wet and dry groups complied with one of the three SANS structural grades. The 5 year old (48 x 73 mm) boards’ showed significantly higher levels of twist and checking compared to 11 year old boards of the same dimension. Only 46.3% of the finger‐jointed products conformed to the density requirements in SANS 1783‐2 (2004) for grade S7. There was a significant difference in density between the three age groups (5, 11 and 18 years) presented in this study. The variation in both MOE and MOR values of the fingerjointed product proved to be significantly lower in comparison to currently used SA pine sources. Based on the results from this study the concept of producing roof trusses from wet, unseasoned and finger‐jointed young Eucalyptus grandis timber has potential. However, additional research on a number of issues not covered in this study is still required for this product including full scale truss evaluations, proof grading, PU adhesive evaluation at elevated temperatures, nail plate load capacity, and the possible need for chemical treatment of the product against Lyctus beetles.