Agricultural engineering

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    Stochastic analysis of wire-connected round timber trusses Edward.
    (University of Zambia, 2001) Lusambo, Edward
    Round timber, as a by-product of forest thinning, can be used for construction of innovative and attractive wooden structures. It forms an inexpensive source of construction material for agricultural structures in developing countries. Several methods of connecting round timber have been proposed and investigated world-wide. This paper considers a method that uses flitch plate and wire lacing connections to achieve stable, low-cost and durable round timber structures. For the structural designer, however, it is also necessary to have methods for structural analysis of such structures. This paper discusses a stochastic finite element analysis procedure that was developed and used to analyse round timber trusses made from eucalyptus poles. Static load versus displacement / characteristics of the trusses were investigated using full-scale trusses. In the deterministic analysis, the wire-connected joints developed for the purpose were modelled using semi-rigid connection elements. The effects of slip at the joints, and the effects of creep and joint movement over a long time were incorporated in the analysis. In the experimental set-up, only the deflection of the mid-point of the bottom chord of the truss was measured. It was observed that the results from the deterministic analysis compared well to full-scale truss tests. Keywords: Timber structures, round timber, stochastic analysis, limit states design.
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    Mechanical and physical properties of plantation grown timber in Zambia.
    (University of Zambia, 2004-07-18) Mulenga, Micheal; Lusambo, Edward
    Zambia is endowed with thousands of square kilometers of land on which both plantation grown and indigenous species of timber flourish. The Zambian standard on structural use of locally grown timber. ZS 032,gives physical and mechanical properties for several indigenous species but only two plantation grown species, namely Eucalyptus Grandis (blue gum) and Pinus Kesiya. In view of the economic potential of plantation grown timbers. such as controlled growth and development of plantations and processing plants. country-wide, it is necessary to enhance the utilization of these species for structural, carpentry and other purposes. Greater structural usage. however, can only be reali=ed after determination and dissemination of the physical and mechanical properties. This paper presents test results for physical and mechanical properties of four plantation grown timbers, Eucalyptus Grandis, Eucalyptus Cloesina, Pinus Kesiya, and Pinus Oorcapa, grown by Copper belt Forestry Company The tests were carried out at the Civil and Environmental Engineering laboratories of the University of Zambia. The physical and mechanical properties determined for Eucalyptus Grandis and Pinus Kesiya, exceed those specified in ZS 032 (1986, when the totalfa ctors of safety are applied. The physical and mechanical properties determined in this study for Eucalyptus Cloesina and Pinus Oorcapa are reasonable estimates. in the absence of code values. Keywords: softwood, hardwood, clear specimens, plantation grown, indigenous species, radial, tangential, perpendicular and parallel to grain.
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    Strength and physical properties of Zambian grown eucalyptus poles.
    (University of Zambia, 2005-05-20) Lusambo, Edward
    Poles used for overhead power and telecommunication lines and buildings are specified by species, physical properties such as moisture content, and dimensions as well as strength properties such as ultimate load. These properties vary from species to species. Design stresses may be determined using testing methods specified in various codes to arrive at grade stresses. For example, in Australia and New Zealand, the poles are assigned one stress grade higher than the highest grade of the same sawn timber. Design stresses jar American preservative-treated round poles were established following tests specified by ASTM Standards D3200. In the United Kingdom, BS 1990 Parts 1 and 2 give specifications for wood poles for overhead power and telecommunication lines. In Zambia, there is no standard that deals specifically with overhead power and telecommunication lines. However, it is necessary to test Zambian plantation-grown poles and establish basic physical and structural properties. This paper aims to present a method that can be used for for establishing a Zambian standard for poles. Eucalyptus poles are used in fencing, overhead power and telecommunication lines, mine props, support structures, building structures and in the production of sawn timber. In all these uses, the physical and strength properties of the poles are of great importance. This paper presents test results on Eucalyptus grandis and Eucalyptus cloesiana poles which were tested following guidelines for testing poles used for overhead power and telecommunication lines are contained in BS 1990 Part 1. Keywords: Poles; Eucalyptus; Structural properties; Testing
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    A dynamic model for naturally ventilated Low cost poultry houses.
    (University of Zambia, 2007-10-22) Lusambo, Edward
    Ventilation as a method of controlling the internal environment in poultry houses serves two main purposes. It provides the desirable levels of temperature and humidity to achieve good poultry performance and it also provides a desired amount of fresh air, without drafts, to all parts of the building. Ventilation also controls ammonia levels to limits appropriate for operating personnel. This paper discusses a simulation model developed to study the dynamic changes of the internal thermal environment in low cost poultry houses in Zambia. The model is based on the interaction of various internal, external and building construction related parameters. The model can be used to predict the temperature in a naturally ventilated poultry house for a given set of input parameters. Furthermore, it can calculate the heating or cooling load required to keep the temperature at desired levels for the birds. It can also be used to study the effects of changing various parameters on the internal thermal environment. The model was validated using data obtained from an open-sided naturally ventilated poultry house housing birds at an average age of 8 weeks. The model was able to predict the internal temperature closely to the measured values. Keywords: Natural ventilation, Dynamic modelling, Poultry houses
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    Low-cost high-quality roof construction with round timber.
    (University of Zambia, 2020-05-03) Lusambo, Edward
    Pole timbers provide an inexpensive source of structural timber in many developing countries and are widely used for traditional buildings. The use of round timber has considerable potential in comparison to the use of sawn timber because of its higher structural strength and its low material cost. There are, however, problems associated with working with non-uniform sections and also with jointing. The traditional methods ofjointing using sisal rope or strips of bark in rural areas do not permit the full strength of the poles to be utilised. Improved low cost methods of connecting poles could lead to stronger structures and more economical use of materials. This paper reviews aspects relating to the use of round timber and describes the design and fabrication of some low-cost, yet high-quality structural systems suitable for roof structures of modern buildings. Keywords: Round timber, Roof structures, Connections, Jointing methods
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    Investigation into the effects of deficit irrigation on potato production in Dedza district-Malawi.
    (The University of Zambia, 2023) Chikankheni, Aina Tennson
    Deficit irrigation strategies in furrow irrigation are important means of saving irrigation water in areas with poor water management. This study was conducted to establish the strengths and weaknesses of the current irrigation practices in Dedza district, to evaluate effects of alternating deficit, fixed deficit, and conventional furrow irrigation strategies on water saving, potato yield and profitability of potato production under different maximum allowable soil moisture depletion levels. The study was done in Dedza district in Malawi. Farmer plot size in irrigation schemes are limited to 0.22 ha of which 81% use gravity-fed canals to convey water with furrow as a dominant irrigation method due to its many advantages. The Certified potato variety “Violet” seeds were used as study material during the experiment which was laid out as a randomized complete block design. It involved three maximum allowable depletion (MAD) levels of 20, 40, and 60% in which furrow irrigation strategies of (i) conventional furrow irrigation (CFI), (ii) alternate furrow irrigation (AFI), and (iii) fixed furrow irrigation (FFI) were applied. A total of 10, 6, and 5 irrigation events were scheduled for the whole season under 20%, 40%, and 60% depletion levels respectively. Compared to the control (CFI), the results showed that AFI and FFI under 20% MAD, saved 30% and 39% of water with slight crop yield reductions of 6% and 14% respectively. Moreover, under 20% MAD, farmers could achieve 17.8% and 7.3% gross margins above the average national value of US$8119.20 with AFI and FFI respectively. Compared to 2.8 US$/m3 for the control, the economic water productivity increased by 39% and 46% for AFI and FFI respectively under the 20% MAD. This research showed that managing the potato crop using AFI or FFI under 20% MAD could allow a farmer in Dedza district to achieve potato tuber yields above the national average while saving water to increase the irrigation scheme membership. The result can be used as the starting point for further research and development of policies that aim at improving potato farmers’ irrigation water and land productivity.