AGE 409

1. AGE 409 INTRODUCTION TO AGRICULTURAL STRUCTURES DESIGNS. (3 Units) Course Lecturers: Prof. E.B. Lucas/ Engr. P.O.O. Dada

2. Course Outline • Introduction to agricultural structures. • Selection of materials in relation to use – steel, wood, concrete and masonry. • Types of structural frames. • Estimating loads, • stress analysis. • Introduction to structural design.- philosophy of design • elastic and plastic design concepts. • Reinforced concrete design. • Design for axial loadings. • Design of beams, foundation, slab, columns, connections and joints. • Computer concept for improved analysis and design. • Design project.

3. Introduction to Structural Analysis Three phases are recognized in a structure on Engineering project. They include: • Planning- factors affecting the layouts and dimensions -- answer basic questions -- aesthetics - sociological, legal, economic and environmental - construction requirement affecting type of structure to be selected • Design- consideration of alternative solution involved in planning phase - choice dependent on economic and constructional features - aspects of competitive bidding. • Construction- procurement of materials, equipment and personnel - fabrication of members and sub-members - transportation to site - field construction and erection

4. Types of structural frames • Beams and Columns • Truss • Arches • Rigid frames • Cylindrical tank • Retaining wall

5. Types of Support • Hinge support • Roller support • Free end or movable roller support • Hinged immovable or fixed end support • Built-in end support

6. Structural Analysis • Types of loads: • Dead loads – stationary • Live loads – moving Stress = F/A Strain = Extension/length Factor of safety (N) =ultimate stress/ design stress

7. Livestock Structures:A facility primarily designed and constructed or remodeled to house animals with the overall aim of increasing productivity.Livestock: Domesticated animals kept under human control. Examples include: Dairy cattle, pigs, sheep, goats, horses and poultry Objectives of keeping Livestock • Food supply source • Raw materials • Manure supply • Transportation • Religion and culture • Social aspects • Sport and recreation • Employment and income

8. Benefits of Livestock Structures • Reduction of drudgery • Protection for animals • Individual and national benefits • Environmental factors affecting animal performance • Temperature • Relative Humidity • Ventilation • Light • Heat and Moisture

9. Livestock Structure (Case Studies) • Poultry, cattle and swine: • Poultry: • Site selection: The site must be well drained and be in a good location. • It must be near to sources of adequate water which must be in good quality and quantity. • Ventilation must be adequate and protected from strong winds • Provision of foot-dips at entrances, wire netting and trenches where applicable • Disease control must be achieved by good sanitation and medical facilities. • Construction details: • The poultry house must be aligned in the east-west direction. • Floors may be made from gravel or well drained soil or concrete • Roofing materials can include corrugated metal sheets (cheap, durable) • Construction should be in done to aid sanitation and proper disposal of waste, dead birds etc.

10. Examples of Livestock Structures • Shed and yards • Battery cage • Barns • Hen basket • Deep litter house

11. Crop Storage Structures: Container or unit designed and fabricated to perform the function of safely keeping crops Justification of crop storage • Seasonal variation • Seeds for next planting season • Economic considerations • To avoid social unrest • Protection from deterioration Classification of Crop Storage Structure • Improvised (indirectly used) eg. Baskets, earthen pots, drums, calabashes. • Traditional (Indigenous) eg underground pits, rhumbu, platforms, ,cribs and poles. • Modern (results of research) eg. Silos, warehouse, evaporative coolers

12. Silos Technical Aspects of silos: Silos can be classified into deep and shallow and this is done on the basis of the following: • Plane of rupture method • Equivalent diameter method • Height to lateral dimension method Pressure in silos: Rankine’s equation:

13. Ventilation Ventilation: circulation of air between an enclosure and it’s surroundings. It could be free (natural) or forced (mechanical means). Factors to consider when designing for good ventilation include: • Amount of heat and moisture generated • Amount of heat and moisture to be exchanged • Amount of air required to achieve the above • Method of supply and desired quantity of air to introduce. Natural ventilation V= AES V is Volume of air flow (m2/s) A is area of inlet opening E is effectiveness of opening (0.35-1.0 for perpedicular winds and 0.4-0.6 for diagonal winds S is wind velocity (m/s)

14. Heat Exchange Temperature of an enclosure is a reflection of the amount of heat present in the enclosure. Heat may be added or removed and air is the medium of exchange. Mn = mass of dry air(Kg/hr) hi = Enthalpy of incoming air as ambient temp. (KJ/kg of dry air) ho = Enthalpy of out going air at conditions inside the enclosure(KJ/kg of dry air) Heat exchange is a function of the insulating value of the building components while moisture exchange depends on vapour permeability.

15. Beams:A beam is a structural member used to resist load acting across its longitudinal axis It is designed to resist: • Bending moment • Transverse/Vertical shearing forces • Deflection Could be wooden, steel or concrete beams. Design of wooden beams should take the following into consideration: • Bending/ shear stresses • Deflection • Prevention of lateral buckling d/b < 3 for lateral stability and position of centriod

16. DeflectionA deformation that accompanies the bending of a beamBending deflectionShearing deflection Deflection of beam is dependent on: • Type of loading • Supports • Span • Modulus of elasticity of material of construction • Maximum deflection where W = load per unit length L = Span E = modulus of elasticity

17. Design of Steel beams Involves the following steps: • Estimation of load to be sustained • Compute the maximum bending moment and section modulus • Compute the shear stress For rectangular steel beam, maximum shear stress is

18. Columns A vertical structural member subjected to axial compression loading. Used where overhead loads are to be carried Classified as long, intermediate or short depending on the span to depth ratio. Short columns fail by yielding Long columns fail by buckling Slenderness Ratio: (Important parameter in design) is the ratio of the effective length to the least lateral dimension. Wooden columns could be • Single load timber • Solid timber with lamination of planks • Open column composed of planks but separated by spaces Design Concepts The FAO and Leonhard Euler method

19. MaterialsofConstruction Engineering properties of construction materials are broadly grouped into the following: • Physical – bulk density, specific gravity, porosity, void ratio, permeability, colour, size, shape and smell • Mechanical- tensile and compressive strength, modulus of elasticity, rupture, shear strength, hardness, impact, endurance and creep behavior • Thermal- thermal conductivity, expansion, contraction and specific heat • Chemical- • Acoustical-

20. Engineering properties • Strength • Durability • Resistance to corrosion • Hardness • Toughness • Resilience • Workability • Dimensional stability

21. Choice of Construction Materials Selection depends on: • Type and functions of the building and specific characteristics • Adequacy of relevant properties • Ease of handling • Appropriateness • Ease of site adjustment • Economic aspects of the building in terms of original investment • Availability of the materials in the area • Availability of skilled labour • Quality and durability of different materials • Cultural acceptability

22. Types of construction materials • Earth: Advantages and disadvantages • Natural fibres- bamboo, leaves, sisal • Wood and wood products • Concrete –cement, aggregates,water

23. Computer in Design • Facilities: De-skilling the operation Simulation and optimization Computer aided drafting Advantages • Very fast • Accurate • Greater scope and limited • Can be modified

24. Use of Computer in Design • Computer aided design (CAD) • Computer aided manufacturing (CAM)

25. Recommended Textbooks • Farm structures in tropical climates by L.P. Bengtnos and J.H. Whitaker (FAO) • Agricultural buildings and structures by J.H. Whitaker • Mid west plan service- structures and environmental handbook