AGE 409 INTRODUCTION TO AGRICULTURAL STRUCTURES DESIGNS. (3 Units) Course Lecturers: Prof. E.B....
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Transcript of AGE 409 INTRODUCTION TO AGRICULTURAL STRUCTURES DESIGNS. (3 Units) Course Lecturers: Prof. E.B....
AGE 409
INTRODUCTION TO AGRICULTURAL STRUCTURES DESIGNS. (3 Units)
Course Lecturers: Prof. E.B. Lucas/ Engr. P.O.O. Dada
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.
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
Types of structural frames
Beams and Columns Truss Arches Rigid frames Cylindrical tank Retaining wall
Types of Support
Hinge support Roller support Free end or movable roller support Hinged immovable or fixed end support Built-in end support
Structural Analysis
Types of loads:Dead loads – stationaryLive loads – moving
Stress = F/A
Strain = Extension/lengthFactor of safety (N) = ultimate stress/ design stress
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 LivestockFood supply source
Raw materials
Manure supply
Transportation
Religion and culture
Social aspects
Sport and recreation
Employment and income
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
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 windsProvision of foot-dips at entrances, wire netting and trenches where applicableDisease 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 concreteRoofing materials can include corrugated metal sheets (cheap, durable)Construction should be in done to aid sanitation and proper disposal of waste, dead birds etc.
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
Silos
Technical Aspects of silos:
Silos can be classified into deep and shallow and this is done on the basis of the following:
a) Plane of rupture method
b) Equivalent diameter method
c) Height to lateral dimension method
Pressure in silos:
Rankine’s equation:2
45(tansin1
sin1 2
wyL
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= AESV is Volume of air flow (m2/s)A is area of inlet openingE is effectiveness of opening (0.35-1.0 for perpedicular
winds and 0.4-0.6 for diagonal windsS is wind velocity (m/s)
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.
hiho
QtMn
Beams:A beam is a structural member used to resist load acting across its longitudinal axis
It is designed to resist:
1. Bending moment
2. Transverse/Vertical shearing forces
3. 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
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
EI
WLb
384
5 4
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
A
V5.1max
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
Materials of Construction
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-
Engineering properties
StrengthDurabilityResistance to corrosionHardnessToughnessResilienceWorkabilityDimensional stability
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
Types of construction materials
Earth: Advantages and disadvantagesNatural fibres- bamboo, leaves, sisal Wood and wood productsConcrete –cement, aggregates,water
Computer in Design
Facilities: De-skilling the operation Simulation and optimization Computer aided drafting
AdvantagesVery fastAccurateGreater scope and limitedCan be modified