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 – stationary
Live loads – moving
Stress = F/A
Strain = Extension/length
Factor 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 Livestock
Food 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 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.
Examples of Livestock Structures
Shed and yards
Battery cage
Barns
Hen basket
Deep litter house
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:
1  sin 

2
L
1  sin 
 wy tan (45 
2
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)
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.
Qt
ho  hi
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.
Mn 
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
Deflection
A deformation that accompanies the bending of a beam
Bending deflection
Shearing deflection
Deflection of beam is dependent on:





Type of loading
Supports
Span
Modulus of elasticity of material of construction
Maximum deflection b  5WL4
384 EI
where W = load per unit length
L = Span
E = modulus of elasticity
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
 max  1.5
V
A
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
Strength
Durability
Resistance to corrosion
Hardness
Toughness
Resilience
Workability
Dimensional 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 disadvantages
Natural fibres- bamboo, leaves, sisal
Wood and wood products
Concrete –cement, aggregates,water
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
Use of Computer in Design
Computer aided design (CAD)
Computer aided manufacturing (CAM)
Recommended Textbooks
1.
2.
3.
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