Architecture - Farm Structures and Environmental Control
Scope of the Architecture domain
In GATE AG this domain means agricultural structures and environmental control: grain bins and silos, farm buildings and livestock housing, greenhouses, plus the ventilation and structural decisions that keep produce and animals inside design conditions.
Storage capacity and bin geometry
Capacity = volume × bulk density. For a cylindrical bin on a conical hopper: V = (π/4)D²H + (1/3)(π/4)D²h, where H is the cylindrical height and h the hopper depth. Typical bulk densities are about 770 kg/m³ for wheat, 720 kg/m³ for maize and 580 kg/m³ for paddy, but use the value stated in the question.
Pressure on bin walls
Grain behaves unlike a liquid: wall friction carries part of the weight, so lateral pressure follows Janssen's equation and approaches an asymptote with depth rather than rising linearly as hydrostatic pressure does. Deep bins therefore do not need walls thickening in direct proportion to depth.
Environmental control
Aeration and ventilation remove heat and moisture; airflow is specified per tonne of grain or per unit bulk volume and is set higher for damp grain. Greenhouses balance solar gain against ventilation and evaporative cooling, with shading and roof vents reducing the cooling load. Livestock housing is driven by the temperature–humidity index, air exchange rate per animal and floor area per animal.
Worked example
A bin of diameter 4 m has a 6 m cylindrical section and a 1 m conical hopper, filled with wheat at 770 kg/m³. Cylinder = 0.7854 × 16 × 6 = 75.40 m³. Hopper = (1/3) × 0.7854 × 16 × 1 = 4.19 m³. Total = 79.59 m³. Capacity = 79.59 × 770 ≈ 61,280 kg, i.e. about 61.3 t.
Traps that cost marks
- Omitting the hopper volume, or the grain peak above the eave in flat storage.
- Using hydrostatic (liquid) pressure for a grain bin instead of Janssen's asymptote.
- Mixing gross and net floor area when sizing a building, or counting a feed alley twice.