Building Loads

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Building Loads
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Introduction

• The design of, selection of materials for and
  construction of Ag structures is based on the
  expected loads, use(s) of the building and the
  acceptable risk of failure.

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Design Decision
Should an agricultural building be designed to
withstand the worse possible storm?
Agriculture buildings can be built to withstand
the worst case scenario, but they would be very
costly.

• There is usually a higher acceptable risk of
  failure for an agricultural building because the
  cost of failure doesnt usually include human
  life.
• They are usually built to a lower standard,
  therefore they have a higher probability of
  failure.
• Most Ag buildings are also usually designed with
  shorter life expectancy than residences and
  commercial buildings.

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Ag structures are subject to complex loads

• a) Forces from different directions
• b) Different intensities of forces
• c) Different frequencies

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4 Common Types of Loads
Dead
Live
Wind
Snow
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Dead Load
Dead load is the weight of the building materials.
Dead loads will vary depending on the type of
construction and materials used.
Is there any relationship between the dead load
of a building and its ability to withstand wind?
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Live Loads
Live loads are estimated on a pound per square
foot basis for structural calculations.
Any load that will change during normal use of
the building.
Equipment
Animals
Materials that are being moved.
Vibration from equipment
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Wind Loads
The effect of wind on a building is not
consistent. On the up wind side of a building,
wall and roof panels experience a positive
pressure, while on the down wind side there is a
negative pressure or suction load. The dashed
line represents the racking forces caused by
wind.
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Wind Loads - cont.
Wind can have multiple effects on buildings.
How does the effect of wind influence building
design and construction?
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Wind--continued

• As the wind blows over and around the building,
  eddy currents are formed which exert varying
  negative pressures in those areas.

The destructive power of wind is dramatically
increased when you include water and/or hail.
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Snow Loads

• Added load from sliding snow
• Increased load for lower roof.
• Drift load behind obstruction
• Increased load in valleys

• Unbalanced snow load
• Balanced snow load
• Increased load because of change in slope

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Snow Loads - cont.

• Results of excessive snow load

Results when snow load exceeds building designed
load
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The expected snow load varies by region.
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T H E E N D