Beams and Columns

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Forging new generations of engineers
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BEAMS AND COLUMNS
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A good design?

• The building dead load is the only known load.
  All other forces will vary in magnitude, duration
  and location.
• The building is designed for design load
  possibilities that may never occur.
• The structural efficiency of a building is
  measured as the ratio of dead to live load.The
  building designer strives to keep the ratio low.

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Beam Design

• Beams are used in floors and roofs.
• Maybe called floor joists, stringers, floor beams
  or girders.
• Loads on beams are either concentrated or
  distributed (uniform loads)
• Designed for Shear, Moment (bending) and
  Deflection

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Beams

• Beams are sized appropriately to safely support
  the loads a structure will carry.
• Beams are primarily subjected to bending and
  shear.
• Deflection and deformation can be calculated.
• Beams are sized to provide the maximum result
  with the minimum materials. A factor of safety
  is included in the design.

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Beam Deflection

• Limit Deflection to
• L/240 of total load (whereas Llength in inches)
• L/300 of total load
• L/360 of total load (building use throughout life
  is unknown) Preferred
• WHY??
• Ceiling cracks in plaster
• Roof ponding (flat roofs)
• Visual or psychological reasons
• Designers judgment

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Beam Types

• Simple
• Continuous
• Cantilever
• Moment
• (fixed at one end)

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Beam Types

• Fixed
• Moments at each end
• Propped- Fixed at one end supported at other
• Overhang

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Columns

• Columns carry primary Axial Loads and therefore
  are designed for compression.
• Additional loads from snow, wind or other
  horizontal forces can cause bending in the
  columns.
• Columns then need to be designed for Axial Load
  and Bending.

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Forces
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Reference Sources

• Jefferis, A., Madsen, D. A. (2001).
  Architectural Drafting and Design. Albany, NY
  Delmar, a division of Thomson Learning.
• Kane, K., Onouye, B., (2002). Statics and
  Strength of Materials for Architecture and
  Building Construction.(2nd ed.). Saddle River,
  NJ Pearson Education, Inc
• Shaeffer, R. E., (2002). Elementary Structures
  for Architects and Builders (4th ed.). Columbus,
  OH Prentice Hall.
• http//www.concretenetwork.com/concrete/footing_fu
  ndamentals/why_soils_matter.htm
• http//www.emporis.com/en/
• http//www.pbs.org/wgbh/buildingbig/lab/forces.htm
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