ENGR 20 Statics

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ENGR 20 Statics

• Raymond Great Hall Ceiling Trusses

Stephen Morse Steven Granados
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Table of Contents

• Background
• History
• Materials and Methods
• Calculations
• Conclusion
• Discussion
• References

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Background
Free body diagram of roof truss

• Purpose
• Discover the forces present in the members of the
  truss under normal conditions

• Determine the maximum tensile and compressive
  forces in the truss members
• Normal conditions
• Extreme conditions

Labeling convention
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Background

• Assumptions
• Roof modeled two ways
• Uniformly distributed load
• Discrete forces acting at the joints
• One truss supports 15 linear ft. of roof
• Weight of roof and hanging lights left as
  variables
• Weights of beams in trusses were ignored
• Length of beams were estimated from ground

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History

• Built in 1962
• Dedicated on October 13, 1962
• Part of Raymond Cluster College
• Built over Baxter Stadium

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Materials and Methods

• Materials
• Wood
• Wood sealant
• Steel gusset plates
• Steel bolts
• Construction Style
• Modernistic English Georgian Architecture
• Unfinished wood beams

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Materials and Methods

• Material Selection
• Cost
• Wood was cheaper than steel
• Aesthetic virtues

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Calculations

• Assumptions Restated
• Roof modeled two ways
• Uniformly distributed load
• Discrete forces acting at the joints
• Weight of roof and hanging lights left as
  variables
• Weights of beams in trusses were ignored
• Length of beams were estimated from ground
• Calculation Methods
• Method of Joints
• Method of Sections

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Calculations
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Calculations
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Calculations
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Calculations
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Calculations
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Conclusion
Calculated Forces

• AB -41.500R 3.607L
• BC -37.865R 0.698L
• CD -51.440R 3.487L
• AJ 27.033R 3.113L
• JI 16.703R 1.908L

• CI 24.090R 1.908L
• BJ -10.005R 1.185L
• JC 7.948R 1.942L
• DI -6R
• Note positive forces denote tension, negative
  denote compression

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Conclusion

• There are no zero force members
• Under normal conditions
• Member AJ bears the maximum load in tension
• LAJ 3637 lb (tension)
• Member CD bears the maximum load in compression
• LCD 6751 lb (compression)

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Conclusion

• Maximum loads under special conditions
• ¼ in. rain adds 1128 lb to overall weight
• LAJ 4165 lb (tension)
• LCD 7754 lb (compression)
• 1 ft. snow adds 5413 lb to overall weight
• LAJ 6168 lb (tension)
• LCD 11566 lb (compression)

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Discussion

• Pros and Cons of Design
• Adequate structural integrity to support roof
• Aesthetically pleasing
• Not as strong as steel
• Weight (solid beams are heavy)
• Anticipated Failure Points
• These will be based on the material properties of
  wood, which will be covered in materials science
• Life Expectancy
• Sealed wood structures can last for hundreds of
  years under good conditions

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Discussion

• Design Improvements
• Addition of zero-force members for redundancy
• Use of steel I-beams instead of solid wood

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References

• Professor Jeff Burmeister
• Don Walker, UOP library archivist and historian
• UOP physical plant
• Pacific Weekly newspaper (library archives)
• Photo file on Raymond College (library archives)
• CSAC http//www.csac.org/Education/glossary/densit
  y.html
• PSC Roofing Tiles http//www.pragatisales.com/roof
  ing_tiles.htm
• Bob Vila Home Improvement Website
  http//www.bobvila.com/HowTo/TipLibrary/Subject/Ca
  rpentry/Engineered_Wood/0389-Plywood_Weight.html