ENGR 20 Statics Raymond Great Hall Ceiling Trusses Stephen Morse Steven Granados

Table of Contents BackgroundHistory Materials and Methods CalculationsConclusionDiscussionReferences

Background Purpose Discover the forces present in the members of the truss under normal conditions Discover the forces present in the members of the truss under normal conditions Free body diagram of roof truss Labeling convention Determine the maximum tensile and compressive forces in the truss members Determine the maximum tensile and compressive forces in the truss members Normal conditions Extreme conditions

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

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

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

Materials and Methods Material Selection Cost Cost Wood was cheaper than steel Aesthetic virtues Aesthetic virtues

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

Calculations

Calculations

Calculations

Calculations

Calculations

Conclusion AB = R – 3.607L AB = R – 3.607L BC = R – 0.698L BC = R – 0.698L CD = R – 3.487L CD = R – 3.487L AJ = R L AJ = R L JI = R L JI = R L CI = R L BJ = R – 1.185L JC = 7.948R L DI = -6R *Note: positive forces denote tension, negative denote compression Calculated Forces

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

Conclusion Maximum loads under special conditions ¼ in. rain adds 1128 lb to overall weight ¼ in. rain adds 1128 lb to overall weight L AJ = 4165 lb (tension) L CD = 7754 lb (compression) 1 ft. snow adds 5413 lb to overall weight 1 ft. snow adds 5413 lb to overall weight L AJ = 6168 lb (tension) L CD = lb (compression)

Discussion Pros and Cons of Design Adequate structural integrity to support roof Adequate structural integrity to support roof Aesthetically pleasing Aesthetically pleasing Not as strong as steel Not as strong as steel Weight (solid beams are heavy) 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 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 Sealed wood structures can last for hundreds of years under good conditions

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

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 html html html PSC Roofing Tiles Bob Vila Home Improvement Website ct/Carpentry/Engineered_Wood/0389- Plywood_Weight.html ct/Carpentry/Engineered_Wood/0389- Plywood_Weight.html ct/Carpentry/Engineered_Wood/0389- Plywood_Weight.html