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Trusses – An Engineering Marvel. Dilpreet Bajwa Daniel Tuhy Michael Brown. Basic Building Structure. Foundation Floors Walls Roof Doors/Windows Stairs Frame Roof Trusses. What is a Truss?.
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Trusses – An Engineering Marvel DilpreetBajwa Daniel Tuhy Michael Brown
Basic Building Structure • Foundation • Floors • Walls • Roof • Doors/Windows • Stairs • Frame • Roof Trusses
What is a Truss? It is an assembly of structural members connected by pins that forms a rigid network of triangles Engineered Truss structure comprises of five or more triangular units. Origin- French Trousse (Collection of things bound together) 18th-19th Century – Churches, Mills, Bridges
Common Materials used in Trusses Wood Steel Hollow Pipes Solid Pipes Bamboo
Application of Trusses Buildings Bridges Electric Poles Conveyors Crane Booms
Components of the Trusses • Top Chord • Bottom Chord • Web • Metal Gussets • Bearing Points
Types of Trusses • Parallel • Triangular • Common Types • King Post (16’) • Queen Post (22’ -44’) • Howe (36’) • Scissors • Fink (33’-60’)
Wood Trusses Wood – Southern Pine, Douglas Fir, Hem-Fir Hard Fibrous Material Orthotropic Nature Longitudinal – Parallel to grain/fibers Radial – Normal to growth Size of lumber – 2x4s …4x10s Quality of lumber Kiln Dried/Seasoned Straightness Machine Stress Rated
Types of Loads on the Roof Live Load - Structural loads or actions are forces. Eg. Impact, Vibration, Vehicle on bridge etc. Dead Load - Dead loads are static forces that are relatively constant for an extended time. Eg. Weight of structure, roof weight
Forces in Trusses • Compression • Tension • Reaction • Shear Forces • Bending Moments • Truss Deflection (Elongation under load) • Axial, Shear and Rotational Displacement
Truss Testing and Certification American National Standards Institute (ANSI) Truss Plate Institute Structural Analysis Computing Stress Indices Selecting Wood Sizes, Grades, Connectors
How Trusses are DesignedTrusses Design Questions ??