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? 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 Designed Trusses Design Questions ??