Truss Terms

Apex

Bearing

Structural support of a truss that occurs at the bottom chord or between the end points of a floor or roof truss. Usually walls, beams, concrete slabs and hangers.

Bottom Chord

A horizontal (or inclined in a scissor truss) member that establishes the lower edge of the truss, usually carrying combined tension and bending stresses.

Butt Cut

A slight vertical cut at the outside edge of a truss bottom chord to ensure a uniform span and tight cuts.

Camber

An upward vertical displacement built into a truss bottom chord to compensate for deflection due to the dead load.

Cantilever

Extension of the bottom chord beyond its support exclusive of overhang.

Clear Span

Horizontal distance between interior edges of support.

Concentrated Load

A load, in addition to uniform design loads, applied at a specific point. Examples include cranes, hoists, HVAC equipment and sprinkler pipes.

Dead Load

Dead loads are the weight of the walls, partitions, framing, floors, ceilings, roofs, and all other permanent construction entering into and becoming a part of a building.

Deflection

Movement of a structural member, like a truss in place, due to the application of loads. Deflection is usually downward, but trusses may deflect upward or horizontally depending on loads and bearings

Design Loads

Applied load determined in accordance with either LRFD load combinations or ASD load combinations, whichever is applicable.

Engineer Certified Drawings

A truss design where loading, sizes and grades of material are called out and detailed and a certified engineer’s seal is affixed to that drawing.

Girder Truss

Usually a multiple-ply truss designed to carry over an opening.

Heel

The point on a truss at which the top and bottom chords meet.

Heel Cut

Joint

Area where two or more ends, surfaces, or edges are attached. Categorized by type of fastener or weld used and the method of force transfer.

Lateral Brace

A member placed and connected at right chord or web member of a truss.

Live Load

Any loading which is not of a permanent nature, ie. snow, wind.

Overall Rise

Vertical distance from the bottom most part of the chord to uppermost point on the peak.

Overhang

The extension of the top chord of a truss beyond the heel measured horizontally.

Panel Points

The point where a web or webs intersect at a chord.

Peak

The point on a truss where the sloped top chords meet.

Pitch

Inches of vertical rise for each 12 inches of horizontal run.

Plumb Cut

Top Chord end cut to provide for vertical (plumb) installation to fascia.

Plumb Rise

Vertical overall measurements at the end of a truss where the top and bottom chords meet.

Purlin

A horizontal member attached to and placed perpendicular to the truss top chord to support the roofing.

Reaction

Forces acting on a truss, through its support that are equal but opposite to the sum of the dead and live loads.

Ridge

Line formed by truss apexes.

Rise

Vertical distance from bottom most part of the bottom inside of the peak.

Shop Drawings

Detailed drawings of a truss showing critical dimensions such as a span, overhang, slope, etc.

Slope

Spacing

The centerline distance between trusses – ie. 24″ O.C./48″ O.C. (on center)

Span

Horizontal distance between outside edges of the supports.

Splice Points

Top and bottom chord splice. The point at which chord members are joined together to form a single member it may occur at a panel point or between panel points.

Top Chord

An inclined or horizontal member that establishes the upper edge of a truss.

Truss

A pre-built component that functions as a structural member. A truss employs one or more triangle in its construction.

Webs

Members that join the top and bottom chords to form triangular patterns that give the truss strength.