3.5 KiB
3.5 KiB
Wood Truss Specifications
Design
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Trusses shall be designed by the truss manufacturer in accordance with:
- Truss Plate Institute (TPI) – National Design Standard for Metal Plate Connected Wood Truss Construction (ANSI/TPI 1-2014)
- International Building Code (IBC §2303.4)
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The design shall include:
- All temporary and permanent bracing. Temporary bracing may remain in place if it does not interfere with architectural requirements.
Submittals
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The truss manufacturer shall prepare a truss submittal package including:
- Product data
- Shop drawings
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Submittal process:
- Manufacturer submits package to the contractor.
- Contractor reviews and approves.
- Contractor forwards package to the architect/engineer for review of general conformance with structural drawings.
- Submittals must be prepared, signed, and sealed by an engineer licensed in the project state.
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Package content:
A. Product Data
- ICC approval for framing members and fasteners designed by others
B. Shop Drawings (include at minimum):
- Project name, location, and building code reference
- Layouts, including temporary and permanent bridging
- Truss profiles showing all joints, bearing points, deflection ratios, and reactions
- Blocking requirements
- Required bearing widths
- Number of plies if >1
- Lumber species and grade
- Plate size, gauge, and location
- Truss-to-truss hardware requirements
- Name and trademark of plate manufacturer and truss fabricator
- Camber
C. Calculations
- Building code reference
- Design loads
- Stress reduction factors for plates
Drag Trusses
- Drag trusses shall be provided above and below all interior shear walls.
- Design must support an allowable linear load equal to that of the shear wall.
- If shear walls exist above and below, the larger allowable shear load shall apply.
Truss Restraint and Bracing
- Restraint/bracing shall comply with BCSI-B3 (permanent restraint/bracing of chords and web members) unless noted otherwise.
Truss Deflection Limits
| Truss Type | Live Load Limit | Total Load Limit |
|---|---|---|
| Floor Trusses | L/360 | L/240 |
| Pitched Roof Trusses | L/240 | L/180 |
| Shallow Roof Trusses (≤ 4:12) | L/360 | L/240 |
Camber
- Camber shall be built into roof trusses to compensate for vertical deflection.
- Maximum camber occurs at mid-span.
Example:
- Pitched roof truss: Camber = 1.0 × actual dead load deflection
Trusses Spanning ≥ 60 Feet
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The truss manufacturer shall contract with a qualified registered design professional for:
- Design of temporary installation restraint/bracing
- Design of permanent individual truss member restraint/bracing