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SECTION 06173

PLATE CONNECTED WOOD TRUSSES

PART 1 GENERAL

1.01 SUMMARY A. Section Includes:

1. Shop fabricated wood trusses for roof and floor framing. 2. Bridging, bracing, and anchorage.

B. Related Sections:

1. Section 06100 - Rough Carpentry.

1.02 REFERENCES A. Reference Standards: See Section 01400. Comply with following:

1. TPI 1 - National Design Standard for Metal Plate Connected Wood Truss Construction; Truss Plate Institute.

2. TPI DSB-89 - Recommended Design Specification for Temporary Bracing of Metal Plate Connected Wood Trusses; Truss Plate Institute.

3. TPI HIB-91 - Commentary and Recommendations for Handling, Installing & Bracing Metal Plate Connected Wood Trusses; Truss Plate Institute.

1.03 SYSTEM DESCRIPTION

A. Design Floor Load:

1. Top Chord Liveload: 40 PSF. 2. Top Chord Deadload: 20 PSF. 3. Bottom Chord Deadload: 5 PSF. 4. Deflection: Maximum L/480 (Live Load) L/360 (Total Load).

B. Design Roof Load:

1. Top Chord Liveload: 21 PSF. 2. Top Chord Deadload: 7 PSF. 3. Bottom Chord Deadload: 10 PSF. 4. Deflection: Maximum L/360 (Live Load), L/240 (Total Load).

C. Minimum Truss Depth To Accommodate Mechanical Ducts: Coordinate ductwork passing

horizontally through trusses with Mechanical Drawings.

1.04 SUBMITTALS A. See Section 01300 - Administrative Requirements, for submittal procedures.

1. Shop Drawings: Indicate framing plans, sizes, pitch, span, and spacing of trusses, loads and truss cambers, framed openings; sizes and grades of lumber; gauge thickness, nominal sizes and locations of connectors at joints; bearing and anchorage details; permanent bracing and bridging and related items. Submit design calculations and shop drawings signed and sealed by a registered Professional Engineer in the State of Maryland. a. Bearing Points: Size truss members to avoid wood crushing at bearing points based on

properties of wall plate material and available wall width indicated on Drawings. 1) Where wood crushing capacity is exceeded, increase number of truss plies or add

bearing block(s) in field and attached according to nail or bold schedule indicated on Shop Drawings.

2) Shop Drawings may be rejected which indicate bearing width greater than that indicated on Drawings or which indicate square inches of bearing required without providing instructions on how to accomplish this.

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b. Shop Drawing and calculations : Bear seal of Professional Engineer registered in State of Maryland.

c. Truss Layout Drawings: Labeled indicating project name, building number and unit type, and individual truss types corresponding to Shop Drawings. 1) Hangers Attached to or Supporting Trusses: Labeled on Truss Layout Drawings

with hanger type and manufacturer indicated. 2) Do not use Framing Drawings (Contract Documents) to quantify exact number of

trusses or framing members required. Provide additional trusses as required to properly support all conditions indicated in Contract Documents.

2. Design Calculations: Submit complete calculations with axial forces, moments, external reactions, plate values, design assumptions, and additional information in accordance with TPI. a. Design Calculations: Bear seal of professional engineer registered in State of

Maryland. 3. Manufacturer's Instructions: Submit manufacturer's instructions for lateral bracing in

accordance with Section 01300. 4. Product Data: Provide truss configurations, bearing and anchor details, bridging and bracing.

1.05 QUALITY ASSURANCE

A. Truss Design, Fabrication, and Installation: In accordance with TPI 1, TPI DSB-89, and HIB-91.

Truss design shall accommodate point loading of shingle storage along any point on ridge members during construction.

B. Manufacturer: Company specializing in manufacturing the products specified in this section with

minimum five years of documented experience. C. Design: Under direct supervision of a Professional Structural Engineer experienced in design of

this Work and licensed in State of Maryland. 1. Multiple Ply Trusses: Attached together to act as single unit under superimposed load.

a. Method of Attachment: Indicated on Shop Drawings including sizes and maximum spacings of fasteners.

b. Give special consideration to end and edge distance of fasteners, avoidance of metal truss connector plates, net section of wood at bolt holes, and cross-grain tension in truss members.

c. Applied Load from Face Mounted Hangers: Provide hangers with flanges tall enough to allow some nailing above neutral axis of truss chord (Above mid-depth of chord).

d. Where bolted connections are required at concentrated loads, fabricate vertical member in truss to receive bolts.

e. Where tributary members frame into truss girder at mid-height, provide continuous prefabricated member at that location to receive face nailed hangers. Alternatively, size field applied ledgers to receive hanger nails and specify attachment points and fastener requirements where ledger intersects truss members.

2. Top Chord Bearings: Design in accordance with TPI PCT (including Supplement) with diagonal webs at top. a. Make test data substantiating design procedures available for review when reaction

limits of TPI PCT are exceeded. b. Design trusses supported at bottom chord bearing notches or end bearing blocks below

chord with due consideration for cross-grain tension and eccentric loads which induce in truss members.

c. Maintain truss web size, location, and orientation where detailed in Drawings unless otherwise noted.

3. Permanent Bracing to Reduce Buckling Length of Axially Loaded Compression Members: Clearly identify which truss members require this field installed bracing on Shop Drawings and including maximum allowable spacing of continuous lateral braces (CLB). a. Anchor each CLB in accordance with TPI HIB, Figure 36 specifying bracing member

sizes and attachments. b. Where CLB are not practical, such as at isolated non-repetitive trusses, design alternate

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T Brace or L-Brace stiffeners and their attachment. c. Take into account any unsheathed truss compression chords as may occur under

piggyback or valley framing. 4. Dimensions: Coordinate with Drawings (Architectural and Structural).

D. Roof Truss Design:

1. Lower Roofs and Trusses Adjacent to Parapets: Design for snow drift and slide off in accordance with Applicable Code. Coordinate these areas with Drawings, identify them on Truss Layout Drawings, and design trusses to reflect actual field conditions.

2. Shop Drawings: Indicate special loading conditions and differentiate between snow live load and dead load in calculations.

3. Mechanical Equipment: a. Verify and coordinate mechanical equipment sizes, locations, and weights with

Mechanical Drawings and indicate on Truss Layout Drawings. Clearly indicate special reinforcement of truss chords under mechanical units where required, including sizes, grades, and method of attachment.

b. Verify and coordinate horizontal and vertical duct opening requirements. 4. Prefabricated Components Subject to Out-Of-Plane Bending (Gable Ends): Design for

flexure in weak axis (flat bending). a. Indicate basic wind speed and design pressures on Shop Drawings. b. Clearly indicate stiffener requirements or maximum spacing requirements for continuous

lateral braces required to reduce bending length of manufactured component member on Shop Drawings.

E. Floor Truss Design:

1. Multiple Supports: Where trusses are designed as continuous over multiple supports, uplift reactions shall not exceed dead weight of wall construction (generally only few hundred pounds or less). Where this condition cannot be met, provide separate simple span trusses. a. Do not use provision to cut top chord after truss erection unless prearranged and

approved by Contractor. 2. Post or Wall Loads from Floor or Roof Above (Trusses cross or aligned with bearing walls or

special girders): Provide trusses with bearing blocks and bearing points to transfer load continuous to foundation.

1.06 REGULATORY REQUIREMENTS

A. Conform to applicable code for loads, seismic zoning, other governing load criteria and fire

retardant requirements.

1.07 PRE-INSTALLATION CONFERENCE A. Hold conference with truss fabricator’s representative, General Contractor, and truss installer in

accordance with Section 01700. Include mechanical equipment installer if appropriate.

1.08 DELIVERY, STORAGE, AND HANDLING A. Handle and erect trusses in accordance with TPI HIB-91.

1. Store trusses off ground and under waterproof cover. 2. Store trusses in vertical position resting on bearing ends.

1.09 FIELD MEASUREMENTS

A. Verify that field measurements are as indicated.

PART 2 PRODUCTS

2.01 MATERIALS

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A. Lumber Grading Rules: As specified in Section 06100 - Rough Carpentry. B. Wood Members: Single top and bottom chord, Stress Group, species, grade, and moisture

content as required by engineer's design. C. Plywood Connectors: Graded by APA; waterproof glue; species and grade as required by

engineer's design. D. Truss Hardware: Provide necessary metal plates bolts, nuts, washers, steel plates, nails, etc.

necessary for truss fabrication. Use correct material of proper size and strength for purpose intended, Structural Notes on Drawings, and applicable building codes. 1. Metal Plates: TPI QSP, hydraulically pressed 20 gauge toothed steel plates, with ASTM

A525 G90 hot-dipped galvanized coating or ASTM A792 AZ50 hot-dipped aluminum-zinc coating.

2. Connections: Size, configuration, and thickness as required to transmit stresses plus eccentricities.

E. Truss Bridging: Type, size and spacing recommended by truss manufacturer.

2.02 ACCESSORIES A. Wood Blocking, Plates, Support Members, and Framing for Openings: In accordance with Section

06100 softwood lumber, S/P/F species, construction grade, 19 percent maximum and 7 percent minimum moisture content.

B. Fasteners: Electro-galvanized steel, type to suit application. C. Bearing Plates: Electro-galvanized, plain steel. D. Hangers:

1. Strap Hangers: Provide solid blocking to receive face nails through straps or provide backup data for alternate installations.

2. Face Nailed Hangers Without Straps: Provide sufficient depth so that nailing can be provided above neutral axis (above mid-depth) of supporting beam.

2.03 FABRICATION

A. Shop fabricate trusses in accordance with recommendations of Truss Plate Institute (TPI)

Reference Standards to achieve structural requirements specified. B. Brace wood trusses in accordance with TPI DSB-89 and TPI HIB-91.

PART 3 EXECUTIONS

3.01 EXAMINATION A. Verify that supports and openings are installed at proper locations and elevations and ready to

receive trusses. Comply with Section 01400.

3.02 PREPARATION A. Coordinate placement of bearing items. B. Coordinate clearances for ductwork, plumbing, and flues with Mechanical Drawings.

3.03 ANCHORS AND SUPPORTS A. General: Provide and install rough hardware and metal fastenings as indicated, specified and

required for proper installation of trusses. Provide nails, spikes, screws and bolts and similar items

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of sizes and types to properly secure members in place.

3.04 ERECTION A. Install trusses in accordance with manufacturer's instructions. Hoist trusses into position taking

care to prevent damage to truss members or joints by out-of-plane bending. 1. Handling and Erection: Comply with TPI HIB. 2. Set members level and plumb, in correct position. 3. Plane of Truss Webs: Vertical, plumb, parallel to each other, and located accurately.

B. Make provisions for erection loads, and for sufficient temporary bracing in accordance with TPI

HIB and DSB, to maintain structure plumb, and in true alignment until completion of erection and installation of permanent bracing. 1. When required by Building Inspector or Truss Fabricator, or elected by erector, to engage

professional engineer or architect to supervise truss erection; provide design and certification of temporary and erection bracing system by structural engineer in accordance with TPI DSB.

C. Bearing and Anchorage: Ensure truss ends have sufficient bearing area, and anchor trusses

securely at bearing points. D. Do not field cut or alter structural members without approval of Architect, Engineer and truss

manufacturer. E. Permanent Bracing for Overall Stability of Structure: Install permanent bracing and bridging prior

to application of loads in accordance with Drawings (including details, sections, and notes). 1. Bracing: Intended to provide lateral stability and transfer wind shear to shear walls and floor

and roof diaphragms. F. Place headers and supports to frame openings required. G. Frame openings between trusses with lumber in accordance with Section 06100. H. Coordinate placement of decking with work of this section. I. After erection, touch-up primed surfaces with primer consistent with shop coat. J. Floor Trusses:

1. Strongbacks: Install at 10 feet (3 m) OC maximum spacing (Two lines of strongbacks at spans over 20 feet (6 m). Anchor each line of strongbacks at both ends as required by TPI PCT. Accomplish by either nailing to rigid wall or with cross bracing.

2. Ladder Trusses (Typical wherever adjacent trusses run parallel to walls): Provide with vertical members of size and spacing as indicated on Drawings. a. Prefabricate or field install wood blocking for transfer of post loads. b. Where ladder trusses are located within designated shear walls, provide bracing per

structural drawings.

3.05 TOLERANCES A. See Section 01400. Comply with following tolerances:

1. Framing Members: 1/2 inch (12 mm) maximum, from true position.

END OF SECTION