timber report

8/7/2019 timber report

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I. TYPES OF WOOD CONNECTORS1. Dowel Type Connectors

y Transmits either lateral or withdrawal loadsy Examples are nails, screws and boltsy Lateral loads transmitted by bearing stresses developed between the fastener and

the members of the connection

y Withdrawal loads axial loads parallel to the fastener axis transmitted throughfriction or bearing connected materials

2. Bearing Type Connectorsy Transmits only lateral loadsy Transmits shear forces trough bearing on the connected materialsy Examples are shear plates and split ring connectors

II. CONNECTOR HARDWARES1. Nails

y Sharpened metal pins that are driven into wood with a hammer or mechanical nailgun

y Resists either lateral or withdrawal forces or combination of the twoy Parts of the nail: point (sharpened end), shank (shaft of the nail) and head (flattened

part of the nail)

y Nail Sizes denoted by penny or d


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y Nail Types

a. Common Nail used primarily for fastening rough framingb. Finishing Nail virtually headless; used for fastening finish woodworkc. Box Nail used for toe nailing and other light framing connections wherelumber splitting is concernd. Casing Nail used for attaching finish components of the buildinge. Spiral Shank Nail very resistant to withdrawal from the wood; used for

attaching floor underlayment

f. Roofing Nail has a large head; used for applying sufficient holding powerin the soft material of which asphalt shingles are made

y Methods of Nailing

a. Face Nailing directly nailing to the face of the wood; strongest of allmethods

b. End Nailing used for holding frame members in alignment until gravityforces and applied sheathing make a stronger connection

c. Toe Nailing can carry about five-sixths as much loads as face nail; used assubstitute for end nailing


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y Types of Nail Shanksa. Ring Shank straight shaft and contains no threading

b. Spiral Shank has threading along the shaft and commonly used inhardwood

2. Screwsy Type of fastener characterized by a helical ridge, known as an external thread or

just thread, wrapped around a cylinder

y Screw Point Typesa. Self-drilling Tapping Screws externally threaded fasteners with the ability

to drill their own hole and form or cut their own internal mating threads

into which they are driven without deforming their own thread and without

breaking during assembly

b. Self-piercing Tapping Screw externally threaded fasteners with the abilityto self-pierce metallic material, form a sleeve by extruding metallic material,

and tap their own mating threads when driven


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y Screw Head Types

y Screw Slot Types


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y Standard Screw Sizes

y Screw Designation


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3. Boltsy Most common wood fastener for connections with most high lateral strength is

required

y Used in tension connections where forces are applied parallel to the bolt axisy Usually used for securing wood-to-steel or wood-to-concrete connectionsy Bolt Connections

y Bolt Types

a. Carriage bolt bolts that need no washers since they have square shoulderunder the head that prevent the bolt from turning as the nut is being

tightened


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b. Lag bolt used to anchor metal, or wood, to wood in areas inaccessible tothe placement of a nut for a through bolt, or where an especially long bolt

would be needed to penetrate a joint fully

c. Machine bolts same with carriage bolts except they have a hexagonalhead

d. Anchor Bolts often called J-Bolts and are used for connecting wood toconcrete

y Typical Bolt Types

y Washers used with bolts to keep a bolt head or nut from causing crushingwhen tightening is taking place

y Side Plates frequently used to transfer load from one wood member toanother by allowing a butt joint rather than an overlapping joint


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y Washer Types Used with Bolts

y Lag Bolt Typical Connection


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4. Specialty Connection Hardwaresy Sill Anchors used in lieu of foundation anchor bolts

y Joist Hangers used to attach single or multiple joists to the sides of the girdersor head joists

y Rafter Clip or Roof Tie Down brackets that connect roof framing members towall framing to resist roof uplift loads


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y Hold Down Brackets brackets that are bolted, nailed or screwed into wallstuds or posts and anchored to the construction below to hold down the end

of a member or assembly

y Epoxy Set Anchors anchor bolts that are drilled and installed with epoxyadhesives into concrete

y Strap Ties prepunched strap or coils of strapping that are used for variety ofconnections to transfer tension loads

y Glulam Rivets/ Timber Rivets high strength fastener which resembles a nailbut has a flattened oval shank with a wedge shaped head


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y Split Rings and Shear Plates load transferring devices that rely on bolts torestrain the assembly; transfers shear either between faces of two timber

members or between a timber member and a metal side plate

Shear Plates Split Rings

Assembly of Split Rings and Shear Plates


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y Adhesives primarily used in factory settings and panelized construction; usedbetween floor joists and floor sheathing and between wall studs and wall

covering


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III. JOINT CONNECTIONSy Type of connection that always meet at an angle

1. Butt Jointy Made by placing a squared-butt end of a timber to a smooth face of another

timber

y Butt end of timbers are cut with same angle and are connected to each other.y Commonly used in roof connections and door jambs

2. Lap Jointsy Made by removing parts of the timber members that are to be connected and

lapping them together

y Connecting timbers should fit together and no additional thickness should bedone


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3. Dovetail Jointsy Noted for its strong tensile strength compared to other methods of joineryy Does not rely on mechanical fasteners and are often used in walls

4. Box Jointy An alternative design for dovetail joint where connecting fingers are rectangular

5. Mortise and Tenon Jointy Made by inserting one end of a member to a hole cut in the other member


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6. Bridle Jointy Made by cutting the receiving timber member to full width of the other timber

7. Tounge and Groovey Made by joining two flat pieces strongly together, end to end, to make a single

flat surface

y Mainly used in flooring and paneling


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IV. SPLICE CONNECTIONSy Connections that extend in the same liney Vertical supports (longitudinal stress) require splices that resist compressiony Trusses, braces, and joists (transverse and angular stress) require splices that

resist tension

y Horizontal supports, such as girders or beams, require splices that resist bendingtension and compression

y Splice Stresses

1. Compression Resistant Splicesa. Butt Splice - constructed by butting the squared ends of two pieces of timber together

and securing them in this position with two wood or metal pieces fastened on opposite

sides of the timber


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b. Halved Splice - constructed by cutting away half the thickness for equal distances fromthe ends of two pieces and fitting the complementary tongues together

2. Tension Resistant Splicesa. Square Splice - modification of the compression halved splice; notches are cut in the

tongues or laps to provide an additional locking shoulder

b. Long, Plain Splice - long overlap of two pieces is desirable to provide adequate bearingsurface and enough room for fasteners to make up for the lack of shoulder lock


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3. Bend Resistant SpliceComplementary Lap Splice - constructed by cutting oblique complementary tongues or

laps in the ends of two pieces of timber

REFERENCES:

Mechanical Connections in Wood Structures 1996by American Society of Civil Engineers

Connectors for Timber and Masonry by Simpson Strong Tie, United Kingdom

Wood Mechanical Fasteners by D.R. Rammer

Wood and Steel Details Builders Guide by Hybrid Builders

Carpentry and Building Construction 1960by US Department of Army

Structural Engineering Handbook: Timber Structures by Kenneth Fridley

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