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Building Design and Construction Handbook - Merritt - Ventech!

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WOOD CONSTRUCTION 10.61<br />

TABLE 10.36 Minimum Spacing for Bolts*<br />

Direction of loading<br />

(a) For bolts in a row<br />

For reduced<br />

design value<br />

For full<br />

design value<br />

Parallel to grain 3D 4D<br />

Perpendicular to grain 3D Required<br />

spacing for<br />

attached<br />

member(s)<br />

(b) Between bolts in a row<br />

Direction of loading<br />

Minimum<br />

spacing<br />

Parallel to grain<br />

Perpendicular to grain:<br />

1.5D<br />

When L/D � 2 2.5D<br />

When 2 � L/D � 6 (5L�10D)/8 When L/D � 6 5D<br />

* L � length of bolt in main member <strong>and</strong> D � bolt diameter.<br />

long bolt would be needed, where one side of a connection is not accessible, or<br />

where heavy withdrawal loads have to be resisted. If desired, lag screws can be<br />

used in conjunction with split rings <strong>and</strong> shear plates.<br />

Lag screws are turned with a wrench into prebored holes with total length equal<br />

to the nominal screw length. Soap or other lubricant may be used to facilitate<br />

insertion <strong>and</strong> prevent damage to screws. Two holes are drilled for each lag screw.<br />

The first <strong>and</strong> deepest hole has a diameter, as specified in the NDS for various<br />

species, depending on the wood density, ranging from 40 to 85% of the shank<br />

diameter. The second hole should have the same diameter as the shank, or unthreaded<br />

portion of the lag screw, <strong>and</strong> the same depth as the unthreaded portion.<br />

The NDS contains design values <strong>and</strong> design provisions for lag screws that conform<br />

to ANSI/ASME St<strong>and</strong>ard B18.2.1. Lag screws loaded in withdrawal should<br />

be designed for allowable tensile strength in the net (root-of-thread) section as well<br />

as for resistance to withdrawal. For single-shear wood-to-wood connections, the lag<br />

screw should be inserted in the side grain of the main member with the screw axis<br />

perpendicular to the wood fibers. Minimum edge <strong>and</strong> end distances <strong>and</strong> spacing for<br />

a lag screw are the same as for a bolt with diameter equal to the shank diameter<br />

of the screw (Tables 10.34 to 10.36).<br />

10.17 SPLIT-RING AND SHEAR-PLATE<br />

CONNECTORS<br />

These are metal devices used with bolts or lag screws for producing joints with<br />

fewer fasteners without reduction in strength. Several types of connectors are available.<br />

Usually, they are either steel rings, called split rings, that are placed in grooves<br />

in adjoining members to prevent relative movement or metal plates, called shear

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