Building Design and Construction Handbook - Merritt - Ventech!

10.66 SECTION TEN
steel nails and spikes conforming to ASTM F1667. Sizes of nails are specified by
the pennyweight, indicated by d. The pennyweight for different types of nails establishes
lengths, shank diameter, and head size of the nail. Common wire nails
and spikes are about the same, except that spikes have a larger diameter than nails
with the same pennyweight designation. Box nails have a smaller diameter than
common nails. For a specific pennyweight, the five types of nails have the same
length.
Edge and end distances and spacing for nails and spikes should be sufficient to
prevent splitting of the wood. If specific code requirements for these distances are
not available, Table 10.38 may be used to establish nailing patterns. Spacing, or
pitch, between fasteners in a row is affected by species, moisture content, and grain
orientation.
When a prebored hole is to be used to prevent splitting of the wood, the hole
diameter should not exceed 90% of the nail or spike diameter for wood with a
specific gravity exceeding 0.6, and should not exceed 75% of the diameter for less
dense wood.
10.20 STRUCTURAL FRAMING CONNECTIONS
Standard and special preengineered metal hangers are used extensively in timber
construction. Stock hangers are available from a number of manufacturers, but most
manufacturers also provide hangers of special design. Where appearance is of prime
importance, concealed hangers are frequently selected.
Figures 10.14 to 10.16 show typical structural framing details such as beam
hangers and connectors and column anchors.
(See ‘‘Heavy Timber Connection Details,’’ WCD No. 5, American Forest and
Paper Association, Washington, D.C., for additional information.)
10.21 GLUED FASTENINGS
Glued joints are generally made between two pieces of wood where the grain
directions are parallel (as between the laminations of a beam or arch). Or such
joints may be between solid-sawn or laminated timber and plywood, where the face
grain of the plywood is either parallel or at right angles to the grain direction of
the timber.
It is only in special cases that lumber may be glued with the grain direction of
adjacent pieces at an angle. When the angle is large, dimensional changes caused
by variations in wood moisture content set up large stresses in the glued joint.
Consequently, the strength of the joint may be considerably reduced over a period
of time. Exact data are not available, however, on the magnitude of this expected
strength reduction.
In joints connected with plywood gusset plates, this shrinkage differential is
minimized, because plywood swells and shrinks much less than does solid wood.
Glued joints can be made between end-grain surfaces. They are seldom strong
enough, however, to meet the requirements of even ordinary service. Seldom is it
possible to develop more than 25% of the tensile strength of the wood in such butt
joints. It is for this reason that plane sloping scarfs of relatively flat slope or finger