Building Design and Construction Handbook - Merritt - Ventech!

10.14.9 Diaphragm Factor
WOOD CONSTRUCTION 10.59
A diaphragm is a large, thin structural element that is loaded in its plane. When
nails or spikes are used in a diaphragm connection, the nominal lateral design value
should be multiplied by the diaphragm factor C di � 1.1.
10.14.10 Toenail Factor
For such connections as stud to plate, beam to plate, and blocking to plate, toenailing
is generally used. The NDS recommends that toenails be driven at an angle
of about 30� with the face of the stud, beam, or blocking and started about onethird
the length of the nail from the end of the member. For toenailed connections,
the nominal lateral design values for connections with nails driven into side grain
should be multiplied by the toenail factor C tn � 0.83.
10.14.11 Adjustments for Fire-Retardant Treatment
For connections made with lumber or other wood products pressure-treated with
fire-retardant chemicals, design values should be obtained from the company providing
the treatment and redrying service. The load-duration factor for impact does
not apply to such connections.
10.15 BOLTS
The ‘‘National Design Specification for Wood Construction,’’ American Forest &
Paper Association, contains design provisions and design values for bolts with diameters
up to 1 in conforming to the ANSI/ASME Standard B18.2.1. Bolt design
values in the NDS apply to connections that have been snugly tightened and to
connections that have loosened due to shrinkage of the wood components.
Following are some important NDS requirements for bolts: Bolt holes should
have a diameter from 1 ⁄32 to 1 ⁄16 in larger than the bolt diameter. In establishment
of design values, careful centering of holes in main members is assumed. Tight fit
of bolts in the holes, requiring forced insertion, is not recommended. A metal plate,
strap, or washer (not smaller than a standard cut washer) should be placed between
the wood and bolt head and between the wood and the nut. The length of bolt
threads subject to bearing on the wood should be kept to a practical minimum.
Two or more bolts placed in a line parallel to the direction of the load constitute
a row. End distance is the minimum distance from the end of a member to the
center of the bolt hole that is nearest to the end. Edge distance is the minimum
distance from the edge of a member to the center of the nearest bolt hole. Figure
10.12 illustrates these distances, the spacing between rows, and the spacing of bolts
in a row. NDS requirements are listed for minimum end distance in Table 10.34,
for minimum edge distance in Table 10.35, and for minimum spacing between rows
and between bolts in a row in Table 10.36. The geometry factor C � discussed in
Art. 10.14.5 is applied to the design value for a bolted connection when the end
distance or spacing between bolts is less than that given in these tables for full
design value.