UFC 4-023-03
25 January 2005
7-2.2
Strength Reduction Factor Φ for Wood Tie Forces
For tension members and mechanical connectors that provide the design tie
strengths, use the appropriate tensile strength reduction factors Φ from AF&PA/ASCE
16-95. For example, use a strength reduction factor of 0.65 for nails, spikes, and wood
screws under lateral load.
7-2.3
Continuity and Anchorage of Ties.
At re-entrant corners or at substantial changes in construction, take care to
ensure that the ties are adequately anchored or otherwise made effective.
7-2.4
Internal Ties.
7-2.4.1
Distribution and Location.
Distribute these ties at each floor and roof level in two directions
approximately at right angles. They must be effectively continuous and must be
anchored to peripheral ties at each end (unless continuing as horizontal ties to columns
or walls). They must, in whole or in part, be spread evenly in the diaphragm or must be
grouped at or in beams, walls or other appropriate positions, but at spacings not greater
than 1.5 lr, where lr is the greater of the distances between the centers of the frames or
walls supporting any two adjacent floor spaces in the direction of the tie under
consideration (i.e., approximately the span length associated with the tie). In walls, they
must be within 0.5 m (1.6 ft) of the top or bottom of the floor diaphragm.
7-2.4.2
Required Tie Force Capacity.
In SI units and in each direction, internal ties must resist a tension (in kN/m
width) equal to the greater of:
a)
(1.0D + 1.0L)
lr
Ft
(kN/m)
3.1
4.6
or
b)
1.0 Ft
(kN/m)
= Dead Load (kN/m2)
where:
D
= Live Load (kN/m2)
L
lr
= Greater of the distances between the centers of
the columns, frames or walls supporting any two
adjacent floor spaces in the direction of the tie
under consideration (m)
Ft
= "Basic Strength" = Lesser of (7.3 + 1.46 no) or 21.9
no
= Number of stories
7-2
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