UFC 4-023-03
25 January 2005
In English units, each external column and every 3.3 ft length of external wall carrying
vertical load must be anchored or tied horizontally into the structure at each floor and
roof level with a design tie strength equal to:
2.0 Ft or (h/8.2) Ft, whichever is smaller
(kip)
where:
h
=
Clear story height (ft)
Ft
=
"Basic Strength" = Lesser of (4.5 + 0.9 Ns) or
13.5
Ns
=
Number of stories including ground and basement
Design the tie connection to masonry in accordance with ACI 530-02.
Tie corner columns in both directions. Space wall ties, where required,
uniformly along the length of the wall or concentrated at centers not more than 5 m
(16.4 ft) apart and not more than 2.5 m (8.2 ft) from the end of the wall. External
column and wall ties may be provided partly or wholly by the same reinforcement as
peripheral and internal ties.
6-2.8
Vertical Ties.
6-2.8.1
Wall Requirements.
Columns and walls that are loadbearing and are required to have vertical ties
must meet the requirements in Table 6-1.
Position vertical ties at a maximum of 5 m (16.4 ft) on center, along the wall,
and 2.5 m (8.2 ft) maximum from any free end of any wall (i.e., there is no return at the
wall end). Vertical ties must extend from the roof level to the foundation. Fully anchor
vertical ties at each end and at each floor level; any joint must be capable of
transmitting the required tensile forces.
For full vertical tying to be considered effective, anchor precast or in-situ
concrete or other heavy floor or roof units in the direction of their span, to adjacent
spans, in such a manner as to be capable of resisting a horizontal tensile force of Ft ,in
kN per meter width (kips per 3.3 ft width), where Ft is given in Section 6-2.5. The wall
must be constrained between concrete surfaces or other similar construction, excluding
wood, capable of providing resistance to lateral movement and rotation across the full
width of the wall.
6-2.8.2
Required Vertical Tie Strength.
In SI units, if the minimum requirements in Table 6-1 are met, a column or
every meter length of a load-bearing wall must provide a required tie strength equal to:
34 A (ha/t)2
or 100 whichever is larger
(kN)
8x106
6-4
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