Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

94 Chapter Five
Downloaded From : www.EasyEngineering.net
d/b Range
Lateral Constraints for Bending Stability
d/b ≤ 2 No lateral support is required; includes 2 × 4,
3 × 4, 4 × 6, 4 × 8, and any members used flat,
examples are 4 × 2, 6 × 2, 8 × 2.
2 < d/b ≤ 4 Ends shall be held in position, as by full depth
solid blocking, bridging, hangers, nailing, bolting,
or other acceptable means; examples are 2 × 6,
2 × 8, 3 × 8.
4 < d/b ≤ 5 Compression edge of the member shall be held
in line for its entire length to prevent lateral
displacement and ends of member at point
of bearing shall be held in position to prevent
rotation and/or lateral displacement; such as a
2 × 10.
ww.EasyEngineering.n
5 < d/b ≤ 6 Bridging, full depth solid blocking, or diagonal
cross-bracing must be installed at intervals not to
exceed 8 feet, compression edge must be held
in line for its entire length, and ends shall be
held in position to prevent rotation and/or lateral
displacement; example is a 2 × 12.
6 < d/b ≤ 7 Both edges of the member shall be held in line
for its entire length and ends at points of bearing
shall be held in position to prevent rotation and/
or lateral displacement; examples are deep and
narrow rectangular members.
Note: d and b are nominal dimensions
TABLE 5-1 Lateral Constraints for Stability of Bending Members
nominal dimensions. For conditions where the support requirements
in Table 5-1 are not met, the designer should follow the requirements
of the NDS to reduce the reference design value by the adjustment
factor C L
in order to determine the allowable stress in bending.
It is often possible to design members to satisfy the conditions in
Table 5-1 to allow the designer to utilize the full allowable bending
stress. One example of providing lateral support for bending members
is by placing decking on the top of beams. Although the beam is
used to support the decking, the decking can be fastened along the
compression edge of the beam throughout the length of the beam to
provide lateral stability. There are other methods that can be used by
the designer to satisfy the requirements of providing adequate lateral
bracing of bending members.
Downloaded From : www.EasyEngineering.net