Unformatted text preview: estressed members may be removed
when sufficient prestressing has been applied to enable them to carry their dead loads and anticipated
Section 5.08: Design -General Considerations (b) Design Methods.
The design of reinforced concrete members shall be made either with
reference to allowable working stresses, service loads, and the accepted straightline theory of flexure as
outlined in Section 5.09 to Section 5.13 (Working Stress Design) or with reference to load factors and
strengths as outlined in Section 5.14 to Section 5.18 (Ultimate Strength Design).
(k) Limiting Dimensions of Columns.
1. Minimum size.
Columns constituting the principal support of a floor or roof shall have
a diameter of at least 25 centimeters (10 inches), or in the case of rectangular columns, a
thickness of at least 20 centimeter (8 inches), and a gross area not less than 600 square
centimeters (96 square inches).
2. Isolated column with multiple spirals. If two or more interlocking spirals are used in a
column, the outer boundary of the column shall be taken at a distance outside the extreme limits
of the spiral equal to the requirements of Section 5.07 (h).
3. Limits of section of column built monolithically with wall. For a spiral column built
monolithically with a concrete wall or pier, the outer boundary of the column section shall be
taken either as a circle at least 38 millimeters (1½ inches), outside the column spiral or as a
square or rectangle, the side of which are at least 38 millimeters (1½ inches) outside the spiral or
4. Equivalent circular column.
As an exception to the general procedure of utilizing the
full gross area of the column section, it shall be permissible to design a circular column and to
build it with a square, octagonal, or other shaped section of the least lateral dimension. In such
case, the allowable load, the gross area considered, and the required percentages of reinforcement
shall be taken as those of the circular column.
5. Limits of Column Section.
In a tied column which has a larger cross section tha
required by considerations of loading, a reduced effective area Ag, not less than one-half of the
total area may be used for determining minimum steel area and load capacity.
(l) Limits for Reinforcement of Columns. The vertical reinforcement for columns shall be not less
than 0.01 nor more than 0.08 times the gross cross-sectional area. The minimum size of bar shall be 16 millimeters in diameter (No. 5). The minimum number of bars shall be six for spiral columns and four
for tied columns.
The ratio of spiral reinforcement Ps, shall be not less than the value given by
PS = 0.45 (Ag / AC - 1) f C / fY ...................................................................... (5.08-1)
fY = the yield strength of spiral reinforcement but not more than 4,200 kilograms per
square centimeter (60,000 pounds per square inch).
Section 5.09: Allowable Stresses. Working Stress Design (a) Notations. The notations used...
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- Fall '12
- Building code, Building officials