D1.L.1.1.3 Compression
The allowable compressive stress for columns shall be as required by clause XVII-2213 of NF-3000 1974.
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Gross Sections of Columns:
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On gross section of axially loaded compression members, when (Kl/r) < Cc ,
Where:
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When (Kl/r) > Cc ,
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When (Kl/r) > 120,
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Member elements other than columns:
- For Plate Girder Stiffeners, Fa = 0.60·Fy
- For webs of rolled shapes, Fa = 0.75·Fy
The above clauses are applicable only when the width-thickness ratio of the element satisfies all the sub-sections of clause XVII-2224 of NF-3000 1974.
If the above-mentioned clauses are not satisfied,
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For un-stiffened compression element, a reduction factor, Qs, is introduced. Detailed values of Qs for different shapes are given in the clause XVII-2225.2 of NF-3000 1974.
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For stiffened compression element, a reduced effective width, be, is introduced.
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For the flanges of square and rectangular sections of uniform thickness:
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For other uniformly compressed elements:
Consequently, a reduction factor, Qa, equal to the effective area divided by the actual area is introduced.
Combining both these factors, allowable stress for axially loaded compression members containing stiffened or un-stiffened elements shall not exceed
Where:
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