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# Allowable Stress Design For Building Columns

The AISC specification for allowable-stress design (ASD) for buildings provides two formulas for computing allowable compressive stress Fa, ksi (MPa), for main members. The formula to use depends on the relationship of the largest effective slenderness ratio Kl/r of the cross section of any unbraced segment to a factor C c defined by the following equation and table below:

Where
E=modulus of elasticity of steel =29,000 ksi ( 128.99 GPa )
Fy=Yield stress of steel, ksi (MPa)

When Kl/r is less than C c ,
Fy=36, Cc =126.1
Fy=50, Cc =107

The effective-length factor K, equal to the ratio of effective-column length to actual unbraced length, may be greater or less than 1.0. Theoretical K values for six idealized conditions, in which joint rotation and translation are either fully realized or nonexistent, are tabulated in Figure below

### Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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## One comment on "Allowable Stress Design For Building Columns"

curtis says:

the E value of 128Gpa is wrong, should be 193-200 Gpa