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**Column Theory - Column Strength Curve**

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**Example I OK – Column is Stable**

A W12x50 is used as a column to support a compressive load of 145 kips. The length is 20 ft and the ends are pinned. Without regard to LRFD or ASD investigate the stability of the column For a W12x50 OK – Column is Stable

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**Example I NG – Column is Unstable**

A W12x50 is used as a column to support a compressive load of 145 kips. The length is 20 ft the bottom is fixed and the top is free. Without regard to LRFD or ASD investigate the stability of the column For a W12x50 NG – Column is Unstable

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**AISC Requirements CHAPTER E pp 16.1-32 Nominal Compressive Strength**

AISC Eqtn E3-1

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AISC Requirements LRFD

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AISC Requirements ASD

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AISC Requirements ASD – Allowable Stress

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**To compute Fcr – ELASTIC BUCKLING**

Recall Assumptions

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**Column is perfectly straight The load is axial, with no eccentricity **

Assumptions Column is perfectly straight The load is axial, with no eccentricity The column is pinned at both ends

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**To compute Fcr – ELASTIC BUCKLING**

Accounts for Imperfections

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**To compute Fcr – INELASTIC BUCKLING**

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Design Strength

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Alternatively Inelastic Buckling

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In Summary

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Example A W14x74 of A992 steel has a length of 20 feet and pinned ends. Compute the design strength for LRFD and the allowable compressive strength for ASD Slenderness Ratio

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Example

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Example LRFD ASD

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