6- Slender Columns(Tan K H, NUS)

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CE 5510

Advanced Structural Concrete Design

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Slender Column Design

Braced Slender ColumnDesign MomentsUnbraced Slender ColumnsAdjustments to Additional Moments

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Class Objectives

•Explain the effect of second order moments on axial force-moment interaction diagram

•Identify a column as slender (or not) Slender means that slenderness effects are to be considered as per code of practice.

•Determine the design moments for a slender column.

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Recommended Reading• James G. MacGregor, “REINFORCED CONCRETE:

Mechanics and Design”, 3rd Ed., Prentice-Hall, 1997, Ch. 12.

• Allen, A. H., “REINFORCED CONCRETE DESIGN TO BS8110 SIMPLY EXPLAINED”, E&FN Spon,

London 1988, Ch. 11• David A. Fanella, “Time-saving design aids for

reinforced concrete, Part 3: Column and walls”, STRUCTURAL ENGINEER, November 2001, pp 42-47.

The next few slides are from the Reinforced Concrete Council

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Introduction

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N – M Relationship (BS 8110)

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N – M Relationship (BS 8110)

Do you know why you can design for flexure only ifthe axial force is less than 0.1 fcuAc ?

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Design Charts for symmetrically reinforced rectangular cross-sections

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What is Buckling?

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What is buckling?

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What is Buckling?

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Slenderness Effects in Structures

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Classification of Structures

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Effective Length

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Effective Length

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Effective Length

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Effective Length (BS 8110)

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Effective Length

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Slenderness Ratio

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Slenderness Ratio

Bending and Axial Load

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Design Methods

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Design Methods

course

This is covered in detail later.

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Simplified Design Method

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Simplified Design Method

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Simplified Design Method

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Braced

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Simplified Design Method

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Simplified Design Method

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Simplified Design Method

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Bending about Both Axes

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Bending about Both Axes

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Bending about Both Axes

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Example: Calculate the area of steel required in the braced column

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ExampleA. H. Allen, pp 113-115

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Example: Slender Braced Column (Allen)

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BS 8110 : 1985

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Slender Beams