Axially and Uniaxially Loaded Columns

8/3/2019 Axially and Uniaxially Loaded Columns

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Axially and Uni-axially Loaded Columns

CVE411 Structural Concrete Design

Jamal A. Abdalla

Textbook: Chapter 9 & 10

ACI 318-05 Code: Chapter 10

Ref. McCormac, J. C. and Nelson Jr., J. K., Design of Reinforced Concrete, 6th Edition, 2005, John Wiley and Sons


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Objectives and Outcomes

y Review the design of axially loaded and unaxially loaded

columns

1. Apply the ACI requirements for reinforced concrete columns

2. Design of axially loaded tied columns and spiral columns

3. Design of uniaxially loaded columns using interaction diagram.

4. Design of shear reinforcement in columns

Objectives:

Outcomes:


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Code requirements for Concrete columns

The ACI Code specifies quite a fewlimitations on the dimensions, reinforcing,

lateral restraint, and other

ite

ms pert

aining

tocon

cretecolumns. Som

eofthe

mostimportant limitations are listed below:

1. The percentage of longitudinal reinforcement may not be less than 1% of

the gross cross-sectional area ofa column.

2. The maximum percentage ofsteel may not be greater than 8% ofthe

gross cross-sectional area ofthecolumn.3. The minimum numbers of longitudinal bars permissibleforcompression

members are as follows:4 forbars within rectangularorcircularties, 3 for

bars within triangularshaped ties, and 6 forbars enclosed within spirals.

4. Minimum widths ordiameters ofcolumns is about8 to 10 in. This is to

allowforthe necessary coveroutside ofties orspirals and to providethe

necessary clearance between longitudinal bars from oneface ofthe

column to the other.

5. When tied columns are used, theties shall not beless than #3, provided

thatthe longitudinal bars are #10 orsmaller. The minimum sizeis #4 for

longitudinal bars largerthan #10 and forbundled bars.

ACI Committee 318, Building Code Requirements for Structural Concrete and Commentary, ACI 318-02 Edition, 2002, American Concrete Institute, Farmington Hills, Michigan


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Tied and Spiral Columns



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Tied and Spiral Columns

AUS Library: Courtesy of Jamal Abdalla


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Tied Columns

])(85.0[80.0 ' stystgcn AfAAfP !

nu PP Je

J

Fortied columns the design strengthis given by:

The LRFDDesign equation is given by:

=0.65 fortied columns

gA

stA

= Gross area ofcolumn

= Area ofsteelreference: McCormac


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Spiral Columns

gA

stA

])(85.0[85.0 ' stystgcn AfAAfP !

nuPP Je

Forspiral columns the design strengthis given by:

The LRFDDesign equation is given by:

J =0.70forspiral columns

= Gross area ofcolumn

= Area ofsteelreference: McCormac


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Design of Spiral Reinforcement


as = area ofspiral


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Columns Under Unaxial Bending



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Column Interaction Diagram

reference: McCormac


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Column Interaction Diagram



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Design Interaction Diagram



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reference: McCormac


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reference: McCormac


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>0.005 0.9


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reference: McCormac


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reference: McCormac


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Shear in Columns

Ref McCormac J C and Nelson Jr J K Design of Reinforced Concrete 6th Edition 2005 John Wiley and Sons

Axially and Uniaxially Loaded Columns

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