twenty six concrete construction: columns & frames - - PowerPoint PPT Presentation

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twenty six concrete construction: columns & frames - - PowerPoint PPT Presentation

Jun 12, 2023 235 likes •373 views

A RCHITECTURAL S TRUCTURES : F ORM, B EHAVIOR, AND D ESIGN A RCH 331 D R. A NNE N ICHOLS S PRING 2018 lecture twenty six concrete construction: columns & frames http://www.building.co.uk Concrete Columns 1 Architectural Structures

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SLIDE 1

S2018abn

lecture

Concrete Columns 1 Lecture 26 Architectural Structures ARCH 331

ARCHITECTURAL STRUCTURES: FORM, BEHAVIOR, AND DESIGN ARCH 331

  • DR. ANNE NICHOLS

SPRING 2018

http://www.building.co.uk

twenty six

concrete construction:

columns & frames

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SLIDE 2

S2018abn Concrete Columns 2 Lecture 26 Architectural Structures ARCH 331

Concrete in Compression

  • crushing
  • vertical cracking

– tension

  • diagonal cracking

– shear

  • c

f 

http://www.bam.de

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SLIDE 3

S2018abn Concrete Columns 3 Lecture 26 Architectural Structures ARCH 331

Columns Reinforcement

  • columns require

– ties or spiral reinforcement to “confine” concrete (#3 bars minimum) – minimum amount of longitudinal steel (4 bars minimum)

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SLIDE 4

S2018abn Concrete Columns 4 Lecture 26 Architectural Structures ARCH 331

Slenderness

  • effective length in monolithic with

respect to stiffness of joint:  & k

  • not slender when

u

kL 22 r 

*not braced

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SLIDE 5

S2018abn Concrete Columns 5 Lecture 26 Architectural Structures ARCH 331

Effective Length (revisited)

  • relative rotation

b c

l EI l EI    

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SLIDE 6

S2018abn Concrete Columns 6 Lecture 26 Architectural Structures ARCH 331

Column Behavior

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SLIDE 7

S2018abn Concrete Columns 7 Lecture 26 Architectural Structures ARCH 331

Column Design

  • c = 0.65 for ties, c = 0.75 for spirals
  • Po – no bending
  • Pu  cPn

– ties: Pn = 0.8Po – spiral: Pn = 0.85Po

  • nominal axial capacity:

– presumes steel yields – concrete at ultimate stress

s t y s t g c

  • A

f A A f P     ) ( 8 5 .

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SLIDE 8

S2018abn Concrete Columns 8 Lecture 26 Architectural Structures ARCH 331

Columns with Bending

  • eccentric loads can cause moments
  • moments can change shape and induce

more deflection (P-)

P 

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SLIDE 9

S2018abn Concrete Columns 9 Lecture 26 Architectural Structures ARCH 331

Columns with Bending

  • for ultimate strength behavior, ultimate

strains can’t be exceeded

– concrete 0.003 – steel

  • P reduces

with M

s y

E f

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SLIDE 10

S2018abn Concrete Columns 10 Lecture 26 Architectural Structures ARCH 331

Columns with Bending

  • need to consider

combined stresses

  • linear strain
  • steel stress at or

below fy

  • plot interaction

diagram

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SLIDE 11

S2018abn Concrete Columns 11 Lecture 26 Architectural Structures ARCH 331

Design Methods

  • calculation intensive

– handbook charts – computer programs

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SLIDE 12

S2018abn Concrete Columns 12 Lecture 26 Architectural Structures ARCH 331

Design Considerations

  • bending at both ends

– P-  maximum

  • biaxial bending
  • walls

– unit wide columns – “deep” beam shear

  • detailing

– shorter development lengths – dowels to footings