twenty five http:// nisee.berkeley.edu/godden concrete - - PowerPoint PPT Presentation

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twenty five http:// nisee.berkeley.edu/godden concrete - - PowerPoint PPT Presentation

Jul 08, 2023 624 likes •846 views

A RCHITECTURAL S TRUCTURES : F ORM, B EHAVIOR, AND D ESIGN A RCH 331 D R. A NNE N ICHOLS S PRING 2019 lecture twenty five http:// nisee.berkeley.edu/godden concrete construction: flat spanning systems Concrete Spans 1 Architectural Structures

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S2019abn Concrete Spans 1 Lecture 25 Architectural Structures ARCH 331

lecture

twenty five

concrete construction:

flat spanning systems

http:// nisee.berkeley.edu/godden

ARCHITECTURAL STRUCTURES: FORM, BEHAVIOR, AND DESIGN ARCH 331

  • DR. ANNE NICHOLS

SPRING 2019

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S2019abn Concrete Spans 2 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • economical & common
  • resist lateral loads
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S2019abn Concrete Spans 3 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • flat plate

– 5”-10” thick – simple formwork – lower story heights

  • flat slab

– same as plate – 2 ¼”–8” drop panels

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S2019abn Concrete Spans 4 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • beam supported

– slab depth ~ L/20 – 8”–60” deep

  • one-way joists

– 3”–5” slab – 8”–20” stems – 5”-7” webs

The Architect’s Studio Companion

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S2019abn Concrete Spans 5 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • two-way joist

– “waffle slab” – 3”-5” slab – 8”-24” stems – 6”-8” webs

  • beam supported slab

– 5”-10” slabs – taller story heights

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S2019abn Concrete Spans 6 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • simplified frame analysis

– strips, like continuous beams

  • moments require

flexural reinforcement

– top & bottom – both directions of slab – continuous, bent or discontinuous

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S2019abn Concrete Spans 7 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • one-way slabs (wide beam design)

– approximate analysis for moment & shear coefficients – two or more spans – ~ same lengths – wu from combos – uniform loads with L/D  3 –  n is clear span (+M) or average of adjacent clear spans (-M)

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S2019abn Concrete Spans 8 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

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S2019abn Concrete Spans 9 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

  • two-way slabs - Direct Design Method

– 3 or more spans each way – uniform loads with L/D  2 – rectangular panels with long/short span  2 – successive spans can’t differ > longer/3 – column offset no more than 10% span

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S2019abn Concrete Spans 10 Lecture 25 Architectural Structures ARCH 331

Reinforced Concrete Design

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S2019abn Concrete Spans 11 Lecture 25 Architectural Structures ARCH 331

Shear in Concrete

  • at columns
  • want to avoid

stirrups

  • can use shear

studs or heads

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S2019abn Concrete Spans 12 Lecture 25 Architectural Structures ARCH 331

Shear in Concrete

  • critical section at d/2 from

– column face, column capital or drop panel

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S2019abn Concrete Spans 13 Lecture 25 Architectural Structures ARCH 331

Shear in Concrete

  • at columns with waffle slabs

http:// nisee.berkeley.edu/godden

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S2019abn Concrete Spans 14 Lecture 25 Architectural Structures ARCH 331

Openings in Slabs

  • careful placement of holes
  • shear strength

reduced

  • bending &

deflection can increase

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S2019abn Concrete Spans 15 Lecture 25 Architectural Structures ARCH 331

General Beam Design

  • f’c & fy needed
  • usually size just b & h

– even inches typical (forms) – similar joist to beam depth – b:h of 1:1.5-1:2.5 – bw & bf for T – to fit reinforcement + stirrups

  • slab design, t

– deflection control & shear

6

2

bh S 

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S2019abn Concrete Spans 16 Lecture 25 Architectural Structures ARCH 331

General Beam Design (cont’d)

  • custom design:

– longitudinal steel – shear reinforcement – detailing

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S2019abn Concrete Spans 17 Lecture 25 Architectural Structures ARCH 331

Space “Frame” Behavior

  • handle uniformly distributed loads well
  • bending moment

– tension & compression “couple” with depth – member sizes can vary, but difficult

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S2019abn Concrete Spans 18 Lecture 25 Architectural Structures ARCH 331

Space “Frame” Behavior

  • shear at columns
  • support conditions still important

– point supports not optimal

  • fabrication/construction can dominate

design

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S2019abn Concrete Spans 19 Lecture 25 Architectural Structures ARCH 331

Folded Plates

  • increased bending stiffness with folding
  • lateral buckling avoided
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S2019abn Concrete Spans 20 Lecture 25 Architectural Structures ARCH 331

Folded Plates

  • common for roofs
  • edges need

stiffening

http:// nisee.berkeley.edu/godden

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S2019abn Concrete Spans 21 Lecture 25 Architectural Structures ARCH 331

Folded Plates

– State Farm Center (Assembly Hall), University of Illinois – Harrison & Abramovitz 1963 – Edge-supported dome spanning 400 feet wound with 614 miles of one-fifth inch steel wire

www.library.illinois.edu