Lecture Twenty-Four Machiavelli, The Prince Lecturer: Wu Shiyu.
twenty two lecture - Texas A&M University
Transcript of twenty two lecture - Texas A&M University
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Su2013abn Concrete Spans 1
Lecture 22
Architectural Structures
ARCH 331
ARCHITECTURAL STRUCTURES:
FORM, BEHAVIOR, AND DESIGN
ARCH 331
DR. ANNE NICHOLS
SUMMER 2013
lecture
twenty two
concrete construction: flat spanning systems,
columns & frames
http:// nisee.berkeley.edu/godden
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Su2013abn Concrete Spans 2
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠economical & common
⢠resist lateral loads
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Su2013abn Concrete Spans 3
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠flat plate
â 5â-10â thick
â simple formwork
â lower story heights
⢠flat slab
â same as plate
â 2 Âźââ8â drop panels
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Su2013abn Concrete Spans 4
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠beam supported
â slab depth ~ L/20
â 8ââ60â deep
⢠one-way joists
â 3ââ5â slab
â 8ââ20â stems
â 5â-7â webs
The Architectâs Studio Companion
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Su2013abn Concrete Spans 5
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠two-way joist
â âwaffle slabâ
â 3â-5â slab
â 8â-24â stems
â 6â-8â webs
⢠beam supported slab
â 5â-10â slabs
â taller story heights
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Su2013abn Concrete Spans 6
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠simplified frame analysis
â strips, like
continuous beams
⢠moments require
flexural reinforcement
â top & bottom
â both directions of slab
â continuous, bent or
discontinuous
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Su2013abn Concrete Spans 7
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠one-way slabs (wide beam design)
â approximate analysis for moment & shear
coefficients
â two or more spans
â ~ same lengths
â wu from combos
â uniform loads with L/D 3
â n is clear span (+M) or average of
adjacent clear spans (-M)
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Su2013abn Concrete Spans 8
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
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Su2013abn Concrete Spans 9
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
⢠two-way slabs - Direct Design Method
â 3 or more spans each way
â uniform loads with L/D 3
â rectangular panels with
long/short span 2
â successive spans
canât differ > longer/3
â column offset no more
than 10% span
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Su2013abn Concrete Spans 10
Lecture 22
Architectural Structures
ARCH 331
Reinforced Concrete Design
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Su2013abn Concrete Spans 11
Lecture 22
Architectural Structures
ARCH 331
Shear in Concrete
⢠at columns
⢠want to avoid
stirrups
⢠can use shear
studs or heads
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Su2013abn Concrete Spans 12
Lecture 22
Architectural Structures
ARCH 331
Shear in Concrete
⢠critical section at d/2 from
â column face, column capital or drop panel
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Su2013abn Concrete Spans 13
Lecture 22
Architectural Structures
ARCH 331
Shear in Concrete
⢠at columns with waffle slabs
http:// nisee.berkeley.edu/godden
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Su2013abn Concrete Spans 14
Lecture 22
Architectural Structures
ARCH 331
Openings in Slabs
⢠careful placement of holes
⢠shear strength
reduced
⢠bending &
deflection can
increase
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Su2013abn Concrete Spans 15
Lecture 22
Architectural Structures
ARCH 331
General Beam Design
⢠fâc & fy needed
⢠usually size just b & h
â even inches typical (forms)
â similar joist to beam depth
â b:h of 1:1.5-1:2.5
â bw & bf for T
â to fit reinforcement + stirrups
⢠slab design, t
â deflection control & shear 6
2bhS
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Su2013abn Concrete Spans 16
Lecture 22
Architectural Structures
ARCH 331
General Beam Design (contâd)
⢠custom design:
â longitudinal steel
â shear reinforcement
â detailing
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Su2013abn Concrete Spans 17
Lecture 22
Architectural Structures
ARCH 331
Space âFrameâ Behavior
⢠handle uniformly distributed loads well
⢠bending moment
â tension &
compression
âcoupleâ with
depth
â member sizes
can vary,
but difficult
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Su2013abn Concrete Spans 18
Lecture 22
Architectural Structures
ARCH 331
Space âFrameâ Behavior
⢠shear at columns
⢠support conditions still important
â point supports not optimal
⢠fabrication/construction can dominate
design
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Su2013abn Concrete Spans 19
Lecture 22
Architectural Structures
ARCH 331
Folded Plates
⢠increased bending stiffness with folding
⢠lateral buckling avoided
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Su2013abn Concrete Spans 20
Lecture 22
Architectural Structures
ARCH 331
Folded Plates
⢠common for roofs
⢠edges need
stiffening
http:// nisee.berkeley.edu/godden
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Su2013abn Concrete Spans 21
Lecture 22
Architectural Structures
ARCH 331
Folded Plates
â State Farm Center (Assembly Hall), University of Illinois
â Harrison & Abramovitz 1963
â Edge-supported dome spanning 400 feet wound with 614 miles of one-fifth inch steel wire
www.library.illinois.edu
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Su2013abn Concrete Spans 22
Lecture 22
Architectural Structures
ARCH 331
Concrete in Compression
⢠crushing
⢠vertical cracking
â tension
⢠diagonal cracking
â shear
⢠cf
http://www.bam.de
cf
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Su2013abn Concrete Spans 23
Lecture 22
Architectural Structures
ARCH 331
Columns Reinforcement
⢠columns require
â ties or spiral reinforcement
to âconfineâ concrete
(#3 bars minimum)
â minimum amount of longitudinal steel
(#5 bars minimum: 4 with ties, 5 with spiral)
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Su2013abn Concrete Spans 24
Lecture 22
Architectural Structures
ARCH 331
Slenderness
⢠effective length in monolithic with
respect to stiffness of joint: & k
⢠not slender when
22r
kLu 22r
kLu
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Su2013abn Concrete Spans 25
Lecture 22
Architectural Structures
ARCH 331
Effective Length (revisited)
⢠relative rotation
b
c
lEI
lEI
b
c
lEI
lEI
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Su2013abn Concrete Spans 26
Lecture 22
Architectural Structures
ARCH 331
Column Behavior
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Su2013abn Concrete Spans 27
Lecture 22
Architectural Structures
ARCH 331
Column Design
⢠c = 0.65 for ties, c = 0.75 for spirals
⢠Po â no bending
⢠Pu cPn
â ties: Pn = 0.8Po
â spiral: Pn = 0.85Po
⢠nominal axial capacity:
â presumes steel yields
â concrete at ultimate stress
stystgco AfAAfP )(85.0
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Su2013abn Concrete Spans 28
Lecture 22
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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Su2013abn Concrete Spans 29
Lecture 22
Architectural Structures
ARCH 331
Columns with Bending
⢠for ultimate strength behavior, ultimate
strains canât be exceeded
â concrete 0.003
â steel
⢠P reduces
with M
s
y
E
f
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Su2013abn Concrete Spans 30
Lecture 22
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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Su2013abn Concrete Spans 31
Lecture 22
Architectural Structures
ARCH 331
Design Methods
⢠calculation intensive
â handbook charts
â computer programs
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Su2013abn Concrete Spans 32
Lecture 22
Architectural Structures
ARCH 331
Design Considerations
⢠bending at both ends
â P- maximum
⢠biaxial bending
⢠walls
â unit wide columns
â âdeepâ beam shear
⢠detailing
â shorter development lengths
â dowels to footings