Concrete Structures - Engineering Class Home Pages

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Nov 26, 2013 (3 years and 4 months ago)

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Concrete structures Copyright Prof Schierle 2011 1
Concrete Structures
Pantheon Rome
Concrete structures Copyright Prof Schierle 2011 2
Pantheon Rome
Concrete structures Copyright Prof Schierle 2011 3
Concrete Structures Types:
•Site cast
•Precast
•Prestressed
•pre-tensioned
•post-tensioned
Advantages:
•Widely available
•Can be recycled
•Many finishes
•Takes any form
•Fire resistant
•Durable
Challenges:
•Heavy weight
(large seismic forces)
•Requires rebars
to resist tension
•Possible cracks
without prestress
Concrete structures Copyright Prof Schierle 2011 4
Concrete properties:
•strong in compression
•weak in tension
•steel re-bars resist tension
Concrete structures Copyright Prof Schierle 2011 5
Strength / time (%) Creep / time Stress / strain
Max aggregate size Slump test Water/cement ratio
Concrete structures Copyright Prof Schierle 2011 6
Concrete Strength Design (LRFD)
Concrete strengthdesignis based on
ultimate concrete strength, reduced by 
1 = Ultimate bending stress
2 = Bending stress assumed in strength design
3 = Strain of balanced beam
c = distance from top to neutral axis
d = effective depth (from top to centroidof steel)
f’’c
= specified concrete compressive strength
As = steel cross section areaA
s
= b d 
fy
= steel yield strength
a = depth of concrete stress blocka = c 1
1 = 0.85 for f’
c
≤ 4 ksi, reduced 0.5 per 1 ksi> 4 ksi, min 1 = 0.65
Z = lever arm of resistant momentZ = d-a/2
C = concrete compressionC = 0.85 f’
c
a b
T = steel tensionT= A
s
fy
= Percentage of reinforcement = As / bd
Approximate design
M = 0.85 f’
c
a b Z(M = resisting moment)
Estimate a ~ 0.2 d
Estimate Z ~ 0.9 d
Steel reinforcing (max)
As
= (M / Z) / (0.75 fy)
Balanced beam
Balanced beam is a reference with concrete and
steel reinforcing of equal strength.
But actual reinforcing is less to assure ductile behavior
(steel yields before brittle concrete failure).
Considering similar triangles in 3 for E
s= 29,000 ksiand balanced b
cb
/ 0.003 = d / (0.003 + f
y/Es
), thus or
For equilibrium (H = 0, C = T)0.85f’
c 1 cb
b = A
s fy
Thusc
b
=A
s fy
/ (0.85 f’
c
1 b)
Since As = bdb
and
For equilibrium (H = 0, C = T)0.85 f’
c
ab= A
s
fy
Thusa = A
s
fy
/ (0.85 f’
c
b)
For moment equilibrium (M = 0) M = (C or T ) (d-a/2) = A
s
fy
(d-a/2)
Substituting a and A
s
= bdand (0.59 = (1 / 0.85) / 2) yields
The nominal moment M = Rbd2
, where R = Resistance factor
The nominal design moment M
n
includes a reduction factor Mn
= M
Reduction factors 
Stress typeReduction factor 
Bending= 0.90
Shear and torsion= 0.85
Compression (spiral reinforcing)= 0.75
Compression (tied reinforcing) and bearing= 0.70
Reinforcement percentage 
Minimum = 0.2 ksi/ f
y
Recommended = 0.18 f’
c
/ fy
Maximum (75% of balanced reinforcing)= 0.75 b
Minimum Resistance factor(at min. = 0.2 ksi/ f
y)R = 0.192
Note: Balanced reinforcing implies steel and concrete provide
equal (balanced) strength; less steel provides ductile steel behavior,
rather than brittle concrete failure.
Concrete structures Copyright Prof Schierle 2011 7
One way systems
:
Slab an beams Rib slab
Two way systems:
Waffle on beams Solid waffle resist post shear
Concrete structures Copyright Prof Schierle 2011 8
Post strength vs. F’c, Fy and reinforcing % of post area
Tied posts left:
1 F
y
= 40 ksireinforcing
2 F
y
= 60 ksireinforcing
Compressive strength (k):
P= 0.8(0.85 f’
c)(Ag–As)+fyAs
Compressive stress
F = P/Ag
Spiral posts right:
1 F
y
= 40 ksireinforcing
2 F
y
= 60 ksireinforcing
Compressive strength (k)
P= 0.85(0.85 f’
c)(Ag–As)+fyAs
Compressive stress
F = P/Ag
Ag
= post cross section area
As
= area of steel reinforcing
f’c
= specified comp. strength
fy
= reinforcing yield strength
p = % reinforcing
Concrete structures Copyright © G G Schierle, 2010 press Esc to end, for next, for previous slide ‹#›
Concrete structures Copyright © G G Schierle, 2010 press Esc to end, for next, for previous slide ‹#›
Concrete structures Copyright Prof Schierle 2011 11
Steel post footing
Two-way reinforcing
Template plate to set anchor bolts
Post with base plate
Base plate replaces template plate
Concrete structures Copyright © G G Schierle, 2010 press Esc to end, for next, for previous slide ‹#›
Sagrada Familia Barcelona -Architect: Antonio Gaudi
Concrete structures Copyright Prof Schierle 2011 13
Site cast concrete
facilitates free forms
but requires costly formwork
Cooling tower Notre Dame du haut Ronchamp
Concrete structures Copyright Prof Schierle 2011 14
La Tourette Lyon 1960
Convent
Architect: Le Corbusier
Chandigarh 1953-63
State Assembly
Architect: Le Corbusier
Concrete structures Copyright Prof Schierle 2011 15
Unite d'Habitation
Marseilles, 1952
Architect: Le Corbusier
Concrete structures Copyright Prof Schierle 2011 16
Hellas Research Foundation, Crete
Architect: Panos Koulermos
Engineer: Helas Research Foundation
Concrete structures Copyright Prof Schierle 2011 17
Post top drop panels
(size to resist shear)
Robert Maillart: Mushroom posts
Drop panel Stepped drop panel Tapered drop panel
Concrete structures Copyright Prof Schierle 2011 18
Two-way system
Waffle slab (5’ x 5’ waffles)
Solid post waffles
resist shear
Concrete structures Copyright Prof Schierle 2011 19
Two-way system
Waffle slab on beam
Solid waffles resist shear
Three-way waffles
Concrete structures Copyright Prof Schierle 2011 20
Habitat 67 -Expo 67 Montreal
Architect: Moshe Safdie
Concrete structures Copyright Prof Schierle 2011 21
Terrace Homes Taipei China, 1981
200 MFD / SFD units
Architect: Schierle
Engineer: CSE
RC moment frame / shear wall interaction
for seismic safety
Concrete structures Copyright Prof Schierle 2011 22
Senior Housing San Francisco 1970
Architect: Wong / Schierle
Engineer: Elsesser
Concrete structures Copyright Prof Schierle 2011 23
Stanford Student Housing 1970 –Architect: Wong / Schierle, Engineer: Elsesser
Concrete structures Copyright Prof Schierle 2011 24
UIC University Hall Chicago
Architect: Walter Netsch SOM
Engineer: SOM
Concrete structures Copyright Prof Schierle 2011 25
Casa Terragni, Como
Architect: Teragni
Combined moment frame and shear wall
Shear wall provides good wind resistance
Ductile moment frame resists seismic load
Concrete structures Copyright Prof Schierle 2011 26
Rome Train station, 1947-50
Architects: Calini, Montouri, Fadigati, Pintonello, Vitellozzi
Concrete structures Copyright Prof Schierle 2011 27
Church of the light Osaka 1989
Architect: Tadao Ando
Hyogo Chapel
Architect: Tadao Ando
Concrete structures Copyright Prof Schierle 2011 28
St. Mary’s Cathedral Tokyo, 1964
Architect: Kenzo Tange
Engineer: Yoshikatsu Tsuboi
Concrete structures Copyright Prof Schierle 2011 29
Falling Water Residence Pennsylvania
Architect: Frank Lloyd Wright, 1935
Concrete structures Copyright Prof Schierle 2011 30
Guggenheim Museum New York, 1959
Architect: Frank Lloyd Wright
Concrete structures Copyright Prof Schierle 2011 31
CNIT Exhibit Hall, Paris, 1956-58
Architect: Camelot, MaillyZehrfuss
Engineer: Nicholas Esquilan
Equilateral triangle plan
Longest shell span 225 m (738’)
Concrete structures Copyright Prof Schierle 2011 32
Sidney Opera House
Architect: Jörn Utzen
Engineer: Ove Arup
Concrete structures Copyright Prof Schierle 2011 33
Bahai Worship House New Delhi 1980
Architect: Fariburz Sahba
Engineer: Flint and Neill
Concrete structures Copyright Prof Schierle 2011 34
Palazzetto dello Sport Rome, 1958
Architect: Annibale Vitellozzi
Engineer: Pier Luigi Nervi
Site cast concrete rib dome
Diameter: 61 m (200 feet)
Simon Glynn 2005
Concrete structures Copyright Prof Schierle 2011 35
Olympic Dome Rome, 1962
Architect: Piacentini and Nervi
Engineer: Pier Luigi Nervi
Diameter: 100 m (328 feet) to outer
tension ring
Precast concrete elements
Lara K. Davis, M Arch candidate
MIT Department of Architecture
Concrete structures Copyright Prof Schierle 2011 36
Heinz Isler: concrete shells
Café-Restaurant Chur 1975Tennishall Grenchen 1978
Garden Center Zuchwil 1962
Swimming Pool Brugg 1981
Concrete structures Copyright Prof Schierle 2011 37
Felix Candela Shells
Bacardi Rum Factory, 1960
Xochimilco Restaurant, 1958
Concrete structures Copyright Prof Schierle 2011 38
Train
station
Savona, Italy
Architect: Antonio Nervi
Engineer: Pier Luigi Nervi
Folded Plate
Kimbell Art Museum Fort Worth, 1972
Architect: Louis Kahn
Engineer: August Komendant
Cylindrical Shell
Photo: Michael Bodycomb, © 1977 Kimbell Art Museum, reproduced with permission
Concrete structures Copyright Prof Schierle 2011 39
Hoover Dam Colorado1936
Arch form resists water pressure
primarily in compression
Hoover bridge 2010
Concrete structures Copyright Prof Schierle 2011 40
Robert Maillart
Swiss bridges
(Three-hinge arches)
Salginatobel Bridge 1929
Arve Bridge, 1936 (near Geneva)
Concrete structures Copyright Prof Schierle 2011 41
Kremasta Lake Bridge, Greece, 443 m (484 yards)
Engineer: Aristarchos Oikonomou
Concrete structures Copyright Prof Schierle 2011 42
Milau ViaductArchitect: Norman Foster
Engineer: Ove Arup
Concrete structures Copyright Prof Schierle 2011 43
Milau ViaductArchitect: Norman Foster
Engineer: Ove Arup
Concrete structures Copyright Prof Schierle 2011 44
Precast Concrete
Challenges:
•element joints
•transportation cost
Advantages:
•repetitive use of formwork
•factory quality control
Concrete structures Copyright Prof Schierle 2011 45
Prestressed Concrete
Pre-tensioned (in factory) Post-tensioned (site-cast)
Concrete structures Copyright Prof Schierle 2011 46
Prestressed Concrete
Precast slab and beams Precast walls and post
Concrete structures Copyright Prof Schierle 2011 47
Cal State Hayward Cafeteria
Architect: Wong
Engineer: Elsesser
Concrete structures Copyright Prof Schierle 2011 48
Precast concrete
Precast posts
Precast frames
Concrete structures Copyright Prof Schierle 2011 49
Precast tree posts
Beverly Hills
USC
Concrete structures Copyright Prof Schierle 2011 50
Precast façade elements
Concrete structures Copyright Prof Schierle 2011 51
Precast wall panels
Concrete structures Copyright Prof Schierle 2011 52
Concrete is strong and durable