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Analysis, Design, and Construction Practices in Environmental Engineering
Concrete Structures, Part 1 of 2
ACI Fall 2010 ConventionOctober 24 - 28, Pittsburgh, PA
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2/4/2011
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ACI Web Sessions
This ACI Web Session includes two speakers presenting at the ACI fall convention held in Pittsburgh, PA, October 24 –28, 2010.
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Analysis, Design, and Construction Practices in Environmental Engineering
Concrete Structures, Part 1 of 2
ACI Fall 2010 ConventionOctober 24 - 28, Pittsburgh, PA
ACI Fellow Charles Hanskat is Managing Principal at Concrete Engineering Group, LLC, a firm he founded in 2008 located in Northbrook, Illinois. He is a licensed professional engineer in 22 states. Mr. Hanskat has been involved the design, construction, and evaluation of environ-mental concrete and shotcrete structures for
nearly 35 years. He is an active voting member of many ACI technical and Board committees. He is also a Board member on the American Shotcrete Association (ASA) and chair of the ASA Sustainability Committee. He has served on AWWA technical committees developing standards for prestressed concrete for over 25 years. He holds a Bachelor's and Master's degree in Civil Engineering from the University of Florida.
Charles Hanskat, PrincipalConcrete Engineering Group, LLC
EECS are large structures
Carry very high loads over large areas
Loads are vertical and horizontal
Structures are expected to be liquid‐tight
Contents can be aggressive
Environment can be aggressive
Under all expected environmental exposures and loading conditions the structure will remain essentially liquid‐tight and maintain its full structural integrity for 50 to 100 years.
The structure will do this with minimal maintenance.
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Introduction and General Commentary
Chapter 3 – Materials
Chapter 4 – Durability Requirements
Chapter 7 – Details of Reinforcement
Chapter 9 – Strength and Serviceability
Chapter 10 – Flexure and Axial Loads
Chapter 14 – Walls
Chapter 18 – Prestressed Concrete
The liquid‐tightness of a structure will be reasonably assured when:
The concrete mixture is well proportioned, well consolidated without segregation, and properly cured.
Crack widths and depths are minimized.
Joints are properly spaced, sized, designated, water‐stopped, and constructed.
Adequate reinforcing steel is provided, properly detailed, fabricated, and placed.
Impervious protective coatings or barriers are used where required.
For minimum permeability of concrete use:
Low water‐cementitious materials ratio
Extended periods of moist curing
Smooth forms or troweling
Pozzolans may also reduce permeability
For increased workability and improved consolidation consider using:
Water‐reducing agents
Pozzolans
Air entrainment
Reduces segregation and bleeding
Resistance to the effect of freeze‐thaw cycles
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General standards for materials of construction
Where aggregates are alkali‐reactive, impose restrictions on materials to minimize deterioration
Do not use admixtures containing chlorides
Water‐cementitious materials ratio
Cementitious content
Cement type
Minimum compressive strength
Use of pozzolans
Air entrainment
Chloride ion content
Chemical effects
Erosion
Coatings and liners
Leakage control at joints
Minimum Cementitious Material Content
Nominal Maximum Aggregate Size, in.
Coarse Aggregate (ASTM C 33) Size No.
Minimum Cementitious Materials (lb/yd3)
1‐1/2 467 515
1 57 535
3/4 67 560
1/2 7 580
3/8 8 600
Total Air Content for Frost‐Resistant Concrete
Nominal Maximum Aggregate Size, in.
Air Content, percent
Severe Exposure Moderate Exposure
3/8 7‐1/2 6
1/2 7 5‐1/2
3/4 6 5
1 6 4‐1/2
1‐1/2 5‐1/2 4‐1/2
2 5 4
3 4‐1/2 3‐1/2
Other benefits of air entrainment:
Improves workability and consolidation
Reduces segregation and bleeding
Reduces permeability
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Special Exposure Conditions
Exposure ConditionMax. w/cm
RatioMin. fc’,
psi
Concrete w/ low permeability exposed to water, wastewater, and corrosive gases
0.45 4,000
Concrete exposed to freezing and thawing in a saturated condition or to deicing chemicals
0.42 4,500
Corrosion protection of reinforcement in concrete exposed to chlorides
0.40 5,000
Requirements for Concrete
Exposed to Deicing Chemicals
Cementitious Materials Maximum % of Total Cementitious Materials
Fly ash or other pozzolans conforming to ASTM C 618
25
Slag conforming to ASTM C 989 50
Silica fume conforming to ASTM C 1240 10
Total of fly ash or other pozzolans, slag, and silica fume
50
Total of fly ash or other pozzolans and silica fume 35
Benefits of pozzolans:
Improve workability and consolidation
Reduce permeability
Improve sulfate resistance
Improve resistance to alkali reactivity with aggregates
Concrete Exposed to Sulfate‐Containing Solutions
Sulfate Exposure
Water Soluble Sulfate in soil (%)
Sulfate in water, ppm
Cement Type
Maximum w/cm
Specified Compressive Strength fc’ psi
Negligible 0.00‐0.10 0‐150 ‐ 0.45 ‐
Moderate 0.10‐0.20 150‐1,500
II, IP(MS), IS(MS),
I(PM)(MS), I(SM)(MS)
0.42 4,500
Severe 0.20‐2.00 1,500‐10,000
V 0.40 5,000
Very Severe
Over 2.00 Over 10,000
V plus pozzolan
0.40 5,000
Use ASTM C1012 to test for sulfate resistance of mixtures using SCMs.
Other considerations for sulfate resistance:
Adequate cover of reinforcement
Sufficient moist curing
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Comparison of Durability Requirements
Condition
ACI 318‐08 ACI 350‐06
w/cm f’c w/cm f’c
Low permeability (P1) 0.50 4,000 0.45 4,000
Freeze/thaw in moist condition (F2)
0.45 4,500 0.42 4,500
Moderate sulfate exposure (S1)
0.50 4,000 0.42 4,500
Maximum Chloride Ion Content for
Corrosion Protection of Reinforcement
Type of MemberMaximum Water Soluble Chloride Ion in Concrete,
% by wgt cement
Prestressed concrete 0.06
Reinforced concrete 0.10
Common metals used:
Aluminum
Stainless Steel (Type 316)
Galvanized Steel
Epoxy Coated Steel
Aluminum stair with carbon steel bolts
Steel connection to concrete wall
Cast iron hatch cover
Chemical Exposure Groupings
Group 1
Not considered harmful to concrete
May be desired to prevent the absorption of liquids into the concrete
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Group 2
Will stain concrete
Where appearance is a concern
Group 3
Attack and weaken concrete
Generally require a protective lining
Group 3 ‐ Three subgroups:
Group 3A – Slow Attack of Concrete
Group 3B – Attack of Concrete
Group 3C – Rapid Attack of Concrete
Corrosive Gases:
Hydrogen Sulfide
Chlorine
Ozone
Oxygen
Carbon Dioxide
Methane
Hydrogen sulfide attack at cast iron gate
and manhole rungs
Hydrogen sulfide corrosion at concrete
surfaces
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Corrosion and coating failure at clarifier launders
Minimum f’c = 5,000 psi
Maximum w/cm ratio = 0.40
Maximum air content = 6 percent
Minimum 610 lbs cm/cy of concrete
Hard, dense, clean aggregates
Severe exposure to chemicals or gases
External waterproofing
Crack bridging capability
NSF compliance for potable water
Vapor transmission – breathable vs. vapor barrier
Coatings vs. plastic linings
ACI 515.1R
"Effects of Substances on Concrete Guide to Protective Treatments," Portland Cement Association
"Evaluation of Protective Coatings for Concrete," County Sanitation Districts of Los Angeles County
Coating deterioration
Waterstops
Joint sealants
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Expansion joint with steel rail across joint
Concrete cover requirements – increased relative to ACI 318
Shrinkage reinforcement requirements
Maximum spacing of reinforcement is 12 inches
Exposed rebar –insufficient cover Damage due to
leakage through cracks
Shrinkage cracks
Environmental Durability Factor (EDF), "Sd":
Limits steel stresses at service load levels
Reduces tension cracking
Improves liquid‐tightness
Improves corrosion protection and durability
Normal Environmental Exposure:
pH greater than 5
Sulfate exposure less than 1,000 ppm
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Sd = 1.0 for all prestressed reinforcement
Why don't EDFs apply to prestressing?
Concrete is precompressed
Stress in prestressed reinforcement is not directly related to concrete cracking
A minimum residual compressive stress 125 psi is required for liquid‐containing elements
Corrosion protection for unbonded single‐strand prestressing tendons
Unbonded prestressing steel shall be completely encased with sheathing
Sheathing shall be liquid-tight and continuous over entire length
Sheathing shall meet the hydrostatic pressure testing requirements of ACI 423.6 with a hydrostatic pressure of 10 psi
Tendons shall be protected against corrosion in accordance with ACI 423.6, as required for “aggressive environments”
ACI 350.4R, Guideline for the Design of Environmental Engineering Concrete Structures
Satish Sachdev, Chair of the subcommittee ACI-350A, General and Concrete, retired as President and CEO of Klein and Hoffman, Inc. in January 2006 after serving the firm for 36 years, and is currently working in the firm as a senior consultant. Klein and Hoffman, Inc. is a consulting structural engineering firm head-
quartered in Chicago, IL. One of its main businesses is consulting for water and wastewater projects. Mr. Sachdev was chairman of the committee ACI-350, Environmental Engineering Concrete Structures, for 7 years, an ACI member for more than 30 years,was elected Fellow of the Institute in 2007, and received Delmar L. Bloem Award of the Institute, in 2008. He received his B.Sc. in civil engineering from Panjab University in India, and his M.Sc. in civil engineering from University of Wisconsin at Madison.
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cag107sem1-aci350(Draft 9-final).ppt/61
Design Considerations• Rectangular Tanks• Circular Tanks
By Satish Sachdev, FACI, S.E., P.E.
cag107sem1-aci350(Draft 9-final).ppt/62
Rectangular Tank Configurations
• Cantilever Wall• Wall and strut• Covered Tank (with Roof)
cag107sem1-aci350(Draft 9-final).ppt/63
Cantilever Wall
4' WIDE CATWALK ALL AROUND
A
A
cag107sem1-aci350(Draft 9-final).ppt/64
Cantilever Wall
Section A-A
WALL THICKNESS:
L /10 = 16 /10 = 1.6 ft = 19.2 in
Wall Thickness > 12 in
Select Wall Thickness = 20 in
cag107sem1-aci350(Draft 9-final).ppt/65
Wall and Strut
4' WIDE CATWALK ALL AROUND
A Strut
A
B B
cag107sem1-aci350(Draft 9-final).ppt/66
Wall and Strut
Section A-A Section B-B
WALL THICKNESS:Wall Thickness = L/24 = 8 in
Wall Thickness > 12 inSelect Wall Thickness = 12 in
Strut depth = L / 18.5 40 / 18.5 = 2.16 ft = 25.94 in.
Select strut depth = 30 in.
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cag107sem1-aci350(Draft 9-final).ppt/67
Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/68
Covered Tank
S ec tion A -A S ec tio n B -B
Slab Thickness= L / 24 (one-end continuous)25 / 24 = 1.04 ft. = 12.5 in.
Select slab thickness= 12 in. Deflections are not expected to be significant
cag107sem1-aci350(Draft 9-final).ppt/69
Analysis: Concerns
• For cantilever wall, the end walls could act as two-way slab
• Near the junction of the two walls, the vertical moments gradually diminish
• For wall and strut, the response could be different at strut locations in comparison with other locations along the wall
• For covered tank, the roof-wall interaction need to be considered
• The finite element method (FEM) is used to consider the above effects
cag107sem1-aci350(Draft 9-final).ppt/70
FEM- Cantilever Wall
Expansion Joint
cag107sem1-aci350(Draft 9-final).ppt/71
FEM- Wall and Strut
Expansion Joint
cag107sem1-aci350(Draft 9-final).ppt/72
FEM- Covered Tank
Expansion Joint
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cag107sem1-aci350(Draft 9-final).ppt/73
Response
Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
Expansion Joint
cag107sem1-aci350(Draft 9-final).ppt/74
Zone 1- Near Expansion Joint
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/75
Zone 2- Middle of Long Wall Between Strut Locations
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/76
Zone 3- Middle of Long Wall at Strut Locations
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/77
Zone 4- Last Strut Location, Near End Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/78
Zone 5- Near End Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
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cag107sem1-aci350(Draft 9-final).ppt/79
Response
Zone 6 Zone 7
ExpansionJoint
cag107sem1-aci350(Draft 9-final).ppt/80
Zone 6 – Middle of End Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/81
Zone 7- End Wall - Corner
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Cantilever Wall Wall and Strut Covered Tank
cag107sem1-aci350(Draft 9-final).ppt/82
Summary of Results:Bending Moment
Zone
Cantilever Wall & Strut Covered Tank
-ve +ve -ve +ve -ve +ve
1 43.2 - 15.3 8.1 22.6 17.8
2 42.6 - 15.8 7.2 20.8 13.6
3 42.8 - 15.3 8.1 21 16.5
4 36.3 1.1 15.3 8.1 20 11.3
5 9.1 0.7 6.3 3.4 7.5 3.6
6 23.4 5.2 20.7 6.1 17.2 10.1
7 8.8 2.0 8.0 2.6 7.4 3.6
cag107sem1-aci350(Draft 9-final).ppt/83
Beam Analysis
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
Hei
gh
t (f
t)
Free End Pinned End Fixed End
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
Hei
gh
t (f
t)
Free End Pinned End Fixed End
cag107sem1-aci350(Draft 9-final).ppt/84
Beam Analysis
Maximum Bending Moment (kip-ft/ft)
+ve -ve
Cantilever - 42.6
Fixed-Fixed 0.7 12.7
Fixed-Pinned 5.3 16.9
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cag107sem1-aci350(Draft 9-final).ppt/85
Cantilever Wall- Frame vs FEM
Zone 1 Zone 2 Zone 3
ExpansionJoint
cag107sem1-aci350(Draft 9-final).ppt/86
Zone 1- End Near Exp. Joint
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Beam
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Beam
cag107sem1-aci350(Draft 9-final).ppt/87
Zone 2 -Middle
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Beam
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Beam
cag107sem1-aci350(Draft 9-final).ppt/88
Zone 3 – Near End Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Beam
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Beam
cag107sem1-aci350(Draft 9-final).ppt/89
Cantilever Wall- Frame vs FEM
Zone 4 Zone 5
ExpansionJoint
cag107sem1-aci350(Draft 9-final).ppt/90
Zone 4 – Middle of End Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Beam
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Beam
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cag107sem1-aci350(Draft 9-final).ppt/91
Zone 5 –End Wall Near Middle Wall
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Beam
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Beam
cag107sem1-aci350(Draft 9-final).ppt/92
Zone 1
Wall and Strut- Frame vs FEM
Zone 1
cag107sem1-aci350(Draft 9-final).ppt/93
Zone 1 – At Strut Location
0
4
8
12
16
0.00 0.05 0.10 0.15
Displacement (in)
He
igh
t (f
t)
Shell Frame
0
4
8
12
16
-45 -30 -15 0 15
Bending Moment (kip-ft/ft)
He
igh
t (f
t)
Shell Frame
cag107sem1-aci350(Draft 9-final).ppt/94
Notes
• Aspect ratio of the tank wall affects the response
• Two-way reinforcement of the wall end where it frames into another wall is necessary
• For covered tank, frame analysis using a 1 ft strip of the tank is appropriate
cag107sem1-aci350(Draft 9-final).ppt/95
Design Parameters
f’c = 4500 psi fy = 60 ksi
b =12 in h =20 in
γ (Load Factor) =1.4
Φ = 0.9 (Flexure) Φ = 0.75 (Shear)
M= 43.2 kip-ft/ft V=6 kip/ft
Assume Normal Exposure
Design of Cantilever Wall
cag107sem1-aci350(Draft 9-final).ppt/96
Design of Cantilever Wall: Flexure
• Assume bar spacing = 8 in at wall base and bar diameter = 1 in.
• fsmax = 28.27 ksi for β=1.2
• Sd = 1.36• Mu = 1.4 x 1.36 x 43.2 = 82.2 kip-ft/ft
22max)2/2(4
320
b
sds
f
s
y
d f
fs
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cag107sem1-aci350(Draft 9-final).ppt/97
• ρ = 0.0055
• ρb = 0.0311 ρ < 0.7 ρb o.k.
• ρmin =0.0033 ρ > ρmin O.K.
• ρtemp = 0.005 (on two faces), ρ > ρtemp o.k.
• As = 1.12 in2/ft
)200
;'3
(maxminyy
c
ff
f
Design of Cantilever Wall: Flexure
cag107sem1-aci350(Draft 9-final).ppt/98
• Vu = 1.4 x 6 = 8.4 kip/ft
• Vc = 27.4 kip/ft
• φVn = 0.75 x 27.4 = 20.5 kip/ft
• φVn > Vu O.K.
bdfV cc '2
Design of Cantilever Wall: Shear
cag107sem1-aci350(Draft 9-final).ppt/99
Circular Tank
cag107sem1-aci350(Draft 9-final).ppt/100
Notation
D = Inside diameter of tank in feet
dw = Effective depth of wall
FEM = Finite element method
HW = Wall height in feet
HL = Liquid height in feet
tW = Wall thickness in inches
TW = Tension in wall in kips per foot of wall height
TF = Tension in footing
VW = Wall base shear in kips per foot of wall length
MIF = Wall moment in vertical direction in interior face
cag107sem1-aci350(Draft 9-final).ppt/101
• D = 120 feet
• HL = 12 feet (all cases)
• HW = 12 feet or 15 feet
• tW = 14 inches
• No roof
• Similar to large circular clarifier
• Severe exposure
Tank Parameters
cag107sem1-aci350(Draft 9-final).ppt/102
• Fixity of footing usually not known accurately
• Design for worse case of: Pinned base
Fixed base
Wall
Slab
Wall Footing
Base Fixity
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cag107sem1-aci350(Draft 9-final).ppt/103
• PCA table method Water height must equal wall height
Overly conservative if wall height exceeds water height
Does not consider launder effect
Does not consider openings in wall
Limited parameter range
Easy, fast, and cheap
Task Analysis Methods
cag107sem1-aci350(Draft 9-final).ppt/104
• Finite element method Can be used for wide range of parameters
Time consuming and expensive
Water height may be less than wall height
Opening effects can be included in design
Launder effects can be included in design
Task Analysis Methods (cont.)
cag107sem1-aci350(Draft 9-final).ppt/105
PCA Table Analysis Method (cont.)
cag107sem1-aci350(Draft 9-final).ppt/106
Finite Element Model
FEM Program Used - STAAD PRO 2006
Number of surface elements - 4,914
Number of nodes - 4,536
Mesh size - 1 ft. x 1 ft.
cag107sem1-aci350(Draft 9-final).ppt/107
Hydrostatic Load
120’
CASE 1
HW=12’, HL=12’, and tW=14”
Finite Element Model (cont.)
cag107sem1-aci350(Draft 9-final).ppt/108
CASE 2
HW=15’, HL=12’, and tW=14”
Hydrostatic Load
120’
Finite Element Model (cont.)
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cag107sem1-aci350(Draft 9-final).ppt/109
CASE 3HW=15’, HL=12’, tW=14”, and Launder (12” thick)
Hydrostatic Load
120’
Launder 3’
3’
3’
Finite Element Model (cont.)
0123456789
10111213141516
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Unfactored Hoop tension (kips / ft)
Hei
ght (
ft)
PCA Table - Case 1
FEM Method - Case 1
FEM Method - Case 2
FEM Method - Case 3
Hoop Tension – Fixed BaseCASE 1
(HW=HL)
CASE 2
(HW>HL)
CASE 3
(with Launder)
Comparison of Hoop Tension
0123456789
10111213141516
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19Unfactored Hoop Tension (kips / ft)
Hei
ght (
ft)
PCA Table - Case 1
FEM Method - Case 1
FEM Method - Case 2
FEM Method - Case 3
Hoop Tension – Pinned BaseCASE 1
(HW=HL)
CASE 2
(HW>HL)
CASE 3
(with Launder)
Comparison of Hoop Tension (cont.)
Moment – Fixed BaseCASE 1
(HW=HL)
CASE 2
(HW>HL)
CASE 3
(with Launder)
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10111213141516
-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3Moment (ft-kips/ft)
Hei
ght (
ft)
PCA Table - Case 1FEM Method - Case 1FEM Method - Case 2FEM Method - Case 3
Comparison of Moment
Moment – Pinned BaseCASE 1
(HW=HL)
CASE 2
(HW>HL)
CASE 3
(with Launder)
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10111213141516
0 1 2 3 4 5Moment (ft-kips/ft)
Hei
ght (
ft)
PCA Table - Case 1FEM Method - Case 1FEM Method - Case 2FEM Method - Case 3
Comparison of Moment (cont.)
CASE 2
(HW>HL)
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10111213141516
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Unfactored Hoop Tension (kips / ft)
Hei
ght (
ft)
Fixed BasePinned Base
Combined Hoop TensionDiagrams Used for Design
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Combined MomentDiagrams Used for Design
CASE 2
(HW>HL)
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10111213141516
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5Unfactored Vertical Moment (ft-kips / ft)
Hei
ght (
ft)
Fixed basePinned Base
cag107sem1-aci350(Draft 9-final).ppt/116
CASE 2: Reinforcement –Hoop Tension in Wall
TW = 12.8 kips (from FEM analysis)
Tu = 1.4 TW
Tu = 17.9 kips
In severe environmental exposure areas
fs = 17 ksi
Factored hoop tension in wall
Environmental durability factor
= 0.9 (tension-controlled section)
fy = 60 ksi
= 1.4
fsSd = 2.27
fySd =
cag107sem1-aci350(Draft 9-final).ppt/117
CASE 2: Reinforcement –Hoop Tension in Wall (cont.)
TU = Sd Tu
Ultimate hoop tension in wall with environmental durability factor
TU = 40.6 kips
As, min = 0.005 (tw12 in)
As, min = 0.84 in2
Provide #6 @ 12 in EF.
As = 0.88 in2
Minimum horizontal reinforcement
cag107sem1-aci350(Draft 9-final).ppt/118
CASE 2: Reinforcement –Hoop Tension in Wall (cont.)
Reinforcement for hoop tensionTU
fyAs = 0.75 in2
Provide #6 @ 12" EF as hoop reinforcement.
As = 0.88 in2
Actual stress in reinforcement due to hoop tension
TW
Asf = 14.5 ksi
= 0.856 (less than 1.0, hence, ok)fs
As =
f =
f
#6 @ 12” EF
=12.8 kips
0.88 in2
cag107sem1-aci350(Draft 9-final).ppt/119
CASE 2: Reinforcement –Moment in Wall
MIF = 6.3 ft-kips (from FEM analysis)
Mu = 1.4 MIF
Mu = 8.82 ft-kips
= 1.35 (wall thickness is less than 16 in)
Try #6 reinforcing bar.
db = 0.75 in
s = 12 in (12 in max bar spacing)
Factored moment in wall
cag107sem1-aci350(Draft 9-final).ppt/120
Durability factor
= 0.9 (tension-controlled section)
fy = 60 ksi
= 1.4 (load factor)
fs = 17 ksi
For severe environmental exposure260
s2 + 4(2 + db/2)2
fs = 14.9 ksi
Need not be less than 17 ksi for one-way and 20 ksi for two-way members. Therefore use fs = 17 ksi.
fs =
CASE 2: Reinforcement –Moment in Wall (cont.)
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cag107sem1-aci350(Draft 9-final).ppt/121
fy
fsSd = 2.27
Ultimate moment in interior face
MU = Sd Mu
MU = 20.0 ft-kips
Sd =
Reinforcement calculation
tw = 14 in
dw = tw - 3 in
dw = 11 in
CASE 2: Reinforcement –Moment in Wall (cont.)
cag107sem1-aci350(Draft 9-final).ppt/122
Reinforcement calculation
= Asfy (d - )Mu
a = 1.47 As
a
2
= (As) (60 ) (11 - )(20.0)(12)
0.9
1.47 As
2
As = 0.42 in2
Asfy
0.85 ba =
(As) (60)
(0.85) (4) (12)a =
fc
CASE 2: Reinforcement –Moment in Wall (cont.)
cag107sem1-aci350(Draft 9-final).ppt/123
#6 @ 12” EF
Minimum vertical reinforcement for flexural members
As, min 3 fc bwdw
fy 0.42 in2
As, min 200 bwdw
fy 0.44 in2
Use min #6 @ 12 in.#6 @ 12” EF
LapSplice
CASE 2: Reinforcement –Moment in Wall (cont.)
cag107sem1-aci350(Draft 9-final).ppt/124
Resisted byHoop tension reinforcement in footingRadial tension in slab
FormulaReaction at the bottom of wall, VW = 1.7 kips/ft (from FEM analysis)
Diameter of tank, D = 120 ft
TF =2
TF = 2
TF = 102 kips
VW D
(1.7 kips/ft) (120 ft)
Hoop Tension in Wall Footing
cag107sem1-aci350(Draft 9-final).ppt/125
Factored tension in footing
TF = 102 kips
Tu = 1.4 TF
Tu = 143 kips
In severe environmental exposure areas
fs = 17 ksi
CASE 2: Reinforcement –Tension in Wall Footing
cag107sem1-aci350(Draft 9-final).ppt/126
Durability factor
= 0.9 (tension-controlled section)
= 1.4
Sd = fy
fs
Sd = 2.27
Ultimate hoop tension in footing with environmental durability factor
TU = 324 kips
TU = SdTu
CASE 2: Reinforcement –Tension in Wall Footing (cont.)
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cag107sem1-aci350(Draft 9-final).ppt/127
Reinforcement for hoop tension
As =TU
fy
As = 6.00 in2
Provide 6 - #7 @ T&B of footing.
As = 7.2 in2
Calculated stress in reinforcementdue to hoop tension
f =Tf
As
f = 14.2 ksi fs
f= 0.833 (less than 1.0; hence, ok)
6 - #7 T&B
CASE 2: Reinforcement –Tension in Wall Footing (cont.)
cag107sem1-aci350(Draft 9-final).ppt/128
Hoop Tension Reinforcing Bars Wall
Treble Stagger of Reinforcing Bar Splices
Class "B" Lap Splice
Staggering of Hoop Tension Wall Bars
cag107sem1-aci350(Draft 9-final).ppt/129
Add Bars
Wall
Wall Footing
Outlet Opening in Wall
cag107sem1-aci350(Draft 9-final).ppt/130
• Thick slab may be required• Slab may crank large moments into wall• Unless slab weight exceeds uplift, must control
slab deflection• Thick slab required to take advantage of soil on
footing extension
Groundwater
Groundwater Uplift
cag107sem1-aci350(Draft 9-final).ppt/131
Acknowledgement
The Following Committee Members contributed to the Presentation:
1. M. Reza Kianoush, Ph.D., P.Eng.
2. Carl Gentry, M.Sc., S.E., P.E.
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