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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
DESIGN & CONSTRUCTION
CONSIDERATIONS OF
REINFORCED CONCRETESTRUCTURES FOR WATER
UTILITIES
Maine Water Utilities Association
Apr il 12, 2007
Michael E. Malenfant, P.E.
Metcalf & Eddy
2
CONTENTS
• Introduction
• Examples of reinforced concrete
structures for water utilities
• Advantages of reinforced concrete
structures
• Disadvantages of reinforced
concrete structures
• Design considerations
• Construction considerations
• Summary
3
INTRODUCTION
• In 1907, Leonard Metcalf, a Boston civilengineer whose specialty was water supply
issues, and Harrison Eddy, superintendent of
the sewer department in Worcester,Massachusetts, were introduced by a
professor at Worcester Polytechnic. Shortlythereafter, they decided to join forces andcreate an environmental engineering firm
called Metcalf & Eddy.
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
4
Wilmington, Delaware
•10 million galloncovered waterstorage tank
•Underconstruction,
completionDecember 2007
5
6
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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8
Atlanta, Georgia
•Complex ofthree coveredwater storagetanks
•Age from 10years to 80
years
9
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
10
11
12
Framingham, Massachusetts
•115 million gallon covered water storage tank
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
13
14
15
Macon, Georgia
•1.8 million gallonpartially buried
covered water
storage tank
•Constructed in1920
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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17
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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ADVANTAGES
• Easily adaptable to a myriad of different
shapes & architectural treatments• Many contractors have the capability to place
reinforced concrete
• Reinforced concrete contractor will likelyalready be on site
• Durability
• Proven track record of over 100 years
20
DISADVANTAGES
• Owner preferences may dictate against usingreinforced concrete
• Cost considerations due to quantity ofmaterials required
• Construction nuances
• Cracking & durability
21
DESIGN CONSIDERATIONS
• Seismic loads
• Floatation
• Abnormal pressure loads
• Retaining elements• Influence of adjacent / superimposed structures
• Integration into existing facilities
• Security
• Details, Details, Details!
• Liner systems
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
22
SEISMIC LOADS
23
SEISMIC LOADS
24
SEISMIC LOADS
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
25
SEISMIC LOADS
26
SEISMIC LOADS
27
BUOYANCY
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU FreeDocumentation License, Version 1.2 or any later version published by the Free Software Foundation. Photo by
Sean O'Flaherty
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
28
BUOYANCY
• A reinforced concrete reservoir – or any
tank – is a boat. A boat floats if designedright!
• Design checks required: – Buoyant force (uplift) on bottom slab
– Buoyant force causing tank to float
– Reduced base slab friction if tank sliding(uneven backfill) is a design consideration
29
SECURITY
• Any reservoir requires security
considerations.
– How will the reservoir be inspected?
– How will venting be accomplished?
– Will public access be required of the top slab?
30
DETAILS
• Minimum Concrete Strength
• Minimum Reinforcing Steel
• Expansion and Construction Joints
• Waterstops
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
34
EXPANSION JOINTS
35
EXPANSION JOINTS
GOOD LOCATION
BAD LOCATION
36
CONSTRUCTION JOINTS
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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WATERSTOP DETAIL
Base slab to wall interface is most critical and most
difficult to construct of all construction joints:
1. Raised starter wall
2. Bend top steel down at wall
3. Drop top steel down below waterstop for
entire slab
Options 2 & 3 easier to construct than option
1 but require relatively more material
38
WATERSTOP DETAIL
Option 1
Option 3
Option 2
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WATERSTOP DETAIL
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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CONSTRUCTION CONSIDERATIONS
Proper adherence to
specifications
– Mix design
– Placement
– Curing
• Details, Details, Details
• Integration into existing
facilities
41
MIX DESIGN Add ing 1 gallon o f water to 1 yd 3 of concrete will:
1. Increase slump about 1 inch
2. Increase air content about 1%
3. Increase shrinkage about 10% and increase cracking
4. Reduce compressive strength about 200 psi
5. Waste about 25 lbs of cement per cubic yard
6. Increase shrinkage about 10% and increase cracking
7. Decrease freeze-thaw durability about 20%
8. Decrease wear resistance to traffic
9. Increase dusting and other surface defects
10.Increase time needed to finish the concreteSource: Dick Martin, Engineering Services Group, Grace Performance
Chemicals.
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CURING
“Minimum permeability of the concrete will be
obtained by using water-cementitious materials
ratios as low as possible, consistent withsatisfactory workability and consolidation.
Impermeability increases with the age of theconcrete and is improved by extended periodsof moist curing.”
Source: ACI 350-01.
Environmental Structures: Code
Requirements
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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CURING
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DETAILS
• Waterstops & joint construction
• Rebar cover
• Leak testing
• Backfilling procedure
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WATERSTOPS
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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WATERSTOPS
VS.
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REINFORCING STEEL COVER
Source: ACI 350-01.
Environmental Structures:
Code Requirements
48
REINFORCING STEEL COVER
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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REINFORCING STEEL COVER
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LEAK TESTING
Source: ACI 350.1-01. Tightness Testing o f
Environmental Engineering Concrete Structures
1.2.3 —Unless specifically allowed by the
engineer, the tank shall not be tested
before all of the structure is complete and
the tank’s concrete has attained its
specified compressive strength.
1.1.3 —Each cell of multi-cell tanks shall
be considered a single tank and tested
individually unless otherwise directed by
the engineer.
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LEAK TESTING
Source: ACI 350.1-01. Tightness Testing of
Environmental Engineering Concrete Structures
2.3.5 —The water shall be kept at the test
level of unlined concrete tanks for at least
three days prior to the actual test.
2.3.6 —The exterior surfaces of the tank shall be
inspected during the period of filling the tank. If
any flow of water is observed from the tank
exterior surfaces, including joints or cracks, the
defect causing the leakage shall be repaired.
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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BACKFILLING
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SUMMARY
• Engineer helps the ownerdetermine best structuralsystem for the facility.
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SUMMARY
• Proper engineer detailing is a major contributorto the long-term success of the project.
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Design and Construction Considerations of
Reinforced Concrete Structures for Water
Utilities
April 12, 20
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SUMMARY
• Proper concrete mix
design, placement,and curing practicesis the single mostimportant factor
toward the long-termdurability of thestructure.
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SUMMARY
• Reinforced concrete is not a “forever” material.It requires on-going care and maintenance. Awell-defined asset management program willcontribute to the long-term operation of thestructure.
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SUMMARY
The answer to the question of “What
material best suits my project?” is:
“Please tell me a little more aboutyour project.”
Michael E. Malenfant, P.E.
Metcalf & Eddy
Michael.malenfant@m-e.com
781-224-6277
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