1. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
DESIGN & CONSTRUCTION
CONSIDERATIONS OF
REINFORCED CONCRETE
STRUCTURES FOR WATER
UTILITIES
Prepared by
ADNAN NAJEM LAZEM
M.Sc. in Structural Engineering
CONTENTS
1. Introduction
2. Examples of reinforced concretestructures for water utilities
3. Advantages of reinforced concretestructures
4. Disadvantages of reinforcedconcrete structures
5. Design considerations
6. Construction considerations
7. Summary
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2. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
INTRODUCTION
In 1907, Leonard Metcalf, a Boston civilengineer whose specialty was water
supplyissues, and Harrison Eddy, superintendent ofthe sewer department in
Worcester,Massachusetts, were introduced by aprofessor at Worcester Polytechnic.
Shortlythereafter, they decided to join forces andcreate an environmental engineering
firmcalled Metcalf & Eddy.
Wilmington, Delaware
 10 million galloncovered waterstorage tank
 constructioncompleted atDecember 2007
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3. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
IRAQ, BAGHDAD
• Complex ofTwin Apartmentwater storagetanks
• Construction completed at march 2010
• 375,000 cubic meters storage capacity
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4. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
Pile foundation of the RC water tank ―Reservoir‖
Final Stages of the RC Tank Construct
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5. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
ADVANTAGES
1. Easily adaptable to a myriad of differentshapes & architectural treatments
2. Many contractors have the capability to placereinforced concrete
3. Reinforced concrete contractor will likelyalready be on site
4. Durability, Proven track record of over 100 years
DISADVANTAGES
1. Owner preferences may dictate against usingreinforced concrete
2. Cost considerations due to quantity ofmaterials required
3. Construction nuances
4. Cracking & durability
DESIGN CONSIDERATIONS
1. Seismic loads
2. Floatation
3. Abnormal pressure loads
4. Retaining elements
5. Influence of adjacent / superimposed structures
6. Integration into existing facilities
7. Security
8. Details, Details, Details!
9. Liner systems
SEISMIC LOADS
According to ACI 350 in chapter four Art (4.1), for Earthquake pressures above
base,the walls of liquid-containing structures shall bedesigned for the following
dynamic forces in addition tothe static pressures:
a. inertia forces Pw and Pr;
b. hydrodynamic impulsive pressure Pi from the contained liquid;
c. hydrodynamic convective pressure Pcfrom the contained liquid;
d. dynamic earth pressurefrom saturated and unsaturated soils against
the buried portion of the wall;
e. the effects of verticalacceleration.
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6. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
BUOYANCY
A reinforced concrete reservoir – or anytank – is a boat. A boat floats if designedRight.
Therefore a design checks is required:
1. Buoyant force (uplift) on bottom slab
2. Buoyant force causing tank to float
3. Reduced base slab friction if tank sliding(uneven backfill) is a design consideration
SECURITY
Any reservoir requires securityconsiderations.
1. How will the reservoir be inspected?
2. How will venting be accomplished?
3. Will public access be required of the top slab?
DETAILS
1. Minimum Concrete Strength
2. Minimum Reinforcing Steel
3. Expansion and Construction Joints
4. Waterstops
MINIMUM “ACI.350CODE” REQUIREMENT:
1. Min. Concrete Strength=4000 psiat 28 days
2. Air Entrainment=5%±1%
3. Maximum Water-cement Ratio=.45
4. Maximum Slump=4 inches
5. Aggregates per ASTM C33, max. aggregate size=1 inch
6. No admixtures containing calcium chloride
EXPANSION JOINTS:
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7. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
Expansion joints, main location.
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8. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
WATERSTOP DETAIL
Base slab to wall interface is most critical and mostdifficult to construct of all
construction joints:
1. Raised starter wall
2. Bend top steel down at wall
3. Drop top steel down below waterstop forentire slabOptions 2 & 3 easier to construct
than option1 but require relatively more material
CONSTRUCTION CONSIDERATIONS
Proper adherence tospecifications
1. Water proofing process
2. Mix design
3. Placement
4. Curing
5. Deflection of structural membersduring pouring and vibrating of fresh concrete
6. Details, Details, Details
7. Integration into existingFacilities
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9. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
Step 1, Water proofing process
Step 2, Water proofing process
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10. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
Placement of fresh concrete
MIX DESIGN
Adding 1 gallon of water to 1 yd3 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 concrete
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11. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
Deflection of structural members during construction:
CURING
According to ACI 350-01 “Environmental Structures” Code Requirements:
―Minimum permeability of the concrete will beobtained by using water-cementitious
materialsratios as low as possible, consistent withsatisfactory workability and
consolidation.Impermeability increases with the age of theconcrete and is improved by
extended periodsof moist curing.‖
Plastic membraneand water retaining agent were used for curing process
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12. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
MINIMUM CONCRETECOVER OF STEEL REINFORCEMENT:
Checking of Minimum Concrete Cover according to ACI 350.1:
1. Concrete Base=3 inches (4‖ COE)
2. Concrete Walls=2 inches (3‖ COE)
3. Stilling Basin=6‖ (COE)
Checking first carried out before Pouring of fresh concrete
LEAK TESTING
According to ACI 350-01“Environmental Structures” Code Requirements:
1.1.3—Each cell of multi-cell tanks shallbe considered a single tank and tested
individually unless otherwise directed bythe engineer.
1.2.3—Unless specifically allowed by theengineer, the tank shall not be tested before all
of the structure is complete andthe tank’s concrete has attained its specified
compressive strength.
2.3.5—The water shall be kept at the testlevel of unlined concrete tanks for at least three
days prior to the actual test.
2.3.6—The exterior surfaces of the tank shall beinspected during the period of filling the
tank. Ifany flow of water is observed from the tankexterior surfaces, including
joints or cracks, thedefect causing the leakage shall be repaired.
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13. January 24, 2013 [DESIGN & CONSTRUCTION CONSIDERATIONS OF RC STRUCTURES FOR WATERUTILITIES]
BACKFILLING
Backfill and compaction continues as dump trucks haul dirt in and a skid steer and
dozer spread the backfill into eight-inch lifts for compaction.
SUMMARY
1. Engineer helps the ownerdetermine best structuralsystem for the facility.
2. Proper engineer detailing is a major contributorto the long-term success of the
project.
3. Proper concrete mixdesign, placement, and curing practicesis the single
mostimportant factortoward the long-termdurability of thestructure.
4. 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.
REFRENCE:
1. Maine Water Utilities AssociationApril 12, 2007. Michael E. Malenfant, P.E. Metcalf
& Eddy
2. ACI 350-01 “Environmental Structures” Code Requirements.
3. University of technology, engineering consulting office. Baghdad, Iraq.
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