American Water Works Association
ANSI/AWWA D103-97
(Revision of ANSI/AWWA D103-87)
R
AWWA STANDARD
FOR
FACTORY-COATED BOLTED STEEL TANKS
FOR WATER STORAGE
Effective date: Feb. 1, 1998.
First edition approved by AWWA Board of Directors Jan. 28, 1980.
This edition approved June 15, 1997.
Approved by American National Standards Institute Dec. 1, 1997.
AMERICAN WATER WORKS ASSOCIATION
6666 West Quincy Avenue, Denver, Colorado 80235
Copyright © 1998 American Water Works Association, All Rights Reserved
AWWA Standard
This document is an American Water Works Association (AWWA) standard. It is not a specification.
AWWA standards describe minimum requirements and do not contain all of the engineering and
administrative information normally contained in specifications. The AWWA standards usually
contain options that must be evaluated by the user of the standard. Until each optional feature is
specified by the user, the product or service is not fully defined. AWWA publication of a standard
does not constitute endorsement of any product or product type, nor does AWWA test, certify, or
approve any product. The use of AWWA standards is entirely voluntary. AWWA standards are
intended to represent a consensus of the water supply industry that the product described will
provide satisfactory service. When AWWA revises or withdraws this standard, an official notice of
action will be placed on the first page of the classified advertising section of Journal AWWA. The
action becomes effective on the first day of the month following the month of Journal AWWA
publication of the official notice.
American National Standard
An American National Standard implies a consensus of those substantially concerned with its scope
and provisions. An American National Standard is intended as a guide to aid the manufacturer, the
consumer, and the general public. The existence of an American National Standard does not in any
respect preclude anyone, whether that person has approved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the
standard. American National Standards are subject to periodic review, and users are cautioned to
obtain the latest editions. Producers of goods made in conformity with an American National
Standard are encouraged to state on their own responsibility in advertising and promotional
materials or on tags or labels that the goods are produced in conformity with particular American
National Standards.
CAUTION NOTICE: The American National Standards Institute (ANSI) approval date on the front
cover of this standard indicates completion of the ANSI approval process. This American National
Standard may be revised or withdrawn at any time. ANSI procedures require that action be taken
to reaffirm, revise, or withdraw this standard no later than five years from the date of publication.
Purchasers of American National Standards may receive current information on all standards by
calling or writing the American National Standards Institute, 11 W. 42nd St., New York, NY 10036;
(212) 642-4900.
Copyright © 1998 by American Water Works Association
Printed in USA
ii
Copyright © 1998 American Water Works Association, All Rights Reserved
Committee Personnel
The D103 Task Force that developed this standard had the following personnel at
that time:
Francis Grillot Jr., Chair
Consumer Member
A.J. Hamlett Jr., Tulsa Public Works Department, Tulsa, Okla.
(AWWA)
General Interest Member
J.E. Rudina, AEC Engineering, Minneapolis, Minn.
(AWWA)
Producer Members
N.C. Bailey, Conservatek Industries Inc., Conroe, Texas
R.W. Cooper, Columbian Steel Tank Company, Kansas City, Kan.
John Farris, Peabody TecTank Inc., Parsons, Kan.
R.V. Field, A.O. Smith Engineered Storage Products Company, DeKalb, Ill.
Francis Grillot Jr., Temcor, Carson, Calif.
G.C. Margolf, Temcor, Carson, Calif.
D.A. Turner, Peabody TecTank Inc., Parsons, Kan.
L.D. Scott, Trustco Tank Inc., San Luis Obispo, Calif.
Mark Workman, Columbian Steel Tank Company, Kansas City, Kan.
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
The Standards Committee on Steel Elevated Tanks, Standpipes, and Reservoirs that
reviewed and approved this standard had the following personnel at the time of
approval:
E. Crone Knoy, Chair
Consumer Members
S.F. Crumb, Fort Worth Water Department, Fort Worth, Texas
Ed Darrimon, Bay Area Coating Consultants, Modesto, Calif.
W.H. Harris, City of Houston, Houston, Texas
Joseph Ortiz, East Bay Municipal Utility District, Oakland, Calif.
E.J. King,* Connecticut Water Company, Clinton, Conn.
K.A. Nadeau, Connecticut Water Company, Clinton, Conn.
A.R. Terrell Jr., Little Rock Municipal Water Works, Little Rock, Ark.
G.A. Weeks, St. Louis County Water Company, St. Louis, Mo.
* Alternate
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Copyright © 1998 American Water Works Association, All Rights Reserved
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(NEWWA)
(NEWWA)
(AWWA)
(AWWA)
General Interest Members
J.R. Buzek, AEC Engineering, Minneapolis, Minn.
B.R. Conklin, Camp, Dresser & McKee Inc., Cambridge, Mass.
R.D. Davis, MBA Inc., Cinnaminson, N.J.
W.J. Dixon, Dixon Engineering Inc., Lake Odessa, Mich.
M.E. Gilliland, US Army Corps of Engineers, Huntsville, Ala.
J.D. Griffith,* Council Liaison, John Carollo Engineers, Phoenix, Ariz.
E.C. Knoy, Tank Industry Consultants Inc., Speedway, Ind.
H.J. Miedema, Robert Bein, William Frost & Associates, Irvine, Calif.
L.F. Peters, Weston & Sampson Engineers, Peabody, Mass.
Chris Sundberg, CH2M Hill Inc., Bellevue, Wash.
John Wilber,* Standards Engineer Liaison, AWWA, Denver, Colo.
J.A. Williams, Consulting Engineer, Alpharetta, Ga.
R.S. Wozniak, Bow Tech Ltd., Batavia, Ill.
(AWWA)
(NEWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
(NEWWA)
(AWWA)
(AWWA)
(AWWA)
(AWWA)
Producer Members
D.G. Cull, C T Services Inc., Jeffersonville, Ind.
G.A. Larson, Pitt-Des Moines Inc., Clive, Iowa
Francis Grillot Jr., Temcor, Carson, Calif.
B.E. Kromer, Tank Builders Inc., Euless, Texas
S.W. Meier, Chicago Bridge & Iron Company, Plainfield, Ill.
L.D. Scott, Trusco Tank Inc., San Luis Obispo, Calif.
D.A. Turner, Peabody TecTank Inc., Parsons, Kan.
* Liaison, nonvoting
iv
Copyright © 1998 American Water Works Association, All Rights Reserved
(AWWA)
(AWS)
(AWWA)
(SPFA)
(AWS)
(AWWA)
(AWWA)
Contents
All AWWA standards follow the general format indicated subsequently. Some variations from this format may be
found in a particular standard.
SEC.
PAGE
Foreword
I
I.A
I.B
I.C
II
II.A
II.B
II.C
II.D
II.E
II.F
II.G
III
III.A
III.B
III.C
III.D
IV
V
Introduction.......................................... ix
Background........................................... ix
History .................................................. ix
Acceptance ............................................ ix
Special Issues ........................................ x
Purchase ................................................ x
Design and Construction ...................... x
Coatings ................................................. x
Foundations........................................... x
Annual Inspection and
Maintenance....................................... x
Disinfection Procedures and
Cathodic Protection .......................... xi
Recommended Items to Be
Furnished by the Purchaser
and Manufacturer............................. xi
Use of This Standard........................... xi
Purchaser Options and
Alternatives....................................... xi
Information to Be Furnished by the
Manufacturer or Constructor ......... xiii
Items for Consideration by the
Purchaser ....................................... xiii
Modification to Standard................... xiv
Major Revisions.................................. xiv
Comments........................................... xiv
General
Scope ...................................................... 1
Definitions ............................................. 2
Responsibilities of Parties .................... 2
Drawings to Be Furnished ................... 3
References.............................................. 3
2
2.1
2.2
2.3
2.4
2.5
Materials
General .................................................. 5
Bolts and Anchor Bolts......................... 5
Foundation-Reinforcing Steel .............. 5
Plates and Sheets ................................. 5
Structural Shapes ................................. 6
PAGE
2.6
2.7
2.8
2.9
2.10
Castings................................................. 6
Forgings................................................. 6
Electrodes.............................................. 6
Pipe for Fluid Conductors.................... 6
Gaskets and Sealants........................... 6
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
General Design
Types of Joints...................................... 7
Design Loads......................................... 7
Design Criteria ..................................... 8
Tank Shell............................................. 9
Bolted Joints ....................................... 10
Weld Design Values ........................... 11
Top and Intermediate Shell
Girders ............................................. 12
Roof Supports...................................... 14
Steel Thickness................................... 15
Foundation Bolts ................................ 15
Reinforcement Around Openings ...... 16
3.8
3.9
3.10
3.11
4
4.1
4.2
4.3
5
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
Standard
1
1.1
1.2
1.3
1.4
1.5
SEC.
6
6.1
6.2
6.3
6.4
Sizing of Standpipes and
Reservoirs
Standard Capacities ........................... 17
Shell Heights for Standpipes............. 19
Diameters for Reservoirs ................... 19
Accessories for Standpipes
and Reservoirs
Shell Manholes ................................... 19
Pipe Connections ................................ 19
Overflow .............................................. 19
Ladders................................................ 20
Safety Devices..................................... 21
Roof Openings..................................... 21
Vent ..................................................... 21
Additional Accessories
and Exceptions ................................ 21
Welding
General ................................................ 22
Welds ................................................... 22
Preparation of Surfaces to
Be Welded ........................................ 22
Low-Hydrogen Electrodes .................. 23
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Copyright © 1998 American Water Works Association, All Rights Reserved
SEC.
PAGE
6.5
Undercuts and Penetration of
Welds ................................................ 23
Cleaning of Welds ............................... 23
6.6
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Shop Fabrication
Straightening ...................................... 23
Finish of Plate Edges—Welded
Work ................................................. 23
Rolling.................................................. 24
Double-Curved Plates ......................... 24
Manufacturing Tolerances ................. 24
Coatings ............................................... 24
Shipping............................................... 24
8
8.1
8.2
8.3
8.4
8.5
Erection
General ................................................ 24
Bolting ................................................. 24
Gasketing and Sealants ..................... 24
Coating Repair .................................... 24
Cleanup................................................ 25
9
9.1
9.2
9.3
9.4
Inspection and Testing
Shop Inspection................................... 25
Testing ................................................. 25
Disposal of Test Water ....................... 25
Disinfecting ......................................... 25
10
10.1
10.2
10.3
10.4
10.5
Coatings
General ................................................ 25
Coating Repair .................................... 26
Galvanized Coatings ........................... 26
Glass Coatings .................................... 26
Thermoset Liquid Suspension
Coatings............................................ 26
Thermoset Powder Coatings .............. 27
Marking ............................................... 28
Protection............................................. 28
Holiday Testing ................................... 28
10.6
10.7
10.8
10.9
11
11.1
11.2
11.3
11.4
11.5
11.6
11.7
SEC.
12
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
13
13.1
13.2
13.3
13.4
13.5
13.6
13.7
13.8
13.9
13.10
13.11
PAGE
Seismic Design of Flat-Bottom
Water-Storage Tanks
General ................................................ 33
Seismic Design Considerations ......... 33
Seismic Design Loads......................... 33
Local Seismic Data ............................. 45
Piping Connections............................. 46
Foundation Design ............................. 46
Tabulation Forms for Seismic
Data and Example .......................... 47
References ........................................... 51
Structurally Supported
Aluminum Dome Roofs
General ................................................ 51
Definition ............................................ 51
Design Requirements ......................... 51
Materials ............................................. 52
Allowable Stresses.............................. 52
Design.................................................. 53
Roof Attachment Details.................... 54
Physical Characteristics..................... 54
Testing and Sealing............................ 55
Fabrication and Erection ................... 55
Coatings .............................................. 55
Appendix
A
Metric (SI) Equivalents ................. 56
Figures
1
2
3
4
Foundation Design and
Construction
General Requirements........................ 28
Soil-Bearing Value .............................. 28
Factor of Safety ................................... 29
Foundations......................................... 29
Detail Design of Foundations ............ 30
Concrete Design, Materials,
and Construction ............................. 31
Backfill................................................. 32
5
6
7
8
Tensile Straps Aid in Transferring
Vertical Loads Across Horizontal
Joints............................................... 12
Bolted Piping Flanges ........................ 18
Extreme Frost Penetration—Inches
(Based on State Averages) ............. 31
Recommended Depth of Pipe
Cover—Feet Above Top of Pipe ...... 32
Seismic Zone Map for Determining
Zone Coefficient From Table 3 ........ 35
Curve for Obtaining Factor Kp for
the Ratio D/H................................... 37
Curves for Obtaining Factors W1/WT
and W2/WT for the Ratio D/H ........ 38
Curves for Obtaining Factors X1/H
and X2/H for the Ratio D/H ............ 38
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Copyright © 1998 American Water Works Association, All Rights Reserved
SEC.
9
10
11A
11B
PAGE
SEC.
Increase in Axial-Compressive
Buckling-Stress Coefficient of
Cylinders Due to Internal Pressure
(For Use with Unanchored
Tanks) ............................................... 44
Bottom Piping Connection of an
Unanchored Flat-Bottom Tank
(12 in. = 304.8 mm) .......................... 46
Blank Tabulation Form ...................... 48
Completed Tabulation Form for
Design Example ............................... 48
PAGE
Tables
1
2
3
4
5
6
7
A.1
Physical Requirements for Gasket
Material ............................................. 7
Bolted Piping Flanges ........................ 18
Zone Coefficient (Z ) ............................ 35
Force Reduction Coefficient ............... 35
Site Amplification Factor S ............... 36
Use Factor I ........................................ 36
Bolts and Fasteners ........................... 53
Metric (SI) Conversion Factors ......... 56
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This page intentionally blank.
Copyright © 1998 American Water Works Association, All Rights Reserved
Foreword
This foreword is for information only and is not a part of AWWA D103.
I. Introduction.
I.A. Background. This standard covers factory-coated bolted steel tanks for
water storage and is based on the accumulated knowledge and experience of
manufacturers of bolted steel tanks.*
I.B. History. The first version of this standard was prepared in cooperation
with the Bolted Tank Manufacturer’s Association and was issued in 1980. It was
prepared in response to the increasing use of bolted tanks for water storage. AWWA
D103-80 was later updated and approved as AWWA D103-87 on June 14, 1987. The
third and current edition of ANSI/AWWA D103-97 was approved by the AWWA
Board of Directors on June 15, 1997.
I.C. Acceptance. In May 1985, the US Environmental Protection Agency
(USEPA) entered into a cooperative agreement with a consortium led by NSF
International (NSF) to develop voluntary third-party consensus standards and a
certification program for all direct and indirect drinking water additives. Other
members of the original consortium included the American Water Works Association
Research Foundation (AWWARF) and the Conference of State Health and Environmental Managers (COSHEM). The American Water Works Association (AWWA) and
the Association of State Drinking Water Administrators (ASDWA) joined later.
In the United States, authority to regulate products for use in, or in contact with,
drinking water rests with individual states.† Local agencies may choose to impose
requirements more stringent than those required by the state. To evaluate the health
effects of products and drinking water additives from such products, state and local
agencies may use various references, including
1. An advisory program formerly administered by USEPA, Office of Drinking
Water, discontinued on Apr. 7, 1990.
2. Specific policies of the state or local agency.
3. Two standards developed under the direction of NSF, ANSI‡/NSF§ 60,
Drinking Water Treatment Chemicals—Health Effects, and ANSI/NSF 61, Drinking
Water System Components—Health Effects.
4. Other references, including AWWA standards, Food Chemicals Codex, Water
Chemicals Codex,** and other standards considered appropriate by the state or local
agency.
Various certification organizations may be involved in certifying products in
accordance with ANSI/NSF 61. Individual states or local agencies have authority to
*The word tanks is used hereinafter broadly in place of the lengthy phrase standpipes or
reservoirs for water storage.
†Persons in Canada, Mexico, and non-North American countries should contact the
appropriate authority having jurisdiction.
‡American National Standards Institute, 11 W. 42nd St., New York, NY 10036.
§NSF International, 3475 Plymouth Rd., Ann Arbor, MI 48106.
**Both publications available from National Academy of Sciences, 2102 Constitution Ave.
N.W., Washington, DC 20418.
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Copyright © 1998 American Water Works Association, All Rights Reserved
accept or accredit certification organizations within their jurisdiction. Accreditation
of certification organizations may vary from jurisdiction to jurisdiction.
Appendix A, “Toxicology Review and Evaluation Procedures,” to ANSI/NSF 61
does not stipulate a maximum allowable level (MAL) of a contaminant for substances
not regulated by a USEPA final maximum contaminant level (MCL). The MALs of an
unspecified list of “unregulated contaminants” are based on toxicity testing
guidelines (noncarcinogens) and risk characterization methodology (carcinogens). Use
of Appendix A procedures may not always be identical, depending on the certifier.
AWWA D103-97 does not address additives requirements. Thus, users of this
standard should consult the appropriate state or local agency having jurisdiction in
order to
1. Determine additives requirements including applicable standards.
2. Determine the status of certifications by all parties offering to certify
products for contact with, or treatment of, drinking water.
3. Determine current information on product certification.
II. Special Issues.
II.A. Purchase. When tanks are purchased using this standard, the purchaser
must specify certain basic requirements. The purchaser may desire to modify, delete,
or amplify sections of this standard to suit special conditions. It is strongly
recommended that such modifications, deletions, or amplifications be made by
supplementing this standard rather than by rewriting or incorporating sections from
this standard into a separate specification.
II.B. Design and Construction. The details of design and construction covered
by this standard are minimum requirements. A tank cannot be represented as
adhering to the provisions of AWWA D103 if it does not meet the minimum
requirements of this standard.
II.C. Coatings. Tanks covered by this standard shall be supplied with factoryapplied coatings. Field coating is limited to repair of damaged coatings.
Tanks with factory-applied coatings and bolted construction have a long life
expectancy. Regular inspection and repair of damaged or deteriorated areas may be
the determining factors in the length of tank life.
II.D. Foundations. Tank foundations are one of the more important aspects of
tank design. Detailed requirements for tank foundations are covered in Sec. 11 of this
standard. This standard does not require the manufacturer or constructor to be
responsible for the design of the tank foundation unless otherwise specified by the
purchaser. Unless otherwise specified by the purchaser, the purchaser must obtain an
adequate soil investigation at the tank site, including recommendations of the type of
foundation to be used, the depth of foundation required, and the design soil-bearing
pressure. This information, as well as specifications for an adequate soil investigation, should be established by a qualified geotechnical engineer. The top of the
foundation should be 6 in. minimum above the finished grade, unless otherwise
specified by the purchaser.
A drainage inlet structure or suitable erosion protection should be provided to
receive the discharge from the tank overflow. The overflow shall not be connected
directly to a sewer or a storm drain without an air break.
II.E. Annual Inspection and Maintenance. Inspection and maintenance is
important if maximum tank life is to be attained. Inspections should occur at least
every 3 to 5 years. In particular, accumulations of dirt and weeds from around the
outside base of the tank, which may trap moisture and accelerate corrosion, as well
as accumulated silt inside on the floor, should be removed.
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Copyright © 1998 American Water Works Association, All Rights Reserved
II.F. Disinfection Procedures and Cathodic Protection. This standard does not
cover disinfecting procedures* (see Sec. 9.4) or cathodic protection.
1. If the disinfecting is to be done by the tank constructor, the purchaser must
specify how such disinfecting is to be done.
2. The purchaser is responsible for determining the need for, the design of, and
the specifications for cathodic protection (see ANSI/AWWA D104).
II.G. Recommended Items to Be Furnished by the Purchaser and Manufacturer. The following recommendations on items to be furnished by both the
purchaser and the manufacturer are considered good practice, but are not
requirements of ANSI/AWWA D103.
When a bolted steel tank is to be purchased under the provisions of this standard,
the purchaser should provide the following:
1. The site on which the tank is to be built, including sufficient space to permit
the structure to be erected by customary methods.
2. Foundation design and construction unless otherwise specified.
3. Water at the proper pressure for testing, as required, and facilities for
disposal of wastewater after testing.
4. A suitable right-of-way from the nearest public road to the erection site.
5. Any materials furnished by the purchaser to be used by the constructor for
construction of the tank.
The manufacturer should furnish the following:
1. Foundation loads and reactions imposed on the foundations by the tank.
2. Anchor bolts, if required, for wind, earthquake, or other lateral loads, or if
specified to be furnished.
3. All labor and materials, except materials furnished by the purchaser, that
are necessary to manufacture the structure components, including the accessories
required by this standard.
Variations in the responsibilities of both the purchaser and the manufacturer as
previously outlined may be made by the contractual agreement. The purchaser and
the bidder should each furnish information identified in the sections that follow.
III. Use of This Standard. AWWA has no responsibility for the suitability or
compatibility of the provisions of this standard to any application by any user.
Accordingly, each user of this standard is responsible for determining that the
standard’s provisions are suitable for and compatible with that user’s intended
application.
III.A. Purchaser Options and Alternatives. The following information should
be furnished by the purchaser when taking bids for a standpipe or reservoir:
1. For standpipes, the capacity and top capacity level.
2. For reservoirs, the capacity and diameter.
3. Desired time for completion.
4. Site location.
5. Type of road available for access to the site, and whether the road is public
or private.
6. Name of and distance to the nearest town.
7. Name of and distance to the nearest railroad siding.
*Various disinfection procedures are presented in AWWA C652, Standard for Disinfection of
Water-Storage Facilities.
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Copyright © 1998 American Water Works Association, All Rights Reserved
8. Availability of electric power; who furnishes it and at what fee, if any; what
voltage is available; whether direct or alternating current; and, if alternating
current, what cycle and phase.
9. Availability of compressed air and what pressure, volume, and fee are
available, if any.
10. The bottom capacity level of the tank when empty if different from the level
when the tank would be emptied through the specified discharge piping (Sec. 1.2.9).
11. The type of pipe and fittings for fluid conductors and the type of pipe joint if
different from that permitted in Sec. 2.9.
12. If snow loading is to be omitted when the tank is located in an area where
actual snow loading is insignificant (Sec. 3.2.3).
13. Specific wind-load requirements, including whether a sliding check for
unanchored tanks is required (Sec. 3.2.4).
14. Unless the purchaser specifies that seismic design be omitted, all seismic
designs will be based on pseudo-dynamic criteria (Sec. 12). When seismic design is
required, purchaser shall identify which zone—1, 2A, 2B, 3 or 4—is to be used.
15. Locations of manholes, ladders, and any additional accessories required
(Sec. 5).
NOTE: Only one shell manhole will be provided unless the purchaser otherwise
specifies (Sec. 5.1).
16. The number and location of pipe connections, and type and size of pipe to be
accommodated.
NOTE: Connections to the piping furnished by the constructor are to be made by
the purchaser (Sec. 5.2).
17. If a removable silt stop is required (Sec. 5.2.1).
18. Overflow type, whether stub or to ground; size of pipe; pumping and
discharge rates (Sec. 5.3).
19. If the roof ladder for providing access to roof hatches and vents is to be
omitted (Sec. 5.4.3).
20. If safety cages, rest platforms, ladder locks, roof-ladder handrails, or other
safety devices are required, and on which ladders (Sec. 5.5).
NOTE: The purchaser should specify the beginning location of the outside tank
ladder if it is other than 8 ft above the level of the tank bottom.
21. If a special vent is required for screening the tank vent (Sec. 5.7).
22. If shop inspection is required, and whether typical mill-test reports are
required (Sec. 9.1).
23. Unless otherwise specified, soil investigation, including foundation-design
criteria (Sec. 11.2), type of foundation (Sec. 11.4.1), depth of foundation below
existing grade, and design soil-bearing pressure, including factor of safety.
NOTE: The top of the foundation is to be 6 in. minimum above the finish grade
unless otherwise specified by the purchaser (Sec. 11.5.1).
24. If a steel tank bottom or a steel base setting ring is to be used (Sec. 11.4.1,
type 6).
25. When a pile-supported foundation is required, the purchaser should specify
pile type and depth below existing grade (Sec. 11.5.4).
26. If all requirements of ACI 301, Specifications for Structural Concrete for
Buildings, are applicable to the concrete work (Sec. 11.6).
27. Vertical distance from finished ground level to the crown of inlet and outlet
pipes (that is, pipe cover) at tank foundation (Sec. 11.7.2).
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Copyright © 1998 American Water Works Association, All Rights Reserved
28. Completion of the Tabulation Form for Seismic Data when seismic design is
required (Sec. 12.1.2).
29. If vertical acceleration is to be considered and how it is to be applied in
seismic design (Sec. 12.3.7.1).
30. Amount of freeboard for sloshing wave (Sec. 12.3.7.2).
31. If seismic design of roof framing and columns is required (Sec. 12.3.7.3), and
the amount of live loads and vertical acceleration to be used.
32. If local seismic data are available and if they are to be used in place of
acceleration and spectral velocity values (Sec. 12.4) and the reduction factor to be
used if scaled-down response spectra are used (Sec. 12.4.1).
33. If an aluminum dome roof is to be provided as discussed in Sec. 13.
34. If the aluminum dome roof is to be provided, whether the exterior of the
dome is to have a factory-applied baked-on finish.
III.B. Information to Be Furnished by the Manufacturer or Constructor. The following information shall be furnished by the manufacturer or constructor for a
standpipe or reservoir:
1. Dimensions of the standpipe or reservoir, including the diameter, shell
height type of bottom, type of roof, type of coating, details of bolted joints, and type
and size of plates, members, and anchorages shall be identified. The gross moment
and shear imparted to the foundation under seismic and wind loading should also be
identified at the time of the bid.
2. The number, names, and sizes of all accessories. This includes the type of
roof ladder if an alternative method from that required in Sec. 5.4.3 is proposed.
3. If the purchaser specifies that the tank is to be cathodically protected, the
constructor shall certify in the bid that the tank will be erected so as to provide
electrical continuity of all tank components in contact with water.
III.C. Items for Consideration by the Purchaser. The design, construction, and
final placement of a storage tank into service requires cooperation between the
purchaser, manufacturer, and constructor of the tank. Various practices are used to
ensure successful tank placement. The following items are suggested for inclusion in
the purchaser’s specifications, unless local practice dictates otherwise. Please note
that this material is not stipulated in the text of ANSI/AWWA D103.
1. The purchaser may want to provide for field inspection to be performed
either by the purchaser or by a commercial inspection agency, the cost of which shall
be paid by the purchaser. As an option, the purchaser may require the manufacturer
or constructor to perform the inspection work and, at the conclusion of the work, to
submit a written report. The report should include a statement indicating that the
tank has been erected according to the manufacturer’s instructions, that the required
testing has been performed, and that any leaks have been repaired.
2. The roof opening in the tank should be located near the overflow to provide
for visual inspection of the overflow.
3. This standard assumes that the purchaser (owner) provides sufficient water
replacement and circulation to prevent freezing in the tank and riser pipe. Where low
usage may result in the possibility of freezing, the purchaser shall waste water or
provide heat to prevent freezing. The purchaser is referred to National Fire
Protection Association (NFPA)* document NFPA 22, Water Tanks for Private Fire
Protection, for heater sizing. Purchasers are cautioned against allowing ice to build
*National Fire Protection Association, One Batterymarch Park, Quincy, MA 02269.
xiii
Copyright © 1998 American Water Works Association, All Rights Reserved
up for use as insulation because the ice may break loose and damage the tank. Where
reference to ice damage is discussed in the standard, it is in anticipation of improper
operation rather than approval of an icing condition.
4. On completion of the tank erection, it is recommended that the constructor
dispose of all rubbish and other unsightly material caused by the operations and
leave the premises in as good a condition as found at the start of the tank erection. It
is recommended that the purchaser provide appropriate containers for placement and
removal of disposed materials. Section 8.5 of ANSI/AWWA D103 does not list
requirements for cleanup.
5. ANSI/AWWA D103 does not require the manufacturer or constructor to
blind and fill the tank to top capacity level, according to the manufacturer’s
recommendations (see Sec. 9.2). It is common practice for the purchaser to provide
this effort. Should the purchaser require that the manufacturer or constructor
provide this service and a supply of water, this must be provided for in the
purchaser’s specifications.
6. ANSI/AWWA D103 does not require the manufacturer or constructor to
furnish foundation plans (see Sec. 11.1.1). Should the purchaser specify submission of
foundation plans, the purchaser must furnish adequate information relative to the
type of foundation, foundation depth, and allowable soil-bearing pressure. (See
Sec. II.D of the foreword and Sec. 11 for further information.)
7. ANSI/AWWA D103 does not require the manufacturer or constructor to
construct and install a foundation. Should the purchaser require that a foundation be
provided by the manufacturer or constructor, any information other than that
contained in Sec. 11 of this standard must also be provided by the purchaser.
8. It is recommended that the purchaser retain a qualified geotechnical
consultant to conduct a proper soil investigation. Unless otherwise specified by the
purchaser, ANSI/AWWA D103 does not require that the manufacturer or constructor
provide this service (see Sec. 11.3).
9. ANSI/AWWA D103 does not require the manufacturer or constructor to
provide specifications for the preparation of sub-base materials (Sec. 11.4.1.6). Should
the purchaser require that the manufacturer or constructor provide such specifications, this must be provided in the purchaser’s specifications.
III.D. Modification to Standard. Any modification to the provisions, definitions, or terminology in this standard must be provided in the purchaser’s
specifications.
IV. Major Revisions. Major changes made to the standard in this revision
include the following:
1. The format of the foreword has been changed to AWWA standard style.
2. The acceptance clause (Sec. I.C) and the definitions of parties (Sec. 3) have
been revised to approved wording.
3. Changes have been made to Sec. 12, Seismic Design of Flat-Bottomed Water
Storage Tanks, to reflect the changes made to ANSI/AWWA D100, Standard for
Welded Steel Tanks for Water Storage.
4. A new Sec. 13 was created for structurally supported aluminum dome roofs,
which replaces appendix A.
V. Comments. If you have any comments or questions about this standard,
please call the AWWA Standards and Materials Development Department,
(303) 794-7711 ext. 6283, FAX (303) 795-1440, or write to the department at 6666 W.
Quincy Ave., Denver, CO 80235.
xiv
Copyright © 1998 American Water Works Association, All Rights Reserved
American Water Works Association
R
ANSI/AWWA D103-97
(Revision of ANSI/AWWA D103-87)
AWWA STANDARD FOR
FACTORY-COATED BOLTED STEEL
TANKS FOR WATER STORAGE
SECTION 1:
Sec. 1.1
GENERAL
Scope
The purpose of this standard is to facilitate the manufacture, installation, and
procurement of cylindrical bolted steel tanks for the storage of water.
1.1.1 Tank roofs. All tanks storing potable water shall have roofs. Tanks
storing nonpotable water may be constructed without roofs.
1.1.2 Work outlined. The work to be performed by the parties in completing
the activities described in this standard is outlined as follows:
1. Foundation constructor:
Section 2, Materials. See Sec. 2.3 for foundation-reinforcing steel.
Section 11, Foundation Design and Construction. The constructor or purchaser
is responsible for construction of the foundation. The purchaser is responsible for the
design of the foundation.
2. Manufacturer:
Section 2, Materials (except as indicated in item 1 above.)
Section 3, General Design.
Section 4, Sizing of Standpipes and Reservoirs.
Section 5, Accessories for Standpipes and Reservoirs.
Section 6, Welding.
Section 7, Shop Fabrication.
Section 9, Inspection and Testing. See Sec. 9.1 regarding shop inspection.
Section 10, Coatings (except as indicated in item 3).
Section 12, Seismic Design of Flat-Bottom Water-Storage Tanks.
3. Constructor of tank:
Section 6, Welding. (To be used in the field only after prior acceptance by the
manufacturer and purchaser.)
Section 8, Erection.
Section 9, Inspection and Testing (except as indicated in item 2).
1
Copyright © 1998 American Water Works Association, All Rights Reserved
2
AWWA D103-97
Section 10, Coatings. See Sec. 10.2 regarding coating repair to be done in the
field.
1.1.3 Items not covered. This standard does not cover all details of design and
construction because of the large variety of sizes and shapes of tanks. Where details
for any specific design are not given, the manufacturer, subject to the approval of the
purchaser, shall provide details that are designed and constructed to be as adequate
and as safe as those that would otherwise be provided under this standard.
1.1.4 Local requirements. This standard is not intended to cover storage
tanks erected in areas subject to regulations more stringent than the requirements
contained within this standard. In such cases, this standard should be followed on
purchases made under the provisions of this standard, insofar as it does not conflict
with local requirements. Where more stringent local, municipal, county, or state
government requirements exist, such requirements may govern, and this standard
shall be interpreted to supplement them.
Sec. 1.2
Definitions
The following definitions shall apply in this standard:
1.2.1 Capacity: The net volume that may be removed from a tank filled just
to the top capacity level and emptied to the bottom capacity level. The bottom
capacity level, if not otherwise specified by the purchaser, shall be the water level in
the tank shell when the tank is emptied through the specified discharge piping.
1.2.2 Constructor: The party that furnishes the work and materials for
placement or installation.
1.2.3 Manufacturer: The party that manufactures, fabricates, or produces
materials or products.
1.2.4 Purchaser: The person, company, or organization that purchases any
materials or work to be performed.
1.2.5 Reservoir: A flat-bottom cylindrical tank having a shell height equal to
or smaller than its diameter.
1.2.6 Standpipe: A flat-bottom cylindrical tank having a shell height greater
than its diameter.
1.2.7 Tank: A standpipe or a reservoir used for water storage.
Sec. 1.3
Responsibilities of Parties
1.3.1 Manufacturer’s responsibility. The manufacturer shall furnish a structure free of defective materials, including coatings. This responsibility shall be in
effect for a period of one year from the date of completion but not more than 14
months from the date of delivery. Any materials proven to be defective within this
time shall be replaced or repaired by the manufacturer.
1.3.2 Constructor’s responsibility. The constructor shall erect the structure
free of defects in workmanship. This responsibility shall be in effect for a period of 12
months from the date of acceptance but not more than 12 months from the date of
completion of installation by the constructor. Any faulty workmanship found within
those periods shall be repaired by the constructor.
1.3.3 Inspection and repair of tank. The purchaser must provide the constructor and the manufacturer with the opportunity to inspect and repair the tank, if
required, within the responsibility periods enumerated in Sec. 1.3.1 and 1.3.2. Failure
of the purchaser to provide an opportunity to inspect within these periods will relieve
the constructor and manufacturer of responsibility unless otherwise agreed.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Sec. 1.4
3
Drawings to Be Furnished
After award of the contract the manufacturer shall prepare the anchor-bolt
layout, when applicable, and assembly drawings, which are to be submitted to the
purchaser for approval unless waived, before proceeding with any fabrication. If
required by the purchaser, details of all bolted and welded joints shall be referenced
on the drawings.
Sec. 1.5
References
This standard references the following documents. In their latest editions, they
form a part of this standard to the extent specified within the standard. In any case
of conflict, the requirements of this standard shall prevail.
AA* SPC—Standards for Aluminum Sand and Permanent Mold Castings.
AA SAS—Specifications for Aluminum Structures (Sec. 1).
AAMA† 605—Voluntary Specification for High Performance Organic Coatings
on Architectural Extrusions and Panels.
ACI‡ 301—Standard Specification for Structural Concrete.
ACI 318—Building Code Requirements for Structural Concrete.
AISC§ ASD—Specification for Structural Steel Buildings—Allowable Stress
Design.
AISI** 1010—Carbon Steel: Plates; Structural Shapes; Rolled Floor Plates; Steel
Sheet Piling.
AISI SG-673—Specification for the Design of Cold-Formed Steel Structural
Members.
ANSI††/ASTM‡‡ A6—Standard Specification for General Requirements for
Rolled Steel Bars, Plates, Shapes, and Sheet Piling.
ANSI/ASTM A36—Standard Specification for Carbon Structural Steel.
ANSI/ASTM A53—Standard Specification for Pipe, Steel, Black and HotDipped, Zinc-Coated, Welded and Seamless.
ANSI/ASTM A181—Standard Specification for Carbon Steel for Forgings, for
General-Purpose Piping.
ANSI/ASTM A194—Standard Specification for Carbon and Alloy Steel Nuts for
Bolts for High-Pressure and High-Temperature Service.
ANSI/ASTM A216—Standard Specification for Steel Castings, Carbon, Suitable
for Fusion Welding, for High-Temperature Service.
ANSI/ASTM A572—Standard Specification for High-Strength Low-Alloy
Columbium-Vanadium Structural Steel.
*Aluminum Association, 818 Connecticut Ave., Washington, DC 20006.
†Architectural Aluminum Manufacturers Association, 35 E. Wacker Dr., Chicago, IL 60601.
‡American Concrete Institute, Box 19150, Redford Station, Detroit, MI 48219.
§American Institute of Steel Construction, One E. Wacker Dr., Ste. 3100, Chicago, IL
60601-2001.
**American Iron and Steel Institute, 1101 17th St. N.W., Washington, DC 20036.
††American National Standards Institute, 11 W. 42nd St., New York, NY 10036.
‡‡American Society for Testing and Materials, 100 Barr Harbor Dr., West Conshohocken, PA
19428-2959.
Copyright © 1998 American Water Works Association, All Rights Reserved
4
AWWA D103-97
ANSI/ASTM A607—Standard Specification for Steel, Sheet and Strip, High
Strength, Low-Alloy, Columbium or Vanadium, or Both, Hot-Rolled and Cold-Rolled.
ANSI/ASTM A668—Standard Specification for Steel Forgings, Carbon and Alloy,
for General Industrial Use.
ANSI/ASTM A715—Standard Specification for Steel Sheet and Strip, HighStrength, Low-Alloy, Hot-Rolled, with Improved Formability.
ANSI/AWS* A5.1—Specification for Carbon Steel Electrodes for Shielded Metal
Arc Welding.
ANSI/AWWA C652—Standard for Disinfection of Water-Storage Facilities.
ANSI/AWWA D104—Standard for Automatically Controlled, Impressed-Current
Cathodic Protection for the Interior of Steel Water Tanks.
API† 6A—Specification for Wellhead Equipment.
API 12B—Specification for Bolted Tanks for Storage of Production Liquids.
ASTM A48—Standard Specification for Gray Iron Castings.
ASTM A123—Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on
Iron and Steel Products.
ASTM A153—Standard Specification for Zinc Coating (Hot-Dip) on Iron and
Steel Hardware.
ASTM A240—Standard Specification for Heat-Resisting Chromium and ChromiumNickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels.
ASTM A283—Standard Specification for Low and Intermediate Tensile
Strength Carbon Steel Plates.
ASTM A307—Standard Specification for Carbon Steel Bolts and Studs,
60,000 psi Tensile Strength.
ASTM A325—Standard Specification for Structural Bolts, Steel, Heat Treated,
120/105 ksi Minimum Tensile Strength.
ASTM A490—Standard Specification for Heat-Treated Steel Structural Bolts,
150 ksi Minimum Tensile Strength.
ASTM A563—Standard Specification for Carbon and Alloy Steel Nuts.
ASTM A568—Standard Specification for Steel, Sheet, Carbon, and HighStrength, Low-Alloy, Hot-Rolled and Cold-Rolled, General Requirements for.
ASTM A570—Standard Specification for Steel, Sheet and Strip, Carbon, HotRolled, Structural Quality.
ASTM B695—Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel.
ASTM D395—Standard Test Methods for Rubber Property—Compression Set.
ASTM D412—Standard Test Methods for Vulcanized Rubber and Thermoplastic
Rubbers and Thermoplastic Elastomers—Tension.
ASTM D471—Standard Test Method for Rubber Property—Effect of Liquids.
ASTM D573—Standard Test Method for Rubber—Deterioration in an Air Oven.
ASTM D1171—Standard Test Method for Rubber Deterioration—Surface Ozone
Cracking Outdoors or Chamber (Triangular Specimens).
ASTM D1229—Standard Test Method for Rubber Property—Compression Set at
Low Temperatures.
*American Welding Society, P.O. Box 351040, Miami, FL 33125.
†American Petroleum Institute, 1220 L St. N.W., Washington, DC 20005.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
5
ASTM D1751—Standard Specification for Preformed Expansion Joint Filler for
Concrete Paving and Structural Construction (Nonextruding and Resilient Bituminous Types).
ASTM D2240—Standard Test Method for Rubber Property—Durometer Hardness.
ASTM D2244—Standard Test Method for Calculation of Color Differences from
Instrumentally Measured Color Coordinates.
NFPA* 22—Standard for Water Tanks for Private Fire Protection.
SSPC† SP8—Pickling.
SSPC SP10—Joint Surface Preparation Standard Near-White Blast Cleaning.
Fed. Spec.‡ TT-S-230—Sealing Compound: Elastomeric Type, Single Component.
Fed Spec. ZZ-R-765—Rubber Silicone: Low- and High-Temperature and Tear
Resistant.
SECTION 2:
Sec. 2.1
MATERIALS
General
All materials to be incorporated in any structure to meet the provisions of this
standard shall be new, previously unused, and in first-class condition, and shall
comply with all of the requirements of this standard.
Sec. 2.2
Bolts and Anchor Bolts
2.2.1 Bolts. Bolts for joining tank panels shall conform to the requirements of
ASTM A307, ASTM A325, ASTM A490, or API 12B. Nuts for these bolts shall
conform to ANSI/ASTM A194 or ASTM A563.
2.2.2 Anchor bolts. Anchor bolts shall conform to the requirements of ANSI/
ASTM A36, ASTM A307, or ANSI/ASTM A572, grade 50.
Sec. 2.3
Foundation-Reinforcing Steel
Reinforcing steel in foundations shall comply with the requirements of ACI 318.
Sec. 2.4
Plates and Sheets
Plate and sheet materials shall be open-hearth, electric-furnace, or basicoxygen-process steel conforming to any of the following ASTM specifications: A36;
A283, grade C or D; A570, grade 30, 33, 36, 40, 45, or 50; A572, grade 42, 50, or 60;
A607, grade 50, 55, or 60; or A715, grade 50. Plates and sheets may be furnished on
the weight basis, with permissible underrun according to the tolerance table for
plates ordered to weight published in ANSI/ASTM A6 and for sheets ordered to
weight published in ASTM A568. Steel grades designating a yield strength of
50,000 psi or more should not be used on 15-ft or smaller diameter tanks that have
form-flanged connections.
*National Fire Protection Association, One Batterymarch Park, Quincy, MA 02269.
†Steel Structures Painting Council, 40 24th St., Ste. 600, Pittsburgh, PA 15222-4643.
‡Federal Specifications, Superintendent of Documents, US Government Printing Office,
Washington, DC 20402.
Copyright © 1998 American Water Works Association, All Rights Reserved
6 AWWA D103-97
Sec. 2.5
Structural Shapes
Hot-rolled structural shapes for use under the provisions of this standard shall
conform to AISC S335. Material shall conform to ANSI/ASTM A36 or AISI 1010.
Aluminum shapes of a suitable alloy for load and service requirements may be used
for portions of the tank not in contact with water. The design of all aluminum
members shall be in accordance with AA SAS and to the loads specified in Sec. 3 of
this standard.
Sec. 2.6
Castings
Iron castings shall conform to ASTM A48, class 30. Steel castings shall conform
to ANSI/ASTM A216, grade WCB. Aluminum castings shall conform to AA SPC.
Sec. 2.7
Forgings
2.7.1 Forgings from plate and sheet materials. Forgings from plate and sheet
materials shall conform to the plate and sheet materials permitted under Sec. 2.4.
2.7.2 Forgings from other than plate or sheet materials. Forgings from other
than plate or sheet materials shall conform to ANSI/ASTM A668, class E.
2.7.3 Forged and rolled pipe flanges. Forged and rolled pipe flanges shall
conform to ASTM A181, class 60.
Sec. 2.8
Electrodes
Manual, shielded-metal, arc-welding electrodes shall conform to the requirements of AWS A5.1. Welding electrodes shall be of any E60XX or E70XX
classification suitable for the electric current characteristics, the position of welding,
and other conditions of intended use. Welding electrodes for other welding processes
shall conform to applicable AWS specifications for filler metal.
Sec. 2.9
Pipe for Fluid Conductors
Inlet, outlet, overflow, and other pipes, and all fittings for fluid use shall be as
specified by the purchaser. If steel pipe is not otherwise specified, it shall conform to
or exceed ANSI/ASTM A53 carbon steel or ASTM A240 300 series stainless steel.
Unless otherwise specified, joints may be either screwed or flanged at the option of
the manufacturer. Pipe and fittings from warehouse stock may be used if certified by
the warehouse to be in accordance with this standard or the purchaser’s specifications.
Sec. 2.10
Gaskets and Sealants
The manufacturer shall use gaskets or sealants or a combination of both in
accordance with the following requirements.
2.10.1 Gaskets. Gasket material shall be of adequate tensile strength and
resilience to obtain a leak-proof seal at all seams and joints. Gasket material shall be
resistant to weather and ozone exposure as designated by ASTM D1171. Physical
requirements are described in Table 1.
2.10.2 Sealants. Sealants shall comply with the following:
1. Resistance to temperature. The sealant shall remain flexible when in
continuous operation over a temperature range of –40°F to +170°F (–40°C to
+76.7°C).
2. Weatherability. The sealant shall be resistant to hardening and cracking.
The sealant shall be essentially solid and contain no plasticizers or extenders that
could cause shrinkage due to weathering. The sealant shall be resistant to ozone and
ultraviolet light.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Table 1
7
Physical requirements for gasket material*
Description
Strip and Extruded
Gasket Material
Tensile strength, initial, psi minimum, ASTM D412
1,200 psi 8,274 kPa
Tensile strength after oven aging as percent of initial, minimum, ASTM D573
70%
Tensile strength after immersion in distilled water as percent of initial, minimum,
ASTM D471
60%
Ultimate elongation, initial, percent of minimum, ASTM D412
175%
Ultimate elongation after oven aging as percent of initial, minimum, ASTM D573
70%
Hardness, Shore A, ASTM D2240
75 ± 5
Hardness change Shore A, after oven aging, ASTM D573
7
Compression set as maximum percent of original, after oven aging, ASTM D395
40%
Low-temperature compression set as maximum percent of original, ASTM D1229
Tear strength, pounds per inch
60%
160 lb/in. 28 kn/m
*Dimensions and tolerances shall be as specified by the manufacturers for the specific standpipe or reservoir requirements.
3. Chemical resistance. The sealant shall be chemically resistant without
extraction to water and shall not swell or degrade under normal water-storage
conditions.
4. Material specification. The sealant shall be acceptable for use on foodcontact surfaces.
5. Primers for sealant. Some sealant materials require the use of a primer on
metal or glass for maximum adhesion. Most of these primers contain a volatile
solvent. After evaporation of the solvent, the primer shall comply with the
requirements of Sec. 2.10.2, item 4.
SECTION 3: GENERAL DESIGN
Sec. 3.1
Types of Joints
3.1.1 Bolted joints. All vertical, horizontal, shell-to-roof, and shell-to-bottom
plates or sheets shall be field bolted. Bolt holes shall be shop punched or drilled for
field assembly. The bolted joints between roof, shell, and bottom sheets and plates
that are required to contain water or to be weathertight shall be sealed with suitable
gasket material, sealant, or gasket material and sealant as required to make a
watertight joint (see Sec. 2.10).
3.1.1.1 It is standard practice for field-assembled tanks to require fit-up
alignments. This is acceptable, and the manufacturer’s erection procedures shall be
followed.
3.1.2 Welded joints. Welding may be used to join shop-fabricated subassemblies that are subsequently bolted into place in the field.
Sec. 3.2
Design Loads
The following loads shall be considered in the design of tank structures and
foundations.
Copyright © 1998 American Water Works Association, All Rights Reserved
8 AWWA D103-97
3.2.1 Dead load. Dead load shall be the estimated weight of all permanent
construction and fittings. The unit weights used shall be 490 lb/ft3 (7,849.1 kg/m3) for
steel and 144 lb/ft3 (2,306.7 kg/m3) for concrete.
3.2.2 Water load. Water load shall be the weight of all of the liquid when the
tank is filled to top capacity level. Unit weight used for water shall be 62.4 lb/ft3
(1,000 kg/m3).
3.2.3 Roof design loads.
3.2.3.1 Snow load. Snow load shall be a minimum of 25 lb/ft2 (1,200 Pa) on
the horizontal projection of the tank for surfaces having a slope of 30° or less with the
horizontal. For surfaces with greater slope, the snow loads shall be neglected. The
snow load may be reduced when the tank is located where the lowest one-day mean
low temperature is +5°F (–15°C) or warmer, and local experience indicates that a
lesser load may be used.
3.2.3.2 The minimum roof-design live load shall be 15 lb/ft2 (720 Pa). The roof
plates or sheets may deflect between structural supports in order to support load.
3.2.4 Wind load. Wind pressure shall be assumed to be 30 lb/ft2 (1,400 Pa) on
vertical plane surfaces, 18 lb/ft2 (860 Pa) on projected areas of cylindrical surfaces,
and 15 lb/ft2 (720 Pa) on projected areas of conical and double-curved plate surfaces.
These quantities are based on a wind velocity of 100 mph (44.7 m/second). For
structures designed for wind velocities of more than 100 mph (44.7 m/second), all
aforementioned unit pressures shall be adjusted in proportion to the square of the
velocity. When a sliding check for an unanchored tank is specified, a coefficient of
friction equal to the tangent of 30 degrees is assumed. The total wind shear force
≤ W (tan 30°).
Where:
W = total weight of tank shell, floor, and roof
3.2.5 Earthquake load. Structures located in zones 1, 2A, 2B, 3, or 4 shall be
designed for seismic loads as defined in Sec. 12 of this standard (for exception, see
Sec. 3.2.5.2).
3.2.5.1 Structures located in zone 0 do not require design for earthquake
resistance.
3.2.5.2 The purchaser may specify that earthquake design is not required on
structures located in zone 1.
3.2.6 Platform and ladder load. A vertical load (and only one such load in
each case) shall be applied as follows: 1,000 lb (453.6 kg) to each platform; 500 lb
(226.8 kg) to any 10 ft2 (0.93 m2) area on the tank roof; 500 lb (226.8 kg) on each
vertical section of the ladder. All structural parts and connections shall be properly
proportioned to withstand such loads. The aforementioned load need not be combined
with the snow load specified in Sec. 3.2.3, but shall be combined with the dead load.
The platform and roof plating may deflect between structural supports in order to
support the loading.
Sec. 3.3
Design Criteria
With the exception of other criteria specifically provided for elsewhere in this
standard, the structural design of all standpipes and reservoirs shall be in
compliance with the following:
1. AISI SG-671.
2. AISC S335.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Sec. 3.4
9
Tank Shell
In the design of the tank shell, the hydrostatic water pressure at the lower edge
of each ring of sheets or plates in the tank shell shall be assumed to act undiminished
on the entire area of the ring.
3.4.1 Shell thickness. When the net tensile stress governs, the thickness of
cylindrical shell plates stressed by pressure of the tank contents shall be calculated
by the formula*
t = 2.6HDSG
---------------------------ft ( S – d )
(Eq 1)
Where:
t = shell plate thickness, in inches
H = height of liquid from the top capacity line just to overflow to the
bottom of the shell course being designed, in feet
D = tank diameter, in feet
S = bolt spacing in line perpendicular to line of stress, in inches
G = specific gravity of liquid (1.0 for water)
ft = allowable tensile stress, in pounds per square inch (Sec. 3.5.3)
d = bolt-hole diameter, in inches
3.4.2 Compressive stress. The allowable compressive stress in each ring of
sheets or plates under wind or earthquake loading combined with dead load shall be
determined by the formula
t
t
2
2
f s = 15,000  ---  100 ---- × 2 –  ---  100 ---- ≤ 15,000
 3 
 3 
R
R
(Eq 2)
Where:
fs = allowable compressive stress, in pounds per square inch
t = shell thickness, in inches
R = shell radius, in inches
3.4.3 Allowable stresses increased by one third. The allowable stresses may
be increased by one third when produced by wind or seismic loading acting alone or
in combination with the design dead and water loads, provided the required section
computed on this basis is not less than that required for the design dead and water
load computed without the one-third stress increase.
* The equations shown throughout this standard are currently for use with the inch-pound
system of units only. Metric equivalents are being developed by the Steel Elevated Tanks,
Standpipes, and Reservoirs Committee and will be published in the next update of this
standard.
Copyright © 1998 American Water Works Association, All Rights Reserved
10
AWWA D103-97
Sec. 3.5
Bolted Joints
In the design of bolted joints, the effect of the gasket and sealant shall be
neglected, provided the compressed thickness of the gasket or sealant does not exceed
1⁄16 in. (1.6 mm).
3.5.1 Minimum spacing. The center-to-center distance between bolts shall
not be less than 2d, where d is the diameter of the bolt, in inches (millimetres). The
distance from the center of any bolt to an edge or seam shall not be less than 1.5d. In
no case shall the center-to-center or edge-to-center distance be less than
P
----------------0.6F y t
(Eq 3)
Where:
P = force transmitted by the bolt, in pounds
Fy = published yield strength of the sheet or plate, in pounds per square
inch
=
thickness of the thinner sheet, in inches
t
3.5.2 Multiple bolt lines. When multiple bolt lines are used, the effective net
section area shall not be taken as greater than 85 percent of the gross area.
3.5.3 Tension on the net section. The tensile stress on the net section of a
bolted connection shall not exceed the lesser of the values determined by the
following formulas:
f t = 0.6F y ( 1.0 – 0.9r + 3rd ⁄ s ) ≤ 0.6F y
(Eq 4)
f t = 0.40F u
(Eq 5)
or
Where:
ft = allowable tensile stress, in pounds per square inch
Fy = published yield strength of the sheet material, in pounds per square
inch
r = force transmitted by the bolt or bolts at the section considered,
divided by the tensile force in the member at that section. If r is less
than 0.2, it may be taken to equal zero
d = diameter of bolt, in inches
s = spacing of bolts perpendicular to line of stress, in inches
Fu = published ultimate strength of the sheet material, in pounds per
square inch
3.5.4 Hole bearing stress. The hole bearing stress on the area d × t shall not
exceed 1.35Fy. The symbols d and Fy are as defined in Sec. 3.5.3; t is the thickness of
the plate under consideration.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
11
3.5.5 Bolt shear. Shear on bolts in live and dead loads shall not exceed the
value as determined from the formula
F u × 0.6 × 0.9
f v = ----------------------------------- = 0.25F u
2.2
(Eq 6)
Where:
fv = allowable shear stress to the affected area, whether tensile stress
area or gross area, in pounds per square inch
Fu = ultimate tensile stress of bolt, in pounds per square inch, as
determined by the formula
FF u = ------A ts
(Eq 6a)
Where:
F = breaking load of the bolt as determined from tensile tests, in pounds
Ats = tensile stress area as determined from the formula
0.9743 2
A ts = 0.7854  d – ------------------

n 
(Eq 6b)
Where:
d = nominal diameter of the bolt, in inches
n = number of threads per inch
3.5.6 Bolt tension. The tensile stress on bolts, other than anchor bolts, shall
not exceed the lesser of the following:
f t = 0.6F y
(Eq 7)
Fu
f t = ------2.2
(Eq 8)
or
The symbols in these expressions are as previously defined in this section,
following Eq 5.
When tensile straps are required in a butt-flanged connection, they shall be
designed in accordance with Figure 1.
Sec. 3.6
Weld Design Values
3.6.1 Structural joints. Welded structural joints shall be proportioned so that
the stresses on a section through the throat of the weld, exclusive of weld
Copyright © 1998 American Water Works Association, All Rights Reserved
12
AWWA D103-97
1,000
900
800
Tensile Load—lb/in.
700
Tensile Load = 9,600 t
600
2
Fy
36,000
t = Shell thickness (in.)
500
Fy = Published yield of the steel
used in the shell (psi)
Tensile Strap
Required
400
Tensile Strap
Not Required
300
200
100
.05
.10
.15
.20
.25
Shell Thickness—in.
.30
NOTE: This chart is applicable only to tanks with formed flange connections having 1/2-in. (12.7-mm) diameter
bolts on 2-in. (50.8-mm) centers at a bolt circle 2 in. (50.8 mm) larger than the shell OD. No increase in allowable
loads is permitted when using this chart.
Figure 1
Tensile straps aid in transferring vertical loads across horizontal joints
reinforcement, do not exceed the following percentages of the allowable working
tensile stress of the structural material joined.
3.6.1.1 Groove welds. Tension, 85 percent; compression, 100 percent; shear,
75 percent.
3.6.1.2 Fillet welds. Transverse shear, 65 percent; longitudinal shear, 50 percent.
NOTE: Stress in a fillet weld shall be considered as shear on the throat, for any
direction of the applied load. The throat of a fillet weld shall be assumed as 0.707 times
the length of the shorter leg of the fillet weld having a flat or slightly convex profile.
Sec. 3.7
Top and Intermediate Shell Girders
3.7.1 Top girder. A tank without a roof shall have a top girder or angle having
a minimum section modulus as determined by the formula
2
HD
V
S = ------------------  ----------
10,000  100
2
Copyright © 1998 American Water Works Association, All Rights Reserved
(Eq 9)
FACTORY-COATED BOLTED STEEL TANKS
13
Where:
S = minimum required section modulus, in cubic inches, of the top angle
or girder, including a portion of the tank shell for the allowable
distance below as specified in the introductory paragraph of Sec. 3.3,
and, if applicable above, the ring attachment to the shell
H = height of the cylindrical portion of the tank shell, in feet
D = tank diameter, in feet
V = wind velocity, greater than 100 mph
3.7.1.1 The total vertical leg of the top girder or angle may be used in the
computations, provided that the vertical leg width does not exceed the width-tothickness ratios set forth in Sec. 3.3.
3.7.2 Intermediate girders. The following formula shall be used to determine
whether intermediate girders are required between the roof or top girder and the
bottom:
6
( 10 ) t---------------------------------h = 10.625
1.5
P(D ⁄ t)
(Eq 10)
Where:
h = vertical distance between the intermediate wind girder and the top
angle of the shell or the top wind girder of an open-top tank, in feet
P = wind pressure, in pounds per square foot. This shall be assumed to be
18 unless the wind velocity is specified to be greater than 100 mph, in
which case
wind velocity, in mph 2
P = 18  -----------------------------------------------------------


100
(Eq 10a)
D = tank diameter, in feet
t = average shell thickness for the vertical distance h, in inches
3.7.2.1 In determining the maximum height of unstiffened shell, an initial
calculation shall be made using the thickness of the top shell course. Additional
calculations shall be based on the average thickness obtained by including part or all
of the next lower course or courses, until the calculated h is equal to or smaller than
the height of shell used in determining the average thickness. If h continues to
calculate greater than the height of the shell used in determining the average
thickness, then no intermediate girder is required.
3.7.2.2 After establishing the location of the first intermediate girder, if
required, repeat the procedure for additional intermediate girders, using the
preceding intermediate girder as the top of the tank. Locating the intermediate wind
girder at the maximum spacing calculated by the preceding rules will usually result
in a shell below the intermediate wind girder having a greater stability against wind
loading than the shell above the intermediate girder. The girder may be located at a
spacing less than the maximum spacing, but the lower shell must be checked for
adequacy against the maximum wind pressure, as previously described or in the
following alternative subparagraphs.
Copyright © 1998 American Water Works Association, All Rights Reserved
14
AWWA D103-97
1. Change the width W of each shell course into a transposed width Wtr of
shell course, having a uniform thickness, by the following relationship:
t uniform 2.5
W tr = W  --------------------
 t

(Eq 11)
actual
Where:
tuniform = uniform thickness into which the entire shell will be transformed
tactual = actual thickness of the plate course being transformed
2. The sum of the transposed width of each course will give the height of an
equivalent transformed shell. For equal stability above or below the intermediate
wind girder, the girder should be located at the mid-height of the transformed shell.
The location of the girder on the transformed shell shall be transposed to the actual
shell by the foregoing thickness relationship, using the actual thickness of the shell
course on which the girder will finally be located and all actual thicknesses above
this course.
3.7.2.3 When intermediate girders are required, they shall be proportioned in
accordance with the formula
2
V 2
hD
S = ------------------ ×  ----------
10,000  100
(Eq 12)
Refer to Sec. 3.7.1 and 3.7.2 for an explanation of these symbols.
Sec. 3.8
Roof Supports
Roof supports or stiffeners, if used, shall be designed in accordance with the
current specifications of AISC (ASD), with the following stipulations or exceptions:
1. The roof sheet will provide the necessary lateral support of roof rafters
from the friction between the roof plates and rafter compression flange, with the
following exceptions:
a. Trusses and open-web joists used as rafters.
b. Rafters having a nominal depth greater than 15 in. (381 mm)
c. Rafters having a slope greater than 2 in 12.
2. The roof rafter and purlin depth may be less than fb/600,000 times the
span length, provided the roof slope is 3⁄4 in 12 or greater. The symbol fb is the
bending unit stress (actual), equal to the bending moment divided by the section
modulus of the member.
3. The maximum slenderness ratio L/r for the column supporting rafters shall
be 175. L is the laterally unsupported length of the column, in inches, and r is the
least radius of gyration, in inches. Columns supporting roofs shall be designed as
secondary members.
4. Roof trusses shall be placed above the maximum water level in climates
where ice may form.
5. Roof rafters shall be placed above the top capacity level. No part shall
project below the top capacity level.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
6.
formula
15
The maximum spacing between roof supports shall be determined by the
2
L =
288F y t
---------------------- ≤ 60
W
(Eq 13)
Where:
L = maximum spacing, in inches
Fy = published yield strength of the roof sheet material, in pounds per
square inch
t = roof sheet thickness, in inches
W = roof dead load plus live load acting on roof surface, in pounds per
square foot
Sec. 3.9
Steel Thickness
Steel thicknesses shall comply with the following:
1. Sheets on roofs having a slope of 1 in 2.75 or greater, for which the tank
diameter does not exceed 35 ft (10.7 m), shall have a minimum thickness of 0.070 in.
(1.8 mm).
2. Sheets on roofs having a slope less than 1 in 2.75, regardless of tank
diameter, shall have a minimum thickness of 0.094 in. (2.4 mm).
3. The minimum thickness of the bottom sheets shall be 0.094 in. (2.4 mm).
4. The maximum thickness of shell plates shall be 3⁄8 in. (9.5 mm); the
minimum thickness shall be 0.094 in. (2.39 mm).
5. The sheet thicknesses in ANSI/AWWA D103 designs are based on the
criteria of hydraulic, wind, and seismic loadings with applicable bolted-joint
efficiencies.
Sec. 3.10
Foundation Bolts
Foundation anchor bolts may be either upset or not upset and shall comply with
the material requirements stated in Sec. 2.2.2. Anchor bolts shall be designed to
resist the maximum uplift force. Allowable stresses may be increased as permitted in
Sec. 3.4.3. The minimum anchor bolt diameter shall be 3⁄4 in. (19.1 mm) and all
anchor bolts shall be galvanized. The allowable tensile stress (Ft) shall be as follows
based upon the gross (nominal) area of the bolt. They shall be proportioned for the
maximum possible uplift, using the tensile stress area (Sec. 3.5.5) of the thread or the
un-upset rod diameter, whichever is smaller, and 70 percent of the allowable tensile
stress from Sec. 3.5.6. In no event should anchor bolts be less than 3⁄4 in. in diameter.
Foundation bolts may extend to within 3 in. of the bottom of the pier, but not
necessarily more than far enough to develop the maximum uplift. Foundation bolts
shall terminate in a right-angle hook, bend, head, or washer plate. The bond for
plain-rod foundation bolts shall be calculated using the following formula:
F t = 0.33F u
Where:
Fu = minimum tensile strength of the bolt, in pounds per square inch
Copyright © 1998 American Water Works Association, All Rights Reserved
16
AWWA D103-97
The tensile capacity of the threaded portion of an upset rod shall be larger than
the body area times 0.6 Fy, where Fy equals minimum yield strength of the bolt, in
pounds per square inch. Anchor bolts may extend to within 3 in. (76.2 mm) of the
bottom of a pier or footing, but not necessarily more than required to develop the
maximum tension. Anchor bolts shall terminate in a right-angle hook, bend, head, or
washer plate. The bond for plain-rod anchor bolts, in addition to the pullout
resistance of the hook, bend, head, or washer plate, shall be calculated by the formula
4.8 f ′c
U = ------------------- ≤ 160
d×2
(Eq 14)
Where:
U = unit bond stress, in pounds per square inch
f ′c = concrete compressive strength, in pounds per square inch
d = diameter of the anchor bolts, in inches
3.10.1 Bolt projection. The threaded ends of foundation anchor bolts shall
project 2 in. (50.8 mm) above the nominal level of the tops of the foundation anchor
bolt nuts to provide for variations in the foundation elevations. Lock nuts shall be
provided or the threaded ends of anchor bolts shall be peened to prevent loosening of
anchor nuts.
Sec. 3.11
Reinforcement Around Openings
All welded or bolted connections greater than 4 in. (101.6 mm) in diameter in
the tank shell and other locations that are subject to hydrostatic pressure, where the
thicknesses are established in accordance with the design criteria given in Sec. 3.3,
shall be reinforced. The reinforcement may be the flange of a fitting, an additional
ring of metal, a thicker plate, or any combination of these.
3.11.1 Tank shell. The amount of reinforcement for an opening in the tank
shell shall be computed as follows:
The minimum cross-sectional area of the reinforcement shall not be less than
the product of the maximum dimension of the hole cut in the tank shell and any bolt
holes in the line perpendicular to the direction of the maximum stress and the
required shell thickness. The cross-sectional area of the reinforcement shall be
measured perpendicular to the direction of maximum stress coincident with the
maximum dimension of the opening (100 percent reinforcement). All effective
reinforcement shall be made within a distance equal to the maximum dimension of
the hole in the shell. The direction of reinforcement shall be perpendicular to the
maximum stress. The reinforcement shall be in either direction from the centerline of
the shell opening.
3.11.2 Fittings. In the computation of the net reinforcing area of a fitting
having a neck (such as a boilermaker’s flange or a manhole saddle), the following
portions of the neck may be considered as part of the area of reinforcement.
1. That portion extending outward from the outside surface of the shell for a
distance equal to four times the neck wall thickness or, if the neck wall thickness is
not uniform within that distance, to the point of transition.
2. That portion lying within the shell thickness.
3. If the neck extends inwardly, that portion extending inward from the inside
surface of the shell for a distance as specified in item 1 above.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
17
3.11.2.1 The aggregate strength of the weld attaching a fitting to the shell or
any intervening reinforcing plate, or both, shall at least equal the proportion of the forces
passing through the entire reinforcement that is computed to pass through the fitting.
3.11.2.2 The aggregate strength of the weld attaching any intervening
reinforcing plate to the shell shall at least equal the proportion of the forces passing
through the entire reinforcement that is computed to pass through the reinforcing plate.
3.11.2.3 The attachment weld joining the flanged fitting or reinforcing plate to
the shell shall be considered effective along the outer periphery only for the parts
lying outside of the area bounded by parallel lines drawn tangent to the shell opening
perpendicular to the direction of maximum stress. The outer peripheral welding,
however, shall be applied completely around the reinforcement. All of the inner
peripheral weld shall be considered effective. The outer peripheral weld shall be of a
size equal to the thickness of the shell or reinforcing plate, whichever is less.
3.11.2.4 Manhole necks, nozzle necks, reinforcing plates, and shell openings
that have sheared or oxygen-cut surfaces shall have uniform and smooth surfaces,
with the corners rounded, except where these surfaces are fully covered by
attachment welds.
3.11.2.5 Flange unions.
3.11.2.5.1 Piping flanges shall conform to the requirements given within this
standard, except that, if specified by the purchaser, alternative types having
equivalent strength, tightness, and utility may be furnished.
3.11.2.5.2 Except as otherwise provided in Sec. 3.11.2.5.1, bolted piping flanges
shall be attached by bolts or bolt studs, and shall conform to the following:
1. Flanges shall be furnished in the sizes given in Table 2, as specified by the
purchaser, and shall conform to the provisions of Table 2 and Figure 2.
2. The inner flange shall be provided with bolt-head or bolt-stud nut
retainers.
3. The length of thread shall conform to the requirements of Table 2. In all
other respects, the threads shall conform to the requirements of API 6A.
3.11.2.5.3 When bolted piping flanges conforming to Table 2 and Figure 2 are
furnished, the tank members shall be drilled for flange attachment in accordance
with the following stipulations:
1. The bolt-circle diameter and the number of bolt holes shall be as shown in
Table 2 and Figure 2.
2. Bolt-hole sizes shall be optional with the manufacturer, but shall conform
with the bolt-fit tolerance as shown in Table 2.
3. Flange bolt holes shall straddle the radial centerlines on roofs and bottoms,
and vertical centerlines on staves, except that for the 4-in. (101.6-mm) diameter, fivehole flange the odd hole shall be located on the centerline toward the center for the
roof or the top of the sheet.
SECTION 4:
Sec. 4.1
SIZING OF STANDPIPES AND RESERVOIRS
Standard Capacities
The standard capacities for standpipes and reservoirs shall be as published by
the manufacturer and shall be calculated to the nearest 1,000 gal (m3).
Copyright © 1998 American Water Works Association, All Rights Reserved
18
AWWA D103-97
Table 2
Bolted piping flanges
Size—in.
2
Diameter of bolt circle, in. (mm)
4
Number of bolts
4
3
4
(101.6)
53⁄ 8 (136.5)
6 3⁄ 8 (161.9)
9
(101.6)
4
5
6
(101.6)
6
(127.0)
8
(228.6)
111⁄4 (285.8)
(152.4)
8
(203.2)
Diameter of bolts, in. (mm)
1
⁄ 2 (12.7)
5
⁄ 8 (15.9)
5
⁄ 8 (15.9)
5
⁄ 8 (15.9)
5
Diameter of bolt holes, in. (mm)
5⁄ 8
(15.9)
3⁄4
3⁄4
3⁄4
3⁄4
Minimum thread length, Y, in. (mm)
7⁄ 8
(22.2)
13⁄ 16 (30.2)
51⁄ 8 (130.2)
65⁄ 8 (168.3)
Depth of counterbore
(19.1)
(19.1)
15⁄ 16 (33.3)
19⁄ 16 (39.7)
(19.1)
13⁄4 (44.5)
Optional with manufacturer
101⁄ 2 (266.7)
O
,,,,
,,,,
,,,,,,,,
,,,,
,,,,
,,,,,,,,
Counterbore
73⁄4 (196.9)
Without Counterbore
,,,,,,,
,,,,,,,
,,,,,,,
Outside diameter of flange, O, in. (mm)
Y
Outer Flange
Inner Flange With
Bolt Head Retainer
Counterbore
Y
o
Without Counterbore
Art reproduced by permission from the American Petroleum Institute.
NOTE: Sections through flanges are shown at bolt holes.
Figure 2
(19.1)
⁄ 8 (15.9)
Bolted piping flanges
Copyright © 1998 American Water Works Association, All Rights Reserved
123⁄4 (323.94)
FACTORY-COATED BOLTED STEEL TANKS
Sec. 4.2
19
Shell Heights for Standpipes
The purchaser shall specify the required shell height for standpipes in
accordance with the manufacturer’s modular sizes.
Sec. 4.3
Diameters for Reservoirs
The purchaser shall specify the required reservoir diameter, with an allowable
variation to conform with the manufacturer’s standard modular sizes and capacity.
SECTION 5:
Sec. 5.1
ACCESSORIES FOR STANDPIPES
AND RESERVOIRS
Shell Manholes
One manhole, unless otherwise specified, shall be provided in the first ring of
the tank shell at a location to be designated by the purchaser. In tanks with one
manhole, a sheet opposite the manhole may be removed for additional ventilation if
required for inspections or recoating. If any manhole cover weighs more than 50 lb
(22.7 kg), a hinge or davit shall be provided.
5.1.1 Size and shape. Manholes may be either circular, 24 in. (610 mm) in
diameter; square, 24 in. (610 mm) × 24 in. (610 mm); or elliptical, 18 in. (457 mm) ×
22 in. (558.8), minimum size. Flush rectangular manholes with a minimum length of
24 in. (610 mm) in the shortest direction and a maximum length of 48 in. (1,219 mm)
in the longest direction are also acceptable. Cutouts for rectangular manholes must
have a minimum 6 in. (152 mm) radius at the corners.
5.1.2 Reinforcing. The shell plate where the manhole is located shall be
reinforced to comply with Sec. 3.11, and all portions of the manhole, including the
bolting, the cover, and reinforcement of the neck, shall be designed to withstand the
weight and pressure of the tank contents.
Sec. 5.2
Pipe Connections
The pipe connections shall be of the size specified by the purchaser. They are
usually attached to the tank bottom. Point of attachment shall be designated by the
purchaser (see foreword, Sec. III.C, item 5).
5.2.1 Silt stop. If a removable silt stop is required, it shall be at least 4 in. in
height, and the fitting or piping connection shall be flush with the tank floor when
the stop is removed. If a removable silt stop is not required, the fitting or connecting
pipe, or both, shall extend above the floor by at least 4 in.
5.2.2 Shell connections. Shell connections are permitted, provided the purchaser makes adequate provisions to protect the pipe from freezing and provides
adequate pipe flexibility to account for shell rotation and deflections of the shell when
filled.
5.2.3 Flexibility. Sufficient piping flexibility to accommodate seismic movements and settlement in the piping system shall be provided to protect the
connections.
Sec. 5.3
Overflow
The tank shall be equipped with an overflow of the type and size specified by the
purchaser. If a stub overflow is specified, it shall project at least 12 in. beyond the
Copyright © 1998 American Water Works Association, All Rights Reserved
20
AWWA D103-97
tank shell. If an overflow to ground is required, it shall be brought down the outside
of the tank shell and supported at proper intervals with suitable brackets. The
overflow to the ground shall discharge over a drainage inlet structure or a splash
block. It shall terminate at the top in a weir box or other appropriate intake. A top
stiffener shall not be cut or partially removed. The overflow pipe and intake shall
have a capacity at least equal to the pumping rate as specified by the purchaser, with
a water level not more than 6 in. (152.4 mm) above the weir. The overflow pipe shall
terminate at the bottom with an elbow. If carbon steel is specified by the purchaser,
the overflow pipe shall have screwed or welded connections if it is smaller than 4 in.
(101.6 mm) in diameter, or flanged or welded connections if it is 4 in. (101.6 mm) in
diameter or larger. The purchaser shall specify the maximum flow rate, in gallons per
minute, for which the overflow shall be designed. Internal overflows are not
recommended but may be provided if specified by the purchaser. The internal
overflow pipe shall have a minimum thickness of 1⁄4 in. (6.4 mm).
Sec. 5.4
Ladders
5.4.1 Outside tank ladder. The constructor shall furnish a tank ladder on the
outside of the shell beginning 8 ft (2.4 m), or as specified, above the level of the tank
bottom, and located to provide access to the roof manway. The minimum clear width
of step surface for rungs shall be 16 in. (406.4 mm), and rungs shall be equally spaced
not less than 11 in. (279.4 mm), nor more than 15 in. (381 mm), on center. The
perpendicular distance from the centerline of the rungs to the tank wall shall not be
less than 7 in. (177.8 mm). Rung size shall not be less than 3⁄4 in. (19 mm) in
diameter, or equivalent section. The maximum spacing of supports attaching the
ladder to the tank shall not exceed 10 ft (3 m). The minimum design live load shall
be 2 loads of 250 lb (113.4 kg), each concentrated between any two consecutive
attachments to the tank. Each rung in the ladder shall be designed for a single
concentrated load of 250 lb (113.4 kg), minimum. The design loads shall be
concentrated at such a point or points as will cause the maximum stress in the
structural ladder member being considered. Side rails may be of any shape having
section properties adequate to support the design loads and providing a means of
securely fastening each rung to the side rail so as to lock each rung to the side rails.
5.4.2 Inside tank ladder. Inside tank ladders are not recommended. If an
inside ladder is required, it shall comply with the requirements of Sec. 5.4.1.
5.4.3 Roof ladder. Unless otherwise specified, the constructor shall furnish
access to roof hatches and vents. Such access shall be reached from the outside tank
ladder according to the following:
1. For slopes 5 in 12 or greater, a ladder or stairway shall be provided.
2. Slopes less than 5 in 12 and greater than 2 in 12 shall be provided with a
single handrail and nonskid walkway.
3. Slopes 2 in 12 or less do not require a handrail or nonskid surface.
5.4.4 Minimum requirements. Minimum requirements for ladders, hatches,
and so forth can be found in OSHA 29 CFR Part 1910, “Occupational Safety and
Health Standards,” General Industry Standards. NOTE: Regardless of the access
protection provided to tank roof hatches and vents, weather conditions on tank roofs
are extremely variable and workers and their supervisors are expected to exercise
good judgment in matters of safety. Among other things, this may include the use of
safety lines when windy, icing, or other hazardous conditions exist.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Sec. 5.5
21
Safety Devices
If a safety cage, rest platforms, roof-ladder handrails, ladder lock, anti-climb
device, or other safety devices are required by federal or local laws or regulations, the
purchaser shall so specify. None of these are recommended for use inside the tank.
Sec. 5.6
Roof Openings
5.6.1 Ladder. The manufacturer shall furnish a roof opening, which shall be
placed near the outside tank ladder and which shall be provided with a hinged cover
and a hasp for locking. The opening shall have a clear dimension of at least 24 in.
(610 mm) in one direction and 15 in. (381 mm) in the other direction. The opening
shall have either (1) a curb at least 4 in. (101.6 mm) in height, and the cover shall
have a downward overlap of at least 2 in. (50.8 mm), or (2) a gasketed weathertight
cover, in lieu of the 4-in. (101.6-mm) curb and 2-in. (50.8-mm) overlap. When a
combined screened vent-manhole cover equipped with locking hasp is provided at the
roof center opening, the ladder opening may be omitted.
5.6.2 Roof center. An additional opening, with a removable cover having an
opening dimension or diameter of at least 20 in. (508 mm) and 4-in. (101.6-mm)
minimum height neck, shall be provided at, or near, the center of the tank. In lieu of
the 4-in. (101.6-mm) neck, a gasketed, weathertight cover is also acceptable.
Sec. 5.7
Vent
If the tank roof is of tight construction, a suitable vent shall be furnished above
the maximum water level. The vent shall have a capacity to pass air so that at the
maximum possible rate of the water, either entering or leaving the tank, excessive
pressure will not be developed. The overflow pipe shall not be considered a tank vent.
WARNING: An improperly vented tank may cause external pressures to act on
the tank, which will cause buckling even at a low pressure differential.
5.7.1 Location. Even if more than one vent is required, one tank vent shall
always be located near the center of the roof. The vent shall be designed and
constructed to prevent the ingress of birds or animals.
5.7.2 Screening. When governing health authorities require screening
against insects, a pressure-vacuum screened vent or a separate pressure-vacuum
relief mechanism shall be provided which will operate in the event that the screens
frost over or become clogged with foreign material. The screens or relief mechanism
shall not be damaged by the occurrence and shall return automatically to the
operating position after the clogging is cleared.
NOTE: The purchaser should clean the screens and check the pallets or relief
mechanism for operation at least once a year, but preferably each spring and fall.
Sec. 5.8
Additional Accessories and Exceptions
Any additional accessories required to be furnished shall be specified by the
purchaser. Exceptions to the provisions of this section may be specified by the
purchaser to suit special situations.
Copyright © 1998 American Water Works Association, All Rights Reserved
22
AWWA D103-97
SECTION 6:
Sec. 6.1
WELDING
General
The field assembly of all vertical, horizontal, shell-to-roof, and shell-to-bottom
plates or sheets shall be by bolting. Welding shall be limited to the shop installation
of nozzles, vents, manways, connections, and subassemblies. Field welding is to be
kept to a minimum and used only after acceptance by the manufacturer and
purchaser.
Sec. 6.2
Welds
All welds in the tank and structural members shall be made according to the
minimum requirements of AWS. Manufacturers shall maintain a welder training
program and shall be able to certify if requested that these welds were made by AWS
qualified welders and inspected according to AWS standards. These welds are to be
made to ensure complete fusion with the base metal, within the limits specified for
each joint, in strict accordance with the following procedure.
6.2.1 Weather conditions. Welding shall not be performed when the surfaces
of the parts to be welded are wet from rain, snow, or ice; when rain or snow is falling
on such surfaces; or during periods of high winds, unless the welder or welding
operator and work are properly protected. Welding shall not be done when the base
metal temperature is less than 0°F (–17.8°C). When the base metal temperature is
within the range 0°F–32°F (–17.8°C–0°C), the base metal within 3 in. (76.2 mm) of
the place where welding is to be started shall be heated until it is warm to the touch.
6.2.2 Peening. Peening of weld layers may be used to prevent undue
distortion. Surface layers shall not be peened.
6.2.2.1 Peening shall be performed with light blows from a power hammer
using a blunt-nosed tool.
6.2.3 Contour. All welds that are to be grit blasted before coating should be
rough ground to remove any high points prior to grit blasting. Welds that will not be
grit blasted shall be ground to a smooth contour.
6.2.3.1 Undercutting of base metal in the plate adjoining the weld shall be
repaired.
6.2.3.2 All craters shall be filled to the full cross section of the weld.
6.2.4 Reinforcement. The reinforcement of butt welds shall be as small as
practicable, preferably not more than 1⁄16 in. (1.6 mm). In no case shall the face of the
weld lie below the surface of the plates being joined.
6.2.5 Gouging. Gouging at the root of welds and gouging of welds to remove
defects may be performed with a round-nosed tool or by arc or oxygen gouging.
6.2.6 Cleaning between beads. Each bead of multiple-pass weld shall be
cleaned of slag and other loose deposits before the next bead is applied.
Sec. 6.3
Preparation of Surfaces to Be Welded
Surfaces to be welded shall be free from loose scale, slag, heavy rust, grease,
paint, and any other foreign material except tightly adherent mill scale. A light film
of weldable rust-preventive coating or compound may be disregarded. Such surfaces
shall also be smooth, uniform, and free from fins, tears, and other defects that
adversely affect proper welding. A fine film of rust adhering to cut or sheared edges
after wire brushing need not be removed.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Sec. 6.4
23
Low-Hydrogen Electrodes
The use of low-hydrogen electrodes will be helpful when welding is performed at
low temperatures. When the designated low-hydrogen covered electrodes are used,
preheating of the steel is not required unless the metal temperature is 32°F (0°C) or
lower. After filler metal has been removed from its original package, it shall be
protected or stored so that its characteristics or welding properties are not affected.
In the case of low-hydrogen electrodes, this means keeping the electrodes warm and
dry up to the time they are removed from the rod-storage oven. Low-hydrogen
electrodes shall be stored, and rebaked if necessary, in accordance with electrode
conditioning recommendations contained in AWS A5.1.
Sec. 6.5
Undercuts and Penetration of Welds
Welds shall be examined visually for compliance with the following:
6.5.1 Butt and lap joints subject to primary stress. For butt and lap joints
subject to primary stress due to weight or pressure of tank contents, there shall be
complete joint penetration and no undercutting.
6.5.2 Butt joint subject to secondary stress. For butt joints subject to secondary stress, there shall be complete joint penetration and no undercutting.
6.5.3 Lap joints subject to secondary stress. For lap joints subject to secondary stress, the maximum undercut permitted shall be 12 1⁄2 percent of the thinnest
sheet measured at each edge of the weld.
Sec. 6.6
Cleaning of Welds
The manufacturer shall remove weld scale or slag, spatter, burrs, and other
sharp or rough projections in a manner that will leave the surface suitable for the
subsequent cleaning and coating operation. Weld seams need not be chipped or
ground, provided they may be satisfactorily cleaned and coated.
SECTION 7:
Sec. 7.1
SHOP FABRICATION
Straightening
Any required straightening of material shall be done by methods that will not
damage the steel. Minor cold straightening is permitted. Cold straightening may be
done by hammering, or preferably, by rolling or pressing. Heat may be used in
straightening more severe deformations.
Sec. 7.2
Finish of Plate Edges—Welded Work
The plate edges to be bolted or welded may be universal mill edges or they may
be prepared by shearing, machining, chipping, or by mechanically guided oxygen or
plasma arc cutting. Edges of irregular contour may be prepared by oxygen or plasma
arc cutting.
7.2.1 Oxygen or plasma arc cutting. When edges of plates are oxygen or
plasma arc cut, the surface obtained shall be uniform and smooth and shall be
cleaned of slag accumulations before welding. All cutting shall follow closely the lines
prescribed.
7.2.2 Shearing. Shearing may be used for material 3⁄8 in. (9.5 mm) or less in
thickness.
Copyright © 1998 American Water Works Association, All Rights Reserved
24
AWWA D103-97
Sec. 7.3
Rolling
Plates and sheets shall be cold rolled or pressed to suit the curvature of the tank
and the erection procedure.
Sec. 7.4
Double-Curved Plates
Plates and sheets that are curved in two directions may be pressed or rolled
either cold or hot.
Sec. 7.5
Manufacturing Tolerances
7.5.1 Tanks with horizontally flanged shell joints. Parts fabricated and punched
for tanks with horizontally flanged shell joints shall comply with the dimensions and
tolerances of API 12B.
7.5.2 Tanks with horizontally lapped shell joints. The tolerance on bolt-hole
spacing for tanks with horizontally lapped shell joints shall be ±1⁄32 in. (0.8 mm)
between any two holes, measured in the flat before forming.
Sec. 7.6
Coatings
Bolted tanks are supplied with factory-applied coatings (refer to Sec. 10 for
coatings).
Sec. 7.7
Shipping
All material shall be loaded, transported to the site, unloaded, and stored in
such a manner as to prevent damage.
SECTION 8:
Sec. 8.1
ERECTION
General
The manufacturer shall provide instructions for the erection of the tank, and the
tank shall be erected in accordance with these instructions.
Sec. 8.2
Bolting
All bolts shall be located and installed in accordance with the instructions on
erecting the tank provided by the manufacturer.
Sec. 8.3
Gasketing and Sealants
Gasketing and sealants or both shall be supplied by the manufacturer and
installed between all joints in compliance with the erection instructions. The
constructor shall exercise care in properly locating and installing any special gaskets
(chime lap gaskets, tapered inserts, and so forth) supplied by the manufacturer.
Sec. 8.4
Coating Repair
The coating shall be visually inspected by the constructor and any damage to
the factory-applied coatings shall be repaired in strict compliance with the
manufacturer’s recommendations (see Sec. 10.2).
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
Sec. 8.5
25
Cleanup
On completion of the erection, the constructor shall, if required by the
purchaser’s specifications, dispose of all rubbish and other unsightly material caused
by the operations and shall leave the premises in as good a condition as found at the
start of the tank erection.
SECTION 9:
Sec. 9.1
INSPECTION AND TESTING
Shop Inspection
9.1.1 Shop inspection. The purchaser may, if specified, require shop inspection by a commercial inspection agency, the cost of which shall be paid by the
purchaser. Shop inspection shall at a minimum consist of a visual inspection of the
fabricating practices and operations to determine compliance with this standard.
9.1.2 Mill-test reports. When specified by the purchaser, copies of certified
mill-test reports shall be furnished by the manufacturer. The manufacturer shall
obtain copies of all mill-test reports.
9.1.3 Coating thickness test data. When specified, the manufacturer shall
supply certified test data on the coating thickness.
Sec. 9.2
Testing
9.2.1 Repair of leaks. Any leaks found shall be repaired by the constructor. It
is preferred that repair of joints be made while the water level is above the point
being repaired. See the foreword, Sec. III.C, item 7, for recommendations on blinding
and filling the tank, which is not covered by this standard.
9.2.2 Holiday testing. When specified, independent field holiday detection
testing shall be performed on the interior coated surfaces below maximum water
level in accordance with the manufacturer’s recommendations.
Sec. 9.3
Disposal of Test Water
The purchaser shall provide a means of disposing of test water with a
connection to the inlet pipe or drain pipe.
Sec. 9.4
Disinfecting
Regardless of the sequence used for testing the tank, it shall be disinfected after
the final test and the tank may then be filled with potable water and placed into
service. Disinfection shall not be the responsibility of the constructor or manufacturer
unless otherwise specified by the purchaser (see ANSI/AWWA C652).
SECTION 10:
Sec. 10.1
COATINGS
General
Bolted tanks are manufactured by several tank manufacturers and coated in
their own facilities and shipped worldwide. The following generic systems are
representative of those in general use. Equivalent generic systems, for which
documentation consisting of test data, service history, and toxicological information
Copyright © 1998 American Water Works Association, All Rights Reserved
26
AWWA D103-97
have been provided by the tank manufacturer, shall be considered for use in storage
tanks under the provisions of this standard.
Sec. 10.2
Coating Repair
It shall be the responsibility of each tank manufacturer to provide a procedure
for field repair and touch-up of damaged coatings.
Sec. 10.3
Galvanized Coatings
When hot-dip galvanized coatings are to be supplied, zinc metal suitable for
immersion in drinking water shall be applied to the tank parts after fabrication in
accordance with the recommended practice of the American Hot Dip Galvanizers
Association* in compliance with ASTM A123 and ASTM A153.
Sec. 10.4
Glass Coatings
When glass fused-to-steel coatings are provided, the coatings shall be applied
according to the tank manufacturer’s recommendations. Glass coatings are to comply
with the following.
10.4.1 Surface preparation. The steel shall be cleaned of all oils and lubricants. Mill scale and rust must be removed from the steel surface by grit blasting in
accordance with SSPC SP10 or by pickling in compliance with SSPC SP8.
10.4.2 Coatings.
10.4.2.1 The steel is to be primed with applications of catalytic nickel oxide
when tanks are fabricated from hot-rolled steel. Hot-rolled steel is susceptible to fish
scaling, which is a hydrogen defect that can be controlled by applications of catalytic
nickel oxide. Such a primer is necessary if both sides of hot-rolled steel are glass coated.
10.4.2.2 Glass coatings can be applied by wet spraying, flow coating, dipping,
or electrophoretic deposition. The coating thickness shall be between 6 mils
(0.15 mm) and 19 mils (0.48 mm).
10.4.2.3 The glass coating must be cured or fused to the steel by firing. This is
most conveniently done in a furnace, but can be carried out by means of induction or
resistance heating. The temperature should be above 1,200°F and preferably in the
range of 1,450°F to 1,600°F.
10.4.3 Inspection. The coating shall be inspected for any visible defects or
holidays. If severe conditions are encountered, a wet-pad resistance test should be
used to determine the extent of microscopic defects on the tank interior surfaces only
(Sec. 10.9).
Sec. 10.5
Thermoset Liquid Suspension Coatings
When thermoset liquid suspension epoxies are used, the coatings shall be
applied according to the tank manufacturer’s recommendations. Coatings are to
comply with the following.
10.5.1 Surface preparation. Surface preparation shall comply with the following.
10.5.1.1 The steel shall be thoroughly cleaned by a wash-rinse followed
immediately by hot air drying.
10.5.1.2 The steel shall then be grit blasted on both sides in accordance with
SSPC SP10. The surface anchor pattern shall be a minimum of 1 mil (0.03 mm).
*American Hot Dip Galvanizers Association, 1000 Vermont Ave. N.W., Washington, DC 20005.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
27
10.5.2 Coatings. The coatings are to be applied in compliance with the
following.
10.5.2.1 Within 30 min of blast cleaning (Sec. 10.5.1.2), the interior surfaces of
the tank shall receive one coat of amine-cured thermoset epoxy in strict accordance
with the manufacturer’s recommendations.
10.5.2.2 The exterior surfaces of the tank shall receive one coat of epoxy
primer or equal as determined by the tank manufacturer.
10.5.2.3 The interior and exterior coatings (Sec. 10.5.2.1 and 10.5.2.2) shall be
oven heated until the coats have a tacky finish, with partial thermal cross-linking.
10.5.2.4 The interior surfaces of the tank shall receive a second coat of aminecured epoxy to provide a total of 5-mil (0.13-mm) minimum dry film thickness.
10.5.2.5 The exterior surfaces of the tank shall receive a finish coat of acrylic
baking enamel and be thermally cured. Minimum dry film thickness shall be a total
of 3 mils (0.08 mm).
10.5.2.6 The interior and exterior finish coats shall be oven-heated at 425°F–
525°F (218.3°C–273.8°C) for a minimum of 10 min to completely thermal cross-link
both thermoset coatings.
10.5.2.7 Exterior coatings may be modified by agreement between the
purchaser and the tank manufacturer.
10.5.3 Inspection.
10.5.3.1 Inspection of interior. A representative sampling of interior coated
surfaces shall be inspected and accepted by the tank manufacturer prior to shipment.
The inspection shall include a nondestructive mil-thickness test (Mikrotest or equal),
a holiday detection test (Tinker Razor or equal), and methyl ethyl ketone (MEK)
solvent test consisting of 20 wipes or equal.
10.5.3.2 Inspection of exterior. A representative sampling of exterior coated
surfaces shall be inspected and accepted by the tank manufacturer prior to shipment.
The inspection shall include a nondestructive mil-thickness test (Mikrotest or equal).
Sec. 10.6
Thermoset Powder Coatings
When thermoset powder coatings are used, the coatings shall be applied
according to the tank manufacturer’s recommendations. Thermoset powder coatings
are to comply with the following.
10.6.1 Surface preparation. The steel shall be steel-grit blasted on all sides in
accordance with SSPC SP10.
10.6.2 Application. The coating is to be applied in compliance with the
following.
10.6.2.1 After blast cleaning, the interior and exterior surfaces shall be drypowder coated by electrostatic application with a powder coating.
10.6.2.2 The dry powder shall be deposited at a rate to yield 3 mil-minimum
dry film thickness.
10.6.2.3 The surfaces shall be oven cured in accordance with the dry-powder
coating manufacturer’s standard practice and specifications.
10.6.3 Inspection.
10.6.3.1 Inspection interior. A representative sampling of interior coated
surfaces shall be inspected and accepted by the tank manufacturer prior to shipment.
The inspection shall include a nondestructive mil-thickness test (Mikrotest or equal),
a holiday detection test (Tinker Razor or equal), and methyl ethyl ketone (MEK)
solvent test consisting of 20 wipes or equal.
Copyright © 1998 American Water Works Association, All Rights Reserved
28
AWWA D103-97
10.6.3.2 Inspection exterior. A representative sampling of exterior coated
surfaces shall be inspected and accepted by the tank manufacturer prior to shipment.
The inspection shall include a nondestructive mil-thickness test (Mikrotest or equal).
Sec. 10.7
Marking
All of the tank components shall be given a piece mark number for ease of
assembly. In lieu of this, the tank manufacturer’s standard practice may be used.
Sec. 10.8
Protection
All coated parts shall be protected from damage during shipment.
Sec. 10.9
Holiday Testing
All holiday tests shall be nondestructive and shall use an electric DC meter and
a wet sponge device. The maximum voltage of the meter shall be 67.5 volts. The
sponge shall be dipped in tap water as required to keep it uniformly damp, not
soaked or dry. No “conductive” or “wetting” additives shall be used in the tap water.
Refer to the tank manufacturer’s recommendations for setting, testing, and operation
of the meter by a trained technician.
SECTION 11:
Sec. 11.1
FOUNDATION DESIGN AND
CONSTRUCTION
General Requirements
The foundations are important because unequal settlement changes the distribution of stresses in the structure and may cause leakage or buckling of the plates.
11.1.1 Foundation plans. The manufacturer (or constructor) is not required
to furnish foundation plans unless specified by the purchaser. Should the purchaser
require foundation plans by the manufacturer or constructor, see Sec. II.D and III.C
of the foreword for additional information. Anchor bolts, when required, shall be
designed and furnished by the manufacturer.
11.1.2 Foundation installation. Foundations may be installed by either the
purchaser or the constructor (see the foreword, Sec. II.D and III.C). The earth around
the foundation shall be regraded sufficiently to permit efficient work during tank
erection and to prevent ponding of water in the foundation area. The tops of the
foundations shall be accurately located at the proper elevation.
11.1.3 Water load. Water load as defined in Sec. 3.2.2, shall be considered as
live load as defined by ACI 318 (see Sec. 11.6). The appropriate factors for all live
loads shall be used in foundation design.
Sec. 11.2
Soil-Bearing Value
The purchaser shall specify the allowable soil-bearing pressure using an
appropriate factor of safety (Sec. 11.3). However, in no case shall the specified bearing
pressure exceed that which would cause intolerable settlements and impair the
structural integrity of the tank.
11.2.1 Soil investigation. A soil investigation shall be provided by the
purchaser to determine the following:
1. The presence or absence of rock, old excavation, or fill.
2. Whether the site is a suitable place on which to build the structure.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
29
3. The classification of soil strata, after appropriate sampling.
4. The type of foundation that will be required at the site.
5. The elevation of groundwater, and whether dewatering is required.
6. The bearing capacity of the soil, and the depth at which footings must be
founded.
7. Whether piling will be required for support of foundations, and the length
of such piling.
8. The elevations of the existing grade and other topographical features that
may affect the foundation design or construction.
9. The homogeneity and compressibility of the soils across the tank site, so
that the possibility of total and differential settlement of the structure may be
evaluated.
Sec. 11.3
Factor of Safety
The following minimum factors of safety shall be used in determining the
allowable soil-bearing pressure. The ultimate bearing capacity should be based on
sound principles of geotechnical engineering. See the foreword, Sec. III.C, item 10, for
additional information.
11.3.1 Standpipes and reservoirs. A factor of safety of 3 shall be provided,
based on calculated ultimate bearing capacity when all direct loads and wind are
considered.
11.3.1.1 A factor of safety of 2.25 shall be provided, based on calculated
ultimate bearing capacity when all direct loads and earthquake loads are considered.
Sec. 11.4
Foundations
All tanks shall be supported on a concrete ringwall, concrete slab, or
structurally compacted granular berm as specified by the purchaser. The top of the
foundation shall be a minimum of 6 in. (152.4 mm) above the finished grade, unless
otherwise specified by the purchaser. Tanks that require anchor bolts shall be
supported on a ringwall or a concrete slab.
11.4.1 Types of foundations. The tank foundation shall be one of the following
types.
11.4.1.1 Type 1. Tanks supported on ringwalls. A sand or fine stone cushion at
least 3 in. (76.2 mm) thick shall be provided above the earthen interior under the tank
bottom. A 1-in. minimum space between the tank bottom and the top of the ringwall
shall be filled with a nonshrink grout or a 1:1.5 cement-sand grout. The grout shall
fill the entire space beneath the tank from the outside edge of the tank bottom to the
cushion. In no case shall the width of grout placed under the tank bottom be less
than 6 in. The top of the foundation shall be thoroughly saturated with water before
grout is placed. The materials and labor for grouting shall be furnished by the
constructor. In lieu of grout under the shell, the shell may be supported on a
minimum 1⁄2-in. (12.7-mm)-thick cane-fiber joint filler meeting the requirements of
ASTM D1751 if the foundation under the shell meets the tolerances of Sec. 11.6.1.
11.4.1.2 Type 2. Tanks supported on concrete slabs. A sand or fine stone
cushion not less than 1 in. (25.4 mm) thick shall be provided between the flat bottom
and the concrete slab foundation. In lieu of a cushion, the bottom may be supported
on a minimum 1⁄2-in. (12.7-mm)-thick cane-fiber joint filler meeting the requirements
of ASTM D1751. The tank shell shall be supported with grout or, alternatively, fiber
joint filler if the foundation under the shell meets the tolerances of Sec. 11.6.1. When
grouted, a 1-in. (25.4-mm) minimum space between the tank bottom and the top of
Copyright © 1998 American Water Works Association, All Rights Reserved
30
AWWA D103-97
the concrete shall be filled with a nonshrink grout or a 1:1.5 cement-sand grout. The
grout shall fill the entire space beneath the tank from the outside edge of the tank
bottom to the cushion. In no case shall the width of grout placed under the tank
bottom be less than 6 in. (152.4 mm). The top of the foundation shall be thoroughly
saturated with water before grout is placed. The materials and labor for grouting
shall be furnished by the constructor.
NOTE: When a steel base-setting ring is used in conjunction with a concrete slab,
no grout or fiber joint filler is required (see Sec. 11.4.1.6 for Type 6 foundations).
11.4.1.3 Type 3. Tanks within ringwalls. Tanks may be placed on a cushion
within a concrete ringwall. The cushion shall consist of a minimum of 6 in.
(152.4 mm) of sand or fine stone. The inside of the ringwall is to be a minimum of
3
⁄4 in. (19 mm) outside the bottom plates of the tank. Adequate provisions for
drainage inside the ringwall must be made.
11.4.1.4 Type 4. Tanks supported on granular berms. The berm shall be wellgraded stone or gravel. The berm shall extend a minimum of 3 ft (0.9 m) beyond the
tank shell and from there have a maximum slope of 1:1.5. The berm under the shell
shall be level within ±1⁄8 in. (3.2 mm) in any 10 ft (3 m) of circumference and within
±1⁄2 in. (12.7 mm) in the total circumference. Adequate protection shall be provided to
ensure against foundation washout.
11.4.1.5 Type 5. Tanks supported on granular berms with steel retainer
rings. The berm shall be well-graded stone or gravel. The berm shall extend to the
retainer ring. The size and coating of the steel retainer ring shall be specified by the
purchaser and shall be a minimum of 12 in. (304.8 mm) from the shell or a sufficient
distance to ensure berm stability under the shell in the event that the steel retainer
ring is removed. The berm under the shell shall be level within ±1⁄8 in. (3.2 mm) in
any 10 ft (3 m) of circumference and within ±1⁄2 in. (12.7 mm) in the total
circumference.
11.4.1.6 Type 6. Tanks with base setting ring embedded in concrete slab. The
base setting ring shall be supported on a ringwall foundation prior to placement of
slab concrete. A minimum clear distance of 3 in. (76.2 mm) between the top of the
slab and the bottom of the base setting ring shall be provided. The outside curb shall
have a minimum width of 8 in. (203.2 mm), and its top shall be level within ±1 in. of
the top of the slab. A minimum of one elastomer water stop shall be bonded to the
inside base setting ring surface at a minimum distance of 2 in. below the top of the
concrete slab. Shrinkage-reinforcing steel shall be used in the concrete slab adjacent
to both the inside and the outside of the base setting ring in accordance with
ACI 318. For concrete slabs supported on grade, the manufacturer shall provide
specifications for the preparation of sub-base material, if required by the purchasers
specifications (see foreword, Sec. III.C, item 11).
Sec. 11.5
Detail Design of Foundations
11.5.1 Height above ground. The tops of the concrete foundations shall be a
minimum of 6 in. (152.4 mm) above the adjacent grade, unless otherwise specified by
the purchaser.
11.5.2 Minimum depth of foundations. The minimum depth of foundations
shall be determined from Figure 3. The extreme frost penetration depths in Figure 3
shall be the minimum depth of foundation below the ground line. Foundation depth
shall be increased in localities where soil or other factors are favorable to deep frost
penetration and may be reduced for piers resting on rock. Consult local records for
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
o
125
o
5"
o
120
o
115
110
o
o
105
100
o
o
95
70" 80" 90" 100"
o
45
o
90
o
85
80
o
o
75
70
o
65
100"
90"
100"
90"
31
100"
90"
80"
o
45
70"
40"
60"
50"
40"
30"
20"
30"
10"
60"
o
40
50"
50"
Consult local
records for
this area
o
35
0"
o
35
5"
20"
o
o
30
30
10"
0"
5"
5"
0"
0"
o
25
0
o
115
Figure 3
o
40
o
110
o
105
o
100
o
95
o
90
100
Kilometers
200 300 400
o
85
o
25
500
o
80
o
75
Extreme frost penetration—inches (based on state averages)
the extreme frost penetration in the circled area of Figure 3. Uplift or soil-bearing
requirements may dictate greater depths. Minimum depth shall be 12 in. (304.8 mm).
11.5.3 Size of top. The tops of foundations shall project at least 3 in. beyond
the tank shell. In base setting ring applications, the top of the foundation should
project a minimum of 8 in. (203 mm) beyond the tank shell. The top corners shall be
either neatly rounded or finished with a suitable bevel. When anchor bolts are
required, the foundations shall extend at least 9 in. (228.6 mm) beyond the tank shell.
11.5.4 Pile foundations. If a pile-supported foundation is required, the purchaser
shall specify the pile type and depth below existing grade to be used for bidding and
design capacities for live and dead loads, including the weight of all soil above the
footing, and for live and dead loads combined with wind or seismic loads or both.
Sec. 11.6
Concrete Design, Materials, and Construction
The design of the concrete foundations, the specifications for the cement and
aggregate, and the mixing and placing of the aggregate shall be in accordance with
ACI 318, except as may be modified in this section and the following subsections.
Concrete work shall conform to all requirements of ACI 301, except as modified by
agreement between the purchaser and constructor.
11.6.1 Tolerances on concrete foundations. Ringwalls and slabs, after grouting
or before placing the cane-fiber joint filler, shall be level within ±1⁄8 in. (±3.08 mm) in
any 30-ft (9.1-m) circumference under the shell. The levelness on the circumference
shall not vary by more than ±1⁄4 in. (6.4 mm) from an established plane. The tolerance
on poured concrete before grouting shall be ±1 in. (25.4 mm).
Copyright © 1998 American Water Works Association, All Rights Reserved
32
AWWA D103-97
11.6.2 Finish. The top portions of foundations, to a level 6 in. (152.4 mm)
below the proposed ground level, shall be finished to a smooth form finish in
compliance with ACI 301. Any small holes may be troweled over with mortar as soon
as possible after the forms are removed.
11.6.3 Anchor bolts. It is the responsibility of the constructor to locate the
anchor bolts within 1⁄4 in. (6.35 mm) of the manufacturer’s anchor bolt layout design.
11.6.4 Base-setting ring. If a base-setting ring is required, it is the responsibility of the constructor to level the setting ring within 1⁄16 in. (1.54 mm) of level and
concentric within 1⁄4 in. (6.35 mm). The constructor shall locate the manufacturersupplied base-setting ring in conformance with the manufacturer’s design.
Sec. 11.7
Backfill
For tanks with ringwall foundation, all topsoil, organic material, and undesirable material within the ringwall shall be removed and replaced with a controlled,
load-bearing backfill specified by the designer of the foundation. The natural soils
and load-bearing backfill within the ringwall shall be capable of supporting the tank
bottom without general settlement or localized settlement causing breakdown of the
tank bottom adjacent to the ringwall.
11.7.1 Material and compaction. Load-bearing backfill shall be suitable nonfrozen material placed and compacted in uniform horizontal lifts to the degree of
compaction required by the foundation design. The water load and ringwall height
shall be considered in determining the required degree of compaction.
11.7.2 Pipe cover. Pipe cover shall be provided in compliance with Figure 4
unless local conditions dictate that more or less cover should be used.
71
/
7 2
5 51/2
6 1/
2
6
4 41/2
3 3 1/2
6
6 1/2
2 21/2
6 1/2
6
7
7 1/2
7
6 1/2
6
2
51/2
5
41/2
4
21/2
2
Recommended depth of pipe cover—feet above top of pipe
Copyright © 1998 American Water Works Association, All Rights Reserved
6
2
51 /
5
41 /
4
31 /2
3
31/2
3
Figure 4
61
/2
1 /2
7
21/2
2
0
Kilometers
100 200 300 400 500
FACTORY-COATED BOLTED STEEL TANKS
SECTION 12:
Sec. 12.1
33
SEISMIC DESIGN OF FLAT-BOTTOM
WATER-STORAGE TANKS
General
12.1.1 Applicability. This section shall be used as prescribed by Sec. 3.2.5.
12.1.2 Tabulation form for seismic data. A sample tabulation form for seismic data, for use by the purchaser, is included in Sec. 12.7. It is followed by an
example to demonstrate the use of the form. The tabulation form for seismic loads
shall be completed by the purchaser.
Sec. 12.2
Seismic Design Considerations
12.2.1 Effective-mass method. The design of ground-supported, flat-bottom
tanks recognizes the reduction in seismic load due to the sloshing of the contained
liquid. This design procedure is referred to as the effective-mass method. See the
references in Sec. 12.8 for details of this design method.
12.2.2 Anchored and unanchored tanks. Flat-bottom tanks may be anchored
or unanchored to resist earthquakes.*
12.2.2.1 Anchored tanks could be susceptible to tearing of the shell if
anchorage is not properly designed. Care must be taken to ensure that anchor-bolt
attachments are stronger than the anchor bolt. Experience shows that properly
designed anchored tanks retain greater reserve strength to seismic overload than
unanchored tanks. Anchorage shall be designed such that anchor bolts yield before
the shell attachment fails.
12.2.2.2 Seismic resistance of an unanchored tank is related to the height-todiameter ratio of the structure.
Sec. 12.3
Seismic Design Loads
The following design loads are based on a consistent probability of seismic
disturbance in the United States. A use factor has been included based upon use and
importance of the storage tank. Allowable stresses in this section apply only to
loading conditions, which include seismic loads defined in this standard. Static load
and wind conditions are covered by Sec. 3. Allowable stresses for anchor bolts shall
conform to AISC (ASD) allowable stresses.
12.3.1 Effective-mass procedure. The effective-mass procedure considers two
response modes of the tank and its contents: (1) the high-frequency amplified
response to lateral ground motion of the tank shell and roof together with a portion
of the liquid contents that moves in unison with the shell, and (2) the low-frequency
amplified response of a portion of the liquid contents in the fundamental sloshing
mode. The design requires the determination of the hydrodynamic mass associated
with each mode and the lateral force and overturning moment applied to the shell
resulting from the response of the masses to lateral ground motion.
*If an unanchored tank design is used, the maximum thickened bottom annulus width (radial
direction) used to resist overturning shall be limited to 7 percent of the tank radius. For the
maximum thickness of the bottom annulus, refer to Sec. 12.3.3.2. The tank must be anchored
if these criteria cannot be met.
Copyright © 1998 American Water Works Association, All Rights Reserved
34
AWWA D103-97
The base shear and overturning moment due to seismic forces applied to the
bottom of the shell shall be determined in accordance with the following formulas:
Base shear:
18ZI
V ACT = ------------- [ 0.14 ( W s + W r + W 1 ) + SC 1 W 2 ]
Rw
(Eq 15)
Overturning moment:
18ZI
M = ------------- [ 0.14 ( W s X s + W r H t + W 1 X 1 ) + SW2 X 2 C 1 ]
Rw
(Eq 16)
Where:
VACT = actual lateral shear, in pounds
M = overturning moment applied to the bottom of tank shell, in footpounds or other consistent units
Z = zone coefficient from Figure 5 and Table 3
I = use factor from Table 6
Rw = force reduction coefficient from Table 4
Ws = total weight of tank shell bottom, and significant appurtenances in
pounds. The bottom shall not be included in the calculation for
overturning moment in Eq 16
Xs = height from the bottom of the tank shell to the center of gravity of the
shell, in feet
Wr = total weight of the tank roof (including framing and knuckle) plus
permanent loads, if any, as specified by the purchaser, in pounds.
Only that portion of the roof that bears on the shell shall be
considered for the overturning moment in Eq 16
Ht = total height of the tank shell, in feet
W1 = weight of effective mass of tank contents that moves in unison with
the tank shell, in pounds (Sec. 12.3.2)
X1 = height from the bottom of the tank shell to the centroid of lateral
seismic force applied to W1, in feet (Sec. 12.3.2)
S = site amplification factor from Table 5. Assumed to be 1.5 unless
otherwise specified by purchaser
W2 = weight of effective mass of the first mode sloshing contents of the
tank, in pounds (Sec. 12.3.2)
X2 = height from the bottom of the tank shell to the centroid of lateral
seismic force applied to W2, in feet (Sec. 12.3.3)
C1 is determined as follows:
For the condition where Tw < 4.5 seconds:
1
C 1 = ----------6T w
Copyright © 1998 American Water Works Association, All Rights Reserved
(Eq 16a)
FACTORY-COATED BOLTED STEEL TANKS
Zone coefficient (Z)
Table 3
Zone Coefficient
Zone*
Z
1
0.075
2A
0.15
2B
0.20
3
0.30
4
0.40
*For determination of zone, see Figure 5.
Table 4
Force reduction coefficient
Force Reduction Coefficient
Rw
Structure
Anchored flat-bottom tank
4.5
Unanchored flat-bottom tank
3.5
2A
3
2B
3
1
0
1
4
3
2A
2B
0
3
2B
4
4 3
3
1
0
1
3
2A
2B
3
0
Alaska
1
2B
3
1
1
2B
1
1
0
Hawaii
2B
3
4
2B
3
0
4
10
20
30
0
4
Guam
10
MILES
3
Puerto
Rico
0
MILES
3
3 Tutuila
4
25
MILES
50
Reproduced from the Uniform
Building Code,TM copyright 1997,
0
with the permission of the publisher,
the International Conference of
Building Officials.
Zone “0” indicates no seismic design required.
Figure 5
1
1
0
Aleutian Islands
2A
2A
2B
2A
1
3
1
1
4
2A
Seismic zone map for determining zone coefficient from Table 3
Copyright © 1998 American Water Works Association, All Rights Reserved
0
100
200
MILES
300
35
36
AWWA D103-97
Table 5
Site amplification factor S
Soil Profile Type
Site Amplification Factor*
A
B
C
D
1.0
1.2
1.5
2.0
*The following is an explanation for the determination of the site amplification factor, which shall be supplied by the
purchaser. Site effects on tank response shall be established based on the following four soil profile factors:
1.
Soil Profile Type A is a profile with:
a. Rock of any characteristic, either shale-like or crystalline in nature. Such material may be characterized by a shear
wave velocity greater than 2,500 ft/second (760 m/second).
b. Stiff soil conditions where the soil depth is less than 200 ft (61 m) and the soil types overlying rock are stable deposits
of sands, gravels, or stiff clays.
2. Soil Profile Type B is a profile with deep, cohesionless or stiff clay conditions, including sites where the soil depth
exceeds 200 ft (61 m) and the soil types overlying rock are stable deposits of sands, gravels, or stiff clays.
3. Soil Profile Type C is a profile with soft to medium-stiff clays and sands characterized by 30 ft (9.1 m) or more of soft
to medium-stiff clay with or without intervening layers of sand or other cohesionless soils.
4. Soil Profile Type D is a profile containing more than 40 ft (12.2 m) of soft clay characterized by a shear wave velocity
less than 500 ft/second (152.4 m/second).
In locations where the soil profile type is not known in sufficient detail to determine the soil profile type, soil profile type
C shall be assumed.
Table 6
Use factor I*
1.25
Sole supply
Fire protection
Multiple supply and fire protection
1.0
Multiple supply and no fire protection
*An I of 1.25 shall be used unless otherwise specified by the purchaser.
For the condition where Tw ≥ 4.5 seconds:
0.75
C 1 = ----------2
Tw
(Eq 16b)
Tw = first mode sloshing wave period, in seconds, which is determined as
follows:
Tw = Kp D
1⁄2
(Eq 16c)
Where:
Kp = factor from Figure 6 for the ratio of tank diameter, in feet, to
maximum depth of water, in feet, D/H, or other consistent units
D = tank diameter, in feet
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
37
1.0
0.9
Kp
0.8
0.7
0.6
0.5
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
D/H
Figure 6
Curve for obtaining factor Kp for the ratio D/H
NOTE: The overturning moment determined by this formula is that applied to
the bottom of the shell only. The tank foundation is subjected to an additional
overturning moment due to lateral displacement of the tank contents. This may need
to be considered in the design of some foundations, such as pile-supported concrete
slabs.
12.3.2 Effective mass of tank contents.
12.3.2.1 The weight of the effective mass of the tank contents that moves in
unison with the tank shell W1 (Eq 15 and 16) and the weight of the effective mass of
the first mode sloshing contents W2 (Eq 15 and 16) may be determined by
multiplying WT (Eq 17) by the ratios W1/WT and W2/WT, respectively. These ratios
may be obtained from Figure 7 for the ratio D/H,
Where:
WT = total weight of tank contents, in pounds. This value is determined by
the formula
2
2
πD
W T = 62.4GH  ----------- = 49GHD
 4 
(Eq 17)
Where:
D = tank diameter, in feet
H = maximum depth of water in the tank, in feet
G = specific gravity (1.0 for water)
12.3.2.2 The heights X1 and X2 (Eq 16), from the bottom of the tank shell to
the centroids of the lateral seismic forces applied to W1 and W2 (Eq 16), may be
determined by multiplying H by the ratios X1/H and X2/H, respectively. These ratios
may be obtained from Figure 8 for the ratio D/H.
12.3.2.3 The curves in Figures 7 and 8 are based on a modification of equations
in “Nuclear Reactors and Earthquakes” (see Sec. 12.8, reference 1). Moment arms X1
and X2 are valid for tanks supported on ringwalls. For tanks supported on slabs, see
reference 1 for additional overturning moment. Alternatively, W1, W2, X1, and X2 may
Copyright © 1998 American Water Works Association, All Rights Reserved
38
AWWA D103-97
1.0
W1
WT
W2
WT
W1
W2
or
WT
WT
0.8
0.6
0.4
0.2
0
0
Figure 7
1.0
2.0
3.0
5.0
4.0
D/H
6.0
7.0
8.0
Curves for obtaining factors W1/WT and W2/WT for the ratio D/H
1.0
0.8
0.6
X1
or
H
X2
H
X2
H
0.4
X1
H
0.2
0
0
Figure 8
1.0
2.0
3.0
4.0
D/H
5.0
6.0
Curves for obtaining factors X1/H and X2/H for the ratio D/H
Copyright © 1998 American Water Works Association, All Rights Reserved
7.0
8.0
FACTORY-COATED BOLTED STEEL TANKS
39
be determined by other analytical procedures based on the dynamic characteristics of
the tank. Where response spectra* are used, the acceleration of the two masses shall
replace the seismic coefficient as follows:
( Ai )
18ZI
A impulsive , ---------, replaces ( 0.14 ) ------------- (in g’s)
Rw
RF
( Ac )
18ZIC 1 S
A convective , ---------- , replaces ------------------------ (in g’s)
Rw
RF
Where:
g = acceleration due to gravity, which is 32.2 ft/second2
RF = reduction factor (see Sec. 12.4.1)
The spectral velocity is related to the convective acceleration as follows:
S v = 5.125A c T w , in ft/second
(Eq 18)
C 1 ZIST w
- , in ft/second
S v = 92.25 -------------------------Rw
(Eq 19)
or
Where:
Sv
Ai
Ac
Tw
=
=
=
=
spectral velocity, in feet per second
impulsive acceleration, in g’s, determined from the response spectrum
convective acceleration, in g’s, determined from the response spectrum
first mode sloshing wave period, in seconds
The other symbols are previously defined in Sec. 12.3.1.
12.3.3 Resistance to overturning.
12.3.3.1 Resistance to the overturning moment at the bottom of the shell may
be provided by the weight of the tank shell, weight of roof reaction on shell, Wrs, and
by the weight of a portion of the tank contents adjacent to the shell for unanchored
tanks, or by anchorage of the tank shell. For unanchored tanks, the portion of the
contents that may be used to resist overturning is dependent on the width of the
bottom annulus. The annulus may be a separate ring or an extension of the bottom
plate if the required thickness does not exceed the bottom thickness. The weight of
the annulus that lifts off the foundation shall be determined by the formula
* When tanks are located in an active fault zone capable of generating a maximum credible
earthquake of Richter magnitude 7.0 or greater, consideration should be given to developing a
response spectra for the site.
Copyright © 1998 American Water Works Association, All Rights Reserved
40
AWWA D103-97
w L = 7.9t b σ y HG ≤ 1.28HDG
(Eq 20)
Where:
wL = maximum weight of tank contents per foot of shell circumference that
may be used to resist the shell overturning moment, in pounds per
foot. Eq 20 applies whether or not a thickened annulus is used
tb = thickness of the bottom annulus, in inches
σy = minimum specified yield strength of bottom annulus, in pounds per
square inch
H = maximum depth of water, in feet
G = specific gravity (1.0 for water)
D = tank diameter, in feet
12.3.3.2 The bottom annulus may be thicker than the bottom shell course, but
the thickness tb, used to calculate seismic stability, shall not exceed the thickness of
the bottom shell course. When the bottom annulus is thicker than the remainder of
the bottom, the total width of the bottom annulus shall be equal to or greater than
that determined by the formula
σy
L ≥ 0.216t b --------- ≤ 0.035D , in feet
HG
(Eq 21)
Where:
L = total width of the bottom annulus measured from the inside of the
shell, in feet, but is not to exceed 0.035D
NOTE: If L exceeds 0.035D, the tank must be anchored.
The other symbols are previously defined in this section, under Eq 20.
12.3.4 Shell compression in unanchored tanks.
12.3.4.1 The maximum longitudinal shell compression stress at the bottom of
the shell when there is no uplift shall be determined by the formula
1.273M 1
σ c =  w t + --------------------- ----------- (psi)

2  12t
s
D
(Eq 22)
These terms are defined in this section, under Eq 16, 17, and 25.
NOTE: There is no uplift when the quantity resulting from Eq 23 is equal to or
less than 0.785.
M
--------------------------------≤ 0.785
2
D (wt + wL )
(Eq 23)
12.3.4.2 The maximum longitudinal shell compression stress at the bottom of
the shell when there is uplift shall be determined by the formula
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
wt + wL
1
– w L ----------- (psi)
σ c = -------------------------------------------------------------------------------------------2.3
12t


s
M
0.6070 – 0.18667  ---------------------------------
 D 2 ( w + w )
t
41
(Eq 24)
L
NOTE: There is limited uplift when Eq 25 yields a quantity greater than 0.785
but equal to or less than 1.54.
M
0.785 < --------------------------------- ≤ 1.54
2
D ( wt + wL )
(Eq 25)
When Eq 25 yields a quantity greater than 1.54, the bottom annulus must be
thickened (maximum thickness = ts) or the tank must be anchored. In thickening the
bottom annulus, the intent is not to force a thickening of the lowest shell course,
thereby inducing an abrupt thickness change in the shell, but rather to impose a
limit on the annulus ring thickness based on the shell design.
In Eq 22, 23, 24, and 25:
σc = maximum longitudinal shell compression stress, in pounds per square
inch
ts = thickness of bottom shell course, in inches
wt = weight of the tank shell and portion of the roof reacting on the tank
shell, in pounds per foot of shell circumference determined by the
formula
W
w t = -------s- + w r s
πD
(Eq 26)
wrs = roof load acting on shell in pounds per foot of shell circumference.
Only permanent roof loads shall be included. Roof live load shall not
be included.
The other symbols are previously defined in this section.
NOTE: The maximum longitudinal shell compression stress σc must be less than
the earthquake allowable stress σe, which is determined in compliance with
Sec. 12.3.7.4.
12.3.5 Shell compression and anchor loads in anchored tanks. When an anchored
tank is required, the maximum longitudinal compression stress at the bottom of the
shell shall be determined by Eq 22. The anchor tensile load is determined as follows:
--------------------- – w t
T B = S L 1.273M
2
D
Where:
TB = anchor tension, in pounds
SL = anchor spacing, in feet
The other symbols have been previously defined in this section.
Copyright © 1998 American Water Works Association, All Rights Reserved
(Eq 27)
42
AWWA D103-97
12.3.6 Hydrodynamic seismic hoop tensile stresses. Hydrodynamic seismic hoop
tensile stresses shall be determined by the following formulas.
1. When vertical acceleration is not specified,
σs = (Ni + Nc ) ⁄ t
(Eq 28)
ZI
Y 2
D
Y- – 0.5  ---tanh  0.866 -----
N i = 11.35 -------- GDH --- H

Rw
H
H
(Eq 29)
for D/H ≥ 1.333:
For D/H < 1.333 and Y < 0.75D:
2
ZI
Y 2
Y - – 0.5  --------------N i = 6.98 -------- GD --------------
0.75D
Rw
0.75D
(Eq 30)
For D/H < 1.333 and Y ≥ 0.75D:
2
ZI
N i = 3.50 -------- GD
Rw
(Eq 31)
2
3.68 ( H – Y )
ZI
17.55 -------- C 1 SGD cosh -------------------------------Rw
D
N c = --------------------------------------------------------------------------------------------------------3.68H
cosh ----------------D
(Eq 32)
For all values of D/H:
2.
When vertical acceleration is specified,
2
2
2
N i + N c + ( Nh av )
σ s = -----------------------------------------------------t
(Eq 33)
Where:
σs = hydrodynamic hoop stress, in pounds per square inch
Ni = impulsive hoop force, in pounds per inch* of shell height, at the design
point
Nc = convective hoop force, in pounds per inch* of shell height, at the
design point
*Derived from reference 1 in Sec. 12.8. When a response spectra is specified that does not
extend out to the period of the sloshing, it is acceptable to calculate spectral velocity by the
formula in Sec. 12.3.2.3.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
43
Nh = hydrostatic force, in pounds per inch of shell height, at the design point
= 2.6GYD
(Eq 33a)
av = vertical acceleration (decimal). This value shall be three fourths of the
impulsive acceleration, unless otherwise specified
t = thickness of the shell ring under consideration, in inches (millimetres)
Y = distance from fluid surface, in feet (positive down) to the bottom of
the ring or design point under consideration
The other symbols have been previously defined in this section.
The hydrodynamic hoop tensile stresses shall be added to the hydrostatic stress
in determining the total stress.
12.3.7 Additional considerations.
12.3.7.1 If vertical acceleration is specified, the purchaser shall indicate the
magnitude of acceleration, if different from that given in Sec. 12.3.6.
12.3.7.2 The purchaser shall specify the amount of freeboard to be provided for
the sloshing wave. Freeboard is defined as the distance from the top capacity level to
the lowest level of the roof framing. If the purchaser chooses to specify no additional
freeboard, some loss of contents and roof damage may occur if the tank is completely
full during an earthquake. The sloshing wave height may be calculated by the formula
ZIC 1 S
d = 7.53D ----------------Rw
(Eq 34)
Where:
d = wave height above top capacity level, in feet
The other symbols have been previously defined in this section.
12.3.7.3 Seismic design of roof framing and columns shall be made if specified
by the purchaser. The purchaser shall specify the amount of live loads and vertical
acceleration to be used in seismic design. Columns shall be designed for lateral water
loads and acceleration as specified by the purchaser. Seismic beam-column design
shall be based on the primary member allowable stresses, set forth in AISC (ASD),
increased by one third for seismic loading.
12.3.7.4 Allowable shell plate stresses in tension for the material used shall be
based on the stress allowable in Sec. 3. A one-third increase in basic allowable shell
plate stress is permitted for seismic loadings.
In compression, the effect of internal liquid pressure on increasing buckling
allowable stresses in Figure 9 shall be included with a safety factor of 2.0 in the
design of unanchored tanks subjected to seismic loading (refer to reference 5 in
Sec. 12.8).* The earthquake allowable stress is determined by the following formulas:
*The concept of increased stability due to internal pressure is supported by field observations
and model tests. The increase in allowable stress due to pressure is permitted for a “once in a
lifetime stress.” Conservative non-pressure allowables are used for operating loads since
consideration must be made for longevity, maintenance, settlement, tolerances, discontinuities,
and so forth.
Copyright © 1998 American Water Works Association, All Rights Reserved
44
AWWA D103-97
1.0
8
6
4
∆ Cc
2
0.10
8
6
4
2
0.01
2
4
0.01
6 8
2
4
6 8
0.10
2
4
6 8
1.0
P
E
R
t
2
10
4
6 8
102
2
The definitions for the symbols used in Figure 9 are as follows:
∆Cc = pressure stabilizing buckling coefficient
P = hydrostatic pressure at point under consideration in pounds per square inch
E = the modulus of elasticity
R = the radius of tank, in inches
t = the thickness of the plate under consideration
Figure 9 Increase in axial-compressive buckling-stress coefficient of cylinders due to internal
pressure (for use with unanchored tanks)
For unanchored tanks:
∆σ c r
σ e = 1.333  f s + ----------
2 
(Eq 35)
Where:
σe = earthquake allowable stress, in pounds per square inch
fs = allowable compressive stress, in pounds per square inch, determined
by the formula in Sec. 3.4.2
∆σcr = critical buckling stress increase due to pressure, in pounds per square
inch, determined by the formula
∆C c Et
∆π c r = ----------------R
Copyright © 1998 American Water Works Association, All Rights Reserved
(Eq 36)
FACTORY-COATED BOLTED STEEL TANKS
45
Where:
∆Cc
E
t
R
=
=
=
=
pressure stabilizing buckling coefficient (see Figure 9)
modulus of elasticity, 29,000,000 psi
thickness of the plate under consideration, in inches
radius of the tank, in inches
For anchored tanks:
σ e = 1.333f s
(Eq 37)
12.3.7.5 Tank sliding. Ground-supported tanks full of product have not been
found to slide off their foundation. When a sliding check is specified by the purchaser,
a coefficient of friction equal to tan 30° can be assumed. The actual lateral base
shear, Vact, shall be less than the allowable lateral base shear, Vallow.
V allow = tan 30° ( W s + W r + W 1 + W 2 ) ( 1.0 – 0.4a v )
(Eq 38)
Where:
Vallow = allowable lateral shear in pounds
Vact < Vallow
NOTE: See Sec. 12.3.1 (Eq 15) for determination of Vact.
2
P
---- [ R ⁄ t ]
E
Where:
∆Cc = pressure stabilizing buckling coefficient (see Figure 9)
P = hydrostatic pressure at point under consideration, in pounds per
square inch
E = modulus of elasticity
t = thickness of the plate under consideration, in inches
R = radius of the tank, in inches
2
P
NOTE: When ---- [ R ⁄ t ] exceeds 2.0, inelastic buckling occurs. Design is beyond
E
the scope of this standard.
Sec. 12.4
Local Seismic Data
When a spectral-response curve is provided for a given location, it may be used
in place of acceleration and spectral velocity values in this section. A 2-percent
damped curve is recommended for determining acceleration of a structure, and a
0.5-percent damped curve is recommended for determining acceleration of the
sloshing liquid. The amplified acceleration shall be determined for the cantilever
beam period of the shell and effective portion of the contained liquid.
Copyright © 1998 American Water Works Association, All Rights Reserved
46
AWWA D103-97
12.4.1 Scaling down site response spectra. Scaling down a site-specific
response spectra is appropriate for ductile modes of failure, such as hoop tension.
Nonductile modes of failure, such as elephant foot buckle at the base of groundsupported tanks may also be scaled down. Buckling loads that may result in total
collapse of the structure shall not be scaled down. Scaling down will depend on the
return period of the earthquake used to generate the response spectra. A reduction
factor, RF, of 2.5 shall be used for ground motion with a mean recurrence interval of
10,000 years. Where information is not available to accurately determine a
recurrence level, the maximum credible ground motion based on seismology, geology,
and seismic and geologic history of the site may be used to determine a site-specific
response spectra. For lower recurrence spectra, the spectra may be scaled down, but
in no case shall the final design acceleration be less than that calculated using values
from Tables 3 through 6 and Eq 15 and 16.
Sec. 12.5
Piping Connections
A minimum 2 in. of flexibility in the vertical and tangential directions in either
direction from the pipe centerline shall be provided for all piping attached to the shell.
12.5.1 Bottom connection for unanchored flat-bottom tanks. The bottom connection on an unanchored flat-bottom tank shall be located inside the shell a
sufficient distance to minimize damage by uplift. At a minimum, the distance
measured to the edge of the connection reinforcement shall be the width of the
calculated unanchored bottom hold-down plus 12 in. (305 mm), as shown in
Figure 10.
Sec. 12.6
Foundation Design
A one-third increase in allowable stress shall be permitted in foundation design.
12.6.1 Anchored flat-bottom tank. Ringwalls and footings for anchored flatbottom tanks shall be proportioned to resist maximum anchor-bolt uplift and
overturning bearing pressure. Water load directly over the ringwall and footing may
be used to resist the maximum anchor bolt uplift, provided the ringwall and footing
are designed to carry the eccentric loading. Water shall not be used to reduce the
anchor bolt load.
12.6.2 Unanchored flat-bottom tank. Calculated toe pressure to satisfy equilibrium on unanchored flat-bottom tanks produces impractical ringwall dimensions.
Minimum Distance
Hold Down
Figure 10
12 in.
Bottom piping connection of an unanchored flat-bottom tank (12 in. = 304.8 mm)
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
47
Some yielding of soil (settlement) may occur under the shell, requiring releveling of
the tank after an earthquake. The foundations under flat-bottom tanks, even tanks
resting directly on earth foundations, have fared well under seismic loadings.
Therefore, the seismic loading does not alter the foundation design criteria or provide
justifications for increased foundations for ring-bearing plates.* Design-bearing
pressure should be determined using the same method as for an anchored tank
condition. This assumption does not permit a larger Rw factor from Table 4. Rw shall
be 3.5.
12.6.3 Unanchored tank vaults. If a vault or ringwall penetration exists, that
portion under the shell shall be designed to carry the calculated shell load on its
unsupported spans.
Sec. 12.7
Tabulation Forms for Seismic Data and Example
Figure 11A presents a blank tabulation form for seismic data to be completed by
the purchaser. An example tabulation form and corresponding design calculations are
presented below.
Example:
Determining the adequacy of using a 0.1495-in. (3.8-mm)-thick bottom shell
course in a 21-ft (6.4-m) diameter by 24-ft (7.3-m) shell-height tank. The tank is
located in seismic zone 4, and there is no soil information available. Assume the tank
is to be anchored.
Ht = 24 ft (NOTE: In this example there is no freeboard, and the maximum
depth of water H is the same as the shell Ht.)
D = 21 ft
G = 1.0
ts = 0.1495 in. (bottom shell course thickness)
Xs = H/2, or 24/2 = 12 ft
Ws = 6,800 lb
Wr = 1,500 lb
wrs = 15 lb/ft
D/H = 21/24 = 0.875
See completed tabulation form (Figure 11B) for seismic data for Z, Rw, I, and S,
with values of 0.4, 4.5, 1.25, and 1.5, respectively.
Solution:
1. Overturning moment (see Sec. 12.3.1, Eq 16)
ZI
M = 18 -------- [ 0.14 ( W s X s + W r H t + W 1 X 1 ) + SW 2 X 2 C 1 ]
Rw
The unknown quantities for this equation are found as follows:
a. W 1 = 0.82W T (see Sec. 12.3.2.1 and Figure 7)
*A “ring-bearing plate” is a plate located under the shell to spread the unanchored shell
compressive stress.
Copyright © 1998 American Water Works Association, All Rights Reserved
48
AWWA D103-97
Bidding
NOTE: These specs are for
Final
Z—Zone coefficient (Table 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rw—Force reduction coefficient (Table 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
S—Site amplification factor (Table 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I—Use factor (Table 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vertical acceleration (optional)
Yes
No
Freeboard (optional) feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Following items pertain to roof:
Seismic design of roof
Yes
No
If yes checked above:
Vertical acceleration, percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Live load included, pounds per square foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Column lateral wave load, pounds per square foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Column horizontal acceleration, percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 11A
Blank tabulation form
Example:
Bidding
NOTE: These specs are for
Final
Z—Zone coefficient (Table 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.4
Rw—Force reduction coefficient (Table 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5
S—Site amplification factor (Table 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5
I—Use factor (Table 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.25
Vertical acceleration (optional)
Yes
No
Freeboard (optional) feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Following items pertain to roof:
Yes
Seismic design of roof
No
If yes checked above:
Vertical acceleration, percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Live load included, pounds per square foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Column lateral wave load, pounds per square foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Column horizontal acceleration, percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 11B
Completed tabulation form for design example
Copyright © 1998 American Water Works Association, All Rights Reserved
0
FACTORY-COATED BOLTED STEEL TANKS
In this formula
2
πD
W T =  ----------- H62.4 (see Sec. 12.3.2.1, Eq 17)
 4 
Substituting the known quantities
2
W T = [ ( π × 21 ) ⁄ 4 ] × 24 × 62.4
= 518,710 lb
W 1 = 0.82 × 518,710
= 425,342 lb
b. W 2 = 0.20W T (see Sec. 12.3.2.1 and Figure 7)
Substituting the known quantities
W 2 = 0.20 × 518,710
= 103,742 lb
c. X 1 = 0.42H (see Sec. 12.3.2.2 and Figure 8)
Substituting the known quantities
X 1 = 0.42 × 24
= 10 ft
d. X 2 = 0.77H (see Sec. 12.3.2.2 and Figure 8)
Substituting the known quantities
X 2 = 0.77 × 24
= 18.5 ft
e. C 1 = 1 ⁄ ( 6T w ) when Tw < 4.5 seconds
or
2
C 1 = 0.75 ⁄ T w when Tw ≥ 4.5 seconds (see Sec. 12.3.1, Eq 16a and 16b)
In these formulas,
Tw = Kp D
1⁄2
(see Sec. 12.3.1, Eq 16c, and Figure 6)
Substituting the known quantities
T w = 0.57 × 21
1⁄2
= 2.61
the formula C1 = 1/(6Tw) governs, and substituting the known quantities,
C 1 = 1 ⁄ ( 6 × 2.61 )
= 0.064
Copyright © 1998 American Water Works Association, All Rights Reserved
49
50
AWWA D103-97
Substituting the known quantities in the overturning moment formula
18 ( 0.4 ) ( 1.25 )
M = ------------------------------------- [ 0.14 ( 6,800 × 12 + 1,500 × 24 + 425,342 × 10 )
4.5
+ 1.5 × 103,742 × 18.5 × 0.064 ] = 1,592,377 ft ⋅ lb
2.
Shell compressive stress for anchored tank
1.273M 1
σ c =  w t + --------------------- ----------- (see Sec. 12.3.5, Eq 22)

2  12t
s
D
The unknown quantity for this equation is found as follows:
w t = W s ⁄ πD + wr s (see Sec. 12.3.4.2, Eq 26)
Substituting the known quantities
w t = 6,800 ⁄ π ( 21 ) + 15
= 118 lb/ft
Substituting the known quantities in the shell compressive stress formula
1
1.273 × 1,592,377- × ----------------------------σ c =  118 + ----------------------------------------------
 12 ( 0.1495 )
2
21
= 2,628 psi
3.
Earthquake allowable compressive stress
σ e = 1.333f s (see Sec. 12.3.7.4, Eq 37)
In this equation, try shell thickness t = 0.1495 in. The unknown quantity for
Eq 37 is found as follows:
2
2
t
t
a. f s = 15,000  ---  100 ---- 2 –  ---  100 ---- 
 3 
3
R
R 
(see Sec. 3.4.2)
Substituting the known quantities
2
0.1495
2
0.1495
f s = 15,000  ---  100 ------------------------ 2 –  ---  100 ------------------------ 
 3 
 3
10.5 × 12
10.5 × 12 
= 2,279 psi
Substituting the known values in the earthquake compressive stress formula (Eq 37)
σ e = 1.333 ( 2,279 )
σ e = 3,038 psi
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
51
Conclusion:
Since the earthquake compressive stress of 3,038 psi is greater than the shell
compressive stress of 2,628 psi, the shell thickness of 0.1495 in. is acceptable for an
anchored tank.
Sec. 12.8
References
1. 1963. Nuclear Reactors and Earthquakes. Burbank, Calif.: Lockheed
Aircraft Corporation, under a grant from the US Atomic Energy Commission. Tech.
Info. Doc. 7024; Ch. 6 and Append. F.
2. 1971. Earthquake Engineering for Nuclear Reactors. San Francisco, Calif.:
J.A. Blume & Associates.
3. Baker, E.H., et al. Apr. 1968. Shell Analysis Manual. NASA-CR-912.
Downey, Calif.: NAA Inc.
4. Baker, E.H., L. Kovalevsky, and F.L. Rish. 1972. Structural Analysis of
Shells. New York, N.Y.: McGraw-Hill Book Company.
5. Housner, G. W. 1954. Earthquake Pressures on Fluid Containers. Pasadena,
Calif.: California Institute of Technology.
6. Velestos A.S. & J.Y. Yang. 1976. Dynamics of Fixed-Base Liquid Storage
Tanks. Houston, Texas: Rice University.
NOTE: Other suitable references in addition to these will also accomplish the
intent of the seismic design of this section.
SECTION 13:
Sec. 13.1
STRUCTURALLY SUPPORTED ALUMINUM
DOME ROOFS
General
This section establishes minimum criteria for the design, fabrication, and
erection of structurally supported aluminum dome roofs. Aluminum dome roofs can
be used on any size tank erected in accordance with this standard. When this section
is required by the purchaser, it supersedes conflicting requirements of other sections.
All other requirements of AWWA D103 shall apply.
Sec. 13.2
Definition
The dome shall be a spherical structure conforming to the dimensions of the
tank. The dome structure shall be a fully triangulated space truss complete with noncorrugated closure panels. The dome shall be clear span and designed to be selfsupporting from the tank structure. The dome surface paneling shall be designed as
a watertight system under all design load conditions. All raw edges of the aluminum
panels shall be covered, sealed, and firmly clamped in an interlocking manner to
prevent slipping or disengagement under all load conditions and temperature
changes.
Sec. 13.3
Design Requirements
The tank shall be designed to support the aluminum dome roof. The roof
manufacturer shall supply the tank manufacturer with the magnitude and direction
of all the forces acting on the tank due to the roof loads and details of the roof-to-shell
attachment. The tank shall be designed to support given roof loads and attachment
details. Dissimilar metals shall be isolated to prevent galvanic corrosion. For new
Copyright © 1998 American Water Works Association, All Rights Reserved
52
AWWA D103-97
tanks, the tank manufacturer shall certify that the tank has been designed to
support the aluminum dome roof. For existing tanks, the purchaser or purchaser’s
agent shall make such a verification. The aluminum dome roof shall be supported
from the rim of the tank with primary horizontal thrust contained by an integral roof
tension ring. Provisions shall be made in the design of the connection between the
roof and tank rim to allow for thermal expansion. A minimum range of –40°F to
+140°F (–40°C to +60°C) shall be used for design unless a greater range is specified
by the purchaser.
Sec. 13.4
Materials
13.4.1 General. All materials furnished to meet the provisions of this section
shall be new and shall comply with all the requirements of this section. All aluminum
alloys, properties, and tolerances shall be as defined by the Aluminum Association’s
Aluminum Standards and Data. Unless specified by the purchaser, the aluminum
dome roof materials shall have a mill finish.
13.4.2 Structural frame. All structural frame members shall be made from
AA6061-T6 or a recognized alloy with properties established by the Aluminum
Association.
13.4.3 Roof panels. Roof panels shall be fabricated from AA3000 series or
AA5000 series aluminum with a minimum nominal thickness of 0.050 in. (1.27 mm).
13.4.4 Bolts and fasteners. All fasteners shall be AA7075-T73 aluminum or
austenitic stainless steel or other materials as accepted by the purchaser. Only
stainless steel fasteners shall be used to attach aluminum to steel.
13.4.5 Sealant and gasket material. All sealants shall be silicone compounds
conforming to Fed. Spec. TT-S-00230 unless another material is required for
suitability and compatibility when in contact with potable water. Sealants shall
remain flexible over a temperature range of –80°F to +300°F (–62°C to +148°C)
without tearing, cracking, or becoming brittle. Elongation, tensile strength, hardness,
and adhesion shall not change significantly with aging or from exposure to ozone,
ultraviolet light, or vapors from the water stored in the tank.
All preformed gasket material shall be made of silicone meeting Fed. Spec.
ZZ-R-765D, class 2, grade 50, or a purchaser-approved equal, unless another material
is required for compatibility with potable water stored in the tank.
13.4.6 Skylight panels. Skylight panels, if specified by the purchaser, shall be
clear acrylic or polycarbonate with a minimum nominal thickness of 0.25 in.
(6.4 mm).
Sec. 13.5
Allowable Stresses
13.5.1 Aluminum structural members. Aluminum structural members and
their connections shall be designed in accordance with the Aluminum Association’s
Specifications for Aluminum Structures, except as modified by this section.
For members subjected to axial forces and bending moments due to load
eccentricity or lateral loads, the combined member stresses shall be determined by
adding the stress component due to axial load to the stress components that result
from bending in both the major and minor axes.
Allowable shell buckling loads shall be determined in accordance with the
following formula:
6
1⁄2
2,258 × 10 ( Ix A )
w = ----------------------------------------------------2
( SF )R L
Copyright © 1998 American Water Works Association, All Rights Reserved
(Eq 39)
FACTORY-COATED BOLTED STEEL TANKS
53
Where:
w
Ix
A
R
L
SF
=
=
=
=
=
=
allowable load (pressure), in pounds per square foot
moment of inertia of strut about the strong axis, in inches4
cross-sectional area of strut, in square inches
spherical radius of dome, in inches
average member length, in inches
safety factor (1.65)
13.5.2 Aluminum panels. Aluminum panels shall be designed to support the
loads specified in Sec. 13.6 without exceeding the allowable stresses specified in the
Aluminum Association’s Specification for Aluminum Structures. Panel attachment
fasteners shall not penetrate both the panel and flange of the structural member.
13.5.3 Bolts and fasteners. For fasteners not listed in Table 7, the allowable
stress in bolts and fasteners shall be in accordance with the Aluminum Association’s
Specifications for Aluminum Structures and the AISI Stainless Steel Cold Formed
Structural Design Manual for Aluminum and Stainless Steel Bolts, respectively.
Hole diameters used for fasteners shall not exceed 1⁄16 in. (1.6 mm) plus the
diameter of the fastener used.
Sec. 13.6
Design
13.6.1 Detail drawings and calculations. Detail drawings and calculations
certified by a professional engineer experienced in the design of these structures
shall be provided when specified by the purchaser (refer to Sec. 1.4).
13.6.2 Principles of design. The roof framing system shall be designed as a
moment-resisting, three-dimensional space frame or truss with a membrane covering
(roof panels) providing loads along the length of the individual members. The design
shall consider the increased compression and minor axis bending induced in the
framing members as a result of the tension in the roof panels. The design loads shall
not exceed the allowable buckling loads set forth in Sec. 13.5.1. The actual stresses in
Table 7
Bolts and fasteners
Allowable Tensile
Stress*†
Material
Allowable Shear
Stress*†‡
psi
(MPa)
psi
(MPa)
Austenitic Stainless Steel (§)
30,000
(206.9)
18,000
(124.1)
Austenitic Stainless Steel (**)
42,000
(289.7)
25,000
(172.4)
AA2024-T4 Aluminum
26,000
(179.2)
16,000
(110.3)
AA7075-T73 Aluminum
28,000
(193.0)
17,000
(117.2)
NOTES:
*The root of thread area shall be used for calculating the strength of threaded parts.
†If the thread area is completely out of the shear area the cross-sectional area of shank may be used to determine the
allowable shear load.
‡For wind and seismic loads, these values may be increased by one third.
§For stainless steel bolts with a minimum tensile strength of 90,000 psi (620.5 MPa).
**For stainless steel bolts with a minimum tensile strength of 125,000 psi (861.8 MPa).
Copyright © 1998 American Water Works Association, All Rights Reserved
54
AWWA D103-97
the framing members and panels under all design load conditions must be equal to or
less than the allowable stresses.
The structural analysis shall include the effect of geometric irregularities such
as dormer openings and perimeter support members.
13.6.3 Design loads. In addition to design loads specified in Sec. 3.2, the
following loads shall be considered in the design of the aluminum dome roof.
13.6.3.1 Unbalanced loading. Reduce the live load by 50 percent over one-half
the dome.
13.6.3.2 Panel design load. These loads do not act simultaneously with other
design loads.
Two 250-lb (113.4-kg) loads concentrated on two separate 1 ft 2 (0.093 m 2) areas
of any aluminum panel, or 60 psf (293 kg/m 2) distributed over the total panel area.
13.6.3.3 Wind pressures may also be based on certified wind tunnel test
results.
13.6.3.4 The minimum wind load shall be the load resulting from a wind
velocity of 100 mph (45 m/second) unless a different wind velocity is specified by the
purchaser. Wind loading shall be determined in agreement with Sec. 3.2.4.
13.6.3.5 If the tank is designed for seismic loads, the roof shall be designed for
a horizontal seismic force determined by using the procedures of Sec. 12.
13.6.3.6 The following load combinations shall be considered:
1. Dead load
2. Dead load + Uniform live load
3. Dead load + Unbalanced live load
4. Dead load + Wind load
5. Dead load + Uniform live load + Wind load
6. Dead load + Unbalanced live load + Wind load
7. Dead load + Seismic load
Sec. 13.7
Roof Attachment Details
The structure supports provided to support the aluminum dome roof shall be
bolted or welded to the tank. The number of attachment points shall be determined
by the roof manufacturer in consultation with the tank manufacturer to preclude
overloading the tank shell. The attachment detail shall be suitable to transfer all roof
loads to the tank shell, keeping local stresses within allowable limits.
13.7.1 Roof supports. The roof attachment points may incorporate a slide
bearing with low-friction bearing pads to minimize the horizontal radial forces
transferred to the tank. Alternatively, the roof may be attached directly to the tank
and the top of the tank analyzed and designed to sustain the horizontal thrust
transferred from the roof, including the thrust from differential thermal expansion
and contraction.
13.7.2 Separation of carbon steel and aluminum. Aluminum shall be isolated
from the carbon steel by an austenitic stainless steel spacer or an elastomeric isolator
bearing pad, unless other methods are specified by the purchaser.
Sec. 13.8
Physical Characteristics
The maximum dome spherical radius shall be 1.4 times the diameter of the
tank. The minimum dome spherical radius shall be 0.7 times the tank diameter
unless otherwise specified by the purchaser.
13.8.1 Roof accessories. Roof accessories shall conform to the provisions of
Sec. 5, as applicable.
Copyright © 1998 American Water Works Association, All Rights Reserved
FACTORY-COATED BOLTED STEEL TANKS
55
13.8.2 Skylights. Skylights, if specified by the purchaser, shall be furnished
with a 4 in. (102 mm) or higher curb and shall be designed for the live and wind loads
specified for the roof. The purchaser shall specify the total skylight area to be provided.
Sec. 13.9
Testing and Sealing
13.9.1 Leak testing. After completion, the roof seams shall be leak tested by
spraying the outside with water from a hose with a minimum 50 psig (345 kPa) static
head pressure at the nozzle. Potable water shall be used. The water must not be
sprayed directly on any roof vents. Any water on the inside of the roof shall be
evidence of leakage.
Sec. 13.10
Fabrication and Erection
The manufacturer of the roof and constructor shall perform the work described
in this standard with qualified supervision that is skilled and experienced in the
fabrication and erection of aluminum structures. The dome shall be erected in
accordance with the manufacturer’s instructions.
13.10.1 Fabrication. All roof parts shall be prefabricated for field assembly.
Fabrication procedures shall be in accordance with Sec. 6 of the Aluminum
Association’s Specifications for Aluminum Structures.
13.10.2 Welding. The fabrication and design of welded aluminum parts shall
be in accordance with Sec. 7 of the Aluminum Association’s Specifications for
Aluminum Structures, and ANSI/AWS D1.2, Structural Welding Code—Aluminum.
All aluminum structural welds and components joined by welding shall be visually
inspected and tested by the dye-penetrant method of examination in accordance with
ANSI/AWS D1.2, Sec. 6.7.5. All structural welding of aluminum shall be performed
prior to field erecting of the dome. A full set of satisfactory examination and
qualification records shall be delivered to the purchaser if requested, prior to field
erection.
13.10.3 Shipping and handling. Materials shall be handled, shipped, and
stored in a manner that will not damage the surface of aluminum or the surface
coating of steel.
13.10.4 Workmanship. The roof shall be installed so as to minimize internal
stresses on the structure when bolted together, and to the supports. The basic
component parts of the structure shall be erected with precise fit and alignment.
Field cutting, trimming, relocating of holes, or the application of force to the parts to
achieve fitup is not acceptable.
13.10.5 Maintenance and inspection. The manufacturer of the roof shall
provide a maintenance and inspection manual for those items that may require
maintenance or periodic inspection.
Sec. 13.11
Coatings
Aluminum dome roofs shall have a mill finish. If a color other than mill-finish
aluminum is desired for aesthetic reasons, the exterior of the dome may be specified
to have a factory-applied, baked-on finish.
Exterior coatings may be thermosetting, acrylic, silicone polyester, or fluorocarbon.
NOTE: No coatings are to be applied to the interior surfaces of the dome, either
in the manufacturer’s shop or in the field.
The coating shall meet the requirements of AAMA 605.1 for high-performance
organic coating on architectural extrusions and panels.
The coating shall also meet the weathering requirements specified in ASTM D2244.
Copyright © 1998 American Water Works Association, All Rights Reserved
APPENDIX A
Metric (SI) Equivalents
This appendix is for information only and is not a part of AWWA D103.
Metric units used are those of the International System of Units (SI), which is
officially recognized by all industrial nations. This document may be supplemented
by ASTM * E380, Metric Practice Guide.
Table A.1 lists selected SI conversions for the convenience of users of this
standard.
Table A.1
Metric (SI) conversion factors
Property
To Convert US Customary Units From
To Metric (SI) Units
Multiply by*
Area
square inch (in.2)
square foot (ft2)
millimetre squared (mm2)
metre squared (m2)
metre squared (m2)
6.451 600*E + 02
6.451 600*E – 04
9.290 304*E – 02
Force
pound–force (lbf)
kip (1,000 lbf)
newton (N)
newton (N)
4.448 222 E + 00
4.448 222 E + 03
Force/Area
pound-force/foot2 (lbf/ft2)
newton/metre2 (N/m 2)
4.788 026 E + 01
Impact strength
foot-pound force (ft·lbf)
joule (J)
1.355 818 E + 00
Linear dimension
inch (in.)
foot (ft)
millimetre (mm)
millimetre (mm)
2.540 000*E + 01
3.048 000*E + 02
Mass/Volume
pound–mass/cubic foot (lb/ft 3)
kilogram/metre3 (kg/m 3)
1.601 846 E + 01
Temperature
degrees Fahrenheit (°F)
degrees Celsius (°C)
°C = (°F –32)/1.8
Tensile strength
pounds per inch2 (psi)
kips per inch2 (ksi)
pascal (Pa)
kilopascal (kPa)
megapascal (MPa)
6.894 757 E + 03
6.894 757 E + 00
6.894 757 E + 00
Velocity
miles per hour (mph) (US statute)
metre per second (m/second) 4.470 400*E – 01
Volume
gallon (gal) (US liquid)
metre cubed (m3)
3.785 412 E – 03
*An asterisk (*) after the sixth decimal place indicates that the conversion factor is exact and that all subsequent digits are
zero. The number is followed by the letter E (exponent), a plus or a minus symbol, and two digits that indicate the power
of 10 by which the number must be multiplied to obtain the correct value.
*American Society for Testing and Materials, 100 Barr Harbor Dr., West Conshohocken, PA
19428-2959.
56
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