aluminum dome roofs for water storage facilities

ANSI/AWWA D108-19(Revision of ANSI/AWWA D108-10)

AWWA Standard®

SM

Aluminum Dome Roofs for Water Storage Facilities

Effective date: Nov. 1, 2019.First edition approved by AWWA Board of Directors Jan. 17, 2010.This edition approved June 7, 2019.Approved by American National Standards Institute June 11, 2019.

Copyright © 2019 American Water Works Association. All Rights Reserved

Accessed by account: Vir. Dept. of Health-Office of Drinking Water | User: Sarah Hinderliter | Date: Wed Feb 10 12:47:51 2021 | IP address: 166.67.66.244

AWWA Standards have been usedwith permission and are copyrightedto the American Water WorksAssociation. All rights reserved.

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AWWA StandardThis 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. This standard does not supersede or take precedence over or displace any applicable law, regulation, or code of any governmental authority. AWWA standards are intended to represent a consensus of the water industry that the product described will provide satisfactory service. When AWWA revises or withdraws this standard, an official notice of action will be placed in the Official Notice 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 StandardAn 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 ANSI approval. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute, 25 West 43rd Street, Fourth Floor, New York, NY 10036; (212) 642-4900, or emailing [email protected].

ISBN-13, print: 978-1-62576-354-9 ISBN-13, electronic: 978-1-61300-524-8

DOI: doi.org/10.12999/AWWA.D108.19

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including scanning, recording, or any information or retrieval system. Reproduction and

commercial use of this material is prohibited, except with written permission from the publisher.

Copyright © 2019 by American Water Works Association Printed in USA

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including scanning, recording, or any information or retrieval system. Reproduction and commercial use of this material is prohibited, except with written permission from the publisher. Please send any requests or questions to [email protected].



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Committee Personnel

The Standards Subcommittee on Aluminum Dome Roofs, which developed this standard, had the following personnel at the time:

Tim D. Hopper, Chair

T.W. Bloomer II, Murraysmith, San Diego, Calif.T.D. Hopper, Tank Connection Affiliate Group, Lindale, Tex.M.P. Parker, Statewide Aquastore Inc., East Syracuse, N.Y.D.R. Pyewell, Tanco Engineering Inc., Loveland, Colo.G.R. Stein, Tank Industry Consultants, Indianapolis, Ind.C.M. Wilburn, CST Industries Inc., Conroe, Tex.

The AWWA Standards Committee on Steel and Composite Water Storage Tanks, which reviewed and approved this standard, had the following personnel at the time of approval:

Gregory R. Stein, Chair

General Interest Members

D.M. Algranti, Albert A. Webb Associates, Riverside, Calif.J.W. Birkhoff, Birkhoff, Hendricks & Carter LLP, Dallas, Tex.J.D. Brock, Consulting Services Logistics, Toledo, OhioM.M. Coleman,* Standards Council Liaison, Wade Trim Associates Inc., Detroit, Mich.E. Darrimon, Bay Area Coating Consultants Inc., Denair, Calif.W.J. Dixon, Dixon Engineering Inc., Lake Odessa, Mich.R.E. Gell, O’Brien & Gere Engineers Inc., Syracuse, N.Y.M.L. Hickey, Murraysmith, Portland, Ore.F.S. Kurtz,* Standards Engineer Liaison, AWWA, Denver, Colo.R. Perez, Greeley and Hansen, Indianapolis, Ind.L.D. Scott,† Tank Industry Consultants, Atascadero, Calif.G.R. Stein, Tank Industry Consultants, Indianapolis, Ind.J.I. Strand, CBS Squared Inc., Chippewa Falls, Wis.T.A. Tovey, Jacobs Engineering, Portland, Ore.

* Liaison, nonvoting† Alternate



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Producer Members

C. Brown,* Tnemec Company Inc., Kansas City, Mo.G.A. Burke, Caldwell Tanks Inc., Louisville, Ky.W.J. Czaska, McDermott, Plainfield, Ill.J.W. Davis, Tesla NanoCoatings Inc., Massillon, OhioK.T. Fuller, Phoenix Fabricators and Erectors LLC, Avon, Ind.J. Grendzinski,* Landmark Structures, Wheaton, Ill.B.E. Kromer, Tank Builders Inc., Euless, Tex.K. McGuire, CST Industries Inc., Parsons, Kans.R.L. Moore, Tnemec Company Inc., Kansas City, Mo.R. Pawski, Landmark Structures, Wheaton, Ill.

User Members

J. Camarena, East Bay Municipal Utility District, Oakland, Calif.T.M. Dawson Jr., Emerald Coast Utilities Authority, Pensacola, Fla.M.F. Gaffey, Naval Facilities Expeditionary Warfare Center, Washington Navy Yard, Washington, D.C.N.J. Meder, Connecticut Water Co., Clinton, Conn.R.B. Potts, Louisville Water Company, Louisville, Ky.G. Terrell, Birmingham Water Works Board, Birmingham, Ala.C. Xiao, City of Phoenix Water Services Department, Phoenix, Ariz.

* Alternate



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Foreword

I Introduction .................................... vii

I.A Background ..................................... vii

I.B History ............................................ vii

I.C Acceptance ...................................... vii

II Special Issues ................................... ix

III Use of This Standard ....................... ix

III.A Purchaser Options and Alternatives ............................... ix

III.B Information to Be Provided With Bid ............................................ x

III.C Modification to Standard ................ x

IV Major Revisions ............................... xi

V Comments ...................................... xi

Standard

1 General

1.1 Scope............................................... 1

1.2 Description ..................................... 1

1.3 Design Requirements ...................... 2

2 References ...................................... 2

3 Definitions ..................................... 3

4 Materials

4.1 General ........................................... 4

4.2 Structural Frame .............................. 4

4.3 Roof Panels ..................................... 4

4.4 Bolts and Fasteners .......................... 5

4.5 Sealant and Gasket Material ............ 5

4.6 Skylight Panels ................................ 5

5 Design

5.1 Drawings ......................................... 6

5.2 Principles of Design ......................... 6

5.3 Design Loads ................................... 6

5.4 Allowable Stresses and Allowable Loads ........................................ 7

5.5 Equivalent Metric Equations ........... 8

6 Roof Attachment Details

6.1 Roof Supports ................................. 10

6.2 Separation of Carbon Steel and Aluminum ................................ 10

6.3 Separation of Concrete and Aluminum ................................ 10

7 Physical Characteristics

7.1 Roof Accessories .............................. 10

7.2 Skylights .......................................... 10

8 Testing and Sealing

8.1 Leak Testing .................................... 11

8.2 Shell Seal ......................................... 11

ContentsAll AWWA standards follow the general format indicated subsequently. Some variations from this format may be found in a particular standard.

SEC. PAGE SEC. PAGE



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9 Fabrication and Erection

9.1 Fabrication ...................................... 11

9.2 Welding ........................................... 11

9.3 Shipping and Handling ................... 12

9.4 Quality of Work .............................. 12

9.5 Maintenance and Inspection ........... 12

10 Coatings or Other Finishes............ 12

11 Affidavit of Compliance ................ 12

Appendix

A Commentary for Aluminum Dome Roofs for Water Storage Facilities .................................... 13

Table1 Materials and Stresses for Bolts and

Fasteners ................................... 9

SEC. PAGE SEC. PAGE



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ForewordThis foreword is for information only and is not a part of ANSI*/AWWA D108.

I. IntroductionI.A. Background. In 1982, members of the American Water Works Association

(AWWA) became aware of the increased usage of aluminum domes as roofs on water storage tanks and reservoirs. As a result of this, it was decided to incorporate a reference to aluminum domes in the AWWA standards.

I.B. History. In 1987, Appendix A, Aluminum Dome Roofs for Water-Storage Tanks, became a part of D103-87, AWWA Standard for Factory Coated Bolted Steel Tanks for Water Storage.

In 1996, Section 15, Structurally Supported Aluminum Dome Roofs, was incorporated into D100-96, AWWA Standard for Welded Steel Tanks for Water Storage Tanks.

In 1997, Aluminum Dome Roofs left Appendix status and became Section 13, Structurally Supported Aluminum Dome Roofs, in D103-97, with revisions similar to those in D100-96.

In 2005, D100-05 was issued, incorporating revisions to Section 15, Structurally Supported Aluminum Dome Roofs.

In 2009, the AWWA Standards Committee on Steel Elevated Tanks, Standpipes, and Reservoirs, as part of an initiative to reorganize the AWWA standards under its umbrella, developed a separate standard for aluminum dome roofs that would be applicable to all tanks. That standard is now designated D108, AWWA Standard for Aluminum Dome Roofs for Water Storage Facilities. The first edition of the standard was approved by the AWWA Board of Directors on Jan. 17, 2010. This second edition was approved on June 7, 2019.

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 direct and indirect drinking water additives. Other members of the original consortium included the Water Research Foundation (formerly AwwaRF) and the Conference of State Health and Environmental Managers (COSHEM). AWWA and the Association of State Drinking Water Administrators (ASDWA) joined later.

* American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036.








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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. Specific policies of the state or local agency.2. Two standards developed under the direction of NSF,† NSF/ANSI‡ 60,

Drinking Water Treatment Chemicals—Health Effects, and NSF/ANSI 61, Drinking Water System Components—Health Effects.

3. 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 NSF/ANSI 61. Individual states or local agencies have authority to accept or accredit certification organizations within their jurisdiction. Accreditation of certification organizations may vary from jurisdiction to jurisdiction.

Annex A, “Toxicology Review and Evaluation Procedures,” to NSF/ANSI 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 Annex A procedures may not always be identical, depending on the certifier.

ANSI/AWWA D108 does not address additives requirements. 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 parties offering to certify products

for contact with, or treatment of, drinking water.3. Determine current information on product certification.

* Persons outside the United States should contact the appropriate authority having jurisdiction.† NSF International, P.O. Box 130140, 789 North Dixboro Road, Ann Arbor, MI 48105.‡ American National Standards Institute, 25 West 43rd Street, New York, NY 48105.§ Both publications available from The National Academies Press, 500 Fifth Street NW, Keck 360,

Washington, DC 20001.



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II. Special Issues. This standard has no applicable information for this section.

III. Use of This Standard. It is the responsibility of the user of an AWWA standard to determine that the products described in that standard are suitable for use in the particular application being considered.

Contractual responsibilities for items such as design, material, fabrication, construction, inspection, and testing are not included in this standard and must be addressed by the purchaser.

This standard is based on the accumulated knowledge and experience of purchasers and manufacturers of aluminum dome roofs.

Many aluminum domes built almost 40 years ago are still in service. Properly operated and maintained aluminum dome roofs can have a very long service life.

The term tanks where used in this standard shall apply to welded steel tanks, bolted steel tanks, and concrete tanks or reservoirs.

III.A. Purchaser Options and Alternatives. Proper use of this standard requires that the purchaser 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 modifications, deletions, or amplifications be made by supplementing this standard. This standard is not intended to cover aluminum dome roofs that are to be erected in areas subject to regulations that are more stringent than the requirements contained herein. In such cases, local regulations supersede the requirements of this standard. Where local, municipal, county, or state government requirements exist, such requirements are to govern and this standard should be interpreted to supplement them.

It is the purchaser’s responsibility to supplement or modify this standard for compliance with these local requirements. In addition, the purchaser is to provide clarification of the governing codes where they do not clearly refer to roofs, but where the purchaser intends such stipulations to apply to the tank roof under contract. As an example, if a governing code stipulates a building roof snow load of 40 lb/ft2 (1,915 N/m2) and it is intended that the tank roof be designed for this load, the purchaser is to include this as a clarification.

The details of design and construction covered by this standard are minimum requirements. At a minimum, it is important that all of the design conditions in this standard be met. An aluminum dome roof cannot be represented as an ANSI/ AWWA D108 roof if it does not meet the minimum requirements of this standard.



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III.A.1 Information to be Provided by Purchaser for an Aluminum Dome Roof. This standard provides minimum requirements for the design, construction, inspection, and testing of an aluminum dome roof without any designation of which party must perform these tasks. For this reason, the following information should be provided by the purchaser:

1. Standard used—that is, ANSI/AWWA D108, Aluminum Dome Roofs for Water Storage Facilities, of latest revision.

2. Type of tank—whether bolted, welded, or concrete.3. Tank details—that is, the diameter, height, and details of the top of tank to

which the aluminum dome roof is to attach.4. Site location.5. Desired time for completion.6. Name of town and distance to the nearest town.7. Type of road access available to the site.8. Roof design loads (wind, live, and snow loads) and the applicable building

code if it is different from the AWWA standard for the type of tank being covered by the aluminum dome roof.

9. Locations of all required roof accessories including hatches, vents, and other accessories.

10. Whether roof handrails, walkways, or other safety devices are required and whether requirements in excess of OSHA CFR Part 1910 are required.

11. Details of federal, state, and local requirements (Sec. 4.1).12. Whether compliance with NSF/ANSI 61, Drinking Water System

Components—Health Effects, is required.III.B. Information to Be Provided With Bid1. Dimensions of the aluminum dome roof and design basis.2. The number, names, and sizes of all accessories.3. Appearance coatings or finish information if one is specified.

III.C. Modification to Standard. Any modification to the provisions, definitions, or terminology in this standard must be provided by the purchaser.



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IV. Major Revisions. The major revisions made to this standard in this edition include the following:

1. Definitions for conventionally threaded fastener and lockbolt-type fastener have been added (Sec. 3).

2. The material requirements for bolts and fasteners have been modified (Sec. 4.4). Specific provisions for conventionally threaded aluminum fasteners, aluminum lockbolts, stainless steel lockbolts, and austenitic stainless-steel fasteners have been added.

3. The design requirements for bolts and fasteners have been modified extensively (Sec. 5.4.3 and Table 1).

4. Provisions for roof attachment details have been modified to address submerged bolts that connect aluminum members to carbon steel members (Sec. 6.2).

5. Requirements for fabrication and design of welded aluminum parts have been updated (Sec. 9.2).

6. Requirements for coatings and other finishes have been updated (Sec. 10).7. Appendix A, Commentary for Aluminum Dome Roofs for Water Storage

Facilities, has been added to provide additional guidance on the provisions contained in the body of the standard.

V. Comments. If you have any comments or questions about this standard, please call AWWA Engineering and Technical Services at 303.794.7711, FAX at 303.795.7603, write to the department at 6666 West Quincy Avenue, Denver, CO 80235-3098, or email at [email protected].



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®

Aluminum Dome Roofs for Water Storage Facilities

SECTION 1: GENERAL

Sec. 1.1 ScopeThis standard 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 AWWA standards. When this standard is specified, in the case of conflict between this standard and any other standard, the requirements of this standard shall govern.

Sec. 1.2 DescriptionThe 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 self-supporting 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.

ANSI/AWWA D108-19(Revision of ANSI/AWWA D108-10)

AWWA Standard




2 AWWA D108-19

Sec. 1.3 Design RequirementsThe tank shall be designed to support the aluminum dome roof. 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 shall be provided. The tank shall be designed to support given roof loads and attachment details. Noncompatible metals shall be isolated to prevent galvanic corrosion. A signed and sealed certification shall be provided by an engineer who has reviewed the design of the tank indicating that the tank has been designed to support the aluminum dome roof. The aluminum dome roof shall be supported from the rim of the tank with the 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.

SECTION 2: REFERENCES

This standard references the following documents. These documents in the edition specified, or latest edition if not specified, 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* ADM-2015—Aluminum Design Manual.AA ASD-2013—Aluminum Standards and Data.AA ASM-35—Specifications for Aluminum Sheet Metal Work.AA DAF-45—Designation System for Aluminum Finishes.AAMA† 2604-05—Voluntary Specification, Performance Requirements and

Test Procedures for High Performance Organic Coatings on Aluminum Extrusions and Panels.

AAMA TIR A9-2014—Design Guide for Metal Cladding Fasteners.ACI‡ 318—Building Code Requirements for Structural Concrete and

Commentary.ASTM§ C509-06—Standard Specification for Elastomeric Cellular Preformed

Gasket and Sealing Material.

* The Aluminum Association, Inc., 1400 Crystal Dr., Suite 430, Arlington, VA 22202.† American Architectural Manufacturers Association, 1900 E. Golf Rd., Suite 1250, Schaumburg, IL 60173.‡ American Concrete Institute, 38800 Country Club Dr., Farmington Hills, MI 48331.§ ASTM International, 100 Barr Harbor Dr., West Conshochocken, PA 19428.



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ALUMINUM DOME ROOFS FOR WATER STORAGE FACILITIES 3

ASTM C920-08—Standard Specification for Elastomeric Joint Sealants.ASTM C1115-06—Standard Specification for Dense Elastomeric Silicone

Rubber Gaskets and Accessories.ASTM D4141-14—Standard Practice for Conducting Black Box and Solar

Concentrating Exposures of Coatings.ASTM F468-03—Standard Specification for Nonferrous Bolts, Hex Cap

Screws, and Studs for General Use.ASTM F593-02(2008)—Standard Specification for Stainless Steel Bolts, Hex

Cap Screws, and Studs.ASTM G90-17—Standard Practice for Performing Accelerated Outdoor

Weathering of Materials Using Concentrated Natural Sunlight.AWS D1.2/D1.2M:2003—Structural Welding Code—Aluminum.Federal Specification* A-A-59588—Rubber, Silicone.ISO 3506-1—Mechanical Properties of Corrosion-Resistant Stainless Steel

Fasteners—Part 1: Bolts, Screws and Studs.NSF/ANSI 61—Drinking Water System Components—Health Effects.

SECTION 3: DEFINITIONS

The following definitions shall apply in this standard:1. Conventionally threaded fastener: A mechanical fastener consisting of a

headed fastener with the pin portion having helical threads, produced by either machining or the rolling process, and a nut with matching internal helical threads. The pin section can either be fully threaded or have an unthreaded portion under the head. For this type of fastener, the threaded portion of the pin might lie within the shear plane.

2. Lockbolt-type fastener: A mechanical fastener consisting of a headed fastener with the surface of the pin portion having locking grooves instead of helical threads and, instead of a threaded nut, a sleeve that is locked into place by a tool that swages the sleeve onto the locking grooves. The bolt includes a smooth pin section under the head that does not have locking grooves such that the shear plane of the joint being connected never occurs in the section having the locking grooves.

* US Government Publishing Office, 732 North Capitol Street, NW, Washington, DC 20401.





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4 AWWA D108-19

3. Manufacturer: The party that manufactures, fabricates, or produces materials or products.

4. Potable water: Water that is safe and satisfactory for drinking and cooking.

5. Purchaser: The person, company, or organization that purchases any materials or work to be performed.

6. Reclaimed water: Wastewater that becomes suitable for beneficial use as a result of treatment.

7. Supplier: The party that supplies material or services. A supplier may or may not be the manufacturer.

8. Wastewater: A combination of the liquid and water-carried waste from residences, commercial buildings, industrial plants, and institutions, together with any groundwater, surface water, and storm water that may be present.

SECTION 4: MATERIALS

Sec. 4.1 GeneralMaterials shall comply with the requirements of the Safe Drinking Water Act

and federal regulations for potable water, wastewater, and reclaimed water systems as applicable.

Materials provided 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 AA ASD. Aluminum materials shall be in accordance with the ASTM specifications listed in AA ADM Sec. 1.2. Unless otherwise specified, the aluminum dome roof materials shall have a mill finish.

Sec. 4.2 Structural FrameAll structural frame members shall be made from AA6061-T6, AA6005A-T6,

or other AA6000 series aluminum alloy as defined in AA ADM.

Sec. 4.3 Roof PanelsRoof panels shall be fabricated from AA3000 series or AA5000 series aluminum

with a minimum nominal thickness of 0.050 in. (1.27 mm). Aluminum alloys with a magnesium content greater than 3 percent shall not be used.




Sec. 4.4 Bolts and FastenersAll fasteners shall be aluminum or austenitic stainless steel. Only stainless

steel fasteners shall be used to attach aluminum to carbon steel. When stainless steel fasteners are used to attach aluminum to carbon steel, electrical isolation shall be provided between the dissimilar metals. Bolts may be lockbolt-type fasteners or conventionally threaded fasteners. Regardless of the fastener type, countersunk-type heads shall not be used.

4.4.1 Conventionally threaded fasteners. Conventionally threaded aluminum fasteners shall conform to the requirements of ASTM F468. Conventionally threaded austenitic stainless steel fasteners shall conform to the requirements of ASTM F593.

4.4.2 Lockbolts. Aluminum lockbolts shall conform to the requirements for chemical and mechanical properties of ASTM F468. Stainless steel lockbolts shall conform to the requirements for chemical and mechanical properties of ASTM F593 or ISO 3506-1.

4.4.3 Austenitic stainless steel fasteners. Austenitic stainless steel fasteners shall have a chromium content of 15 to 20 percent and a minimum nickel content of 8 percent. If the chromium content is below 17 percent, the minimum nickel content shall be 12 percent.

Sec. 4.5 Sealant and Gasket MaterialAll sealants and gaskets shall be suitable for contact with potable water

without chemical extraction. Sealants and gaskets shall remain flexible over a temperature range of –40°F to +170°F (–40°C to +77°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.

4.5.1 Sealants. All sealants shall be silicone compounds conforming to ASTM C920 unless another material is specified.

4.5.2 Gaskets. All preformed gasket material shall be made of silicone or neoprene unless another material is specified. Silicone gasket material shall meet Fed. Spec. A-A-59588 and ASTM C1115. Neoprene gasket material shall meet ASTM C509.

Sec. 4.6 Skylight PanelsSkylight panels, if specified, shall be clear acrylic or polycarbonate with a

minimum nominal thickness of 0.25 in. (6 mm).



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6 AWWA D108-19

SECTION 5: DESIGN

Sec. 5.1 DrawingsConstruction drawings for the roof shall be provided, including the following:

1. A drawing showing dimensions of the aluminum dome roof, the sizes of the principal members, the details of the tank attachment, the design loads, and the maximum loads transferred to the tank.

2. The number, names, and sizes of all accessories.3. Appearance coatings or finish information if specified.

Sec. 5.2 Principles of DesignThe 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 due to the tension in the roof panels. The design loads shall not exceed the allowable buckling loads set forth in Sec. 5.4.1. The actual stresses in 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.

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, all in accordance with the AA ADM.

All components of the aluminum dome roof shall be designed by the allowable stress design method.

Sec. 5.3 Design LoadsIn addition to design loads specified in the applicable AWWA standard for

the type of tank being covered and local building code, the following loads shall be considered in the design of the aluminum dome roof:

5.3.1 Unbalanced loading. Reduce the live load by 50 percent over one-half the dome.

5.3.2 Panel design load. These load cases do not act simultaneously with other design loads or with each other.




Load Case 1: Two 250-lb (113-kg) loads concentrated on two separate 1 ft2 (0.093 m2) areas of any aluminum panel.

Load Case 2: A 60-psf (293-kg/m2) uniform load distributed over the total panel area.

5.3.3 Skylight design load. Skylights, if specified, shall be designed for the same loads specified for the roof.

5.3.4 Load combinations. The following load combinations shall be considered:

1. Dead load2. Dead load + uniform live load3. Dead load + unbalanced live load4. Dead load + wind load5. Dead load + uniform live load + wind load6. Dead load + unbalanced live load + wind load7. Dead load + seismic load

Sec. 5.4 Allowable Stresses and Allowable Loads5.4.1 Aluminum structural members. Aluminum structural members and

their connections shall be designed in accordance with the AA ADM, except as modified by this section.

Allowable dome shell buckling loads shall be determined in accordance with the following formula:

w

I ASF R L

x

=´2 258 106 1 2

2

, ( )( )

(Eq 5-1)

where:w = allowable load (pressure), psfIx = moment of inertia of strut about the strong axis, in.4

A = cross-sectional area of strut, in.2

R = spherical radius of dome, in.L = average member length, in.SF = safety factor = 1.65

Alternatively, the stability of the roof may be determined using nonlinear analysis modeling. A minimum safety factor of 1.95 shall be used to account for modeling variations and assumptions.



8 AWWA D108-19

5.4.2 Aluminum panels. Aluminum panels shall be designed to support the loads specified in Sec. 5.3. Aluminum panel design shall comply with the AA ADM and AA ASM-35. Panel attachment fasteners shall not penetrate both the panel and the flange of the structural member supporting it. Lap and lock seams shall not be riveted or otherwise fastened together to restrict relative movement.

5.4.3 Bolts and fasteners. The allowable stresses for some common bolts and fasteners are listed in Table 1. For aluminum fasteners not listed in Table 1, the allowable stresses shall be in accordance with AA ADM or AAMA TIR A9. Grade 18-8 and Grade 18-10 stainless steel fasteners may be used for minor, nonstructural connections or connections using fastener diameters less than 5/16 in. (8 mm). In such connections, the allowable shear stress shall be 12,000 psi (85 MPa) and the allowable tensile stress shall be 18,000 psi (125 MPa).

The root thread area shall be used for calculating the strength of threaded parts. If the thread area is completely out of the shear plane, then the cross-sectional area of the shank may be used to calculate the allowable shear load.

Hole diameters used for fasteners shall not exceed 1/16 in. (1.6 mm) plus the diameter of the fasteners. For slotted holes, the smallest dimension on the slot shall not exceed 1/16 in. (1.6 mm) plus the diameter of the fasteners.

Fasteners (excluding post-set concrete anchors, which are governed by ACI 318) subject to combined shear and tension shall be sized so that the combined stress does not exceed the following:

ft / Ft + fv / Fv ≤ 1.3

Sec. 5.5 Equivalent Metric EquationsMetric equivalents of equations presented in Sec. 5 are as follows:

Equation Number Equivalent Metric Equation Variable Metric Units

5-1 w = 108.1(Ix ∕A)1/2 ∕ [(SF)R2L] w N/m2

Ix mm4

A mm2

R, L m




Table 1 Materials and stresses for bolts and fasteners1

Material2,3,4,5 Diameters

Alloy for ASTM Bolts,

Grade for ISO Bolts

Condition6 for ASTM

Bolts, Class for ISO Bolts

Published Minimum

Ultimate Tensile Strength

Published Minimum

Yield StrengthAllowable

Tensile Stress7

AllowableShear Stress7

psi (MPa) psi (MPa) psi (MPa) psi (MPa)

Stainless steel –

ASTM F593

≤1½ in. See notes 2 and 3

A8 75,000 (500) 30,000 (210) 18,000 (125) 12,000 (85)

<¾ in. See notes 2 and 3

CW9 100,000 (690) 65,000 (450) 39,000 (270) 20,000 (140)

¾ to 1½ in.

See notes 2 and 3

CW9 85,000 (590) 45,000 (310) 27,000 (185) 17,000 (115)

≤¾ in. See notes 2 and 3

SH10 120,000 (830) 95,000 (660) 48,000 (330) 24,000 (165)

¾ to 1 in. See notes 2 and 3

SH10 110,000 (760) 75,000 (520) 44,000 (305) 22,000 (150)

Stainless steel –

ISO 3506-1

All A14, A25, A3, A45,

A55

50 72,500 (500) 30,000 (210) 18,000 (125) 12,000 (85)

All A14, A25, A3, A45,

A55

70 101,500 (700) 65,000 (450) 39,000 (270) 20,300 (140)

All A14, A25, A3, A45,

A55

80 116,000 (800) 87,000 (600) 46,400 (320) 23,200 (160)

Aluminum – ASTM F468

All 6061-T6 See note 11

42,000 (290) 35,000 (240) 18,000 (120) 11,000 (73)


62,000 (430) 40,000 (275) 26,000 (180) 16,000 (110)


68,000 (470) 56,000 (390) 29,000 (200) 18,000 (120)

Notes:1. See Sec. 5.4.3 for allowable stress levels and allowed applications for Grade 18-8 and Grade 18-10 stainless steel fasteners.2. For ASTM F593, the following alloys may be used without modification to the requirements of the ASTM specification: 303,

303Se, 304, 304L, 305, 384, 302HQ, 321, 347.3. For ASTM F593, the following alloys may be used only with special modifications to the requirements of the ASTM specification:

316, 316L. For these alloys, the ASTM F593 specification must be modified to include a minimum nickel content of 12 percent if the chromium content is below 17 percent.

4. For ISO 3506-1, if Grade A1 is selected, the specification must be modified to include a minimum chromium content of 17 percent and a minimum nickel content of 8 percent.

5. For ISO 3506-1, if Grade A2, Grade A4, or Grade A5 is selected, the specification must be modified to include a minimum nickel content of 12 percent if the chromium content is below 17 percent.

6. Condition is based on the manufacturing process for fasteners produced in accordance with ASTM F593.7. Allowable stresses for lockbolts are the same as for conventionally threaded fasteners of the same chemical and mechanical

properties as listed in Table 1.8. For ASTM F593, Condition A fasteners are machined from annealed stock or solution-annealed stock or they are hot formed

and solution annealed.9. For ASTM F593, Condition CW fasteners are headed and rolled from annealed stock and then cold worked thus acquiring

the specified minimum properties listed in Table 1. Fasteners greater than ¾ in. in diameter may be hot worked and solution annealed.

10. For ASTM F593, Condition SH fasteners are machined from strain hardened stock that meets the specified minimum properties in Table 1, or they are cold worked to develop the specified minimum properties in Table 1.

11. Condition for 6061-T6 aluminum fasteners shall be solution treated and artificially aged.12. Condition for 2024-T4 aluminum fasteners shall be solution treated and naturally aged.13. Condition for 7075-T73 aluminum fasteners shall be solution treated and stabilized.












10 AWWA D108-19

SECTION 6: ROOF ATTACHMENT DETAILS

The structure supports provided to support the aluminum dome roof shall be bolted or welded to the tank. An adequate number of attachment points shall be provided 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.

Sec. 6.1 Roof SupportsThe 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.

Sec. 6.2 Separation of Carbon Steel and AluminumAluminum shall be isolated from the carbon steel by an austenitic stainless steel

spacer or an elastomeric isolator bearing pad, unless other methods are specified. In addition, any submerged bolts that connect aluminum members to carbon steel members must use phenolic or glass-reinforced epoxy washers under the head of the bolt and nut as well as a Mylar or glass-reinforced epoxy sleeve for the bolt hole.

Sec. 6.3 Separation of Concrete and AluminumAluminum shall be separated from contact with concrete through the use of

acceptable coatings or tape suitable for contact with potable water.

SECTION 7: PHYSICAL CHARACTERISTICS

Unless otherwise specified, the maximum dome spherical radius shall be 1.4 times the diameter of the tank, and the minimum dome spherical radius shall be 0.7 times the tank diameter.

Sec. 7.1 Roof AccessoriesRoof accessories shall conform to the provisions of the AWWA standard for

the type of tank being covered, as applicable.

Sec. 7.2 SkylightsSkylights, if specified, shall be provided with a 4-in. (102-mm) or higher

curb. The total skylight area to be provided shall be specified.




SECTION 8: TESTING AND SEALING

Sec. 8.1 Leak TestingAfter the roof installation is complete and it is verified the underside of the

roof is dry, the roof seams shall be leak tested by spraying the outside of the seams with water using a garden hose with a minimum 50 psig (345 kPa) static head pressure at the nozzle, held at a distance between 3 and 6 ft (0.9 and 1.8 m). 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. 8.2 Shell SealThe seal between the tank shell and roof need not be airtight. The bottom

of the roof flashing shall extend at least 2 in. (51 mm) below the top of the tank shell. The space between the flashing and tank shell shall be covered with a suitable noncorrosive screen or membrane to prevent the entrance of birds and insects.

SECTION 9: FABRICATION AND ERECTION

The dome shall be erected in accordance with the dome manufacturer’s instructions.

Sec. 9.1 FabricationAll roof parts shall be prefabricated for field assembly. Fabrication procedures

shall be in accordance with AA ADM Section 6.

Sec. 9.2 WeldingThe fabrication and design of welded aluminum parts shall be in accordance

with AA ADM for Aluminum Structures and AWS D1.2/D1.2M. All aluminum welds and components joined by welding shall be inspected by visual testing (VT) and shall be 100 percent liquid-penetrant tested (PT) in accordance with AWS D1.2/D1.2M Sections 5.7 and 5.17. Weld acceptance shall be in accordance with AWS D1.2/D1.2M Section 5.14 with VT acceptance criteria in accordance with AWS D1.2/D1.2M, Table 5.3, Visual Inspection of Statically Loaded Non-Tubular Connections, and Sec. 5.17, PT. All structural welding of aluminum shall be performed prior to field erecting of the dome. Written copies of both Welding Procedure Specifications (WPSs) and Welder Performance Qualification (WPQ) shall be provided, if requested, prior to welding. Welding inspector qualifications



12 AWWA D108-19

shall meet AWS D1.2/D1.2M Sec. 5.1.3. Personnel performing nondestructive testing (NDT) other than visual testing shall be qualified in accordance with AWS D1.2/D1.2M Sec. 5.7.6.

Sec. 9.3 Shipping and HandlingMaterials shall be handled, shipped, and stored in a manner that will not

damage the surface of aluminum or the surface coating if one is applied.

Sec. 9.4 Quality of WorkThe roof shall be installed so as to minimize internal stresses when assembling

the various members or components of the structure. Field cutting, trimming, relocating of holes, or applying force to the parts or components to achieve fit-up shall not be allowed.

Sec. 9.5 Maintenance and InspectionA maintenance and inspection manual for those items that may require

maintenance or periodic inspection shall be provided.

SECTION 10: COATINGS OR OTHER FINISHES

The standard finish for interior and exterior surfaces of aluminum dome roofs shall be a mill finish. For exterior surfaces of the dome, a factory-applied baked-on color finish or a nonglare mechanical finish may be specified. Coatings shall not be applied to interior surfaces.

If an exterior coating is selected, the finish coat shall conform to the weathering requirements of AAMA 2604 and a 95 percent gloss retention after a minimum of 1,252 MJ/m2 of UV spectrum exposure in accordance with ASTM D4141 (Procedure C) and ASTM G90 (Cycle 1). If a mechanical finish is selected, it shall be designation type M42, nondirectional textured fine mat, or M43, nondirectional textured medium mat, as detailed in AA DAF-45.

SECTION 11: AFFIDAVIT OF COMPLIANCE

The purchaser may require an affidavit from the manufacturer or supplier that the material provided complies with the applicable requirements of this standard.



https://envoi.awwa.org/resolver.cgi?D4141D4141M

https://envoi.awwa.org/resolver.cgi?G90

13

APPENDIX ACommentary for Aluminum Dome Roofs for Water Storage Facilities

This appendix is for information only and is not a part of ANSI /AWWA D108.Numbers following the “A” reference the applicable section in the body of the standard.

SECTION A.1: GENERAL (REFER TO SEC. 1 OF ANSI/AWWA D108)

Sec. A.1.1 ScopeIn addition to covering aboveground and elevated water storage

tanks, aluminum triangulated flat covers are being used increasingly to cover large in-ground water reservoirs (both earthen and concrete lined). While these basins are not specifically referenced in the standard, the design of the aluminum triangulated flat cover structures, which are used to cover them, closely resembles the aluminum dome design detailed within the standard; therefore, most of the guidelines detailed throughout the standard can apply to aluminum triangulated flat covers for in-ground water reservoir covers.

Sec. A.1.2 DescriptionIn areas where local height restrictions limit the rise of a structure

above grade, it may become necessary to column-support the aluminum cover. The need to column-support an aluminum dome roof is a function of the tank diameter, the maximum allowable height of the dome, the minimum roof live load specified, and the environmental loadings applicable to the specific aluminum dome design.

SECTION A.2: REFERENCES (REFER TO SEC. 2 OF ANSI/AWWA D108)

The references listed in Section 2 of this standard are a part of this standard. The following documents contain additional information related to aluminum dome roofs for water storage tanks:



14

1. ASCE 8-02—Specification for the Design of Cold-Formed Stainless Steel Structural Members

2. The Aluminum Association CFC60—Guidelines for Use of Aluminum with Food & Chemicals

3. AASHTO Division 2 Section 25 Elastomeric Bearings4. Federal Specification TT-S-00230C

SECTION A.4: MATERIALS (REFER TO SEC. 4 OF ANSI/AWWA D108)

Sec. A.4.4 Bolts and FastenersLockbolts are commonly used as structural fasteners on aluminum.

However, lockbolts are outside the scope of ASTM F468, ASTM F593, and ISO 3506-1. Lockbolts are allowed by this standard. Lockbolts are required to meet the same alloy and strength requirements of conventionally threaded fasteners that meet ASTM F468, ASTM F593, or ISO 3506-1. The allowable stress of a lockbolt is the same as the allowable stress of a conventionally threaded fastener with the same alloy, the same minimum tensile strength, and the same minimum yield strength.

Sec. A.4.5 Sealant and Gasket MaterialA.4.5.2 Gaskets. Due to the adverse effects of ultraviolet

exposure on neoprene, it is recommended that if neoprene gaskets are used, the dome design incorporate some means of encapsulating the gaskets to prevent ultraviolet exposure to the gaskets. This is not applicable if silicone gaskets are used.

SECTION A.5: DESIGN (REFER TO SEC. 5 OF ANSI/AWWA D108)

Sec. A.5.2 Principles of DesignThe current version of the AA ADM holds provisions for both

allowable stress design method and strength-based design (load and resistance factor design) method.







15

Sec. A.5.3 Design LoadsThe purpose of the design loads, as stated in the standard, is to

define a minimum design load criteria for all dome roofs to be installed on water storage tanks. In many cases, design load requirements, as required by ASCE 7 and/or other governing local codes, will prove to be more stringent. For example, while ASCE 7 and most governing local codes do allow for a reduction in the roof snow load (pf) as slope increases, they do not allow the roof snow load (pf) to be reduced to zero when the slope of the roof exceeds 30 degrees. To ensure local code compliance, or as required for local permitting when applicable, it is recommended that ASCE 7 and any locally adopted building codes be reviewed by the aluminum dome designer and the most stringent used for the design in cases where it is determined that these codes are more stringent than the requirements of the standard.

A.5.3.1 Unbalanced loading. The unbalanced load case as stated in the standard, which calls for reduction of the live load by 50 percent over one-half the dome, will not control the aluminum dome structure design over the uniform live load in some cases. In many cases, unbalanced snow load distributions for aluminum domes, as required by ASCE 7 and/or other governing local codes, will prove more stringent and will control the design of the aluminum dome structure. To ensure local code compliance, it is recommended that ASCE 7 and local building codes be reviewed by the aluminum dome designer and considered when it is determined that they are more stringent.

A.5.3.2 Panel design load. The purpose of the panel design load, as provided in this standard, is to ensure that the aluminum dome panel material, panel thickness, and attachment to the dome frame are capable of supporting minimum point loads and distributed loads, including the appropriate safety factors as defined in the AA ADM. If, however, the applicable design loads (live load, snow load, and wind load) for a specific project exceed the panel design loads, as provided in this standard, the panel material, panel thickness, and attachment to the dome frame shall be designed considering the higher loads, including the appropriate safety factors as defined in the AA ADM.



16

Sec. A.5.4 Allowable Stresses and Allowable LoadsA.5.4.1 Aluminum structural members. The minimum factor

of safety stated herein is derived from the AA ADM, which defines the factors for ultimate strength and yield strength to be 1.95 and 1.65, respectively.

SECTION A.6: ROOF ATTACHMENT DETAILS (REFER TO SEC. 6 OF ANSI/AWWA D108)

Sec. A.6.1 Roof SupportsFor aluminum domes on larger tanks (typically 140 ft in diameter

and greater) or in areas with higher-than-average live loads or ground snow loads (pg), or both, it is often a more efficient approach to rigidly attach the dome supports (non-sliding) to the tank shell and allow the tank shell and its wind girder to serve as the tension ring for the aluminum dome.

For this approach, careful coordination is needed between the tank supplier/tank maintenance company and the aluminum dome supplier to ensure that the higher-than-usual radial loads transferred to the tank shell from a fixed support dome are properly accounted for in the tank shell and wind girder design.

The attachment of the dome attachment to the tank shell, while rigid, must have a sufficient means of isolation to prevent galvanic corrosion caused by the dissimilar metals of the aluminum dome and the tank shell. Further, radial deflection of the tank shell must be held within acceptable limits, as defined by the dome designer. This approach is not typical for bolted steel tanks and is discouraged for these types of tanks.

In some cases, concrete tanks can be designed to accommodate a fixed-support aluminum dome. Typically, the tank has reinforced embedded plates designed to resist the applicable loads of the dome and are located at each dome support point.



17

SECTION A.7: PHYSICAL CHARACTERISTICS (REFER TO SEC. 7 OF ANSI/AWWA D108)

Sec. A.7.2 SkylightsThe use of skylight panels for aluminum dome roofs for water

storage tanks has been known to promote biological growth and is not recommended in many cases. Consideration should be given when specifying skylight panels for aluminum domes to be used in service over potable water.

SECTION A.8: TESTING AND SEALING (REFER TO SEC. 8 OF ANSI/AWWA D108)

Sec. A.8.2 Shell SealThe most common shell seal materials used for aluminum dome

roofs on water storage tanks include the following:Fiberglass insect screen (maximum 18 × 16 mesh with FRP wire)

provides continuous-perimeter venting and promotes airflow beneath the dome. This screen material can be used on water storage tanks of all material types (e.g., concrete, welded steel, bolted steel). The material tends to be flexible, which allows for ease of installation.

Stainless steel insect screen (maximum 18 × 16 mesh with 300 series wire) also provides full-perimeter venting and can be used on tanks of all material types. Stainless steel is a resilient material that is often preferred for aluminum domes on low-rise or in-ground tank installations where the threat of animal intrusion exists.

Solid aluminum counterflashing restricts perimeter airflow. This material typically consists of a minimum 0.05-in. thick 3003-H16 aluminum sheeting that is attached to the vertical leg of the dome’s flashing and spans inward to the tank shell. This material is commonly used for aluminum domes on welded steel or bolted steel water storage tanks. It is typically not recommended for concrete tanks due to the width of the dome flashing required. If this material is selected,



18

careful consideration must be given to sizing the roof vents. Vents shall conform to the provisions of the AWWA standard for the type of tank being covered and must be sized to solely accommodate the associated airflow during maximum filling and emptying rates of the tank.

Fabric airseal (e.g., Ventlon®, Hypalon® coated glass woven fabric) restricts perimeter airflow completely and provides the most positive seal at the interface of the aluminum dome and tank. Fabric airseal can be used on tanks of all material types. As with solid aluminum counterflashing, careful consideration must be given to sizing the roof vents.

SECTION A.10: COATINGS OR OTHER FINISHES (REFER TO SEC. 10 OF ANSI/AWWA D108)

Aluminum dome panels that are treated with a mechanical finish (M42 or M43 nondirectional textured finish as described in AA DAF-45) are much more prone to water staining than standard mill finish panels. They also require special handling and storage practices prior to installation of the panels. Dome panels and flashing with an M42 or M43 finish, especially while nested and crated for shipping and storage, must be kept indoors and dry at all times to reduce water staining.



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