1、ACI 345.2R-13Guide for Widening Highway BridgesReported by ACI Committee 345First PrintingJuly 2013Guide for Widening Highway Bridges Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any print
2、ed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.The technical committees responsible for ACI committee reports and standards strive to avoid ambiguities, omissions, and errors in these documents. In spite of these efforts, the users of AC
3、I documents occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. Users who have suggestions for the improvement of ACI documents are requested to contact ACI via the errata website at www.concrete.org/committees/errata.a
4、sp. Proper use of this document includes periodically checking for errata for the most up-to-date revisions.ACI committee documents are intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibi
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7、n, lost revenues or lost profits, which may result from the use of this publication.It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. ACI does not make any representations with regard to hea
8、lth and safety issues and the use of this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations, including but not limited to, United States Occupational Safety and Health Administration
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10、vailable in print, by download, on CD-ROM, through electronic subscription, or reprint and may be obtained by contacting ACI.Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP).American Concrete Institute38800 Country Club Driv
11、eFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgISBN-13: 978-0-87031-827-6ISBN: 0-87031-827-6American Concrete InstituteAdvancing concrete knowledgeMany highway bridges become functionally obsolete due to inad-equate width before they become structurally deficien
12、t. Widening is generally more economical than complete replacement. Thus, there is a mandate to share the results of research and experi-ence pertaining to bridge widening. This guide discusses technical issues related to the widening of concrete bridges and bridges with concrete decks. The primary
13、focus of this document is on bridge decks, even though substructure issues are raised and discussed. The effects of differential movements between the existing and new portions are discussed, including movements due to traffic on the existing structure during construction. General recommendations ar
14、e made pertaining to the choice of structure type, design details, and construction methods and materials.The materials, processes, quality-control measures, and inspec-tions described in this document should be tested, monitored, or performed as applicable only by individuals holding the appro-pria
15、te ACI certifications or equivalent.Keywords: bridge decks; bridge widening; bridges (structures); concrete construction; deflection; formwork (construction); reinforced concrete; reinforcing steel; substructure; superstructure; traffic vibration.ContentsCHAPteR 1IntRoDUCtIon AnD sCoPe, p. 11.1Intro
16、duction, p. 11.2Scope, p. 2CHAPteR 2DeFInItIons, p. 22.1Definitions, p. 2CHAPteR 3GeneRAL DesIGn ConsIDeRAtIons, p. 23.1General, p. 23.2Appearance and function, p. 33.3Differential movement, p. 4CHAPteR 4DesIGn AnD ConstRUCtIon DetAILs, p. 74.1General, p. 74.2Demolition, p. 74.3Avoidance of damage d
17、ue to dead load deflections, p. 84.4Closure placement details, p. 114.5Substructure details, p. 13CHAPteR 5sUMMARY oF ReCoMMenDAtIons, p. 13CHAPteR 6ReFeRenCes, p. 13CHAPteR 1IntRoDUCtIon AnD sCoPe1.1IntroductionDesign and construction engineers should investigate several potential issues if a bridg
18、e is to be considered for widening. These include retention of bridge elements, traffic control, structural constraints, economy and feasibility, expected increase in traffic volume, life span, and construc-ACI 345.2R-13Guide for Widening Highway BridgesReported by ACI Committee 345Michael C. Brown,
19、 Chair Rita K. Oglesby, SecretaryJesse L. BeaverOliver K. GepraegsRobert J. Gulyas*Yail Jimmy KimAlan B. MatejowskyClaudia P. PulidoHarold R. SandbergJohan L. SilfwerbrandMichael M. SprinkelPaul J. St. JohnRichard E. WeyersMark Erik WilliamsJerzy Z. ZemajtisConsulting MembersJames C. AndersonByron T
20、. DanleyFouad H. FouadAllan C. HarwoodYash Paul VirmaniJeffrey P. Wouters*Deceased.Subcommittee Chairs.ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who ar
21、e competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be l
22、iable for any loss or damage arising therefrom.Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Archi
23、tect/Engineer.ACI 345.2R-13 supersedes ACI 345.2R-98(05) and was adopted and published July 2013.Copyright 2013, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic
24、 or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.1tion limitations. Certain elementary procedures should be followed to s
25、tudy the feasibility of widening. These include:a) Review the drawings and specifications of the original structure.b) Review any revisions of engineering documents (for example, plans, specifications, and design calculations) that might have been approved during the original construction.c) Thoroug
26、hly inspect the structure and note changes to in-place conditions, such as deterioration of structural members due to environmental factors (for example, deicing salts, weathering, and collision of heavy trucks).d) Obtain additional subsurface information to accommo-date increased superstructure loa
27、ds, including soil borings.e) Review previous changes or upgrades to the structure.f) Perform structural analysis with allowance for existing deterioration to confirm that the existing elements are adequate for increased loads (due to widening and compli-ance with current design standards). If the e
28、xisting elements are part of the replacement, all possible geometric properties need to be considered.One of the first considerations for widening a bridge is to determine whether to retain structurally adequate parts of the bridge deck. Entire bridge deck replacement should be considered if the bri
29、dge deck is severely deteriorated, the existing bridge deck will become less than a half of the new bridge deck width, or both (Seible et al. 1991; “Operation Bridgeguard” 1992). If the bridge deck, or a portion of it, is to be retained and connected to a new deck, the design should provide for bend
30、ing moment and shear transfer through the longitudinal joint between the new and old portions of the bridge deck. The steel passing through the construction joint should be protected from possible increases in corrosion potential between the old and new concrete.Another important matter is the consi
31、deration of whether substructures, such as footings, pier caps, and abutments, should be widened to accommodate widening a superstruc-ture. Potential interaction between the new substructure and the existing substructure should be considered. The design professional should be aware of possible probl
32、ems that could occur when a bridge is widened on both sides. In most cases, the existing portion is trapped between new sections, making it difficult to replace the middle section.1.2scopeThis document provides design professionals and constructors with general guidelines for bridge widening. The wi
33、dening of highway bridges is commonly conducted to improve the functionality of existing structural systems. Several factors contribute to this demand:a) Increased traffic volumes requiring additional lanesb) Safety hazards of narrow bridges requiring wider shouldersc) Provision for bikeways and ped
34、estrian walkwaysGovernment-funded programs are enabling public agen-cies to widen many functionally obsolete bridges as needed to improve safety. If a bridge was designed for current live loads and has not deteriorated appreciably, widening is likely more cost-effective than complete replacement. It
35、 is imperative to perform in-depth nondestructive testing (NDT) and invasive testing to quantify the level of existing concrete deterioration and section losses in existing sections, and design protection methods to prevent future deteriora-tion prior to investing in widening a structure.Many proble
36、ms unique to bridge widening are not encoun-tered in new bridge work. Failures or serious maintenance problems can be created by misunderstanding these prob-lems. Each bridge widening is unique.This guide emphasizes construction practices, but because construction sequence, structure type, framing d
37、etails, and other decisions critical to the success of the work are deter-mined during the design phase, some discussion of design concepts must be included. Structural analysis and design for widening bridges are not addressed. Much of the discus-sion that follows also applies to new bridges constr
38、ucted in stages, part width at a time.CHAPteR 2DeFInItIons2.1DefinitionsACI provides a comprehensive list of definitions through an online resource, “ACI Concrete Terminology,” http:/terminology.concrete.org.CHAPteR 3GeneRAL DesIGn ConsIDeRAtIons3.1GeneralCertain aspects of structural type selection
39、, framing consid-erations, and design details are unique to bridge widening. AASHTO (2010) and others (Silano et al. 1992) provide specific design guidelines. Questions a design professional should consider before commencing design include:a) By widening the superstructure, does the substructure als
40、o require widening?b) Was widening the substructure foreseen in the design of the existing bridge?c) Should one or both sides be widened?d) Is a parallel structure justified as an alternative to widening?e) Does widening the structure provide adequate vertical clearance?f) Have geotechnical/ground c
41、onditions been evaluated?g) Does widening provide an acceptable life for the existing section?In general, current bridge codes and design loads appli-cable to the route on which the structure is located should be used for bridge widening. Constructing a widening to current standards creates the oppo
42、rtunity of later replacing or strengthening all or portions of the original bridge so that the entire structure can be upgraded.Bridges to be constructed for special purposes (for example, military bridges) may require higher design loads than stan-dard truck loads shown in AASHTO (2013) due to heav
43、ier traffic loads, a lack of load limits, or a lack of enforcement of load limits. Specific structural considerations may be neces-sary for widening a bridge in seismic regions; for example, American Concrete Institute Copyrighted Materialwww.concrete.org2 GUIDe FoR WIDenInG HIGHWAY BRIDGes (ACI 345
44、.2R-13)to avoid a possible progressive collapse of a bridge during a seismic event (Asnaashari et al. 2005), precast concrete girders can be spliced together.3.2Appearance and functionWhen a bridge structure is selected for widening, factors such as aesthetic and historical considerations, roadway g
45、eometrics, and maintenance of traffic should be considered.3.2.1 Aesthetic and historic considerationsAesthetic and historic factors can favor maintaining the original appear-ance of a classical design or landmark structure. Figure 3.2.1a shows open-spandrel concrete arches that have been widened wi
46、th thin prestressed members matching the depth of the original superstructure. The prestressed members actually carry the entire bridge deck loads, and the arches were left in place to maintain the appearance of the historic bridge. A bridge widening design can sometimes require different structural
47、 types when compared to the existing bridge. For example, the arch-shaped steel truss bridge over Auckland Harbor in New Zealand was widened with steel box girders outside the truss on both sides, the soffits of which matched the curve of the original lower chords (Fig. 3.2.1b). To all but the most
48、astute viewer, the architectural integrity of the original design was not altered.The widening should be accomplished in a manner such that the existing structure retains its original aesthetic outlook.3.2.2 Roadway geometricsIf the widening consists of doubling the bridge width (for example, two to
49、 four lanes divided), the work is generally much less complicated and less costly when the widening is done entirely on one side. The widening can be built as an independent bridge without the problems of making closure placements or matching deflec-tion characteristics. Traffic handling during construction is also simplified. When vertical clearances beneath separation structures are insufficient to allow for falsework during bridge widening, the use of precast concrete or steel girders is gener-ally required. The widened portion must provide adequate vertic
