345.2R_13.pdf

ACI 345.2R-13 Guide for Widening Highway Bridges Reported by ACI Committee 345 First Printing July 2013 American Concrete Institute® Advancing concrete knowledge Guide 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 printed, 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 ACI 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.asp. 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Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP). American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 U.S.A. Phone: 248-848-3700 Fax: 248-848-3701 www.concrete.org ISBN-13: 978-0-87031-827-6 ISBN: 0-87031-827-6 ACI 345.2R-13 Guide for Widening Highway Bridges Reported by ACI Committee 345 Michael C. Brown, Chair Rita K. Oglesby, Secretary Jesse L. Beaver Harold R. Sandberg Jerzy Z. Zemajtis Allan C. Harwood Oliver K. Gepraegs Johan L. Silfwerbrand Yash Paul Virmani Robert J. Gulyas* Michael M. Sprinkel Consulting Members Jeffrey P. Wouters Yail Jimmy Kim† Paul J. St. John James C. Anderson Alan B. Matejowsky Richard E. Weyers Byron T. Danley * Deceased. Claudia P. Pulido Mark Erik Williams† Fouad H. Fouad † Subcommittee Chairs. Many highway bridges become functionally obsolete due to inad- CHAPTER 2—DEFINITIONS, p. 2 equate width before they become structurally deficient. Widening 2.1—Definitions, p. 2 is generally more economical than complete replacement. Thus, there is a mandate to share the results of research and experi- CHAPTER 3—GENERAL DESIGN ence pertaining to bridge widening. This guide discusses technical CONSIDERATIONS, p. 2 issues related to the widening of concrete bridges and bridges with 3.1—General, p. 2 concrete decks. The primary focus of this document is on bridge decks, even though substructure issues are raised and discussed. 3.2—Appearance and function, p. 3 The effects of differential movements between the existing and new 3.3—Differential movement, p. 4 portions are discussed, including movements due to traffic on the existing structure during construction. General recommendations CHAPTER 4—DESIGN AND CONSTRUCTION are made pertaining to the choice of structure type, design details, DETAILS, p. 7 and construction methods and materials. 4.1—General, p. 7 The materials, processes, quality-control measures, and inspec- 4.2—Demolition, p. 7 tions described in this document should be tested, monitored, or 4.3—Avoidance of damage due to dead load deflections, performed as applicable only by individuals holding the appro- p. 8 priate ACI certifications or equivalent. 4.4—Closure placement details, p. 11 Keywords: bridge decks; bridge widening; bridges (structures); concrete 4.5—Substructure details, p. 13 construction; deflection; formwork (construction); reinforced concrete; reinforcing steel; substructure; superstructure; traffic vibration. CHAPTER 5—SUMMARY OF RECOMMENDATIONS, p. 13 Contents CHAPTER 6—REFERENCES, p. 13 CHAPTER 1—INTRODUCTION AND SCOPE, p. 1 1.1—Introduction, p. 1 CHAPTER 1—INTRODUCTION AND SCOPE 1.2—Scope, p. 2 1.1—Introduction Design and construction engineers should investigate ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and several potential issues if a bridge is to be considered for inspecting construction. This document is intended for the use widening. These include retention of bridge elements, traffic of individuals who are competent to evaluate the significance control, structural constraints, economy and feasibility, and limitations of its content and recommendations and who expected increase in traffic volume, life span, and construc- 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 liable for any loss or damage arising therefrom. ACI 345.2R-13 supersedes ACI 345.2R-98(05) and was adopted and published July 2013. Reference to this document shall not be made in contract Copyright © 2013, American Concrete Institute. documents. If items found in this document are desired by All rights reserved including rights of reproduction and use in any form or by any the Architect/Engineer to be a part of the contract documents, means, including the making of copies by any photo process, or by electronic or they shall be restated in mandatory language for incorporation mechanical device, printed, written, or oral, or recording for sound or visual reproduc- by the Architect/Engineer. tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. 1 2 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) tion limitations. Certain elementary procedures should be It is imperative to perform in-depth nondestructive testing followed to study the feasibility of widening. These include: (NDT) and invasive testing to quantify the level of existing a) Review the drawings and specifications of the original concrete deterioration and section losses in existing sections, structure. and design protection methods to prevent future deteriora- b) Review any revisions of engineering documents (for tion prior to investing in widening a structure. example, plans, specifications, and design calculations) that Many problems unique to bridge widening are not encoun- might have been approved during the original construction. tered in new bridge work. Failures or serious maintenance c) Thoroughly inspect the structure and note changes problems can be created by misunderstanding these prob- to in-place conditions, such as deterioration of structural lems. Each bridge widening is unique. members due to environmental factors (for example, deicing This guide emphasizes construction practices, but because salts, weathering, and collision of heavy trucks). construction sequence, structure type, framing details, and d) Obtain additional subsurface information to accommo- other decisions critical to the success of the work are deter- date increased superstructure loads, including soil borings. mined during the design phase, some discussion of design e) Review previous changes or upgrades to the structure. concepts must be included. Structural analysis and design f) Perform structural analysis with allowance for existing for widening bridges are not addressed. Much of the discus- deterioration to confirm that the existing elements are sion that follows also applies to new bridges constructed in adequate for increased loads (due to widening and compli- stages, part width at a time. ance with current design standards). If the existing elements are part of the replacement, all possible geometric properties CHAPTER 2—DEFINITIONS need to be considered. One of the first considerations for widening a bridge is 2.1—Definitions to determine whether to retain structurally adequate parts of ACI provides a comprehensive list of definitions through the bridge deck. Entire bridge deck replacement should be an online resource, “ACI Concrete Terminology,” http:// considered if the bridge deck is severely deteriorated, the terminology.concrete.org. existing bridge deck will become less than a half of the new bridge deck width, or both (Seible et al. 1991; “Operation CHAPTER 3—GENERAL DESIGN Bridgeguard” 1992). If the bridge deck, or a portion of it, is CONSIDERATIONS to be retained and connected to a new deck, the design should provide for bending moment and shear transfer through the 3.1—General longitudinal joint between the new and old portions of the Certain aspects of structural type selection, framing consid- bridge deck. The steel passing through the construction joint erations, and design details are unique to bridge widening. should be protected from possible increases in corrosion AASHTO (2010) and others (Silano et al. 1992) provide potential between the old and new concrete. specific design guidelines. Questions a design professional Another important matter is the consideration of whether should consider before commencing design include: substructures, such as footings, pier caps, and abutments, a) By widening the superstructure, does the substructure should be widened to accommodate widening a superstruc- also require widening? ture. Potential interaction between the new substructure and b) Was widening the substructure foreseen in the design of the existing substructure should be considered. The design the existing bridge? professional should be aware of possible problems that c) Should one or both sides be widened? could occur when a bridge is widened on both sides. In most d) Is a parallel structure justified as an alternative to cases, the existing portion is trapped between new sections, widening? making it difficult to replace the middle section. e) Does widening the structure provide adequate vertical clearance? 1.2—Scope f) Have geotechnical/ground conditions been evaluated? This document provides design professionals and g) Does widening provide an acceptable life for the constructors with general guidelines for bridge widening. existing section? The widening of highway bridges is commonly conducted In general, current bridge codes and design loads appli- to improve the functionality of existing structural systems. cable to the route on which the structure is located should Several factors contribute to this demand: be used for bridge widening. Constructing a widening to a) Increased traffic volumes requiring additional lanes current standards creates the opportunity of later replacing b) Safety hazards of narrow bridges requiring wider or strengthening all or portions of the original bridge so that shoulders the entire structure can be upgraded. c) Provision for bikeways and pedestrian walkways Bridges to be constructed for special purposes (for example, Government-funded programs are enabling public agen- military bridges) may require higher design loads than stan- cies to widen many functionally obsolete bridges as needed dard truck loads shown in AASHTO (2013) due to heavier to improve safety. If a bridge was designed for current traffic loads, a lack of load limits, or a lack of enforcement of live loads and has not deteriorated appreciably, widening load limits. Specific structural considerations may be neces- is likely more cost-effective than complete replacement. sary for widening a bridge in seismic regions; for example, American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 3 Fig. 3.2.1b—Widened bridge with steel box girders, Auck- land Harbor in New Zealand. Fig. 3.2.1a—Concrete arch widening with prestressed sections. to avoid a possible progressive collapse of a bridge during a seismic event (Asnaashari et al. 2005), precast concrete girders can be spliced together. 3.2—Appearance and function When a bridge structure is selected for widening, factors such as aesthetic and historical considerations, roadway geometrics, and maintenance of traffic should be considered. 3.2.1 Aesthetic and historic considerations—Aesthetic 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 with thin prestressed members matching the depth Fig. 3.2.3—Traffic allowed on a bridge during deck slab of the original superstructure. The prestressed members widening. actually carry the entire bridge deck loads, and the arches were left in place to maintain the appearance of the historic construction personnel, and the potential damage to the bridge. A bridge widening design can sometimes require work. Another consideration is the effect of the widening different structural types when compared to the existing on the safety of the public using the roadway, waterway, or bridge. For example, the arch-shaped steel truss bridge over railway beneath the bridge and any traffic-related impact Auckland Harbor in New Zealand was widened with steel that the widening can have on that roadway. Ideally, a box girders outside the truss on both sides, the soffits of convenient alternate route should be used as a detour during which matched the curve of the original lower chords (Fig. bridge-widening operations, so that all traffic can be kept 3.2.1b). To all but the most astute viewer, the architectural off the bridge. More commonly, however, the high cost of integrity of the original design was not altered. a temporary detour bridge dictates that traffic be carried on The widening should be accomplished in a manner such the bridge during widening, as shown in Fig. 3.2.3. This may that the existing structure retains its original aesthetic outlook. create congestion at the work site and result in vibrations 3.2.2 Roadway geometrics—If the widening consists of and deflections of the bridge (Whiffen and Leonard 1971; doubling the bridge width (for example, two to four lanes Arnold 1980; Furr and Fouad 1981; Transportation Research divided), the work is generally much less complicated and less Board 1981; Deaver 1982; Silfwerbrand 1992; Harsh and costly when the widening is done entirely on one side. The Darwin 1983). widening can be built as an independent bridge without the When a detour is not feasible and traffic must be carried problems of making closure placements or matching deflec- through the work area, proper sequencing of construction tion characteristics. Traffic handling during construction is operations is essential to minimize these problems. It is also simplified. When vertical clearances beneath separation normally preferable to do as much of the work as possible structures are insufficient to allow for falsework during bridge before the removal of existing curb and railing. Sometimes it widening, the use of precast concrete or steel girders is gener- is possible to complete the entire widening before removing ally required. The widened portion must provide adequate the existing rails, including making the connection between vertical clearance both before and after construction. old and new bridge decks. Otherwise, temporary barriers or 3.2.3 Maintenance of traffic—Prime concerns of widening railings must be provided after the existing bridge railings are the convenience of the traveling public, the safety of have been removed. American Concrete Institute Copyrighted Material—www.concrete.org 4 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) The U.S. Department of Transportation (2009) details bridge deck riding surface as well as increasing member the minimum traffic control standards for construction stiffness. Vehicle speed and weight restrictions may not be a and maintenance operations on streets and highways. This critical issue for the magnitude of traffic-induced vibrations manual sets forth principles and standards that apply to both (Kim et al. 2009). rural and urban areas and is intended to direct the safe and In situations where the vibrations are carried into freshly expeditious movement of traffic through construction and placed concrete through reinforcing steel extending from the maintenance zones and provide for the safety of the work existing bridge, damage to new concrete may occur (Silfw- force. In addition to the requirements of this manual, supple- erbrand 1992). Adequate construction methods can preclude mentary protection may be requested by the owner. such damage, for example, by attaching the forms to the The following should be indicated in the contract docu- existing bridge, with proper traffic control, or both. ments: the sequence of construction operations, permis- When a reinforcing bar moves relative to the concrete, the sible lane closure periods, minimum temporary roadway displaced concrete will flow readily back and forth with the widths, temporary traffic striping requirements, signing bar because it is still in its plastic state. As initial set begins, layouts, locations and details of temporary barrier railings, only weak, water-diluted grout flows back to surround the bar. and minimum construction openings for roadways or rail- Also, cracks may develop in the plastic concrete and fill with ways under the bridge. Contractors should be encouraged to weak material along a horizontal plane with adjacent bars or propose alternative schemes. along sloping planes running from the bar to the surface of the When high volumes of traffic need to be carried on a bridge bridge deck. This condition can result in a severe reduction in which both sides are to be widened, it may be necessary in bond to reinforcement and premature bridge deck spalling. to complete one side before the other is started to minimize Similar damage can occur in new bridge decks if live loads disruption of traffic. from workers or equipment are allowed directly on poorly When heavy volumes of commuter traffic prevent closing supported reinforcing steel on the outside of a construction the existing bridge lanes except during brief off-peak joint bulkhead. For this reason, during placing and finishing periods each day, special measures may be needed (Precast/ operations, workers and equipment near the perimeter of a Prestressed Concrete Institute 1980; Sprinkel 1985). For reinforced concrete bridge deck should be restricted to planks example, precast bridge deck slabs and concrete-filled steel or runways supported from the forms, rather than bearing grating can be placed during nighttime or weekend closures. directly on any reinforcing steel that extends through bulk- heads and into the concrete being placed. 3.3—Differential movement Although it would seem that any movement of reinforcing Deflection characteristics and differential expansion steel extending from a structure carrying traffic into freshly behavior should be considered when a new deck is added or placed concrete would result in the defects described, certain connected to existing decks. practices will generally eliminate such damage. These prac- 3.3.1 Vibrations from traffic—Traffic-induced vibration tices should be employed on all bridge deck closure place- has been blamed for distress occasionally observed in new ments or in other situations where concrete is placed against construction that connects to structures carrying live loads. an existing structural element carrying traffic, and include Once concrete is placed, consolidated, and finished, it gener- the following. ally should not be disturbed until it has gained sufficient 3.3.1.1 Use of moderate-slump concrete (2 to 3 in. [50 to initial strength. For example, over 65 percent of a speci- 75 mm])—Surveys found frequent delamination in bridge fied compressive strength may be achieved after 7 days of decks built or widened in the 1950s and 1960s (Transporta- casting when a concrete is mixed with ordinary portland tion Research Board 1981). This damage was noted in bridge cement (Gonnerman and Lerch 1951). This requirement decks connecting to existing structures carrying traffic. Such leads to concerns about permitting traffic on bridge decks damage was attributed to the use of high-slump concrete during concrete-placing operations. Experience and research (more than 4 in. [100 mm]) that probably contained excess have shown, however, that damage due to traffic-induced water. Laboratory research also showed that high-slump vibrations is very rare when the forms and reinforcing steel concrete mixtures are especially sensitive to segregation are supported by the same structural members (Whiffen and in the plane of the reinforcing steel (Arnold 1980). Similar Leonard 1971; Arnold 1980; Furr and Fouad 1981; Trans- damage was not noticed when the slump was reduced. portation Research Board 1981; Deaver 1982; Harsh and 3.3.1.2 Reinforcing details—Furr and Fouad (1981) Darwin 1983; Silfwerbrand 1992). In these cases, fresh reported that reinforcing dowels extending straight from old concrete, reinforcement, and forms are in synchronous concrete and lapping with the new bridge deck reinforcing movement. None of these reports were able to identify any bars in fresh concrete did not cause any defects in the fresh occurrences of damage for these conditions. Therefore, concrete. Splicing dowel bars to existing reinforcement may special precautions, such as closing the bridge to traffic in be necessary for cantilever slabs. such situations, are generally not necessary even though Good practice also requires that when bridge deck vibrations may cause some minor cracks during the curing closure placements are to be employed, the reinforcing bars of concrete members (Ng and Kwan 2007). or dowels extending from the existing concrete to the new Effective ways to reduce the amplitude of traffic-induced concrete should not be connected to the reinforcing bars of the vibrations are to maintain a smooth structure approach and closure placement during concrete placement. They should American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 5 Fig. 3.3.1.2—Closure placement reinforcing details. Fig. 3.3.2a—Transverse view showing vertical lip at longi- Fig. 3.3.2b—Longitudinal view showing proximity of wheel tudinal joint in traveled lane. path to joint. out of the traveled lanes whenever possible; however, most be adequately connected prior to, but as close to, casting the frequently the joint between new and existing bridge decks concrete (Fig. 3.3.1.2). Measures should be taken to avoid the occurs within the traveled way. If bridge decks with longitu- formation of corrosion macrocells with the new bars being dinal joints in the traveled lanes are not structurally connected, cathodic sites and the existing bars being anodic sites. differential deflections will create offsets in the riding surface Some damage was observed in California when a single that could result in potentially hazardous vehicle control prob- row of dowels was drilled and grouted into the face of the lems. Figures 3.3.2a and 3.3.2b show two different views of a existing bridge deck midway between the steel mats used in joint with differential deflection. Figure 3.3.2c shows attempts the widening (Shaw and Stewart 1974). This problem was to minimize differential deflections; however, such situations solved when two rows of dowels were used, one secured to may not be recommended because maintenance of joint seals each plane of steel in the new bridge deck (refer to the left- between bridge deck slabs can be difficult, hazardous to side elevation in Fig. 3.3.1.2). workers, expensive, and delay road users. 3.3.1.3 Forming details—When the closure is placed, its Whenever a new bridge deck joins the existing bridge deck supporting form should be secured to both the old and the within the roadway, the two should be structurally connected new structure. (McMahon and Womack 1965; Whiffen and Leonard 1971; 3.3.2 Superstructure deflection characteristics—Differen- Shaw and Stewart 1974; Arnold 1980; Furr and Fouad 1981; tial deflections between new and existing superstructures are Transportation Research Board 1981; Deaver 1982; Harsh not a problem if the joint between the two occurs in a median and Darwin 1983). The amount of reinforcement across the or untraveled area. Generally in such cases, the superstruc- joint should be the same amount that is in the decks being tures are not structurally connected. Joints should be located connected. Additional analysis may be required when signif- American Concrete Institute Copyrighted Material—www.concrete.org 6 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) Fig. 3.3.2c—Attempt to minimize differential deflections by means of a continuous bituminous wedge. icant lateral loads are expected, such as seismic loads. Inad- equately connected bridge decks typically allow the leakage of water through the joint, which can cause corrosion and other related damage of the bridge structure (Fig. 3.3.2d). If proper attention is not given to construction sequence and details (for example, use of closure placements between the new bridge deck and the existing bridge deck), large differen- tial deflections can cause overloading of the existing structure or distress in the new work along the joint line (Fig. 3.3.2e). Fig. 3.3.2d—Corrosion-related damage under leaking Deflection characteristics should be taken into account longitudinal bridge deck joint. when a new bridge deck is to be connected rigidly to the existing bridge deck. In such cases, the design professional should consider the relative deflection characteristics of the existing and the new portions of the bridge. Appreciable differences in stiffness between existing and new superstructures may cause the transfer of a larger portion of live load between the structures than would other- wise not occur. Refined analysis, such as finite element modeling, is recommended to adequately predict the effects of uneven live load. For spans where differential deflection from live load or dead load (creep) is expected to exceed 1/4 in. (6 mm), the design professional should specify the sequence of attaching new work to the existing bridge deck. Generally, a delay in the attachment of diaphragms and the placement of bridge deck closure is needed. This is discussed in more detail in Chapter 4. Differential live load deflections or relative move- ments between the first girder of a widening and the adjacent girder of the existing bridge cause shear stresses in the new bridge deck concrete and closure placement between the two girders. Furr and Fouad (1981) reported the magnitude of the change in differential deflection due to dynamic loading— 0.12 in. (3.0 mm)—that would cause cracking in a 7 in. (175 mm) concrete slab. Field measurements of typical bridges in Georgia (Deaver 1982) and Texas (Furr and Fouad 1981) Fig. 3.3.2e—Bridge deck soffit spalls under reinforcing steel dowels. American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 7 showed that deflections actually occurred in bridge deck the new structure is in the median or if rigid attachment of slabs by traffic immediately adjacent to the widening during the widening to the existing structure is not required for concrete placement. overall stability, the existing and new structures may not Surveys of bridge deck widenings with temporary vertical be connected and differential settlements are tolerated. It is displacement control measures in place during concrete usually necessary for the new foundation to be compatible placement (Shaw and Stewart 1974; Furr and Fouad 1981; with the current condition of the existing one in terms of Transportation Research Board 1981; Deaver 1982) showed settlement. little evidence of distress due to differential deflection caused by traffic. This is probably due to the fact that, in CHAPTER 4—DESIGN AND CONSTRUCTION addition to practices recommended previously, one or more DETAILS of the following measures were taken: a) Diaphragms between adjacent girders or a rigid tempo- 4.1—General rary blocking system were used to equalize girder deflec- Standards and guides used for new bridge construc- tion until the bridge deck slab pour strip gained sufficient tion should be used for bridge widening. These include the strength. Sometimes the forming system itself offers suffi- “AASHTO LRFD Bridge Design Specifications” (AASHTO cient rigidity. 2013), “AASHTO Guide Specifications for Highway b) A smooth riding surface was maintained on the bridge Construction” (AASHTO 2010), state-specific bridge design deck and the approach roadway, and a good grade match was manuals, ACI 343R, and ACI 345R. It should be noted that obtained where they joined. these provisions are not necessarily used for every project c) Traffic speed, allowable loads, or both, were reduced on because each widening represents a unique situation. Some the existing bridge during and immediately after placing new construction operations unique to widening are discussed in bridge deck concrete. While no recommended speeds were this chapter. given, it is generally understood that the lower the speed, the less the risk of deck cracking. User service level will be 4.2—Demolition a factor in the speed that is selected. Reduced vehicle traffic Most bridge widening projects require that a portion of speeds of 20 mph (30 km/h) have been reported in practice. the existing bridge be removed. This is usually the railing d) The traffic lane adjacent to the connecting joint was or sidewalk and sometimes portions of the bridge deck, closed for a few days after placing new bridge deck concrete. substructure, or wing-walls. Methods of removal that could The total load would have approximately been reduced by damage the existing structure to remain should not be the amount of the AASHTO lane load not present during the permitted. lane closure. 4.2.1 Shored excavation—Bridge widening generally e) Temporary shoring was installed under the existing involves shored excavation immediately adjacent to the bridge during this period. existing bridge and removal of portions of the existing bridge Although all of these measures have been used, Items c (Fig. 4.2.1). When groundwater is concerned, the design and d are generally more economical when compared to professional should minimize the depth of excavation. others. They require only a short-term restriction of traffic. Shoring of excavations is usually the responsibility of 3.3.3 Differential longitudinal shortening for post- the contractor. Construction engineers should monitor this tensioned applications—For cast-in-place, longitudinally- phase of the work carefully because public safety and safety post-tensioned concrete widening, it is essential that the new of the existing bridge or adjacent highway facilities can be work be allowed to shorten initially without restraint from jeopardized by the failure of shoring. Specifications should the existing bridge. If connected during post-tensioning, restraints will cause some of the stressing force to be trans- ferred into the existing bridge, creating undesirable stresses in it and reducing the prestressing force in the new work. When the two are to be rigidly connected in their completed state, a specific construction sequence and the use of delayed closure placements are strongly recommended. 3.3.4 Differential expansion characteristics for transverse expansion joints—Whenever the widening is to be connected to the existing bridge, it is important that transverse bridge deck joints be located in the superstructure of the widening in the same longitudinal locations where such joints occur in the existing bridge. 3.3.5 Differential foundation settlement—The amount of tolerable differential foundation settlement between old and new construction depends on the configuration of the Fig. 4.2.1—Shoring to protect roadway during abutment widening. If the joint between the existing structure and widening. American Concrete Institute Copyrighted Material—www.concrete.org 8 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) being corroded away, supplement the existing reinforcement by lapping new reinforcement. 4.2.2.2 Before beginning the removal of a portion of a monolithic concrete element, a saw cut should be made without damaging the reinforcing steel along the limits of removal on all faces of the element that will be visible in the completed work. 4.2.2.3 Removal can be done by waterjetting (hydrodemo- lition), which can remove concrete efficiently without damaging the reinforcement or introducing microcracking or other damage into the remaining concrete (Weyers et al. 1993). Removal can also be conducted with light chipping tools (for example, jack or chipping hammer) that are auto- mated or operated manually. 4.2.2.4 Unless designed to be used in the new work, rein- forcing dowels and bars exposed during removal of the rail, curb, or sidewalk should be cut off below the finished surface with some chipping and the recess should be filled with a nonshrink grout (ASTM C1107/C1107M). When dowels or existing reinforcing bars are in a patch or overlay area, they should be cut off at the bottom of the overlay or patch. Addi- tional dowels may be necessary. Generally, bridge widening involves removal of curbs, sidewalks, or railings. This often exposes a rough surface not suitable for traffic (Fig. 4.2.2.4a). Unless a concrete or bituminous overlay is to be placed, the area must be refin- ished. The degree of refinishing, which can vary from minor patching to a complete leveling course (Fig. 4.2.2.4b), should be specified in the contract documents. Refinishing can consist of simply grinding off a few high spots or filling in local depressed areas with concrete repair materials. If the surface is too rough and requires extensive Fig. 4.2.2.4a—Area under old rail prepared for refinishing. grinding or patching, it is generally better and more econom- ical to mill off the entire surface (for example, rotomill and require that shoring be designed by a professional engineer hydrodemo) to a depth of at least 3/4 in. (19 mm) below the and monitored by qualified personnel. adjacent bridge deck and place a concrete overlay (Flynn 4.2.2 Removal and refinishing of concrete—Care should 1992; Loveall 1992). In either case, the recommendations in be taken during concrete removal to avoid damaging any ACI E706 should be followed in patching or overlaying the reinforcing steel that is to remain in place. The following are bridge deck surface. suggested specification provisions. Figures 4.2.2.4c through 4.2.2.4e show unsatisfactory 4.2.2.1 When portions of a bridge are to be removed, the patches adjacent to a newly widened bridge deck. In such removal operations should preferably be performed without cases, it would have been more desirable to have scari- damage to any remaining structure. In practice, the owner fied the old bridge deck surface and repaired it as part of a will decide between expedient demolition, which may combined bridge-widening and rehabilitation plan. include hoe ram and heavy hydraulic crunching jaws, and demolition methods that can minimize the damage of the 4.3—Avoidance of damage due to dead load remaining structure. Suggested methods to ensure limited deflections damage include a requirement for a demolition plan from Two important facts should be recognized when consid- the contractor to incorporate shallow saw cuts at the edge ering dead load deflection: 1) portions of the superstructure of the bridge deck to remain, and concrete removal with widening should initially be built above the grade of the tools that are limited in weight class such as a maximum 30 existing structure to allow for dead-load deflection; and 2) lb (14 kg) jack hammer and 15 lb (7 kg) chipping hammer. the deflected superstructure widening should meet the grade Existing reinforcement that is to be incorporated in the of the existing structure when the final connection is made new work should be protected from damage and should be between bridge decks. If dead-load deflection is not prop- cleaned thoroughly of all adhering concrete material before erly accommodated, construction, maintenance, and traffic- being embedded in new concrete. If existing reinforcement safety problems may occur. has 20 percent or more section lost as indicated by the ribs When discussing dead-load deflections, it is necessary to divide superstructures into two groups: 1) unshored American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 9 Fig. 4.2.2.4d—Corner spall repair needed after widening. Fig. 4.2.2.4b—Bridge deck refinishing complete with concrete overlay in place. Fig. 4.2.2.4e—Severe edge spall needing immediate perma- nent repair. construction, such as precast prestressed concrete girders or steel girders, where the largest percentage of girder deflec- tion occurs when the bridge deck is placed; and 2) shored construction, such as cast-in-place concrete superstructure construction, where the deflection occurs when the false- work is released. In precast concrete girders, the effect of creep deflection should be considered. The creep deflection is influenced by several factors—namely, the dimensions of the girder, concrete mixture, environmental conditions (for example, relative humidity and temperature), concrete age, and the magnitude of loading (AASHTO 2010). 4.3.1 Unshored construction—Figure 4.3.1 shows the different stages of simple-span precast or steel-girder deflec- Fig. 4.2.2.4c—Excessive spalled area at widening. tion as the bridge deck concrete is placed from one end of the girder to the other. The concept is the same for continuous American Concrete Institute Copyrighted Material—www.concrete.org 10 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) Fig. 4.3.3—Spalls in bituminous concrete surfacing over longitudinal expansion joint. Fig. 4.3.1—Dead-load deflection and camber. 4.3.3 Prestressed concrete construction—For the same spans, whereas the design will change. Analysis of these span lengths, prestressed members generally deflect less than sketches illustrates the importance of using a closure place- reinforced concrete structures; therefore, their use decreases ment between the new bridge deck and the existing bridge the difficulty of getting a good grade match between new deck so that the grade of the widening will match that of the and existing bridge decks. The use of prestressed concrete existing bridge. Differential settlement between the existing structures, however, does not eliminate the need for a closure deck and the widening is of importance when concrete is placement, but may affect closure width and ability to place cast. One end of the screed needs to rest on the existing deck, closures in traveled lanes. Differential longitudinal elastic whereas the other end rests on the forming system to match shortening during stressing requires that superstructures the grades. remain unconnected until all prestressing work is complete. 4.3.2 Cast-in-place concrete construction—The elastic This longitudinal shortening continues as a result of creep. deflection of cast-in-place concrete structures, which is only For some structures, creep can be of sufficient magnitude approximately one-fourth to one-third of the total deflec- to warrant a greater delay in placing the closure. Accurate tion, occurs immediately after the falsework is released. The prediction of dead-load deflection is more important when remaining deflection (creep) continues at a diminishing rate, existing bridges are widened in comparison to new bridges, which becomes negligible after approximately 5 years (ACI as it is essential that the bridge deck grades match. The total 318). A theoretical analysis of stresses caused by differential dead-load deflection varies with the strength and maturity deflection that occurs between the new and existing struc- of the concrete when the falsework is released (Roberts tures usually predicts that distress will occur when connected 1972; Scordelis and Seible 1983). It is, therefore, neces- rigidly and even when a delayed closure placement is used. sary to consider a time frame that the falsework will support Minimal distress may occur if the procedures in this guide the widening when determining the camber of the bridge, are followed because the long-term deformation of concrete with particular importance for long-span bridges. This time allows these theoretical overstresses to dissipate before period should be included in the contract documents. damage is caused to the structures. When the design calls for connecting new and existing When the total dead-load deflection, including creep, of substructures on continuous, multiple-span, post-tensioned, the new cast-in-place structure is expected to exceed 3/8 in. rigid-frame structures, the piers, caps, and superstructure (10 mm), it is common practice to use a closure placement of the existing bridge must remain unconnected to the new after the falsework is released. This is done to minimize the structure until after the new structure is stressed. The only stresses caused by differential deflections and the transfer of exceptions are piers or caps at the point of zero movement dead load from the new to old structure. Good engineering during stressing (for example, the center pier of a symmet- practice suggests that the closure width and the length of the rical three-pier frame). delay period (after falsework release and before placing the The previously discussed problems created by traffic closure placement) should relate to the amount of dead-load vibrations, dead-load deflections, and longitudinal short- deflection that can occur after the closure is placed. This is ening due to post-tensioning may be mitigated by the use discussed in more detail in 4.4.5. of longitudinal expansion joints. When the junction of the American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 11 widening to the existing bridge deck falls within the traveled way, however, longitudinal expansion joints are generally avoided because such joints are more difficult to maintain (Fig. 3.3.2d and 4.3.3). 4.4—Closure placement details Closure placements may not be needed on very short spans or on very narrow widenings if the bridge deck concrete is placed fast enough to permit dead-load deflection and the concrete placement is completed before final strikeoff and initial set of the concrete. Retarding admixtures may be used to ensure that initial elastic deflections have completely taken place before the concrete begins to set. When closure placements between the new bridge deck and the existing bridge deck are used, the construction sequence and details employed are critical to the successful performance of the structure. The recommended width of closure placements should allow for an adequate develop- Fig. 4.4.1—Widening slab bridges. ment length, including reinforcement laps. A closure placement accomplishes two purposes: 1) it anchors is provided in ACI 318. In all circumstances, strict permits the widening to remain isolated from live-load conformance with the adhesive manufacturer’s recommen- deflections and vibrations from traffic on the existing bridge; dations is required. and 2) it allows dead-load deflection and prestressing short- The holes should be drilled by methods that do not shatter ening of the widening to reach a stage where the portion of or damage the concrete adjacent to the holes. They should be the new bridge deck that connects to the old will not be over- located at least 3 in. (75 mm) from the edge of the concrete stressed due to differential movements between old and new and be no more than 1/4 in. (6 mm) larger than the diam- structures. eter of the dowels or as recommended by the manufacturer. 4.4.1 Attachment to existing bridge—Structures with large The holes must be free of dust and drilling slurry and in a bridge deck overhangs should have a sufficient width of surface-dry condition before placing the grout or epoxy. The concrete removed from the overhang to permit lap-splicing holes are then filled with grout or epoxy before the dowels the original transverse bridge deck reinforcing with that of are inserted. the widening. As an alternative to conventional holes, horizontal holes Structures with small or no overhangs should either be approximately 3/4 in. (20 mm) larger than the dowel may be connected to the widening with dowels (Fig. 3.3.1.2 and drilled and the dowels are bonded in place with nonshrink 4.4.1) or have sufficient transverse reinforcement exposed grout. The dowel is centered in the hole and the grout is then to permit splicing by welding or mechanical connections. injected into the hole so that filling is accomplished outward Existing reinforcement may not be weldable and preheating from the base of the hole. A gasket is used around the dowel may be required. at the face of the hole to retain the grout while allowing the Cutting a seat into the existing exterior girder as a means air to escape. Alternatively, a vertical inlet and vent holes of support has proven to be unsatisfactory because of diffi- can be drilled from the top of the bridge deck into the hori- culty in reinforcing the area around the seat. zontal dowel hole to allow the air and excess predampening Double rows of dowels, as shown in Fig. 4.4.1, perform moisture to vent to the top if the exterior face of the dowel better than a single row. Dowels can be smooth or deformed hole is sealed with a tight gasket around the dowel. For and may be anchored into the existing concrete with grout either injection method, confirmatory investigation should or adhesive. This method requires a hole sloped one vertical be undertaken to ensure that the grout fully encapsulates to three horizontal or steeper so the fluid grout will not the dowel. The manufacturer’s literature is a good source of escape. Nonshrink grout (ASTM C1107/C1107M) performs finding adequate injection methods. better than other portland-cement grouts for this use (Dusel 4.4.2 Reinforcement—During placement of bridge deck et al. 1979). Epoxy may be preferred when high strength is concrete in the widening, reinforcing bars protruding from necessary. the new bridge deck into the closure space should be kept The maximum service design load for adhesive-bonded completely free of contact with the existing reinforcing dowels is usually taken as 25 percent of the pullout force— steel, concrete forms, or attachments (Fig. 3.3.1.2). for example, a safety factor of 4, determined in accordance During placement of the bridge deck closure concrete, with ASTM E1512 (ACI 355.4). If sustained loads are the new and existing transverse reinforcing steel within the expected, the total displacement (initial plus creep) should closure should be connected securely together or to common not exceed 0.03 in. (0.8 mm) when tested at 40 percent of the longitudinal reinforcement, as shown in Fig. 3.3.1.2. ultimate load, in accordance with the creep testing procedure Reinforcing bars extending from the existing bridge deck of ASTM E1512. Strength design of post-installed adhesive should be straight rather than hooked. Reinforcing bars American Concrete Institute Copyrighted Material—www.concrete.org 12 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) extending from the existing bridge deck that are too short to give sufficient development length may be extended by approved mechanical connections or full-strength welds. Welding can be used when the extension being welded is free from restraint during the welding process to permit shortening of the bar as the weld cools. AWS D1.4/D1.4M contains recommended details for making welded splices in reinforcing steel and requires making a chemical analysis of the steel to determine its weldability. The document provides procedures for welding splices if chemical composition is unknown. In addition, AASHTO LRFD (AASHTO 2010) includes additional limits on maximum slip. Several types of mechan- ical connectors are available that meet the ACI 318 criteria of development of at least 125 percent of the yield strength of the bar. AASHTO LRFD (AASHTO 2010) includes limits on maximum slip not included in ACI 318. Fig. 4.4.7—Corrosion of epoxy-coated reinforcement at the Longitudinal reinforcing bars should be placed in the leaking closure pour construction joint. closure placement to distribute shrinkage cracks and mini- The amount of creep deflection in concrete members is a mize crack width per the distribution reinforcement require- direct function of the level of applied stresses. The rate of ments in AASHTO LRFD (AASHTO 2010). creep decreases with the age of the concrete and the length 4.4.3 Forms—Forms for the bridge deck closure place- of time since the formwork has been removed. Any creep ment should be supported from the superstructure on both deflection of the girders in the widening that occurs after the sides of the closure. They then act as an articulated ramp to bridge deck closure has been placed will produce stresses in spread the effect of any differential vertical movements over the closure and adjacent bridge deck. These stresses will, in the widths of the closure. These forms should not be placed turn, however, be reduced by creep in the closure concrete. between old and new structures until all other concrete in The rate of deflection of the girders must be considered the widening has been placed and the falsework is released. to decrease to a level that can be tolerated by the closure 4.4.4 Concrete—Specific requirements are necessary for concrete before closure concrete is placed. encasing reinforcing steel that is subject to vibration from These combined actions, with younger concrete in the external forces during the first few days after placement closure than in the widening, make the required delay period (Whiffen and Leonard 1971; Arnold 1980; Furr and Fouad very difficult to calculate and is normally based on experi- 1981). This applies to closure placements and bridge deck ence. For several years, the California Department of Trans- widenings when traffic is allowed on the old bridge during portation (Caltrans) has required that whenever the false- construction. An appropriate specification for the concrete for work is removed at the earliest permitted date, the closure bridge decks will include performance criteria for concrete concrete should not be placed until at least 60 days after the mixture design development and quality control as well falsework is removed (Caltrans 1991). As an alternative, if as quality assurance that is used to accept concrete during the falsework is left in place for at least 28 days after casting, construction. If the quality of existing concrete is consider- then the closure concrete should not be placed sooner than ably different from that of new concrete, constructed bridge 14 days after falsework removal. decks may need a corrosion protection system to preclude 4.4.6. Diaphragms—When bridge deck closure placements the potential of corrosion propagation. are employed, diaphragms connecting new to old girders are 4.4.5 Time of placement—The timing of the placement left disconnected until all other work is completed, except of concrete for closure placements depends on the type of for the placement of the closure. The diaphragms are then structure. For steel girders or precast prestressed concrete connected just before the placement of the closure. girder bridges, closure placements can be made as soon as 4.4.7 Maintenance—Experience indicates that one or the majority of new dead load (for example, any overlay, both of the longitudinal construction joints in a closure sidewalk, or other) is on the widening. For widenings pour can leak. The joints may leak because of shrinkage of consisting of more than one girder, the exterior railing need the concrete in the closure pour as well as shrinkage of the not be placed before closure. concrete in widened portion of the bridge deck. Reinforce- For cast-in-place concrete construction, a delay after ment, including epoxy-coated reinforcement, across the removal of falsework should be provided to allow the rela- leaking joint can corrode, lose section, and fail as shown in tively rapid early dead-load deflection to occur before the Fig. 4.4.7 (Sprinkel et al. 2010). The problem can be reduced bridge decks are connected. The length of the delay period, by using concrete materials that do not have high exotherm along with the width of the closure placement, should be and drying shrinkage. These infill sections are highly engineered to accommodate the dead-load deflection that restrained and small shrinkages will induce large tensile will occur in the widening after the closure is placed. stresses leading to cracking upon later shrinkage. Leaking American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 13 Fig. 4.5a—Partial pier elevation. joints can be routed and sealed with an epoxy or injected with epoxy to prevent leakage and costly repairs. Fig. 4.5b—Partial footing elevation. 4.5—Substructure details Typically, the new substructure is attached rigidly to the existing substructure, as shown in Fig. 4.5a. The dowel bars possibility of damage to the new work caused by: 1) vibra- connecting existing and widened piers transfer interfacial tions of traffic on the existing bridge; 2) dead-load deflec- stresses and may also provide the continuity of reinforcing tion of the widening that occurs as bridge deck concrete is steels. In cases where measurable settlement (greater than placed or as falsework is removed; or 3) shortening of the 1/2 in. [12.5 mm] total instantaneous settlement) is antici- new bridge deck work if it is longitudinally post-tensioned. pated from the geotechnical analysis, closure placements For continuous post-tensioned bridge decks of rigid-frame in footing and substructures have been used to prevent the bridges, the new substructures should also not be connected transfer of load from new to old structures (McGraw-Hill to the existing bridge in any way that would prevent the Companies, Inc. 1991). For example, elastic shortening longitudinal shortening of the new work. For cast-in-place of the piles at the Hackensack Bridge (Soto 1978) due to spans, it may be advisable to delay making this final connec- the dead load of the new pier was allowed to occur before tion for several days after the falsework is released to allow the old and new substructures were connected by a closure for some of the more rapid early dead-load deflection caused placement (Fig. 4.5b). by creep in the concrete to occur (refer to 4.4.5 for suggested delay times). CHAPTER 5—SUMMARY OF RECOMMENDATIONS The recommended method of making structural connec- Many design and construction issues are unique to the tions between widenings and existing bridge decks is to leave widening of bridges. Most of the major problems can be a gap between the two sections with a width appropriate for avoided by adequate decisions regarding the choice of struc- the selected reinforcing bar splice method, which is later filled ture type, whether or not to connect the bridge deck of the with concrete. This closure placement should be reinforced widening to the bridge deck of the existing bridge, and the with top and bottom mats of reinforcing bars that extend out method and sequence of making such connections. of both the new and existing bridge deck slabs. All reinforce- In terms of general appearance, the type of bridge used ment must be tied together securely to minimize differential for the widening does not have to be the same as the movements and corresponding damage to the fresh closure existing. Economy, site geometrics (for example, roadway concrete caused by vibrations from traffic. These reinforcing or waterway clearances), and aesthetics should determine steel ties should not be made, however, until just before the choice. the closure concrete is placed. Likewise, the connection of The joint between the widening and the existing bridge diaphragms between the existing bridge and the widening, decks generally occurs within the area that will be traversed and the installation of the forms for the closure placement, by vehicles. In these cases, it is recommended that the bridge should not be done until just before the closure is placed. decks be structurally connected. If the two spans are to be connected structurally, however, the live-load deflection CHAPTER 6—REFERENCES characteristics of the superstructure chosen for the widening Committee documents are listed first by document number should be similar to those of the existing bridge. and year of publication followed by authored documents When the bridge deck of a widening is to be connected listed alphabetically. structurally to the existing bridge deck, it is generally recommended that the final connection be delayed until the American Concrete Institute widening is nearly complete. Consequently, it will avoid the ACI 318-11—Building Code Requirements for Structural Concrete and Commentary American Concrete Institute Copyrighted Material—www.concrete.org 14 GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) ACI 343R-95—Analysis and Design of Reinforced Kim, Y. J.; Tanovic, R.; and Wight, R. G., 2009, “Recent Concrete Bridge Structures (Reapproved 2004) Advances in Performance Evaluation and Flexural Response ACI 345R-11—Guide for Concrete Highway Bridge Deck of Existing Bridges,” Journal of Performance of Constructed Construction Facilities, V. 23, No. 3, pp. 190-200. ACI 355.4-11—Qualification of Post-Installed Adhesive Loveall, C. L., 1992, “Experience with a Thick Reinforced Anchors in Concrete and Commentary Overlay for Bridge Deck Rehabilitation,” Proceedings of ACI E706—Repair Application Procedures the Third International Workshop on Bridge Rehabilitation, Technical University Darmstadt, Darmstadt, Germany. American Welding Society McGraw-Hill Companies, Inc., 1991, “Interstate Rehab AWS D1.4/D1.4M-11—Structural Welding Code—Rein- Called Biggest Job in Illinois,” V. 226, Engineering News forcing Steel Record, New York. McMahon, J. E., and Womack, J. C., 1965, “Bridge ASTM International Widening Problems,” Report No. 951120, HPR-1 (2), ASTM C1107/C1107M-11—Standard Specification for DO422, California Division of Highways. Packaged Dry, Hydraulic-Cement Grout (Nonshrink) Ng, P. L., and Kwan, A. K. H., 2007, “Effects of Traffic ASTM E1512-01(2007)—Standard Test Methods for Vibration on Curing Concrete Stitch: Part II—Cracking, Testing Bond Performance of Bonded Anchors Debonding, and Strength Reduction,” Engineering Struc- tures, V. 29, No. 11, pp. 2881-2892. AASHTO, 2010, “Guide Specifications for Highway “Operation Bridgeguard,” 1992, World Highways/Routes Construction,” ninth edition, American Association of State Du Monde, V. 2, No. 1, Nov.-Dec. Route One Publishing, Highway and Transportation Officials, Washington, DC. Kent, UK AASHTO, 2013, “AASHTO LRFD Bridge Design Speci- Precast/Prestressed Concrete Institute, 1980, “Precast fications,” sixth edition with 2013 interim revisions, Amer- Prestressed Concrete Short Span Bridges (Spans to 100 ican Association of State Highway and Transportation Offi- Feet),” Chicago, IL. cials, Washington, DC. Roberts, J. E., 1972, “Effects of Curing and Falsework Arnold, C. J., 1980, “Concrete Bridge Decks: Does Struc- Support Periods on Dead Load Deflections of Reinforced tural Vibration Plus Excess Water Form the Fracture Plane?” Concrete Slab Bridges,” California Division of Highways. Research Laboratory Section, Michigan Department of Scordelis, A. C., and Seible, F., 1983, “Time-Depen- Transportation. dent Behavior of a Skew Reinforced Concrete Box Girder Asnaashari, A.; Grafton, R. J.; and Johnnie, M., 2005, Bridge,” Concrete International, V. 5, No. 1, Jan., pp. 84-92. “Precast Concrete Design—Construction of San Mateo- Seible, F.; Priestley, M. J. N.; and Krishnan, K., 1991, Hayward Bridge Widening Project,” PCI Journal, V. 50, No. “Bridge Superstructure Rehabilitation and Strengthening,” 1, pp. 26-43. Transportation Research Record No. 1290, Transportation Caltrans (California Department of Transportation), 1991, Research Board. “Widening Existing Bridges,” Section 9-3, Bridge Memo to Shaw, T. V., and Stewart, C. F., 1974, “Effectiveness Designers Manual. of Attached Bridge Widenings,” Report No. CA-DOT- Deaver, R. W., 1982, “March 1982 Bridge Widening ST-4165-1-74-2, California Division of Highways. Study,” Final Report, FHWA/GA-82/008, GDOT Research Silano, L. G.; Swindlehurst, J.; and Parkinson, F. H., 1992, Project No. 7604, Georgia Department of Transportation. “Steel Structures,” Bridge Inspection and Rehabilitation: A Dusel, J. P.; Stoker, J. R.; and Nordlin, E. F., 1979, “Devel- Practical Guide, John Wiley and Sons, Inc. opment of a Rebar Dowel Anchorage System for Attaching Silfwerbrand, J. L., 1992, “Influence of Traffic Vibra- the California Type 25 Barrier to Existing Bridges,” Report tions on Repaired Concrete Bridge Decks,” Proceedings of No. FHWA-CA-TL-69-16, Caltrans, June. the Third International Workshop on Bridge Rehabilitation, Flynn, L., 1992, “Contract Drives Raleigh ‘Beltline’ Darmstadt, Germany, pp. 416-474. Rubblization,” Roads and Bridges, V. 30, No. 1, Jan. Soto, M. H., 1978, “Some Considerations in Widening and Furr, H. L., and Fouad, F. H., 1981, “Bridge Slab Concrete Rehabilitation of Bridges,” Transportation Research Record Placed Adjacent to Moving Loads,” Research Report No. 664, Bridge Engineering, V. 1, Transportation Research 266-1F, Study 21-5-79-266, Texas Transportation Institute, Board, Washington, DC. State Department of Highways and Public Transportation, Sprinkel, M. M., 1985, “Prefabricated Bridge Elements College Station, TX. and Systems,” NCHRP Synthesis 119, Transportation Gonnerman, H. F., and Lerch, W., 1951, “Changes in Research Board, Washington, DC. Characteristics of Potland Cement as Exhibited by Labora- Sprinkel, M. M.; Weyers, R.; Blevins, C.; Ramniceanu, tory Yests over Period 1904 to 1950,” ASTM Special Publi- A.; and Weyers, S. A., 2010, “Failure and Repair of Deck cation 127, ASTM International, West Conshohocken, PA. Closure Pour on Interstate 81,” Transportation Research Harsh, S., and Darwin, D., 1983, “Effects of Traffic- Board, Washington, DC. Induced Vibrations on Bridge Deck Repairs,” Project No. Transportation Research Board, 1981, “Effects of Traffic- P-0255, Kansas Department of Transportation. Induced Vibrations on Bridge Deck Repairs,” NCHRP Synthesis of Highway Practice No. 86, Washington, DC. American Concrete Institute Copyrighted Material—www.concrete.org GUIDE FOR WIDENING HIGHWAY BRIDGES (ACI 345.2R-13) 15 U.S. Department of Transportation, 2009, Manual for sion: A Methods Application Manual,” National Research Uniform Traffic Control Devices for Streets and Highways, Council, Washington, DC. Federal Highway Administration. Whiffen, A. C., and Leonard, D. R., 1971, “Survey of Weyers, R. E.; Prowell, B. D.; Sprinkel, M. M.; and Traffic-Induced Vibrations,” Report LR418, Transport and Vorster, M., 1993, “Concrete Bridge Deck Protection, Road Research Laboratory, England. Repair, and Rehabilitation Relative to Reinforcement Corro- American Concrete Institute Copyrighted Material—www.concrete.org American Concrete Institute® Advancing concrete knowledge As ACI begins its second century of advancing concrete knowledge, its original chartered purpose remains “to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading knowledge.” In keeping with this purpose, ACI supports the following activities: · Technical committees that produce consensus reports, guides, specifications, and codes. · Spring and fall conventions to facilitate the work of its committees. · Educational seminars that disseminate reliable information on concrete. · Certification programs for personnel employed within the concrete industry. · Student programs such as scholarships, internships, and competitions. · Sponsoring and co-sponsoring international conferences and symposia. · Formal coordination with several international concrete related societies. · Periodicals: the ACI Structural Journal and the ACI Materials Journal, and Concrete International. 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