Accelerated bridge construction chapter 9 prefabrication of the substructure and construction issues Accelerated bridge construction chapter 9 prefabrication of the substructure and construction issues Accelerated bridge construction chapter 9 prefabrication of the substructure and construction issues Accelerated bridge construction chapter 9 prefabrication of the substructure and construction issues Accelerated bridge construction chapter 9 prefabrication of the substructure and construction issues
CHAPTER Prefabrication of the Substructure and Construction Issues 9.1 Rapid substructure construction a greater challenge than that of rapid superstructure In Chapter 8, superstructure prefabrication techniques and modular construction methods, such as using special girders (Inverset, NEXT beams, and Wolf girders), the need for precast connections, and case studies of successful deck components in many states were discussed This chapter deals with rapid construction applications for the equally important bridge substructure and foundations A list of successful substructure projects that were completed in recent years in different states was given in Chapter (Tables 5.4, 5.6, and 5.7) Case studies and detailed discussions on substructure construction are given in Sections 9.7 and 9.8 In this chapter, the substructure, totally prefabricated bridges, and emergency replacement of the existing substructure (when the superstructure is lifted off the top of bearings and reused) using precast units are addressed The methods of construction management for rapid delivery are equally (and simultaneously) applicable to both the substructure and superstructure components It is important to understand that prefabricated bridge elements and systems (PBES) focus not only on the conventional prefabricated bridge beams and decks but on the prefabrication of all bridge elements, including abutments, piers, footings, walls, parapets, and approach slabs A glossary of ABC terminology applicable to all the chapters is listed for ready reference in Appendix Maintaining minimum clearances to prevent accidents: For ABC substructure design and construction, the AASHTO requirements for vertical clearance over an interstate (16 ft, 6 in minimum) and over a railroad (23 ft) dictate the clear height of the abutments and piers Some existing bridges not meet this important requirement; such bridges have therefore become functionally obsolete and are candidates for replacement Prefabrication construction of substructure will control and achieve the required clearances To raise the bridge deck elevation, the elevations of the approaches and the highway need to be raised There are difficulties with raising the highway elevation, and lowering of the underpass may be required For bridges on rivers with navigable traffic, movable bridges are more expensive for daily operations and long-term maintenance In addition, a number of states have approved legislation that mandates minimizing traffic disruption during replacements Early construction and delivery of the substructure is therefore a step in the right direction Innovative construction methods, materials, and systems are needed for reducing onsite construction time Accelerated Bridge Construction http://dx.doi.org/10.1016/B978-0-12-407224-4.00009-5 Copyright © 2015 Elsevier Inc All rights reserved 399 400 CHAPTER 9 Prefabrication of the Substructure and Construction Issues Advantages: The advantages of using ABC for the superstructure have been discussed For the substructure, when compared to conventional construction, the advantages include the following: • Nighttime work hours are not required for lifting bridges into the existing footprint • Rapid construction has the ability to provide a bridge on the same alignment • Construction of a new bridge adjoining the existing bridge is not required • Partial lane closure is not required Historically, bridge deck, girders, and parapets have been replaced with prefabricated construction using the existing substructure This practice will continue until all existing bridges of the older generation are completely replaced, when entirely new substructure will be required In the distant past, the LRFD method was not in vogue The design requirements for substructure components have generally been more conservative (with higher factors of safety on loads and materials) than for the supported superstructure components Also, the structural behavior of the superstructure is generally better understood than that of the substructure, which is subjected to soil interaction As a result, substructure design criteria based on load combinations for flood design, which has a probability of peak flood occurring once in 100 or 500 years, is more conservative For example, higher bending moments from lateral loads result in vertical members such as piers, abutments, and wingwalls and their foundations than in the horizontal deck elements The brunt of lateral forces from floods, winds, earthquakes, etc., and resulting bending stress is borne to a far greater extent by the substructure than by the superstructure Foundations: For stability and geotechnical considerations, the footing sizes are kept larger Deep foundations (when used) would last much longer than the superstructure and are not replaced as often as the superstructure components Therefore, during the life of a bridge, the deck and the girders take more repeated impact loads than the distant substructure components Bearing retrofits are used with modern bearings (such as seismic isolation bearings) and for replacing rusted rocker and roller bearings The deck or the bearings are likely to be replaced more than once, while the abutments and the piers remain unchanged or undergo minimal changes However, in the case of floods causing erosion or for earthquakes, the substructure fails first, causing the superstructure to fail next The use of prefabrication for the substructure components (such as footings and the deep foundation) is comparatively limited and required only for substructure repairs and retrofit Only small span prefabricated piers and arch bridges (such as CON/SPAN) have used ABC techniques for the substructure Reinforced concrete has traditionally been used for pier bents and abutment walls for conventional construction Precast abutment and pier walls, with vertical cast-in-place joints, need to be posttensioned for stability and water tightness Summary: Hence, the percentage of prefabricated piers and abutments being transported using self-propelled modular transporters (SPMTs) and erected at the site is comparatively lower than the prefabricated superstructure components, and the substructure prefabrication technology is still in the development stage for replacing an existing bridge The substructure work we discuss here is generally applicable to the following conditions: • Emergency repairs and retrofit of a substructure on an existing footprint (such as the aftermath of floods or an earthquake) • Total replacement of bridges on an existing or a new footprint • Extending the widths of abutments and piers for deck widening • Planning of an entirely new bridge on a new highway 9.2 An overview of rapid substructure construction 401 Avoiding lane closure: The staging of construction is possible by closing down lanes, but staged construction may lead to less rapid delivery An assembled single-lane bridge (with traffic in each direction) can be transported using an SPMT If not, a lateral slide-in or roll-in roll-out method can be used if feasible Climatic hold-ups: The construction season is dependent upon weather conditions and may not be the same for every state in the United States Nationally and locally, the use of ABC for substructure continues to grow In peak winter months, for example, factory manufacture is possible but erection may take longer There is a learning curve associated with using some ABC technologies, which will take a concerted and coordinated effort by owners, designers, and constructors alike 9.1.1 Prefabrication of substructures in Europe and Japan The SPER system is a method of rapid construction of piers using precast concrete panels as both structural elements and as formwork for cast-in-place concrete Tall hollow piers use panels for inner and outer formwork, while shorter solid piers use panels for the outer formwork only The system provides similar seismic resistance as a conventional cast-in-place system 9.2 An overview of rapid substructure construction In the United States, bridges are located on one of the following networks and are classified as such: • Interstate • Arterial • Collector • Local ABC and rapid substructure construction will be especially helpful for the replacement of bridges located on the more important interstate and arterial roads carrying high average daily traffic (ADT) It is an unusual situation if the substructure needs to be replaced while the superstructure is in satisfactory condition In some cases, superstructures can be lifted off the bearings and reused In most cases, the entire bridge is replaced, except when using the lateral slide-in or roll in–roll out technique, which can preserve the superstructure The main substructure components are the following: Precast cantilever wall abutment types • Full-height abutment • Mid-height abutment • Stub and semi-stub abutments • Spill-through abutment Modern types include: • Integral abutments (Figure 9.1) • Semi-integral abutments • Mechanically stabilized earth (MSE) wall abutments (Figure 9.2) Precast retaining walls can be constructed in place of conventional cast-in-place construction (Figure 9.2) 402 CHAPTER 9 Prefabrication of the Substructure and Construction Issues FIGURE 9.1 Author-designed integral abutment on Route 46 on Peckman’s River in New Jersey FIGURE 9.2 Mechanically stabilized earth wall under construction with precast segments Precast pier types Multiple bents and flared caps are aesthetically pleasing Some common shapes are: • Solid wall • Hammerhead • Multiple column bents (hollow or solid concrete, segmented, post-tensioned, and reinforced) (Figure 9.3) Modern types include: • Multiple pile bents • Integral pier The author designed precast multicolumn pier bent for a U.S Route 50 bridge located in southern New Jersey (Figure 9.3) 9.2 An overview of rapid substructure construction 403 FIGURE 9.3 Use of precast multicolumn pier bent by the author for a U.S Route 50 bridge located in southern New Jersey The use of precast abutment and pier elements may require posttensioning in order to provide a composite and watertight connection More recently, grouted rebar couplers, which have been used in building construction for about 40 years, are being specified as a more rapid and less costly alternative for component connections The height of bridges seldom exceeds 20 ft and the width for a two-lane bridge is less than 40 ft, compared to the much longer span lengths of girders carried by SPMTs The transportation of precast substructure components for assembled pier bents is therefore not as common as that for superstructure components Foundation types • Shallow footings: Precast footing slabs • Deep foundations: Piles, pile caps, and drilled shafts or caisson wall Pile foundation is designed as end bearing or friction piles The following shapes of cross-section are commonly used: • Steel H pile or W sections • Steel pipe pile • Concrete pile or steel encased • Prestressed concrete pipe • Steel sheet piles For the selection of the foundation, the expertise of a geotechnical engineer should be utilized Prefabricated footings: The soil beneath the precast footing slabs needs to be well compacted and made level to receive the heavy 3–4-ft-thick precast reinforced concrete footing slabs; otherwise, 404 CHAPTER 9 Prefabrication of the Substructure and Construction Issues differential settlement can occur Due to allowance for tolerances in casting the footing slab, the underside of footing slabs is not likely to be level So far, there has not been sufficient experience reported regarding soil behavior in relation to precast footing slabs Any damaged cast-in-place footings can be strengthened by driving micropiles, but this is an expensive operation On the other hand, conventional cast-in-place concrete will flow into the uneven soil surface without leaving any air pockets, and there will be no lack of contact between the footing and the soil Foundations of bridges located on waterways: • Preliminary or general checks that include checking for scour in bridge bents located in water with possible scour should also include checking the bent piles for buckling failure In addition, checking the bents is required for transverse to bridge centerline pushover failure (from combined gravity and added flood water loadings) • Installing spurs or bendway weirs at a bend that is migrating toward a bridge abutment is good practice Spurs will redirect the flow away from the abutment • Hydraulic countermeasures: This includes placement of armoring such as riprap around any exposed foundation • Structural countermeasures: This includes underpinning of footings that were undermined by using grout or grout bags Bearing types Bearings can be classified as substructure components The following types of modern bearings are commonly used: • Type 1: Multirotational • Multirotational (pot-bearing) guided • Multirotational (pot-bearing) unguided • Multirotational (disc-bearing) guided • Multirotational (disc-bearing) unguided • Type 2: Elastomeric • Elastomeric with polytetrafluoroethylene (PTFE) (e.g., Teflon) • Elastomeric, fabric type with PTFE (e.g., Teflon) • Elastomeric, steel laminated • Elastomeric, fabric laminated • Elastomeric, steel laminated with external load plate • Elastomeric, steel laminated with lead core • Elastomeric, laminated with PTFE (e.g., Teflon) 9.2.1 Substructure replacement A survey of structural deficiencies is required to establish the need for replacement (please refer to the textbook by Khan, M.A., 2010 Bridge and Highway Structure Rehabilitation and Repair McGrawHill, pages 54 and 363) In the past, there has often been overdesign using gravity and massive walltype abutments, piers, and foundations This had a built-in advantage in that when it came to replacement, only the superstructure was replaced 9.2 An overview of rapid substructure construction 405 Steps to avoid foundation soil scour and pile failure after construction include the following: P ile design: For bridges located on rivers subject to floods, the ultimate bearing capacity of axially loaded piles must be limited to the compressive and/or tensile loads determined for reduced capacity for any projected scour Pile capacity: This must be limited to the ultimate limit as established by L-pile analysis Pile group effects must be considered Use of a dynamic screening tool for pile bents: An evaluation procedure developed by the Alabama Department of Transportation and Auburn University may be employed It is a screening tool described in macro- and microflood charts (Refer to Ramey, G.E., Brown, D.A., Hughes, M.L., Hughes, D., Daniels, J., May 2007 Screening tool to assess adequacy of bridge pile bents during extreme flood/scour events, ASCE, Practice Periodical on Structural Design and Construction, vol 12, No 2) Cantilever wingwalls: Precast wall panels of uniform height and splayed panels of varying height are required A considerable amount of work has been done on precast wall panels Examples of proprietary wall systems include the following: Mesa Retaining Wall Systems: Mesa segmental concrete facing units are used in conjunction with Tensar structural geogrids Mesa units not require mortar, so the considerable time, labor, and material of cast-in-place construction are eliminated Heights up to 50 ft are possible A high level of structural integrity can be achieved with a typical SRW type connection (See the Design Manual for Mesa Retaining Wall Systems, Tensar Earth Technologies Inc., Atlanta, GA) Allan Block Segmental Retaining Walls: Heavy-duty professional retaining walls are built Different types of construction include gravity walls and walls reinforced with soil reinforcement options, such as geogrids and earth anchors This type of segmental retaining wall was reviewed by the author for the design of walls by the RBA Group for the New Jersey Oak Tree Road Project, located in Edison, New Jersey (See the Installation Guide for Allan Block Segmental Retaining Walls, Allan Block Corporation, Edina, MN) MSE retaining walls: Mechanically stabilized earth or MSE, which is soil constructed with artificial reinforcing, can be used for retaining walls and bridge abutments Although the basic principles of MSE have been used throughout history, MSE was developed in its current form in the 1960s The reinforcing elements used can vary but include steel and geosynthetics MSE is the term usually used in the United States for “reinforced earth.” The author has used this type of modular wall on bridge projects (For more information, see “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes: Design & Construction Guidelines,” March 2001).1 Cantilever retaining walls with parapets: Precast wall panels can be used at the approaches of a bridge to retain embankments on either side of highway, with the parapets serving as the sidewalks The design of uniform height walls as secondary elements of a bridge and highway project is similar to the proprietary walls described above 1 Available at http://isddc.dot.gov/OLPFiles/FHWA/010567.pdf 406 CHAPTER 9 Prefabrication of the Substructure and Construction Issues 9.3 Design of precast substructure elements The details for precast substructure elements are based on a design process called emulative detailing This is a process developed by a joint committee of the American Concrete Institute (ACI) and the American Society of Civil Engineers (ASCE) The process is documented in the publication entitled “ACI 550.1 – Emulating Cast-in-Place Detailing in Precast Concrete Structures.” This process emulates cast-in-place connections with precast elements Conventional cast-in-place (CIP) construction is not monolithic Construction joints are common CIP construction joints are typically detailed with dowels and lap splices with the exception of column connections Emulation design replaces the traditional lap splice with a mechanical coupler These couplers are allowed by the AASHTO LRFD Design Specifications AASHTO requires that the couplers develop 125% of the specified yield strength of the connected bar This is more than adequate in most cases for use in connection emulation for categories such as abutments and walls The one exception is column connections in high seismic zones Use grouted splice couplers in connection emulation details for accelerated bridge construction based on the following Several companies make similar proprietary precast products They easily meet the AASHTO requirements for mechanical connectors They can develop the specified tensile strength of the bars and can easily be cast into precast elements Seismic considerations: The design of column connections is especially difficult for high seismic zones These connections develop plastic hinges to dissipate the seismic forces on the structure There are no prefabricated bridge connections tested in the United States for plastic hinging to date Grouted splice couplers have been researched in Japan A review of the test results shows that the behavior of the grouted splice couplers is almost identical to the behavior of a continuous mild reinforcing column The coupler showed slightly lower drop-off of moment capacity at the higher ductility ratios These connections are currently allowed in high seismic zones in the United States for vertical construction such as buildings The seismic section of the current ACI 318 code classifies these connections as type mechanical connectors The ACI code specifies that these connectors are required to develop 100% of the specified tensile strength of the connected bar Designers are encouraged to review the ACI code provisions When working with precast substructure elements, it is important to identify changes, modifications, and enhancements to the AASHTO bridge construction specifications in order to assist states and bridge owners who want to implement ABC Implement the use of the decision-making matrix to further assist the project Precast elements and hybrid bridge systems will become standard practice; thus, it will be important to create standard specifications for MSE walls, geosynthetic reinforced soil (GRS), continuous flight augured (CFA) piles, geofoam, and micropiles as we move forward 9.4 Substructure construction techniques using SPMT units Advantages of the use of SPMTs were discussed earlier With the increased use of PBES, some agencies have developed standard drawings and details Similar to the prefabrication of superstructure, the substructure prefabrication methods are being recommended and promoted by FHWA, NCHRP, and also by some individual states (and addressed in their design manuals and construction specifications) 9.4 Substructure construction techniques using SPMT units 407 In addition, FHWA has published several manuals, including the 2009 Connection Details for Prefabricated Bridge Elements and Systems and the 2011 Accelerated Bridge Construction Manual Also, the SHRP2 RO4 project has evaluated the different systems in use and published a toolkit of standard drawings, erection schemes, and sample design calculations called Innovative Bridge Designs for Rapid Renewal: ABC Toolkit.2 The use of SPMTs is required for transporting abutment and pier precast components SPMTs are high load capacity transport dollies that can be ganged together longitudinally and transversely to fit the bridge length, width, and weight Some transporters have wheel sets that can rotate 360°, giving the ability to move: • Laterally • Longitudinally • Diagonally • Pivoting about a central point or moving in an arc The transporters have their own propulsion system composed of hydraulic drive motors and their own hydraulic lifting system These attributes allow for transporting, raising/lowering, and setting a complete bridge within tight confines The entire bridge can be built nearby with SPMTs used to move the bridge to its final location (Figure 9.2) 9.4.1 Limited experience in transporting prefabricated footing and abutment components The use of prefabricated footing and abutment components is restricted in practice, mainly due to the transportation difficulties of large footings and tall vertical wall components The “Manual on Use of Self-Propelled Modular Transporters to Remove and Replace Bridges”3 by the FHWA (June 2007) only gives examples of the transport and assembly onsite of prefabricated superstructure components Precast MSE wall segments can be transported by SPMTs However, for assembly at the site, several vertical cast-in-place joints will be required for continuity Besides lateral earth pressure, heavy dead and live load vertical reactions need to be transmitted to the footings and vertical joints located near bearings may have stress concentrations The seismic response of such discontinuities (with the resulting lateral seismic forces during an earthquake) needs to be investigated, preferably by laboratory tests on scaled models, before allowing heavy axle loads from truck traffic Maryland State Highway Administration (MSHA): The MSHA completed its first SPMT move in 2012 for Nursery Road over the Baltimore–Washington Parkway The project involved demolition and construction of two single-span bridges with two nighttime parkway closures During the first nighttime closure, the existing bridges were removed by SPMTs Each superstructure was constructed several hundred yards from the existing bridge on shoring in a staging area located in the parkway median 2 See 3 See http://www.trb.org/Main/Blurbs/168046.aspx for more information https://www.fhwa.dot.gov/bridge/pubs/07022/chap00.cfm 408 CHAPTER 9 Prefabrication of the Substructure and Construction Issues Recent projects in Maryland serve as good examples of the use of SPMTs Installation times ranged from to 8 h depending on the travel path complexity, which involve factors such as: • Length, grade, and curvature • The bridge geometry (skew, span continuity) • The specified joint widths, which allows more room to set the bridge Utah: The Utah Department of Transportation (UDOT) is considered a leader in the use of SPMTs, having installed nearly 40 bridges in the last few years UDOT has developed their own SPMT manual that includes design, construction, and heavy lift instructions • In 2011, UDOT installed the Sam White Lane Bridge over I-15, which was the longest U.S bridge to date (with two spans of 354 ft long by 77 ft wide) Steel beams and a lightweight concrete deck were utilized to reduce the number of SPMTs and travel path preparation Iowa complete ABC projects: The 2012 Iowa U.S Bridge over Keg Creek required a 16-day road closure and complete off-site prefabrication, excluding the drilled shafts The heaviest elements were the pier cap beams weighing 168,000 pounds using normal weight concrete and solid sections Smaller weights would have been possible if roadway transport was required The project was intended to demonstrate an ABC concept for a typical multispan stream crossing that could be standardized for use on a large number of projects All elements were prefabricated in a staging area near the bridge The use of 204 ft by 44 ft modular steel beam and deck units on precast piers and abutments was specified Massachusetts ABC Projects: The 2011 MassDOT Fast 14 project involved rehabilitation and superstructure replacement of 14 bridges on I-93 in one construction season as compared to conventional construction taking four construction seasons with substantial traffic impact Under this design-build project, the contractor utilized modular steel beam and deck units designed as simple spans but made continuous with “link slabs.” Link slabs are heavily reinforced cast-in-place continuity slabs that are purposely not bonded to the beams Traffic crossovers were used only during 10 weekends between June and August 2011 Abutment seats: On the following weekdays, the abutment seats were replaced and other preparatory work was performed During the second nighttime closures, the new bridges were moved into place The move and setting took about an hour, concluding with grouting the anchor bolts and placing steel plates over the deck joints in time for opening to morning traffic For cost details and guidance before planning a similar bridge, please contact the state DOT Pennsylvania initiatives Pennsylvania historically has taken advantage of ABC techniques to save time and money and increase efficiency PennDOT publication (DM 4) has standard design and publication (BD Series) or construction drawings (BC Series) for each of these structure types Strike-off letters are used for interim changes in the specifications: • Prefabricated deck beams such as adjacent box beams (to save deck forming and material cost) • Prefabricated culverts and arches (to minimize stream diversion work) • Glue-laminated timber slabs (for fast and low-cost construction on low-volume roads) 9.8 ABC alternative contracting methods 427 Benefits of CMGC: • Cost certainty • Risk reduction • Schedule optimization • Collaboration • Model to implement innovation There are more than 10 agencies in the United States with CMGC experience, with Utah DOT and the Utah Transit Authority taking the lead Fourteen state DOTs currently have CMGC authority This type of management is also applicable where the project cost is high and multiple subcontractors and subconsultants are on the team For more information on CMGC, see the Utah DOT Website at http://www.udot.utah.gov/main/ 9.8.4 Design-build management Design-build construction is another contracting method that is gaining popularity, as it can provide significant cost and time savings for the owners Design-build provides a single point of responsibility for an entire project; the progress and quality of the project including oversight of the design concept is managed by the contractor A historical perspective of design-build is given below in chronological order, where bridge construction was an art rather than a science 9.8.4.1 Ancient practice 1800 BC—Code of Hammurabi (Design-Build) 450 BC—Classical Greece (Design-Build) 1200 AD—Middle Ages Cathedrals (Design-Build) 1450—Renaissance: Emergence of design-bid-build 9.8.4.2 Modern practice 1960s—Private sector reemergence of design-build and CMAR 1980s—Public sector reemergence of design-build 1993—Establishment of the Design-Build Institute of America 1996—Passage of Federal Acquisition Reform Act of 1996 The design-build team leader is the single source of responsibility for the owner and is normally the member who is financially and legally capable of entering a contract and guaranteeing completion of the work Most often, this is the general contractor, the firm having the necessary balance sheet and bonding capacity However, it can be the engineer or an outside party Design-build delivery is still termed experimental in transportation FHWA will allow any fair and transparent selection method to be evaluated and approved under SEP-14 To date, the FHWA has approved the use of design–build in more than 150 projects, representing just over half of the states Many European countries started using design-build delivery before the United States Table 9.16 shows a comparison between CMGC and D-B Methods 428 CHAPTER 9 Prefabrication of the Substructure and Construction Issues Table 9.16 Comparison of CMGC and Design-Build Where Owner Spends Effort CMGC Design-build Define goals Project restrictions RFP development Proposal evaluations Risk analysis Innovation analysis Design decisions Cost comparisons Contractor construction Define goals Performance spec RFP development Proposal evaluations DB design DB construction 9.8.5 Administrative issues for prefabrication Contract and bid documents The following process is applicable to ABC Variations are possible where instead of pure ABC, only a partial ABC method is selected For the selection of fabricators, the CMGC will negotiate on the basis of comprehensive bid documents (such as plans, specifications, and estimates (PSE)) There are two approaches for the first phase of management: For small-span bridges, ready-made proprietary documents provided by the fabricator may be checked by the designer and reused with minor changes For medium and long spans, the following typical documents prepared by the designer are required: a Construction plans for the precast members b Specifications for fabricating bridge components c Materials and cost estimates based on material types shown in the drawings, which help in arriving at the cost to be incurred The fabricator therefore plays an expert role in the CMGC and D-B management systems In the second phase of management, the general contractor still requires specifications from the designer for the following sensitive operations The first step is preparing the detailed construction schedule showing activities on the critical path In addition, the following steps are required: • Soil investigation and foundation construction • Lifting and placing assembled members on SPMTs • Erecting substructure bridges and placing cranes at optimum locations • Coordination with utility companies • Installing sensors for remote structural health monitoring (SHM) • Testing the bridge for live load before allowing daily traffic Postdesign construction tasks for the general contractor’s team 9.9 Construction specifications and details for accelerated completion 429 • Responses to fabricator’s/subcontractor’s queries prior to their selection • Bid approval process • Construction coordination, field meetings • Answering requests for information (RFIs) related to drawings • Design change notices (DCNs) when required • As-built drawing preparation after completion 9.8.6 Progress in lateral sliding technique for substructure components The conventional cast-in-place techniques require longer roadway closures unless traffic can temporarily be carried off alignment on the new bridge A complicated aspect of this method is the construction of the foundations, piers, and abutments Multiple options are available for substructure construction, including: • Waiting until the existing bridge is demolished and then using prefabricated substructure elements • Using the existing substructure when possible with minor repairs • Constructing the substructure beneath the existing bridge using spread footings • Driving low headroom pile types (i.e., auger cast piles, micro piles) when a shorter bridge is possible • Constructing the new bridge with an integral cap beam and back wall that functions as an abutment and setting it on substructure units constructed outside the width of the existing bridge Many of the construction methods that use lateral slide or launching techniques involve constructing the complete or nearly complete bridge off alignment and moving components into place using heavy lift equipment such as SPMTs, large-capacity cranes, strand jacks, and gantry lifts It is expected that with the growing advances in details and materials, some of the difficulties currently present in these construction methods (such as limited site access or bridges on rivers) will eventually be resolved 9.9 Construction specifications and details for accelerated completion 9.9.1 Assembly plans Most bridge construction projects require contractors to submit erection plans Prefabricated substructures also require a level of preconstruction planning Write project specifications to require that the contractor submit an assembly plan for the construction of the entire structure, including the precast substructure Include as a minimum the following in the assembly plan: • Size and weight of all elements • Picking points of all elements • Sequence of erection • Temporary shoring and bracing • Grouting procedures • Location and types of cranes • A detailed timeline for the construction, including time for curing grouts and closure pours • The CABA Manual provides guidance with the design and detailing of precast concrete structure elements according to PennDOT DM-4 and AASHTO LRFD bridge design specifications, except as noted otherwise (Reference CABA Bridges, Precast Structure Elements Guidelines, Accelerated Bridge Construction, May 2012) 430 CHAPTER 9 Prefabrication of the Substructure and Construction Issues 9.9.2 Use of precast substructure details sheet The sheet will normally contain, but is not limited to, the following listed details: Plan view of each substructure unit Elevation view of each substructure unit Typical transverse sections as needed Individual piece plans, elevations, and sections showing the following: a Dimensions b Internal reinforcing details, including grouted splice couplers c Lifting points d Approximate shipping weight of the piece Connection details, including grouted reinforcing splice couplers Tolerance details for all applicable pieces Bar details Table of estimated quantities Dimensions on the precast substructure detail sheet include the following: Structural dimensions: Draw all views and details in feet and inches to the nearest ⅛ in Reinforcing steel: Show reinforcement dimensions and locations in all views, including bar details in feet and inches to the nearest ¼ in All measurements are to the centerline of the reinforcements Cover: Show cover for substructure elements with 3 in clear cover for bottom mats of reinforcement for footings and 2 in clear cover for other substructure elements Angles: Show in degrees, minutes, seconds to the nearest whole second if such precision is available 9.9.3 Accelerated bridge guide details for substructures The PCI Northeast Bridge Technical Committee has a series of guideline drawings that represent the design and detailing of precast concrete substructures These sheets provide examples of different substructure types for the use of accelerated bridge construction in the Northeast These guideline drawings may be used unless the state design manual recommends other bridge details 9.9.4 Need for post-construction repairs Conventional repairs to the substructure not normally require ABC or prefabrication of the members The following types of repairs, where limited use of ABC is applicable, occur more frequently: • Bearings retrofit • Pier jacketing • Column strengthening • Scour countermeasures retrofit • Foundation strengthening by micropiles • Seismic retrofit 9.9 Construction specifications and details for accelerated completion 431 9.9.5 Sample specifications for concrete and reinforcement properties Construction documents need to address all important details Typical concrete strengths for ABC may be higher than for cast-in-place construction due to higher shear strength required in transportation, lifting, and erection ( ′) • The nominal 28-day concrete strength fc for precast substructure elements typically a much higher strength is 5000 psi • Specify this strength at a higher level with prior agency approval where higher strengths are required • Specify the final designed concrete strength required on the plans Use of mild reinforcement: Coat all mild reinforcement according to agency specifications Coat all grouted splice couplers with epoxy coating The coating on the bars within the couplers does not need to be removed to make the connection Other precast elements: Allow lap splices in closure pours between elements that are not columns Use threaded mechanical couples for bars that extend beyond the edges of the precast element, except for columns Do not weld reinforcement 9.9.6 Sample specifications for closure pours Closure pour sizes should conform to the construction drawings These will be placed where needed and implemented as directed, designed, and detailed by the designer Concrete compressive strength in the closure pour will be equal or greater than the precast elements (typically 5000 psi) The designer will design and detail closure pours The designer will specify wet curing for at least 7 days to increase the durability of the closure pours The mix will be air entrained and have shrinkage compensating admixtures to prevent cracking and separation of the closure pour concrete, from the adjacent precast concrete Typical properties are as follows: • 6-h strength of 2500 psi • 7-day strength of 5000 psi 9.9.7 Tolerances in prefabricated members The tolerance of casting elements is critical to a successful installation The typical detail drawings include details of recommended tolerances Include these details in all precast substructure projects One of the most important tolerances is the location of the grouted splice couplers Variation in coupler locations will lead to unacceptable misalignments at the coupler locations The following steps are required for achieving required tolerances: • Make the tolerance measurements from a common working point or line in order to specify tolerances of critical elements • Dry fitting the elements is not necessary provided quality assurance/quality control (QA/QC) procedures are followed 432 CHAPTER 9 Prefabrication of the Substructure and Construction Issues • Use mechanical couplers in conjunction with the continuous reinforcement in the connected elements when required All mechanical couplers should conform to AASHTO 5.11.5.2.2 and ACI 318 12.15.3 and meet all agency requirements 9.9.8 Use of grouted splice couplers The grouted reinforcing slice coupler is the only connector allowed between the column and adjacent elements Couplers will develop the minimum specified tensile strength of the attached reinforcing bars Reinforcement will not have lap splices within the column Coupler locations: The preferred configuration is to have the coupler located above the joint The benefit of having the couplers located at the top of a footing is that they are located outside the column hinge zone They still need to develop the tensile strength of the bars Maximum spacing: Detailing should be for spacing that is close to the maximum bar spacing requirements in the AASHTO LRFD bridge design specifications Minimum spacing: The AASHTO requirements for minimum bar spacing are, in part, based on the ability to place concrete properly between the bars Check the clear spacing between the couplers using the following approach: The minimum gap between the couplers should be the greatest of the following: 1 in 1.33 × the maximum aggregate size of the course aggregate The nominal diameter of the connected bars Clear cover: The clear cover for the element is based on the cover over the coupler and the connected reinforcing This requires the connected reinforcing to be placed slightly deeper into the element in order to obtain the required minimum cover over the couplers The dimensional guidelines should be based on a review of the selected manufacturer’s manual that is supplying the precast product Seismic detailing: Grouted splice couplers can be used in plastic hinging zones The standard requirements for column confinement still apply around the couplers The diameter of the spiral and of the ties will need to be increased at the couplers 9.9.9 Column confinement Confinement of column reinforcing is possible with precast concrete elements The AASHTO design specifications not mandate the confinement reinforcing bars to be continuous from the column into the adjacent members footing or cap The confinement reinforcing can be ended in the column and separate confinement reinforcement can be added to the adjacent element Closed loop stirrups: Closed loop stirrups are permitted The commentary in the AASHTO LRFD specifications offers some guidance on the use of individual hoops or ties when compared to spirals 9.10 Precast structure elements guidelines 433 9.9.10 Lifting devices The engineer is responsible for checking the handling stresses in the element for the lifting locations shown on the plans (The criteria of Chapter of the PCI Design Handbook—MNL-120 should be used.) Create design plans that show recommended lifting locations based on the design of the element Other criteria include: • Use two point picks for columns, pier caps, and wall panels, similar to the prestressed beams • Double the number of pick points if element stresses are excessive Add notes to the plan requiring specialized rigging that includes pulleys • Do not show specific lifting hardware on the drawings The contractor may choose alternate lifting locations with approval from the engineer • Use a dynamic load allowance of 15% • The contractor will provide the spacing and location of the lifting devices and submit plan and handling stress calculations to the engineer for approval prior to construction of the panel • The engineer will consult with fabricators for these situations 9.9.11 Handling and storage procedures The contractor is responsible for the handling and storage of all substructure elements in such a manner that does not cause undue stress on the element The contractor will submit a handling and storage plan to the engineer for review, prior to the construction of any element The engineer will inspect all elements and reject any defective elements The rejected elements will be replaced at the contractor’s expense The contractor is responsible for any schedule delays due to rejected elements 9.9.12 Use of vertical adjustment devices The plans may show typical devices and alternate devices that may be used with engineer’s approval Leveling bolts will be preadjusted to approximate required final elevation for the element The designer will detail the type and locations of the devices Significant torque may be required to adjust the leveling bolts for substructure elements Progress meetings: In keeping with the schedule for construction approved by the Highway Agency, regular meetings must be held to iron out any constraints Use of RFI and DCN may also be required 9.10 Precast structure elements guidelines The design and detailing of precast concrete structure elements may be according to the relevant agency and AASHTO LRFD Bridge Design Specifications (FHWA Every Day Counts, Accelerated Bridge Construction May 2012 Initiatives) The designer can detail extended reinforcing with a closure pour to connect the two bent caps if there is a need to connect them 434 CHAPTER 9 Prefabrication of the Substructure and Construction Issues The precast substructure details sheet will normally contain, but is not limited to, the following listed details: Plan view of each substructure unit Elevation view of each substructure unit Typical transverse sections as needed Individual piece plans, elevations, and sections showing the following: a Dimensions b Internal reinforcing details including grouted splice couplers c Lifting points d Approximate shipping weight of the piece Connection details including grouted reinforcing splice couplers Tolerance details for all applicable pieces Bar details Table of estimated quantities Show the following dimensions on the precast substructure detail sheet: Structural dimensions: Draw all views and details in feet and inches to the nearest ⅛ in Reinforcing steel: Show reinforcement dimensions and locations in all views including bar details in feet and inches to the nearest ¼ in All measurements are to the centerline of the reinforcements Cover: Show cover for substructure elements with 3 in clear cover for bottom mats of reinforcement for footings and 2 in clear cover for other substructure elements Angles: Show in degrees, minutes, and seconds to the nearest whole second if such precision is available Width: Keep the narrowest width of the element and any projecting reinforcing below 12 ft This is to keep the shipping costs reasonable Widths over 12 ft will require investigation, and 14 ft is the maximum width Weight: Keep the maximum weight of each element to less than 100,000 pounds in order to keep the size of site cranes reasonable In some cases, the element weight should be limited to the maximum beam weight on the project Weights above 50 tons will require investigation Height: Keep the maximum height of any element including any projecting reinforcing to less than 8 ft so the element can be transported below existing bridges Element heights above 8 ft will require investigation The limits can be increased for design-build projects The designer can work with both the fabricator and contractor to size the elements based on the available equipment and the proposed shipping routes Show pier bents as single-, double-, or triple-column bents The designer can choose to use two independent double-column pier bents if four columns are required in a pier Detail an open joint between the bents 9.11 Important sheet checklist Using a checklist helps in preventing omissions The list items can be revised as required and refined with experience 9.11 Important sheet checklist 435 Plan view Accurate, measurable detail should be used, with exceptions to enhance clarity: Label and locate the control line at each substructure unit Match the terminology on the layout, such as reference line, centerline, or profile grade line Show abutment numbers, bent number, or both Reference control dimensions at all working points These are usually the intersection of the control line and the centerlines of bents and abutments Overall dimensions of each substructure unit Beam lines located and numbered Skew angles Label joint locations and type Design data a Elevation view Accurate, measurable detail should be used, with exceptions to enhance clarity: Elevations necessary to establish the grade of the substructure Elevations of all beam seats to the nearest 1/16 in Joint spacing Joint types Typical transverse sections Accurate, measurable detail should be used, with exceptions to enhance clarity: Piece width dimensions Control line or centerline of bearing (if applicable) Typical section reinforcing Reinforcing cover The designer can detail extended reinforcing with a closure pour to connect the two bent caps if there is a need to connect them a Individual component details Accurate, measurable details should be used, with exceptions to enhance clarity: Overall dimensions Locations and sizes of blockouts and voids Locations of inserts Internal reinforcing details, including locations of grouted splice couplers Lifting points Approximate shipping weight of each piece a Other details Accurate, measurable details should be used, with exceptions to enhance clarity: Connection details including grouted splice couplers Joint details Installation notes 436 CHAPTER 9 Prefabrication of the Substructure and Construction Issues 5 6 7 olerance details for all applicable pieces T Bar details Table of estimated quantities General notes, including (but not limited to) design criteria, loading, class of concrete, epoxy coating or galvanization, and cross-references to various standard sheets Title block, information block, and engineer’s seal a Final checks Comply with (agency’s) detailing standards Check all details and dimensions against substructure to ensure the details are not in conflict Double-check bars in various details against the bars shown in the bar table Check that the name and number of the bridge is same on all detail sheets, including layout Initial the sheet after back-checking corrected details 9.12 Toolkit of innovative designs for rapid bridge renewal The toolkit is intended to provide standards that can be constructed using common equipment Publications and workshops on ABC were highlighted in Chapter Additional resources are listed in this chapter and in Appendix (Bibliography) There are notable publications from FHWA, ACTT (Accelerated Construction Technology Transfer), and AASHTO, as well as useful workshops on the subject and studies from the many states where many prefabricated bridges were successfully completed Some good starting resources include the following: • Introduction to Prefabricated Bridge Elements and Systems,” a video that can be accessed at FHWA website • Substructure: Bent Caps,” a video showcasing work on Texas SH 66/Lake Ray Hubbard Bridge, available at FHWA website • Total Substructure System Piers,” a video showcasing work on piers on Texas SH 249/Louetta Road Overpass and the Texas US 183 Elevated in Austin • FHWA/AASHTO/TxDOT Precast Concrete Bent Cap Demonstration Workshop Other related resources include: • Prefabricated Bridge Elements and Systems, Federal Highway Administration, www.fhwa.dot.gov/bridge/prefab • Prefabricated Bridge Elements and Systems Cost Study: Accelerated Bridge Construction Success Stories, www.fhwa.dot.gov/bridge/prefab/successstories/091104/index.cfm • Development of a Precast Bent Cap System (Matsumoto, E.E., Waggoner, M.C., Sumen, G., Kreger, M.E., Wood, S.L., Breen, J.E Center for Transportation Research, The University of Texas at Austin, Research Report 1748-2; Sponsored by Texas Department of Transportation) • Grouted Connection Tests in Development of Precast Bent Cap System ( Matsumoto, E.E., Kreger, M.E., Waggoner, M.C., Sumen, G., 2002 Transportation Research Board, Transportation Research Record, Issue Number: 1814) • Innovative Prefabrication in Texas Bridges ( Ronnie Medlock, Michael Hyzak, and Lloyd Wolf, Texas Department of Transportation; www.txdot.state.tx.us/brg/Publications/Innovative_1.pdf) 9.13 Environmental issues with ABC 437 • Laying the Groundwork for Fast Bridge Construction ( Mary Lou Ralls and Benjamin M Tang, FHWA Public Roads Magazine, Nov/Dec 2003) • Precast Post-tensioned Abutment System and Precast Superstructure for Rapid On-site Construction (Scanlon, A., Aswad, A., Stellar, J., 2002 Transportation Research Record, Transportation Research Board) • A Precast Substructure Design for Standard Bridge Systems (Sarah Billington, Robert W Barnes and John E Breen, Research report no 1410-2f, Texas Department of Transportation) • Prefabricated Bridge Elements and Systems in Japan and Europe Summary Report (FHWA International Technology Exchange Programs, May 2004) • Precast/Prestressed Concrete Institute (PCI), Chicago, IL, www.pci.org • Canadian Precast/Prestressed Concrete Institute (CPCI), Ottawa, ON, www.cpci.ca 9.13 Environmental issues with ABC 9.13.1 Environmental concerns for ABC near water A large number of environmental concerns must be addressed related to water, including the following: • Avoiding stream encroachment • Maintaining water quality • Providing fish passage • Avoiding wetlands contamination • Determining construction impact on floodplains Using ABC over a much shorter duration with prefabrication will reduce the adverse impacts on environment considerably compared to cast-in-place construction 9.13.2 Issues related to ecology The benefits of ABC in relation to ecology include the following: • The landscape will be easier to maintain during the project • Issues surrounding the preservation of endangered species can be avoided • Impact to natural vegetation can be minimized by controlling construction access points • Re-vegetation of disturbed areas may not be applicable due to the limited exposure and construction duration 9.13.3 Maintaining air and water quality Air and water quality issues will be less of a problem with ABC: • Noise from construction vehicles will be less of an issue • Relocation hazards of underground and bridge-supported utilities remain unchanged • Reactions with acid producing soils will be minimized 438 CHAPTER 9 Prefabrication of the Substructure and Construction Issues 9.13.4 Other benefits • There will be less impact on the historical and cultural aspects and aesthetics • Temporary works and scaffolding will be minimized • Relocation of labor will be minimized, improving the socioeconomic impact • Right-of-way issues during construction will be minimized by avoiding materials storage, the lack of formwork, and avoiding the use of a site office for a long duration • Permitting considerations and implementing EPA/DEP procedures are easier as adverse effects on fauna and flora are not as severe • Requirements for paint removal and containment and disposal of contaminants are not a factor with factory fabrication • The need for sound walls mounted on the bridge or the adjoining roadway can be avoided 9.13.5 Construction permit approvals For bridges located on streams, a flood hazard area general permit is required Engineering data and documentation needs to be submitted for permit approval As per DEP regulations, the following reports still need to be submitted for DEP consideration irrespective of the method or duration of construction: Environmental Assessment (EA): An EA needs to be provided when the significance of the environmental impact is not clearly established Environmental Impact Statement (EIS): An EIS is required when there are impacts on properties protected by the DOT Act or the Historic Preservation Act Significant impacts on noise and air quality are significantly avoided by factory manufacture and by minimizing site construction EIS documents need to be prepared when a replacement or a new bridge has significant impact on natural, ecological, or cultural resources or on flora and fauna, including endangered species such as bog and wood turtles, wetlands, flood plains, and groundwater Categorical Exclusions (CE): An action that does not have a significant effect on the environment falls under CE There will be limited applications such as for installation of signs, etc Examples provided by FHWA are reconstruction or modification of two-lane bridges, which are different from erecting prefabricated bridges Because the erection of a bridge neither damages (nor is likely to damage) an existing wetland nor adversely affects the historical significance of the bridge itself or its surroundings (except as permitted to a limited extent through the environmental regulations), permit approval is generally not a process that delays the project A pre-construction meeting with the state department of environment protection is desirable to further simplify the construction permit approval process 9.14 Conclusions Superstructure construction is more repetitive and modular in approach than for constructing foundations and abutments in the river environment Management in production has for a great deal assisted by prefabrication of floors in tall buildings At times, substructure fabrication cannot keep pace with the modern methods used in say the car manufacturing or the assembling factories in Detroit But greater 9.14 Conclusions 439 experience will show the ways and means to reduce current delays a little earlier completion Although the structural types of bridges vary, a comprehensive construction methodology and code of practice for typical bridges is required The innovative techniques being used by many agencies and reported in the tables above and in earlier chapters can be utilized for the future The progress for using prefabrication has been slower for substructure compared to that for the superstructure, especially for longer span bridges It is easier to transport horizontal bridge beams and slab panels on an SPMT than the vertical pier bents due to their sizes Also, post-tensioning is required for the panels to make them watertight The general requirements of prefabrication for the superstructure horizontal members also apply to the substructure vertical components However, for emergency bridge replacements on important routes after floods, earthquakes, or accidents, etc., prefabrication of both pier and abutment members would help In the United States, SPMTs and heavy-duty lifting cranes are being assembled and all states have adequate access to these facilities, which are extremely important for ABC The construction season in some states facing extreme weather is only a few months During the offseason, the substructure components can be manufactured and transported to the sites and erected at the start of the next construction season Even within the design-bid-build system, partial ABC is being adopted, at least for precast prestressed beams, composite steel girders, and the use of lightweight concrete Hence, there is a great potential in the future for entire bridges being manufactured away from sites Some of the major operations that need to be considered when using ABC include the following: • Soil report: Because foundation design requires soil investigation, this operation should be started well in advance by the owner, even before the award of the contract • Utility pipes: Advance coordination with the utility companies for supporting their pipes and transferring from pavement elevation to deck elevation is required • Deck drainage: The method of disposal of rainwater from the deck into public sewers also needs to be planned • Electrification: If deck lighting is provided, the power supply needs to be arranged from the electric supply company and negotiations need to be started in advance, as the prefabrication activity is in progress • Precasting concrete and welding: Although prefabrication in a factory may not take as much time as cast-in-place construction under the site conditions, the time required for the plan layout of rebars, the curing of concrete components, and the welding of steel members, etc remains unchanged • Planning: The additional time required for planning a route, obtaining permits for heavy and wide loads, applications for police escort, and the hauling distance for the prefabricated bridge from the factory to the site need to be taken into consideration • Hauling heavy loads: Loading prefabricated components on the SPMTs and unloading them on-site as well as the required lifting and placing operations by the special cranes on-site need to be taken into account in the overall schedule • Stay-in-place formwork: Compared to the cast-in-place construction erection time for temporary formwork or using the permanent stay-in-place formwork, the additional time and cost for hauling, lifting, and placing needs to be compared to make prefabrication as economical as possible • Modular construction: The greatest benefit of prefabrication is for small spans, where the hauling and lifting problems are less and pier construction is avoided Arch structures combine the superstructure girders with the substructure curved columns and are more aesthetically pleasing 440 CHAPTER 9 Prefabrication of the Substructure and Construction Issues • Leading prefabrication companies: There are a wide variety of bridge manufacturing companies in the United States who are successfully conducting their businesses and have developed specialized bridges for repeated use Examples are High Steel Structures, Acrow, Jersey Precast, and CON/SPAN • Need for standardization: AASHTO specifications have recommended minimum vertical and horizontal clearance requirements Similarly, many states have developed standard details for lane widths, shoulder widths, and bicycle tracks, spaces for plants and flowers, etc Span length alternatives to conform to the width of the highway can be used to standardize bridge lengths Such ready-made standard span structures using concrete and steel can be made available off the shelf and ready for delivery to the sites, as required A choice of colors is also available for aesthetic requirements Because the construction contractor normally manages these design-build teams and has cost-saving objectives, incentives and bonuses become paramount in minimizing the man-hours of the personnel spent in the field and design office The construction contractor is now more heavily involved in the selection of structural steel connections and concrete forming details because these are both relatively higher-cost parts of the structure (Reference Concrete International, March 2013, page 50) 9.14.1 Quality control Construction drawings for precast substructures are more specialized than conventional construction drawings Typical review comments on reinforced concrete detailing of abutment walls, pier caps, and columns are therefore necessary Examples are review by expert bridge engineers of the connection details, location of hinges, seismic detailing, lifting points, etc The following review comments (selected from sets of bridge drawings) should be avoided when submitting construction drawings: • Design is incomplete and not clear enough • Details are too complicated for constructability • Follow state standard details • Spend time on preliminary investigation of alternative structural systems • Identify appropriate structural framing systems for gravity and lateral loads • Add a note to structural notes sheet, stating deflection of the precast member should be monitored to avoid overload conditions prior to composite action being achieved • Product limitations in specifications and additional items in specifications that is not necessary • Not enough information on the drawings for the cross-sections for construction • Rebar placing issues and detailing that produces a lot of rebar waste • Excessive steel at a joint can lead to poor consolidation of the concrete To reduce congestion at these member connections, avoid placement of rebar splices within the joint, but rather splice the bars to one side or both sides of the column • Varying the beam widths along a continuous line of beams Congestion at beam/column or beam/ beam intersections • Check deck slopes for drainage • Tolerances and finishes not meeting specifications 9.14 Conclusions 441 • Check shear reinforcement • Drawings should be signed by a registered structural engineer of the state where the bridge is located Concrete pour joint details • Alkali silica reaction (ASR) due to local aggregate properties • Deicing salts that spall the concrete surface • Insufficient precast concrete cover that leads to corrosion of the rebars, especially at underside of deck slab • Allow concrete cover to prevent corrosion of rebars • Quality of backfill material behind abutments and wingwall should follow specifications • Proper inspection required during construction Review of foundation drawings: • Foundation design is too expensive; footings are too big/deep Review soil report • Monitor compaction before placing footings Consider soil improvement techniques • Always get soil borings and a geotechnical report before foundation design and have geotechnical oversight and testing during construction • Use deep piles or drilled piers • Use caissons or auger piles • Use tied spread footings • Check for retaining wall failures from settlement and overturning Note: Appendices 1–11 are provided at the end of the book for ready reference ... ABC 9. 8.2 Design-bid-build The traditional design-bid-build (D-B-B) process separates design and construction The oldest and most well-known contracting method for construction projects, D-B-B... 199 3—Establishment of the Design-Build Institute of America 199 6—Passage of Federal Acquisition Reform Act of 199 6 The design-build team leader is the single source of responsibility for the owner and is... 422 CHAPTER 9 Prefabrication of the Substructure and Construction Issues Other prefabricated substructures in Texas includeLake Ray Hubbard Bridge (2002) and Lake Belton Bridge (2004) Utah bridges