Innovative Bridge Designs for Rapid Renewal (2014)

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165 Conclusions and Suggested Research Overview of ABC Toolkit The ABC Toolkit developed for prefabricated elements and modular systems in the SHRP 2 R04 project consists of the following: • ABC Design standards; • Detailed design examples; • Recommended LRFD design specifications; and • Recommended LRFD construction specifications. The research team developed pre-engineered standards optimized for modular construction and accelerated bridge construction (ABC). Standardizing ABC systems will bring about greater familiarity with ABC technologies and concepts and will also foster more widespread use of ABC. Standard plans have been developed for the most-useful technologies that can be deployed on a large scale in bridge replacement applications. They include complete prefabricated modular systems, as outlined here: • Precast modular abutment systems 44 Integral abutments; 44 Semi-integral abutments; and 44 Precast approach slabs. • Precast complete pier systems 44 Conventional pier bents; and 44 Straddle pier bents. • Modular superstructure systems 44 Concrete deck bulb tees; 44 Concrete deck double tees; and 44 Decked steel stringer system. • ABC bridge erection systems 44 Above-deck driven carriers; and 44 Launched temporary truss bridges. The development of detailed design examples for use by future designers provides step-by-step guidance for the over- all structural design of the prefabricated bridge elements and systems. The design examples pertain to the same standard bridge configurations for steel and concrete used in the ABC Design standards. The intent was to create design examples that could be used in conjunction with the ABC Design stan- dards so that the practitioner will get a comprehensive look at how ABC Designs are performed and translated into design drawings and details. The LRFD design specifications do not explicitly deal with the unique aspects of large-scale prefabrication, including issues such as element interconnection, system strength, and behavior of rapid deployment systems during construction. The work in this project entailed identifying any shortcomings in the current LRFD Bridge Design Specifications that may limit their use for ABC Designs and making recommendations to address these limitations. Recommended LRFD design spec- ifications for ABC bridge design are included in this chapter. Recommended LRFD construction specifications for prefab- ricated elements and modular systems were compiled by the research team with the intent that they would be used in con- junction with the standard plans for steel and concrete modular systems. As such, these specifications for rapid replacement focus heavily on the means and methods required for rapid construction using prefabricated modular systems. A review of various innovative construction contracting and delivery meth- ods that may be used to enhance the implementation and deliv- ery of ABC construction projects is also included. Design Considerations for ABC Standards for Modular Systems Specific design considerations for standardized ABC modular systems developed in Phase III include the following: • Standardized designs for superstructure systems that cover span ranges from 40 ft to 130 ft and that can be transported and erected in one piece. C h A p t e r 4

166 • Substructure modules that have dimensions and weights suitable for highway transportation and erection using conventional equipment. • Designs and specifications that allow the contractor to self- perform the precasting of non-prestressed components. • Prefabricated modules designed to be quickly assembled in the field with full moment connections. • Designs for routine bridges that can be used for most sites with minimal bridge-specific adjustments. • Modules that can be used in simple spans and in continuous spans (simple for dead load and continuous for live load). Details to eliminate deck joints at piers and abutments. • Use of high-performance materials: HPC/UHPC concrete, HPS, or A588 weathering steel. • Modular systems with integral wearing surface so that an overlay is not required. Use of overlay is considered optional as part of a long-term preservation strategy. Use of an inte- gral wearing surface in lieu of an overlay is recommended to expedite construction. Typically an extra 1½-in. monolithic concrete slab thickness above the top layer of rebars serves as an integral wearing surface. This approach has been increas- ingly common in segmental bridge design. At the end of construction, milling ½ in. ensures an excellent final riding surface. The design permits replacement with an overlay in the future, along with removal of the integral wearing surface. • Prefabricated components can be the most cost-effective solution for any alignment. However, straight alignments without skew allow multiple identical components, which tend to be the most economical. Preference should be given, if possible, to straightening the roadway alignment along the bridge length and eliminating skew for lower initial and life-cycle costs. • Lightweight high-performance concrete (LWHPC) can be an option for precast systems to achieve reduced weights that could be beneficial for shipping and erection. These design considerations and concepts are discussed further in the following sections. Modular Substructure Systems Substructure construction takes up a significant portion of the total on-site construction time. Reducing the time it takes to complete substructure work is critical for all rapid renewal projects. With this goal in mind, ABC standards are provided for abutments, wingwalls, and piers that are commonly used in routine bridge replacements. These standards include the following: • Precast modular abutment systems 44 Integral abutments; and 44 Semi-Integral abutments. • Precast complete pier systems 44 Conventional pier bents; and 44 Straddle pier bents. Integral and Semi-Integral Bridges for Rapid Renewal One of the most important aspects of design, which can affect the speed of erection, structure life, and lifetime maintenance costs, is the reduction or elimination of roadway expansion joints and associated expansion bearings. Besides providing a more maintenance-free durable structure, continuity and elimination of joints can lead the way to more-innovative and aesthetically pleasing solutions to bridge design. Providing a joint- and maintenance-free bridge should be an important goal of rapid renewals. The use of integral or semi-integral abutments allows the joints to be moved beyond the bridge. Integral abutment bridges have proven themselves to be less expensive to construct, easier to maintain, and more economi- cal to own over their life span. Integral and semi-integral abut- ments have become the preferred type for most departments of transportation (DOTs). When deck joints are not provided, the thermal movements induced in bridge superstructures by temperature changes, creep, and shrinkage must be accommodated by other means. Typically, provisions are made for movement at the ends of the bridge by one of two methods: integral or semi-integral abut- ments, along with a joint in the pavement or at the end of a reinforced concrete approach slab. The terms “integral bridges” and “integral abutment bridges (IAB)” are generally used to refer to continuous jointless bridges with single and multiple spans and capped-pile stub-type abutments. The most- desirable end conditions for an integral abutment are the stub or propped-pile cap type, which provide the greatest flexibility and hence, offer the least resistance to cyclic thermal move- ments. Piles driven vertically and in only one row are highly recommended. In this manner, the greatest amount of flexibil- ity is achieved to accommodate cyclic thermal movements. A semi-integral abutment bridge (SIAB) is a variant of the integral abutment design. It is defined as a structure in which only the backwall portion of the substructure is directly con- nected with the superstructure. The beams rest on bearings that rest on a stationary abutment stem. The superstructure and backwall move together into and away from the backfill during thermal expansion and contraction. There are no expansion joints within the bridge. Reasons for Jointless Construction for ABC ABC seeks to reduce on-site construction time and to miti- gate long traffic delays through innovative design and con- struction practices. Integral bridges and semi-integral bridges

167 incorporate many innovative features that are well suited to rapid construction. Only one row of vertical piles is used, which means fewer piles. The backwall can be cast simultane- ously with the superstructure. The normal delays and the costs associated with bearings and joints installation, adjust- ment, and anchorages are eliminated. Some of the advantages to jointless construction for ABC projects are summarized as follows: • Tolerance problems are reduced. The close tolerances required when using expansion bearings and joints are eliminated with the use of integral abutments. Bridge seats need not conform exactly to girder flange slope and cam- ber corrections, since the girder loads are ultimately car- ried by the concrete comprising the end diaphragm. Minor mislocation of the abutments creates no fit-up problems. • Rapid construction. With integral abutments, only one row of vertical (not battered) piles is used and fewer piles are needed. The entire end diaphragm/backwall can be cast simultaneously and with less forming. Fewer parts are required. Scheduling problems with suppliers and manu- facturers are avoided. Integral abutment bridges are more quickly erected than jointed bridges, thereby decreasing construction costs. The construction time for IABs is commonly shorter because connections are simple to form and expansion joints are not required. In addition, it is common for IABs to use only one row of vertical piles, meaning a smaller number of piles are typically used than for many jointed bridges, and cofferdams are not required for constructing the intermediate piers. Installing fewer piles and not constructing cofferdams results in decreased construction time and lower bridge construc- tion cost. • Reduced removal of existing elements. Integral abutment bridges can be built around the existing foundations without requiring the complete removal of existing sub- structures. Reduced removal of existing substructures will greatly reduce the overall construction durations of bridge replacements. • No cofferdams. Integral abutments are generally built with capped pile piers or drilled shaft piers that do not require cofferdams. • Improved ride quality. Smooth jointless construction improves vehicular riding quality and diminishes vehicu- lar impact stress levels. It provides for lower-impact loads and reduced snowplow damage to decks. • Added redundancy and capacity for catastrophic events. Integral abutments provide added redundancy and capacity for all types of catastrophic events. In designing for seismic events, considerable material reductions can be achieved through the use of integral abutments by negating the need for enlarged seat widths and restrainers. Further, the use of integral abutments eliminates loss of girder support, the most common cause of damage to bridges in seismic events. Joints introduce a potential collapse mechanism into the overall bridge structure. Integral abutments have consis- tently performed well in actual seismic events and have significantly reduced or avoided problems of backwall and bearing damage that are associated with seat-type jointed abutments. Precast Abutments and Wingwalls Precast modular abutments are composed of separate compo- nents fabricated off site, shipped, and then assembled in the field into a complete bridge abutment. Precast modular abut- ments have been constructed in several states. Integral connec- tion of the superstructure to the substructure will be preferred for ABC construction. Since not all states employ the use of integral abutments, standards have been created for both inte- gral and non-integral abutments. The individual precast com- ponents should be designed to be shipped over roadways and erected using typical construction equipment. To this point, the precast components are made as light as practicable. Voids can be used in the wall section, which will reduce shipping weights and allow for larger elements to be used. Voids are also used to attach drilled shafts or piles to the cap for stub-type abutments. Once the components are erected into place, the voids and shear keys are filled with self-consolidating concrete. Wingwalls are also precast with a formed pocket to slide over wingwall piles or drilled shaft reinforcing. Once in place over the wingwall piles or drilled shaft, the wingwall pocket is filled with high early strength concrete or self-consolidating concrete. Connections Full moment connections between modular substructure components are used to emulate cast-in-place construction. The closure pours are constructed using self-consolidating concrete that can be completed quickly and result in the highest-quality durable connection. Self-consolidating con- crete, also known as self-compacting concrete or SCC, is a highly flowable, nonsegregating concrete that spreads into place, fills formwork, and encapsulates even the most con- gested reinforcement, all without any mechanical vibration. SCC is also an ideal material to fill pile pockets in substructure components. It is defined as a concrete mix that can be placed purely by means of its own weight, with little or no vibration. SCC allows easier pumping, flows into complex shapes, tran- sitions through inaccessible spots, and minimizes voids around embedded items to produce a high degree of homoge- neity and uniformity. As a high-performance concrete, SCC delivers these benefits while maintaining all of concrete’s cus- tomary mechanical and durability characteristics.

168 Precast Complete Piers Precast complete piers are also composed of separate compo- nents fabricated off site, shipped, and assembled in the field into a complete bridge pier. Piers with single-column and multiple-column configurations are common. Foundations can be drilled shafts, which can be extended to form the pier columns. Driven piles may be used with precast pile caps, or precast spread footings may suffice where soil conditions per- mit. Pier columns are attached to the foundation by grouted splice sleeve connectors. Precast columns can be square or octagonal, the tops of which are connected by grouted splice sleeves to the precast cap. Pier bents can have a single column or multiple columns. The precast cap is typically rectangular in shape. Some states, specifically those in high seismic regions, employ the use of integral pier caps. However, the standards in this project were developed only for non-integral piers, which are the most common and most suited for rapid construction. In many cases, the integral pier cap connections are constructed with cast-in-place concrete; however, the connection can also be made with precast concrete. This connection is often quite complicated and congested. There are also tight controls over tolerances and grades. For these reasons, the most common form of connection is a cast-in-place concrete closure pour. In a non-integral pier cap, the superstructure and deck will be continuous and jointless over the piers. Also, non-integral piers would be easier to reuse. Like the precast modular abutment, the components of the precast complete pier have been designed to be shipped over roadways and erected using typical construction equipment. To this point, the precast components are made as light as practical. Precast spread footings can be partial precast or complete precast components. A grout-filled void beneath the footing is used to transfer the load to the soil, avoiding unexpected localized point loads. Column heights and cap lengths will be limited by transportation regulations and erection equipment. Alternatively, the cap length limitation can be avoided by utilizing multiple short caps combined to function as a single pier cap. Precast bearing seats can also be used. Modular Superstructure Systems Modular superstructure systems composed of both steel and concrete girders have been included in the pre-engineered stan- dards. In the Task 6 evaluations, deck bulb tees and decked steel stringer systems received the highest scores, as these are proven systems for rapid renewal. Each modular system is expected to see a 75- to 100-year service life due to the quality of its pre- fabricated superstructure, the use of high-performance con- crete, and the attention given to connection details. Standards for modular superstructures will include the following con- crete and steel systems: • Decked steel stringer system; • Concrete deck bulb tees; and • Deck double tees. Precast Concrete Deck Bulb Tee and Double Tee Conventional precast concrete girders have been well estab- lished for bridge construction in the United States for more than 50 years. There is wide acceptance for their use among owners and contractors because they are easy and economical to build and to maintain. In most cases, the girders are used with a cast-in-place (CIP) deck built on site. For ABC applica- tions the key difference lies in that the girders have an integral deck, thus eliminating the need for a CIP deck. The use of decked precast girders has become increasingly popular in sev- eral states, though they are not available in every state. Addi- tionally, an integral wearing surface, typically 1½ in. to 2 in., can be built monolithically with the deck slab. In the future, the wearing surface concrete can be removed and replaced while preserving the structural deck slab. The precast deck bulb tee girders and double tee girders combine all the posi- tive attributes of conventional precast girder construction with the advantage of eliminating the time-consuming step of CIP deck construction. Contractors familiar with conventional pre- cast girder construction should have no difficulty in adapting to these newer deck girders installed by using an ABC approach. Deck bulb tee and double tee girders are proven systems that have been standardized for use by several Western states, including Utah, Washington, and Idaho. The northeast extreme tee (NEXT) beam, a variation of the double tee, was developed by the PCI Northeast to serve the ABC market. The research team expects the deck girder bids to be very competitive when compared with the girder and CIP deck systems and that they may come in even lower for sites in which constraints to deck casting operations may exist. Cast-in-place closure pours are typically used to connect girders in the field. The girder flanges can be made to different widths to fit site and trans- portation requirements. Decked Steel Stringer System Similar to the concrete deck girder system, the decked steel stringer system is also a proven concept shown to be quite eco- nomical and rapidly constructed. Prefabricated decked steel stringer systems have been a very popular option for acceler- ated construction of bridges in the United States. Their light weight, easy constructability, low cost, and easy availability were seen as advantages over other systems. The length and

169 weight of each module can be designed to suit transportation of components and erection methods. Erection can generally be accomplished with conventional equipment. Cast-in-place closure pours are typically used to connect adjacent units in the field. The modules can be made to different widths to fit site and transportation requirements. Many states are familiar with the Inverset system or a varia- tion of it. The patent for the Inverset system has expired. Stan- dardizing generic designs for commonly encountered spans will provide a big boost to gaining quick acceptance and more widespread use for modular concepts. As for the precast deck girders, the recommended connection will be the full moment connection for the same reasons previously discussed. An integral wearing surface, typically 1½ in. to 2 in., can be built monolithically with the deck slab. In the future, the wearing surface concrete can be removed and replaced, while preserving the structural deck slab. Connections Between Modules The ease and speed of construction of a prefabricated bridge system in the field is paramount to its acceptance as a viable system for rapid renewal. In this regard, the speed with which the connections between modules can be completed has a significant influence on the overall ABC construction period. Additionally, connections between the modular seg- ments can affect the live-load distribution characteristics, seismic performance of the superstructure system, and the superstructure redundancy. Designers need to develop a structure type and prefabrication approach that can be exe- cuted within the time constraints of the project site and also achieve the desired structural performance. Connections play a critical role in this approach. Connections of the mod- ular units are important elements for ABC, as they determine how easily the elements can be assembled and connected together to form the bridge system. Often the time to develop a structural connection is a function of cure times for the closure pour. The number of joints and the type of joint detail are crucial to both the speed of construction and to the overall durability and long-term maintenance of the final structure. The use of cast-in-place concrete closure joints should be kept to a mini- mum for accelerated construction methods due to place- ment, finishing, and curing time. Durability of the joint should be achieved through proper design, detailing, joint material selection, and construction procedures. Posttensioned joints use induced compression to close shrinkage cracks at the joint interface, prevent cracking under live load, and enhance load transfer. The posttensioned joints can be a female-female shear key arrangement infilled with grout or match-cast with epoxied joints if precise tolerances can be maintained. While providing some assurance of good long-term performance, posttensioning requires an additional step and complexity during on-site construction. Its use may not be entirely compatible with ABC goals of rapid field assem- bly and long-term durability of joints. Design Considerations for Connections Design considerations for connections between deck segments include the following: • Full moment connections that are practical to build quickly. • Achieving durability at least equal to that of a precast deck. • Joint details suitable for heavy, moderate, and light truck- traffic sites. • Achieving acceptable ride quality (similar to CIP decks). • Not requiring the use of overlays for durability. An integral wearing surface consisting of an extra thickness of mono- lithic concrete slab may be provided. • Posttensioned connections can be an alternative for ABC construction. • Details can accommodate slight differential camber between adjacent modules. • Rapid strength gain, so that the bridge can be opened to traffic in a matter of hours or days. Full Moment Connections for Modular Superstructure Systems Investigations of joint types and material options performed in the previous tasks have identified full moment connec- tion using ultra-high-performance concrete (UHPC) joints as the preferred connection type for modular superstructure systems to satisfy the criteria for constructability, structural behavior, and durability as noted above. UHPC refers to a class of advanced cementitious materials that displays signifi- cantly enhanced material properties considered very benefi- cial to ABC. When implemented in precast construction, these concretes exhibit properties including compressive strength above 21.7 ksi, sustained tensile strength through internal fiber reinforcement, and exceptional durability when compared with conventional concretes. Conventional materials and construction practices for connection details can result in reduced long-term connection performance as compared with the joined components. UHPC presents new opportuni- ties for the design of modular component connections due to its exceptional durability, bonding performance, and strength. The properties of UHPC make it possible to create small- width, full-depth closure pour connections between modu- lar components. These connections may be significantly reduced in size when compared with conventional concrete

170 construction practice, and could include greatly simplified reinforcement designs. A lab testing program was carried out to further evaluate the performance of UHPC in ABC appli- cations in Task 10C of this project. The UHPC joint detail used had a 6-in. joint width with #5 U bars. UHPC has a strength gain of 10 ksi in 48 hours, which is when deck grinding can begin. It is suitable for Tier 2 projects that use modular systems. (The research team has been informed that new UHPC mixes are available for bridges that would require only overnight closures.) The narrow joint width reduces shrinkage and the quantity of UHPC required, while providing a full moment transfer connection. Tests done at FHWA showed that a 6-in. joint width would be adequate to fully develop #5 bars even when straight bars are used. The New York State DOT has built a few bridges with this detail by using straight bars. The use of straight bars is planned for the second ABC demonstration project under R04. One of the challenges with using U bars is that to satisfy the minimum bend diameter, a deck thickness greater than 6 in. is required. This is not a problem for the decked steel girder bridges, but it requires a thickening of the flanges for deck bulb tee (DBT) girders from 6 in. to 9 in. The use of straight bars in the joints would be preferable for DBT bridges to mini- mize the flange thickness and shipping weights. Headed rebars were not considered because tests under NCHRP Project 10-71 have shown that the size of the heads causes construc- tability issues, making the rebars not well suited for ABC. Self-Performance of Prefabrication by the Contractor This project takes the approach that for ABC to be successful and for costs to come down, ABC designs should allow maxi- mum opportunities for the general contractors to do their own precasting at a staging area adjacent to the project site or in their yards with their own crews. This is particularly true for substructure components that have traditionally been constructed by contractor crews. Substructure components are made of conventional reinforced concrete and can be pre- cast by the general contractor. Components are designed to allow the contractor to self-perform the precasting by paying special consideration to • Components that use non-prestressed reinforcing; • Components that are simple enough to fabricate; • Components that can be assembled quickly in the field; • Components that allow reasonable tolerance for erection; • Maximum repetition of components to reduce formwork cost; and • Components that are suitable for highway shipping and erection with conventional equipment. ABC Standard plans and Details Bridge designs for workhorse bridges can be standardized to allow for repetition and prefabrication. The goal would not be to design each bridge individually, but to use repetitive design standards and adapt the conditions (alignment, span length, width) to the standard. The use of modular systems with standard designs is a proven method of accelerating bridge construction. It should also be noted that with regard to the design of new structures that facilitate rapid recon- struction, it is unrealistic to think that one or a few technolo- gies will become dominant in the future. There will need to be an array of solutions for different site constraints, soil con- ditions, bridge characteristics, traffic volumes, and so forth. Contractors have also developed various proprietary systems and concepts to accelerate bridge construction, and ABC Designs should be open to such innovations as well. In Phase III of this project, ABC details for superstructure and substructure systems that are suitable for a range of spans were developed. The details presented in the plans included with this report are intended to serve as general guidance to practitioners in the development of site-specific designs suit- able for accelerated bridge construction. Bridge designers are well versed with sizing beams and designing reinforcing steel for conventional construction for a specific site, and it would be appropriate for the engineer of record to perform these functions for ABC projects as well. A single set of ABC Designs for national use would not be practical since there are state- specific modifications to LRFD bridge design criteria, including permit load design requirements for Strength II. Individual states may want to modify the details presented to fit their local needs and market conditions. The designer, guided by the standard plans and details and the accompanying set of ABC Design examples will be able to easily complete an ABC Design for a routine bridge replace- ment project. These standard plans will need to be customized to fit the specific site in terms of the bridge geometry, member sizes, and reinforcement details. The overall configurations of the modules, their assembly, and connection details, tolerances, and finishing will remain unchanged from site to site. Repeated use of the same system will allow the continuous refinement of the concept, thereby reducing risks and lowering costs. The research team anticipates that the standard plans would be about 60% to 70% complete in their overall coverage, while providing substantially complete details of the ABC aspects of the project. Much of the remaining work is not as much ABC related as it is customization for the specific bridge site. The standard plans used in conjunction with the ABC Design examples will provide training wheels for designers until they get comfortable with ABC. The following sections provide more information on these ABC standards.

171 Overview of ABC Design Standards Typical designs for superstructure and substructure modules have been grouped into the following span ranges: • 40 ft ≤ span ≤ 70 ft; • 70 ft ≤ span ≤ 100 ft; and • 100 ft ≤ span ≤ 130 ft. The superstructure cross section and module widths are shown for a typical two-lane bridge with shoulders having an out-to-out width of 47 ft, 2 in., as shown in Figure 4.1. While the bridge cross section was chosen to represent a routine bridge structure (as was the demonstration bridge), the design concepts, details, fabrication, and assembly are equally appli- cable to other bridge widths. Posttensioned Spliced Girders for Spans over 130 Feet Standardized designs for superstructure systems cover spans to 130 ft as, at many sites, these are spans that can be transported and erected in one piece. In the span range up to 130 ft, the precast designs use pretensioning without the need for on-site posttensioning. Posttensioning can be used to extend the span length of a precast girder to 200 ft and beyond. Posttensioned splice girders can be used to simplify girder shipping because the girder can be fabri- cated in two or three pieces and can be spliced together in the field. Many details included on the standards can be used for longer-span bridges with additional detailing. The girders are spliced with reinforced concrete closure pours at the site (off-line) and then erected. The posttensioning strand crosses these closure pours and provides the moment capacity at the splice. One useful reference for post- tensioned spliced girder design would be the Precast Bulb Tee Girder Manual published by the Utah DOT (UtahDOT, 2010b). General Information Sheets The sheets containing general information and instructions on the use of ABC standard plans have been included at the beginning of the set to guide users. The general information sheets contain specific instructions to designers so that all the key design and construction issues in ABC projects are ade- quately addressed during the final design and customization processes. The general information sheets introduce the intent and scope of the standard plans. They note that the intent of the design standards is to provide information that applies to the design, detailing, fabrication, handling, and assembly of prefabricated components used in accelerated bridge con- struction and designed in accordance with the AASHTO LRFD bridge design specifications. The details presented in the plans are intended to serve as general guidance in the development of designs suitable for ABC. The details shall not be perceived as standards that are ready to be inserted into contract plans. Their implementa- tion shall warrant a complete design by the engineer of record (EOR) in accordance with requirements for the project site and DOT standards and specifications. The standards were devel- oped to comply with AASHTO LRFD Bridge Design Specifica- tions, 5th ed. The designer shall verify that all requirements included in the latest edition of the AASHTO LRFD Bridge Design Specifications, including interim provisions, are satis- fied and properly detailed in any documents intended or pro- vided for construction. All formwork for the deck shall be supported from the longitudinal girders similar to conven- tional construction methods. Shored construction shall not be assumed. The systems presented in the superstructure design stan- dards consist of prestressed concrete girders with integrally cast decks and a composite decked steel stringer module. Both systems include a full-depth deck as the flange that serves as the riding surface to eliminate the need for a cast-in-place deck. The prefabricated superstructure modules presented in the plans may be used with the prefabricated substructure sys- tems that are a part of these design standards, or they may be used with other new or existing substructures that have been adapted to conform to the bearing requirements for these superstructure modules. Substructures are the portions of the bridge located between the superstructure and the foundation (supporting soil, piles, or drilled shafts). Geotechnical design, pile design, and detail- ing are not considered substructures and are not covered in these design standards. Foundation design is driven by site soil conditions. The substructure details depicted can be adapted to fit other foundation types. The prefabricated substructure systems presented in the plans for precast abutments, wing- walls, and piers are intended to be used with the prefabricated superstructure systems that are part of the design standards, but may be adapted to other superstructures as well. The rein- forcing details and connection details shown are suitable for use in non-seismic or low-seismic areas. The general information sheets also provide guidance on key considerations specific to ABC design and construction of prefabricated modular systems, including • Lifting and handling stresses; • Shop drawings and assembly plan; • Fabrication tolerances; • Site casting requirements; • Geometry control;

172 Figure 4.1. Channel Bridge, Carpenter Road, New York State.

173 • Mechanical grouted splices; • Element sizes; and • General procedure for installation of modules. Organization of ABC Design Standards The systems presented in these ABC Design standards consist of the following items, which are listed in Tables 4.1 and 4.2: • Sheets A1 through A12 44 Semi-integral abutments. 44 Integral abutments. 44 Wingwalls. 44 Pile foundations and spread footings. • Sheets P1 through P9 44 Precast conventional pier. 44 Precast straddle bent. 44 Drilled shaft and spread footing option. • Sheets S1 through S8 44 Decked steel girder interior module. 44 Decked steel girder exterior module. 44 Bearing and connection details. • Sheets C1 through C11 44 Prestressed deck bulb tee interior module. 44 Prestressed deck bulb tee exterior module. 44 Prestressed double tee module. 44 Bearing and connection details. Standard Conceptual Details for ABC Construction technologies The modular systems discussed in the previous sections may be erected with conventional construction techniques when site conditions permit. Given the proper project criteria, Table 4.1. Substructure ABC Standards Sheets (Abutments and Piers) Abutment Sheet No. Description A1 General Notes and Index of Drawings A2 Semi-Integral Abutment Plan and Elevation A3 Abutment Reinforcement Details A4 Wingwall Reinforcement Details 1 A5 Wingwall Reinforcement Details 2 A6 Semi-Integral Abutment Section A7 Integral Plan and Elevation A8 Integral Abutment Section A9 Approach Slab 1 A10 Approach Slab 2 A11 Semi-Integral Abutment Spread Footing Option Plan and Elevation A12 Spread Footing Option Selection Pier Sheet No. Description P1 General Notes P2 Precast Pier Elevation and Details (Conventional Pier) P3 Precast Pier Cap Details (Conventional Pier) P4 Precast Column Details (Conventional Pier) P5 Precast Pier Elevation and Details (Straddle Bent) P6 Precast Pier Cap Details (Straddle Bent) P7 Precast Column Details (Straddle Bent) P8 Foundation Details (Drilled Shaft) P9 Foundation Details (Precast Footing) Table 4.2. Superstructure ABC Standards Sheets (Steel and Concrete Girders) Steel Girder Superstructure Sheet No. Description S1 General Notes and Index of Drawings S2 Typical Section Details S3 Interior Module S4 Interior Module Reinforcement S5 Exterior Module S6 Exterior Module Reinforcement S7 Bearing Details S8 Miscellaneous Details Concrete Girder Superstructure Sheet No. Description C1 General Notes and Index of Drawings C2 Typical Section C3 Girder Details 1 C4 Girder Details 2 C5 Bearing Details C6 Abutment Details C7 Pier Continuity Details C8 Camber and Placement Notes C9 Miscellaneous Details C10 Alternate Typical Section C11 Alternate Girder Details

174 use of conventional equipment would be the first choice for constructing a bridge designed with ABC modularized com- ponents. Unlike conventional stick-built bridges, the appro- priate construction technology for rapid renewal projects built with ABC modular systems should be selected after careful consideration of project and site constraints and the choice of technologies available. Advances in ABC Construction Tech- nologies have introduced innovative techniques for erecting highway structures using adaptations of proven long-span technologies. These ABC Construction Technologies can be grouped for use into the following two categories: • Bridge movement systems. Technologies in which the erec- tion equipment is designed specifically to lift and trans- port large complete or partial segments of preassembled structures. • Bridge erection systems. Technologies in which the erection equipment is designed to deliver individual components of a proposed structure in a span-by-span process. Self-propelled modular transporters (SPMTs), lateral sliding, and launching would be good examples of bridge movement systems. If the best option for a site is to preas- semble the structure completely and then move it to its final position, there are several excellent published refer- ences on bridge movement technologies, such as the Utah DOT SPMT manual and the FHWA SPMT manual, that can guide designers and owners. Movement of preassem- bled complete structures is a well-developed technology in the United States; several specialty firms provide this ser- vice nationally. Phase IV of this project is designing a bridge replacement by using a lateral slide and will develop design standards for such systems. Bridge erection system technologies are intended to be easily transportable, lightweight, modular systems. The use of this type of equipment to deliver fully preassembled structures is not practical, although it is possible on a very small scale. Because the ABC Design standards developed in Phase III are for modular superstructure and substructure systems, the conceptual details for ABC Construction Technologies will focus on bridge erection systems specifically intended to deliver and assemble modular systems. Rapid bridge renewal projects that use modular systems can be categorized into one of the following project types: • ABC Bridge Designs built with conventional construction; or • ABC Bridge Designs built with ABC Construction Technologies. The designer should ascertain whether the bridge renewal project warrants further consideration of specialized ABC Construction Technologies or whether the site and project limits are more suited for conventional equipment and technologies. The use of ABC Construction Technology compels owners and consultants to consider the following variables: • Bridge project type; • Site and traffic constraints; • Available space for construction staging areas (if any exists, where located and what are conditions); • Environment surrounding the project site; and • Project construction time period. The development of ABC Construction Technologies could evolve around the demonstration of which technolo- gies work best with the ABC Designs (both substructure and superstructure) developed in this project. A matrix of questions, shown in Figure 4.2, was created for owners and designers to guide them toward the proper selection of the ABC Construction Technology that best fits a project’s needs. Erection technology selection is a complex process that depends on a number of factors including the number of bridges to be built, the convenience of crane support on the ground or by other means, the span lengths, the condi- tion of the existing bridge to support crane loads, and site restrictions. For rapid renewal applications, the existing bridge must be demolished in a rapid process to allow the erection of the replacement structure. Because the demolition operations require roadway closures and other traffic operations, com- pleting the demolition process quickly and efficiently is often as critical as the replacement bridge erection operations. Typically, the most effective use of field resources is to use the same equipment for the demolition operations and for the replacement structure erection operations. Reuse of the equipment avoids duplication of temporary support condi- tions such as crane mats, causeways, or trestle bridges. Overview of ABC Construction Technologies To assist owners and engineers with implementation of an ABC Construction Technology, a set of standard conceptual details defining terminology and demonstrating the possi- bilities and limits of each ABC Construction Technology was created. Guidelines are also provided for conventional erec- tion of ABC systems by using cranes. These sheets are intended to be used in conjunction with the design standards for modular systems to achieve closer integration of design and construction starting in the design phase. Such an inte- grated design approach is critical to convey the designer’s intended assembly approach to the contractor and to foster more constructible designs. Once a construction technology

175 Figure 4.2. Selection flowchart for ABC Construction Technologies.

176 has been selected, the designer must integrate this technology into the bridge design. ABC Designs Built with Conventional Erection This is the typical construction method employed in most construction with prefabricated systems. Most contractors have cranes in their field resources or can easily acquire them. Bridge component erection can be done using land-based cranes (rubber-tire or crawler) or barge-supported cranes. Cranes can also be supported on a causeway, a sand island, or a trestle bridge for river crossings. The benefits of a causeway include cost savings by using native materials instead of building a crane trestle. Culvert pipes are used to allow water flow. Risks include high water flow that could wash away the causeway or sand island. The contractor and the contractor’s engineer both plan and design specific temporary structures and specific contractor operations. Anticipating the con- struction operations early in the design phase can have sig- nificant benefits. Sections that can be transported and erected in one piece are optimal for ABC. Lengths up to 140 ft may be feasible in certain cases. The weights of prefabricated components should be within the lifting capacities of commonly used cranes. Mobility and crane placement constraints for a site could dictate the largest weights that can be safely handled with conventional erection. Keeping the maximum weight under 50 tons will generally allow greater ease of erection. Components up to 125 tons may be used when needed for longer spans or for wider bridge widths after careful consid- eration of site conditions. Substructure units constitute some of the heaviest elements in a prefabricated bridge. The use of multiple large vertical cavities within the wall elements that are later filled with high early strength concrete allows for larger precast elements and leads to lighter shipping and lift- ing weights. ABC Bridge Designs Built with ABC Construction Technologies Above-deck carriers and launched temporary truss bridges are technologies that allow rapid replacement of structures when ground access for cranes below the bridge may be lim- ited. These technologies could be applied to a river crossing or a bridge over another highway or railway so that traffic disruptions might be minimized both on and under the new bridge. Above-Deck Driven cArriers Above-deck driven carriers (ADDCs) are designed to deliver individual components of a proposed structure in a span-by-span process with minimal disruption to activities and the environment below the structure. Current ADDCs exist in two forms, and both perform a similar function. An ADDC rides over an existing bridge structures and delivers components of a new bridge span by using hoists mounted to overhead gantries with traveling bogies. As shown in the examples in this section, the ADDC equipment can be quite specialized, as in the case of the RCrane Truss system used by railroads to replace existing short bridge spans. Some equipment, like the Mi-Jack Travelift overhead gantry, require specific site adaptations to align their wheelset with the centerlines of the existing girders that support the heavy moving loads. Some examples illustrating the concept are shown in Figures 3.55 and 3.56. One modified ADDC concept is a combination of the RCrane Truss and the Mi-Jack Travelift to create pairs of light- weight steel trusses supporting an overhead gantry system. This lightweight equipment could then be used on structures in which the existing bridge deck or girders are insufficient to support the heavier wheel loads of current ADDC equipment. This construction technology would be multifunctional, would be easily transportable both on urban and rural road systems, and would be mobilized with minimal erection and de-erection time. The trusses of the modified ADDC would be modular- ized into lengths that are easily trucked over both primary and secondary roads (either shipped on flatbed trucks or towed with the mountable rubber-tired bogies). Once assembled at the project site, the system would be equipped with several rubber-tired bogies that would be spaced to reduce and more evenly distribute the localized equipment dead load. Once the modified ADDC is rolled out across the bridge span(s), temporary jack stands would be lowered at the piers and abutments and would bear on the deck where blocking had been added below, from the pier up to the underside of the bridge deck. By bearing at the piers and abutments, the modified ADDC prevents overloading the existing bridge structure during delivery of the bridge components. This ABC Construction Technology would be applicable when an existing bridge or set of twin bridges is planned to be widened and when portions of the existing bridge are to be replaced. With several movements, the ABC Construction Technology could be used to replace an entire bridge. Advantages of ADDCs include the following: • Minimizes disruption to traffic and the environment at lower level of bridge project. • Can be used when conventional crane access is limited by site constraints. • Allows for faster rates of erection due to simplified delivery approach of components.

177 • Component delivery occurs at the end of the existing bridge, which minimizes disruptions at the lower level of the project site. • Decreases the need to work around existing traffic and lessens the need to reduce lanes, shift lanes, or detour lanes, which in turn improves safety for both workers and the traveling public. • Can be used to deliver prefabricated, modular components of ABC substructures and superstructures. LAuncheD TemporAry Truss briDge Launched temporary truss bridges (LTTBs) are designed to deliver individual components of a proposed structure in a span-by-span process with minimal disruption to activities and the environment below the structure. Currently, LTTBs exist in many forms; however, the basic principle of the technology is the same for each. LTTBs are launched across or lifted over a span or set of spans and then act as temporary bridges to deliver the heavier components of a span without inducing large temporary stresses into those components. As shown in the examples here, the pieces of LTTB equipment are designed and modified on the basis of varying sets of criteria from project to project. The equip- ment can be quite specialized in response to the needs of the project and could require extensive modifications from proj- ect to project in response to changes in span lengths and com- ponent weights. The idea behind a modified LTTB is to create a set of standardized lightweight steel trusses that would be assem- bled to a specific length that suits a given project. The truss design and details would follow the quick connect concepts used in crane boom technology and would allow site modi- fications with relatively minimal effort. The lightweight equipment could then be used to bridge new spans to deliver components for a new bridge structure. This con- struction technology would be multifunctional, would be easily transportable both on urban and rural road sys- tems, and could be mobilized with minimal erection and de-erection time. The trusses of the modified LTTB would be modularized into lengths that are easily trucked over both primary and secondary roads (either shipped on flatbed trucks or towed with mountable rubber-tired bogies). Once assembled at the project site, the lightweight equipment could be launched from span to span or could be lifted into position with cranes. Once the modified LTTB has bridged the new span, it would be stabilized and supported at each pier or abutment sub- structure unit. This ABC Construction Technology would be applicable when new bridge structures are to be erected and when an exist- ing bridge or set of twin bridges is planned to be widened. Advantages of LTTBs include the following: • Minimizes disruption to traffic and the environment at lower level of bridge project. • Can be used when conventional crane access is limited by site constraints. • Component delivery occurs at the end of the existing bridge, which minimizes disruptions at the lower level of the project site. • Decreases the need to work around existing traffic and lessens the need to reduce lanes, shift lanes, or detour lanes, which in turn improves safety for both workers and the traveling public. • Increases the possibility of erecting longer spans without significantly increasing the cost of bridge spans because the components of the spans can be delivered without addi- tional temporary erection stresses. • Allows work to proceed on multiple fronts (i.e., when multi-span LTTBs are used, girders can be set while the next girder is delivered). • Temporary loads are introduced directly into piers mini- mizing the need for falsework. • Can be used to deliver prefabricated, modularized compo- nents of ABC substructures and superstructures. Organization of Conceptual Details for ABC Construction Technologies The erection concepts presented in the drawings are intended to assist owners, designers, and contractors in selecting suit- able erection equipment for the handling and assembly of prefabricated modular systems. Examples for the organiza- tion of ABC Construction Technologies sheets are provided in Tables 4.3 and 4.4. Erection concepts presented in the drawings group the bridges into short- and long-span categories by using the fol- lowing criteria: • Short-span bridges 44 Bridges with span lengths up to 70 ft. 44 Maximum prefabricated bridge module weight is 90,000 lb. • Long-span bridges 44 Bridges with span lengths from 70 ft to 130 ft. 44 Maximum prefabricated bridge module weight is 250,000 lb. ABC Design examples The design examples will be instructive in highlighting the differences between CIP construction and modular prefab- ricated construction and the advantages of modular systems.

178 Currently, economical design that uses CIP construction requires simplified fabrication with less emphasis on weight reduction. However, for ABC, shipping weights have to be min- imized for economy and constructability. Shop labor is gener- ally less expensive and easier to control in terms of quality than is field labor. Use of shop-fabricated modular elements also increases the speed of construction. In CIP construction, over- all stability needs to be ensured for all stages of construction, with or without a roadway deck. Per LRFD, stability of the shape must be ensured. Girder stability during construction is not an issue for modular construction as it is for CIP construc- tion. This will allow more efficient designs of steel modular systems, which will minimize material and fabrication expenses while ensuring adequate strength, stiffness, and stability. Once the material of choice, structural steel has been mostly eclipsed by reinforced and prestressed concrete for short-to-medium spans built with conventional construc- tion. Prefabricated modular steel bridges compare favorably with other materials when considering the greater use of shop labor versus field labor, the speed at which bridges can be installed, and the significant reduction in time required to close a given roadway to the public. The light weight of steel modular systems could reverse this trend in ABC designs. Often designers concentrate on optimizing individual spans by minimizing the number of lines of girders and, in so doing, will generally reduce superstructure weights by 5% to 10%. While that is important, it is the careful determina- tion of span arrangement and module dimensions for ship- ping and erection that can add significant savings in ABC design. In fact, the cost of the substructure, particularly the intermediate piers, for each design usually determines the most economical span arrangement. It may be more eco- nomical to reduce the shipping weight of pier components by adding more piers to reduce the superstructure dead loads on each pier. The design examples developed in this task serve as train- ing tools to increase familiarity about ABC among engineers. Three design examples are provided in Appendix F to illus- trate the ABC Design process for the following prefabricated modular systems: • Decked steel girder; • Decked precast prestressed girder; and • Precast pier. The design examples pertain to the same standard bridge configurations for steel and concrete used in the ABC stan- dards. The intent was to create design examples that could be used in conjunction with the ABC Design standards developed in Task 10 so that practitioners would get a Table 4.3. Overview of Drawings for ABC Construction Technologies Drawing No. Description CC3 Short-span bridge replacement using cranes. Single span over waterway. Crane at roadway level at one end. CC4 and CC5 Short-span bridge widening using cranes. Two-span bridge over roadway. Due to critical pick radius, crane on one side on roadway below. CC6 and CC7 Short-span bridge replacement using cranes. Two-span bridge over roadway. Due to critical pick radius, crane on one side on roadway below. CC8 and CC9 Short-span bridge replacement using cranes. Two-span bridge over waterway. Due to critical pick radius, crane on one side on causeway below. CC10 and CC11 Short-span bridge replacement using cranes. Two-span bridge over waterway. Due to critical pick radius, crane on one side on temporary trestle bridge. CC12, CC13, and CC14 Long-span bridge widening using cranes. Three-span bridge over roadway. Due to critical pick radius, two cranes on one side on roadway below. CC15, CC16, and CC17 Long-span bridge replacement using cranes. Three-span bridge over roadway. Due to critical pick radius, two cranes on one side on roadway below. CC18, CC19, and CC20 Short-span bridge replacement using straddle carriers. Two-span bridge over waterway or roadway. Straddle carriers on permanent bridge. CC21, CC22, and CC23 Short-span bridge replacement using straddle carriers. Two-span bridge over waterway or roadway. Straddle carriers on launch beams. CC24, CC25, and CC26 Long-span bridge replacement using above-deck driven carrier. Three-span bridge over waterway or roadway. CC27, CC28, CC29, CC30, and CC31 Long-span bridge replacement using launched temporary truss bridge. Three-span bridge over waterway or roadway. CC32 Erection of prefabricated concrete substructure elements.

179 comprehensive view of how ABC Designs are performed and translated to design drawings and details. The design exam- ples focus on the design of the modules and the connection details. Additional features of the design examples include demonstration of any special LRFD loadings during con- struction and in the final condition, load combinations, stress and strength checks, deformations, and lifting and handling stresses. The design examples have extensive docu- mentation describing the design criteria, the design steps executed, the design philosophy adopted, and the design specifications checks performed. All design examples are based on the LRFD Bridge Design Specifications, 5th ed. AAS- HTO specification references are presented in a dedicated column in the right margin of each page, immediately Table 4.4. ABC Construction Technologies Sheets Sheet No. Description CC1 General Notes CC2 General Notes CC3 Conventional Erection Replacement Single Short-Span Bridge CC4 Conventional Erection Widen Short-Span Bridge over Roadway CC5 Conventional Erection Widen Short-Span Bridge over Roadway CC6 Conventional Erection Replacement Short-Span Bridge over Roadway CC7 Conventional Erection Replacement Short-Span Bridge over Roadway CC8 Conventional Erection Replacement Short-Span Bridge over Waterway (Opt. 1) CC9 Conventional Erection Replacement Short-Span Bridge over Waterway (Opt. 1) CC10 Conventional Erection Replacement Short-Span Bridge over Waterway (Opt. 2) CC11 Conventional Erection Replacement Short-Span Bridge over Waterway (Opt. 2) CC12 Conventional Erection Widen Long-Span Bridge over Roadway CC13 Conventional Erection Widen Long-Span Bridge over Roadway CC14 Conventional Erection Widen Long-Span Bridge over Roadway CC15 Conventional Erection Replacement Long-Span Bridge over Roadway CC16 Conventional Erection Replacement Long-Span Bridge over Roadway CC17 Conventional Erection Replacement Long-Span Bridge over Roadway CC18 Straddle Carriers on Permanent Bridge: Short-Span Bridge CC19 Straddle Carriers on Permanent Bridge: Short-Span Bridge CC20 Straddle Carriers on Permanent Bridge: Staged Construction CC21 Straddle Carriers on Launch Beams: Short-Span Bridge CC22 Straddle Carriers on Launch Beams: Short-Span Bridge CC23 Straddle Carriers on Launch Beams: Staged Construction CC24 ADDC Concept: Plan and Elevation CC25 ADDC Concept: Typical Cross Section CC26 ADDC Concept: Staged Construction CC27 LTTB Concept: Plan and Elevation CC28 LTTB Concept: Typical Cross Section CC29 LTTB Concept: Staged Construction CC30 Typical Erection Truss Module CC31 Typical Rolling Gantry Concepts CC32 Erection Of Prefabricated Concrete Substructure Elements

180 adjacent to the corresponding design procedure. The exam- ples are organized in a logical sequence to make them easy to follow. Each example has a table of contents at the begin- ning to guide the reader and allow easier navigation. The design examples may also be found in Appendix B of the ABC Toolkit. recommended ABC Design Specifications for LrFD The challenge to the future deployment of ABC systems lies partly in the ability to codify the design and construction of these prefabricated modular systems so that they are not so unique from a design and construction perspective. The LRFD design philosophy should explicitly deal with the unique aspects of large-scale prefabrication, including issues such as element interconnection, system strength, and behavior of rapid deploy- ment systems during construction. For rapid replacement, it is possible that the stages of construction may in fact provide the critical load combinations for some structural elements or entire systems. Ongoing developments in material technology and increasing steel and concrete strengths have allowed design- ers to extend the useful span lengths of bridges ever farther. In some cases, the most extreme load case that these ever-longer and more-slender beams will ever experience will occur during shipping and handling prior to final erection. At the current time, under a design–bid–build delivery method, the engineering and design services for the design of a large-scale prefabricated bridge system are performed by dif- ferent entities. The engineer of record is responsible only for the bridge in its final support condition. It is the contractor who typically proposes some innovative method of construc- tion and thus carries the burden to hire a construction engi- neering firm to provide the engineering services required to prove that an innovative erection technique can be used. When design–build procurement is used, greater alignment between design and construction could facilitate greater inno- vation in rapid renewal projects. Closing some of these gaps or inconsistencies in the specifications as related to the engineer- ing and construction of rapid replacement bridges is a worth- while goal for this project and other ongoing projects related to rapid renewal. Guidance should be developed for alerting engineers to an increased obligation for strength, stability, and adequate service performance prior to final construction. Maintaining individual module stability and limiting the erection stresses induced through the choice of pick points (crane lifting points) would be a critical consideration for modular construction. The location of the pick points should be calculated so that the unit is picked straight without roll or stability problems and with erection stresses within allowable limits. The plans should indicate the lifting locations based on the design of the element. The engineer is responsible for checking the handling stresses in the element for the lifting locations shown on the plans. The contractor may choose alternate lifting locations with approval from the engineer. In order to ensure proper lifting locations are identified in the plans, the design community needs guidance or minimum analysis requirements for various erection methods for mod- ular construction. Design criteria proposed for the ABC standards are in accor- dance with the AASHTO LRFD Bridge Design Specifications. The design life, or period of time on which the statistical deri- vation of transient loads is based, is 75 years for these specifi- cations. Therefore, the completed structure will need to satisfy the same design requirements as any conventionally built bridge. Any new bridge system should meet this minimum design life requirement for wide acceptance and implementa- tion. However, it is not necessary or economically feasible for prefabricated systems during construction to be bound by the same criteria as the completed structure. The design of bridges that use large-scale prefabrication is not specifically covered in the LRFD design specifications. The work in this task entailed identifying any shortcom- ings in the current LRFD Bridge Design Specifications that may limit their use for ABC Designs and making recommen- dations for addressing these limitations. The primary deliver- able was to develop recommended specification language for ABC systems suitable for future inclusion in the AASHTO LRFD Bridge Design Specifications. Design issues specific to ABC include the following: • Construction loads. What kinds of loads are unique to rapid construction? For example, loads associated with support conditions during fabrication that may be differ- ent than the permanent supports, loads associated with member orientation during prefabrication, loads associ- ated with suggested lift points, loads associated with vari- ous erection methods, impact considerations for shipping and handling of components, loads associated with cam- ber leveling, and so forth. • Limit states and load factors during construction. What are the applicable limit states during construction? Man- datory strength limit states should be checked, such as STRENGTH I. What is the appropriate load factor for STRENGTH I loads? Limit state for checking of construction vehicles. Check of critical stability or serviceability effects as the component is moved, assembled, and erected. Depend- ing on construction sequencing, abutments may be backfilled and subjected to the full earth pressure during construction prior to placement of the superstructure. Requirements for extreme events during construction. • Constructability checks. Erection analysis to evaluate the lifting and erection stresses in prefabricated components.

181 To what extent is cracking allowed in prefabricated systems during transportation and erection? What are the limiting stresses, deflections, and distortion during construction for steel and concrete components? Requirements for SERVICE III checks in prestressed members. What are the bracing requirements for transportation and erection of elements and systems? Deck thickness allowances for ride- ability in the original design. • Cross frames and diaphragms. What are the requirements for modular construction with regard to these bracing ele- ments during construction? In modular construction, the girder stability is greatly enhanced by the precast deck, which could allow opportunities to ease the requirements for intermediate cross frames and diaphragms and could achieve savings in weight and cost. Additional bracings for temporary support points during construction. • Analysis methods. What are the minimum recommended levels of analysis or stages of analysis required for bridges erected by various unique methods? Consideration of sequence of loading during construction. Are there any unique changes to structural load distribution that must be addressed for certain prefabricated bridge types and con- nection configurations? • Connections. What are the requirements for closure pour design for strength and durability? Development of reinforc- ing steel and lapped splices in closure pours. Requirements for grouted splice couplers. Provisions for UHPC joints. Recommended LRFD Design Specifications for ABC Implementing the recommended ABC Design provisions into the existing sections of the LRFD Bridge Design Speci- fications would be difficult as ABC Design incorporates components from several sections of the code. As such, the specifications are written as if they were to be added as a new LRFD subsection (5.14.6) under Section 5, Concrete Structures, in the LRFD Bridge Design Specifications. See Appendix G for the recommended LRFD design specifica- tions for ABC. recommended ABC Construction Specifications for LrFD These ABC construction specifications pertain specifically to prefabricated elements and modular systems (Tier 2) and are intended to be used in conjunction with the standard plans for steel-and-concrete modular systems developed in SHRP 2 R04. As such, these specifications for rapid replacement focus heavily on the means and methods required for rapid con- struction with prefabricated modular systems. Implementing ABC concepts into the existing sections of the LRFD construction specifications would be difficult since these ABC concepts include elements from several sections. As such, the following is written as if it were to be added as a stand-alone section in the LRFD Bridge Construction Specifi- cations. See Appendix H for the recommended LRFD con- struction specifications for ABC. Innovative project Delivery and Contracting provisions for ABC Introduction Specifications used by DOTs generally attempt to describe how a construction contractor should conduct certain operations by using minimum standards of equipment and materials. These are referred to as prescriptive specifications. However, rapid renewal projects often require more creativity and innova- tion. Alternative specification language is needed that is less prescriptive and concentrates on the measurement of factors critical to the performance of the final product, while ensur- ing that accelerated timelines are met and quality is main- tained. SHRP 2 Project R04, Performance Specifications for Rapid Renewal, is currently developing different performance specifications that can be used effectively in various contract- ing scenarios. This section contains fundamental information on vari- ous innovative construction contracting and delivery meth- ods that may be used to enhance the implementation and delivery of ABC construction projects. Innovative construc- tion contracting methods are typically used to expedite con- struction progress and project delivery and to minimize user delays. These methods range from design–build delivery to contracting provisions such as incentive/disincentive clauses and early purchasing of materials. Delivery methods are pri- marily focused on shortening the time needed to develop and deliver a construction project. Contracting provisions are targeted to minimize user delays and expedite construc- tion progress. Regardless of the contracting method chosen, there are several contracting provisions that are commonly used on ABC projects. For successful ABC implementation, the con- tract must be structured in such a way that there are mean- ingful incentives for on-time or accelerated completion and meaningful disincentives that are applied for delays in deliv- ery, quality, or other contract terms. Additionally, accelera- tion techniques that require long lead times, such as early purchase of materials, are used in ABC contracts to expedite construction progress and minimize delays. This section provides an overview of these methods and pro- cesses. More information can be found at the FHWA website,

182 www.fhwa.dot.gov, and at DOT websites listed in the following references: Caltrans, 2007; Colorado DOT, 2006; FHWA, 2010b; Florida DOT, 2007; Michigan DOT, 2007; Minnesota DOT, 2008; Montana DOT, 2009; and Ohio DOT, 2006. Innovative ABC Project Delivery Methods Innovative project delivery is a natural fit for accelerated bridge construction. The two most common innovative project deliv- ery methods that are in use on ABC projects are design–build and construction manager/general contractor. Design–Build Design–build is the project delivery technique that has gar- nered the most attention in recent years. In its simplest form, design–build places a designer and contractor under the same contract to the owner. Typically, the engineer works for the contractor in these arrangements. The design–build con- cept is predicated on using a performance expectation rather than prescriptive requirements so that an engineer and con- tractor team can provide solutions uniquely tailored to their strengths that provide the fastest and most economical solu- tion to an owner. The primary motivation for design–build contracts is time compression. With only a concept of the project, the engi- neering and contractor are completely responsible for project engineering and construction. Although the goal is primarily time savings, the method has other benefits, such as provid- ing a single point of contact for the owner, reducing owner claims for errors and omissions, allowing maximum contrac- tor flexibility, teaming design and construction expertise in a single team, allowing for innovation in design and construc- tion methods and in contracts with warranty provisions, and allowing for some owner certainty following completion. Critical elements of design–build contracting include select- ing projects appropriate for this method of delivery, develop- ing prequalification procedures, establishing ranking criteria and proposal selection, controlling quality, and considering warranty or future operations. Typically, design–build contracts are awarded after the owner has completed some preliminary design, the envi- ronmental process is complete (or nearly complete), and right-of-way is secured. The level of preliminary design is typically 10% to 30% and depends greatly on the risks asso- ciated with the project. From the contracting agency’s per- spective, the potential time savings is a significant benefit. Since the design and construction are performed through a single procurement, construction can begin before all design details are finalized. Design–build projects are typically tai- lored to large construction projects but can be used on smaller projects. The design–build concept allows the contractor maximum flexibility for innovation in the selection of design, materials, and construction methods. With design–build procurement, the contracting agency identifies the end result parameters and establishes the design criteria. The prospective bidders then develop design proposals that optimize their construc- tion abilities. The submitted proposals may be rated by the contracting agency on factors such as design quality, timeli- ness, management capability, and cost, and these factors may be used to adjust the bids for the purpose of awarding the contract. Advantages of the design–build process include the following: • Project delivery can be accelerated. • The design can be tailored to the contractor’s expertise and equipment. • The team can take advantage of innovative construction processes. • Design–build teams can modify the preliminary designs to save money. • Owners can obligate monies very quickly on projects. Disadvantages of the design–build process include the following: • The owner needs to clearly identify and communicate the desired project outcomes. • The design–build team needs to complete a relatively detailed design process in order to bid the project. Stipends are sometimes used to defer the cost of this process. • The owner does not have complete control over the final design. • Some agencies have reported higher costs with design– build. Construction Manager/General Contractor (CM/GC) The construction manager/general contractor (CM/GC) proj- ect delivery method allows an owner to engage a construction manager during the design process to provide constructability input. In a CM/GC project, the owner has a direct contract with an engineering firm and a separate contract with a construction company. The construction company is the construction man- ager (CM) for the project. The team approach provides for input from all team members throughout the design and construction phases. The ability of the CM to input constructability reviews, construction phasing, erection methods, and cost estimat- ing throughout the design process results in a more con- structible project and reduces project construction delays and project costs.

183 The engineer and construction manager are generally selected on the basis of qualifications, past experience, or a determination of best value. At approximately 60% to 90% design completion, the owner and the construction manager negotiate a “guaranteed maximum price” for the construc- tion of the project that is based on the defined scope and schedule. If this price is acceptable to both parties, they exe- cute a contract for construction services, and the construc- tion manager becomes the general contractor. The CM/GC delivery method is also called the construction manager at- risk method. CM/GC is particularly suited for ABC projects. This method has been successfully used by the Utah DOT on several ABC projects. This method of project delivery is similar to design–build in that the designer and contractor work together to complete a design; however, in CM/GC, both the designer and the con- tractor have contracts with the owner. In CM/GC, the owner does not relinquish control or risk as in design–build. By having control over the entire design process, the owner can stipulate the construction method(s) that will best suit the traveling public. CM/GC includes the following key aspects and advantages: • A preliminary design does not need to be completed prior to selection of the designer or the contractor. • Time savings are possible by fast-tracking design and con- struction activities. • The design engineer is selected by the agency by using a qualifications approach. • The design engineer works under the direction of the agency, not the contractor. • The contractor is selected by the agency by using a qualifi- cations approach. • The selected firms form a design team. The team, working with the owner, develops the design. • This method allows for innovation in ABC Designs through constructability recommendations from the CM. • Since a guaranteed maximum price is established, the CM invests more during the design phase and cost estimating. • This method fixes project cost and completion dates. Disadvantages to the CM/GC method include the following: • Price is negotiated with a CM and not competitively bid. • The department retains design liability. • The guaranteed maximum price approach may lead to a large contingency to cover uncertainties and incomplete design elements. • Use of a guaranteed maximum price may lead to disputes over the completeness of the design and what constitutes a change to the contract. • This method has had limited use and experience nationally on transportation infrastructure projects. Innovative Contracting Provisions for ABC Cost-Plus-Time Bidding Reduction in construction time and specifically the time dur- ing which traffic is disrupted is the desired objective of ABC projects. Cost-plus-time bidding, more commonly referred to as the A+B method, involves time, with an associated cost, in the low-bid determination. The A+B method can be an effective technique for ABC projects to significantly reduce high road-use-delay impacts. Under the A+B method, each bid submitted consists of two components: • The A component is the traditional bid for the contract items and is the dollar amount for all work to be performed under the contract. • The B component is a bid of the total number of calendar days required to complete the project, as estimated by the bidder. Calendar days are used for the B component to avoid any potential for controversy that may arise if work days were used. The bid for award consideration is based on a combina- tion of the bid for the contract items and the associated cost of the time, according to the formula: (A) + (B × road user cost per day) This formula is only used to determine the lowest bid for award and is not used to determine payment to the contractor. A disincentive provision that assesses road-user costs is incorporated into the contract to discourage the contractor from overrunning the time bid for the project. Liquidated damages may also apply with the disincentive. In addition, an incentive provision should be included to reward the con- tractor if the work is completed earlier than the time bid. The maximum amount of incentive is usually limited to a certain percentage of the estimated construction costs. Cost-plus-time bidding is an effective technique for projects that have critical completion dates. A+B+C bidding is similar to A+B bidding except that a third component is added to the equation. The C component is normally used for specific mile- stone time frames or critical completion dates. For example, a contract may have a B component that is tied to final project completion, and a C component that is tied to the completion of a phase of construction. The dollar values assigned to the time components are somewhat subjective, difficult to calcu- late, and sometimes hard to justify in an age of shrinking trans- portation funding. Agencies need to develop a standardized approach to identify these costs and make rational decisions based on the needs of the project and the effects on the travel- ing public. The user costs need to be consistently applied on

184 A+B projects to build confidence and acceptance of this method of procurement. Incentive/Disincentive Clauses Standard incentive/disincentive clauses (I/D clauses) have a long history of use as a method to motivate the contractor to complete work or to open a portion of the work to traffic on or ahead of schedule. I/D clauses provide a bonus for early com- pletion or early opening to traffic. They can also be used as pen- alties for late project completion or for lanes not open to traffic. This method continues to be an effective option on ABC proj- ects. The bonus or penalty is based on road-user-delay costs, and the maximum bonus is usually limited to a percentage of the project costs. Progress clauses may list any additional liqui- dated damages linked to agency costs that apply to late comple- tion. The use of I/D clauses will inevitably bring about a need for careful time tracking. Delays in agency approval of submit- tals may be grounds for time extensions, which will greatly affect the I/D values. An alternate form of I/D clause, known as the no-excuse incentive, is a method used to motivate the contractor to complete work or open a portion of the work to traffic on or ahead of schedule by providing a bonus for early completion or opening. The owner will give the contractor a drop-dead date for completion of a phase or project. If the work is com- pleted in advance of this date, the contractor will receive a bonus. There are no excuses for any reason, such as weather delays, for not meeting the early completion or open-to- traffic date. Conversely, there are no disincentives (other than normal liquidated damages) for not meeting the early com- pletion or open-to-traffic date. This technique is applicable to projects that must be open by a critical date, such as a major sporting event. Lane Rental Like cost-plus-time bidding, the goal of the lane-rental con- cept is to encourage a contractor to minimize the amount of time that through lanes are closed, and therefore limit the associated road-user-delay effects. Under the lane-rental con- cept, a provision for a rental fee assessment is included in the contract. The rental fee rates are stated in the bidding proposal in dollars per lane per time period, which could be daily, hourly, or in fractions of an hour. The rental fee rates are dependent on the number and type of lanes closed and can vary for different hours of the day. The contractor estimates the amount of time for which the rental assessment will apply and must bid a positive lump sum amount for the lane rental. Neither the contractor nor the contracting agency gives an indication as to the anticipated amount of time for which the assessment will apply, and the low bid is determined solely on the lowest amount bid for the contract items. The tally of cumulative lane-rental assessments are then deducted from the original lane-rental lump sum bid on a biweekly or monthly basis until the contract work is completed. The intent of lane rental is to encourage contractors to schedule their work to keep traffic restrictions to a minimum, both in terms of duration and number of lane closures. The lane-rental concept has merit for use on projects that signifi- cantly affect the traveling public; major urban projects are prime candidates for this approach. Lane rental should not be used to reduce overall contract time but to focus on the time that roadway users are affected by construction traffic Early Purchase of Materials Early purchasing of materials is used to expedite the delivery of critical materials for a project. These contracts are let prior to larger contracts to ensure critical materials are on site and ready for installation on or before a specified date so that the larger contracts can remain on schedule. This method has been used on prefabricated elements and steel beams for bridge construction projects and could be particularly bene- ficial on projects subject to accelerated project delivery or critical completion dates. It reduces the risk of project delays from materials requiring long lead times or from potential supply shortages. It could also save cost by removing the risk of price escalation. (Separate payment under a materials-on- hand provision is allowed under FHWA guidelines.) This method requires special provisions be included in both the early purchasing and larger contracts that clearly and logi- cally specify the contractual requirements for each contractor and their obligations for the fabrication, delivery, storage, testing, and acceptance of the materials. Suggested Future Research On the basis of experiences and observations, the R04 team has assembled a number of items that are recommended for future research. Research on UHPC behavior is among the most pop- ular topics being considered. It is suggested that additional test- ing of UHPC bond strength with adjacent conventional concrete be performed. Iowa State University has started some tests with uniaxial pull-off specimens, and the early results indicate the bond strength is significantly less than anticipated during design. Also, a study of UHPC mixes for early strength gain that can be used in overnight closure applications could prove to be very worthwhile. Regarding UHPC, it suggested that long-term monitoring of UHPC joints in ABC systems be put into place in order to gain more insight to joint behavior. Tests could be done for strength and serviceability of the UHPC joint and the adja- cent deck concrete. Testing of transverse UHPC joints that

185 have smaller joint widths or modified reinforcement details different than those used in the Iowa project could also be studied. Research investigating how to improve economy is critical. Can acceptable joint performance be achieved while reducing the number of hairpin bars, replacing them with straight bars, or potentially eliminating the transverse bars inserted through the hairpins? Connections that use grouted coupler details, especially in high-seismic areas, could be inves- tigated as another alternative joint design. Perhaps looking beyond the idea of UHPC and experimenting in the testing of transverse moment connections that use high early strength conventional concrete could provide useful research data that might possibly influence future designs. Can these joints be used with the posttensioning retrofit to save the cost of UHPC for future bridges? Replacing steel fibers with carbon fiber reinforcement in UHPC mixes is another technology that could be investigated. This will eliminate the need for Buy America waivers for the steel fibers. It is suggested that research also be directed to broader- scope project tasks. Such tasks may include research of stan- dardized user cost models for use in ABC projects; guidelines on how to determine incentive/disincentive costs for the ABC period; performance measures for ABC projects; guide- lines for the design and construction of deep foundation systems for ABC projects; and recommended tolerances, specific to ABC construction, for prefabricated elements and systems. Further research into the erection process would provide a greater understanding of potential risks and con- siderations that could develop during construction that are specific to ABC projects. Such research topics regarding erection may include measurement of erection stresses in modular systems so that more accurate impact values may be specified for design. Also, measurement of concrete tensile stresses from the leveling of beam differential camber and validating design approaches to account for these stresses is suggested.