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4C h a p t e r 1 problem Statement and research Objective Bridge deterioration and replacement continue to be ongoing problems in the United States. Accelerated bridge construction (ABC) techniques have the potential to minimize traffic dis- ruptions during bridge renewals, promote traffic and worker safety, and also improve the overall quality and durability of bridges. ABC has been used on emergency replacement proj- ects as well as on planned bridge replacement projects. While most agencies are aware of ABC, very few practice it on a large scale. Accelerated Bridge Construction (ABC) applications in the United States have developed two different approaches: accel- erated construction of bridges in place using prefabricated systems and the use of bridge movement technology and equipment to move completed bridges from an off-alignment location into their final position. Rapid construction of bridges in place offers the promise of limited closures, days or weeks at most, to allow for the com- plete construction of a bridge. This type of construction tradi- tionally relies on extensive prefabrication of bridge elements, including substructure and superstructure components, and the use of cranes to install these elements in their final loca- tion, along with innovative contracting and procurement tech- niques. Special connections designed to integrate elements into a completed bridge are made and the bridge can be opened to traffic in a very short period of time. An alternative to rapid construction of bridges cast in place is the use of preassembled bridges, completed at an off- alignment location and then moved via various methods into the final location using techniques such as lateral sliding, roll- ing, and skidding; incremental launching; and movement and placement using SPMTs (self-propelled modular trans- porters). This can be done, depending on complexity, in minutes, hours, or at most, several days. Very large and com- plex structures can be erected in this fashion; the method distinguishes itself from rapid in-place construction in the scale of the potential project that can be undertaken and the use of complete fabrication at off-site locations. ABC has yet to gain significant traction in the United States. A key objective of this project is to identify impedi- ments and obstacles to greater use of ABC and to seek solu- tions to overcome them. Focus group meetings held with representatives from more than 20 departments of transpor- tation (DOTs) as part of Phase I of the SHRP 2 R04 project identified several factors that have contributed to the slow adoption of ABC. Despite the gradual lowering of costs and life-cycle cost savings, DOTs are hesitant about using ABC techniques because of their higher initial costs. A great impediment to rapid construction is the slow pro- cess of custom engineering every solution. Rather than cus- tomizing every solution, pre-engineered modular systems configured for traditional construction equipment could promote more widespread use of ABC through reduced costs and increased familiarity of these systems among own- ers, contractors, and designers. An objective of the ongoing SHRP 2 R04 project, with HNTB as the prime contractor, is to develop âstandardized approaches to designing and con- structing complete bridge systems for rapid renewals.â The aim therefore is to develop pre-engineered standards for modular bridge substructure and superstructure systems that can be installed with minimal traffic disruptions in renewal applications. The research objective for the R04 project is as follows: To develop standardized approaches to designing, constructing, and reusing (including future widening) complete bridge sys- tems that address rapid renewal needs and efficiently integrate modern construction equipment. ABC entails prefabricating as many bridge components as is feasible considering site and transportation constraints. The successful use of prefabricated elements to accelerate Background
5construction requires careful evaluation of bridge require- ments, site constraints, and an unbiased review of total costs and benefits. This project takes the approach that for ABC to be successful, ABC designs should allow maximum opportu- nities for general contractors to do their own prefabrication at staging areas adjacent to project sites or in their yards using their crews. The R04 team has determined that ABC systems should be ⢠As light as possible, ⢠As simple as possible, and ⢠As simple to erect as possible. In many cases, foundation and substructure construction is the most costly and time-consuming part of constructing a bridge. To get maximum speed and advantage possible from on-site construction with prefabricated bridge installations, consideration should be given to using prefabricated compo- nents for foundations and substructures. A total substructure system may consist of modular abutments and walls and pre- fabricated bent caps supported by prefabricated columns. This project aims to provide design standards for complete prefabricated bridge systems, including foundation strategies for shallow and deep foundation systems in the context of ABC projects. In past years, the potential weak link in prefabricated sys- tems has been the connections between components. Whereas the prefabricated components are constructed in controlled environments, the closure joint construction is exposed to variability inherent in field construction. Transverse and longitudinal deck closure joints are the biggest challenge to achieving long-term durability with minimum mainte- nance and rideability and smoothness requirements. Recent advances in high-performance materials have introduced a new generation of connections that are more durable and also low in maintenance. Scope of Study As noted, a part of the mandate of the ongoing SHRP 2 Project R04, Innovative Bridge Designs for Rapid Renewal, is to develop standard plans and details for promoting more wide- spread use of accelerated bridge construction. A key objective of this project is to identify impediments and obstacles to greater use of ABC and to seek solutions to overcome them. These challenges can be met and successfully addressed if own- ers, designers, and contractors innovate incrementally and col- laboratively. Building on previous experience and constantly pushing the envelope will result in continued successes. Project R04 is composed of three distinct phases over a time period of four years. Phase I, consisting of Tasks 1 through 5, was completed in November 2009. In this phase, the team collected extensive data on ABC projects and identified cur- rent impediments to and challenges in greater use of ABC by bridge owners. Phase II comprised Tasks 6 through 9 and was completed between December 1, 2009, and December 31, 2010. The findings and ABC concepts from Phase I were sub- jected to critical evaluations in Phase II to identify concepts that could be advanced to standard plans in Phase III. Work on Phase III commenced in January 1, 2011, and was com- pleted in March 2012. A synopsis of project activities follows. The literature review consisted of gathering published data, and review of innovative design and construction con- cepts involved many project examples demonstrating differ- ent approaches to ABC. The following topics were included in the discussion: complete bridge systems and component- level solutions, such as innovative superstructure systems; rapid bridge deck installation and replacement concepts; substructure options; and rapid foundation construction concepts for both shallow and deep foundations. The second major focus of the literature review was the use of innovative construction methods as a solution to rapid bridge construc- tion. These topics included bridge movement using self- propelled modular transporters, lateral sliding and skidding of completed bridges, the use of incremental launching alone or combined with other techniques, and other innovative construction techniques. A variety of techniques were used to determine industry opinions and experience about ABC. Electronic web-based surveys, phone interviews, focus group teleconferences and meetings, in-person visits, and various e-mail communications were all used to solicit opinions from owners, engineering designers, contractors, fabricators, vendors, specialty contrac- tors, and specialty engineers. The surveys and communications in general provided data about past experiences, successes and failures of prior projects, institutional obstacles, and responses to other questions that helped the team understand how ABC is used in various locations throughout the country. Sixteen ABC design concepts developed by the R04 team from the Phase I investigations were described with concept sketches and photographs and then advanced to Phase I eval- uations. They include new concepts or adaptations of existing concepts that are proposed as solutions to various ABC prob- lems. The concepts cover two broad themes pertaining to rapid renewal. ⢠Proven concepts, and ⢠New and innovative concepts. These concepts are categorized as follows. They include new concepts, or adaptations of existing concepts, that are proposed as solutions to various ABC problems. ⢠Modular superstructure systems; ⢠Segmental superstructure systems;
6⢠Precast decks; ⢠Precast modular abutment systems; ⢠Precast complete pier systems; ⢠Segmental columns and piers; ⢠Above-deck driven carriers; ⢠Launched temporary truss bridge; ⢠SPMTs and other wheeled carriers; and ⢠Launching, sliding, and lateral shifting. ABC design concepts have been classified into five tiers, based on mobility impact time, as follows: ⢠Tier 1: Traffic impacts within 1 to 24 hours. ⢠Tier 2: Traffic impacts within 3 days. ⢠Tier 3: Traffic impacts within 2 weeks. ⢠Tier 4: Traffic impacts within 3 months. ⢠Tier 5: Overall project schedule is significantly reduced by months to years. Phase II incrementally winnowed the collected findings and ABC concepts from Phase I through screening and further evaluations. It consisted of an engineering and constructabil- ity evaluation of the concepts as well as an identification of obstacles to implementation of the various Phase I concepts. The purpose of these evaluations was to provide recom- mended ABC concepts or techniques that could be advanced to standard plans and field trials in Phase III. Any technology recommended for field trials needed to meet minimum stan- dards of readiness for execution, provide a promise of durabil- ity, and provide value to the owner. Phase II proposed a short list of ABC concepts that could be advanced to the design and implementation phase. The first ABC demonstration project under R04 consisted of replacing the bridge located on US-6 over Keg Creek in Pottawattamie County, Iowa. The replacement structure was a three-span steel/precast modular bridge with precast bridge approaches. The design was performed in Phase II, and the construction was completed in Phase III. The principal objec- tive of the project was to demolish and replace the existing bridge within the 14-day ABC period. A daylong Highways for LIFE (HfL) workshop included a site visit that occurred dur- ing the critical accelerated bridge construction period and provided an opportunity to disseminate information to bridge owners around the country. The workshop highlighted the innovative design and construction features advanced by this project. This demonstration project can affect the future prac- tices of the industry and the U.S. Department of Transporta- tion, as technologies that are successfully implemented on this project could accelerate the adoption of ABC innovations in the United States. Acceleration could be accomplished by creating awareness and educating stakeholders about innova- tive features, which would increase stakeholder confidence in recommending ABC use on other projects. Several different areas of testing needs for ultra-high- performance concrete (UHPC) joints were identified during the design of the demonstration project. UHPC joint testing was performed by Iowa State University, a member of the R04 team. The testing covered the constructability and grindabil- ity of the UHPC joints and negative bending strength of the transverse pier joints. As noted, one goal of this research project is to develop an ABC Toolkit for designers to foster greater use of ABC in bridge renewal and widening projects. The ABC Toolkit will be com- posed of ABC design standards for substructure and super- structure systems, design examples, and sample specifications. In Phase III, the research team developed pre-engineered stan- dards optimized for modular construction and ABC. Stan- dardizing ABC systems will bring greater familiarity with ABC technologies and concepts and should foster more widespread use of ABC. Using standardized designs will serve as a training tool to increase ABC familiarity among engineers. ABC design examples were developed to be used by future designers. They provide step-by-step guidance on overall structural design of bridge components and use the same stan- dard bridge configurations for steel and concrete as used in the ABC design standards. To supplement the design examples (where shortcomings in the AASHTO specifications may exist), the toolkit also provides recommended load and resis- tance factor design (LRFD) provisions for ABC modular sys- tems. 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. Recommended LRFD construction specifications for pre- fabricated elements and modular systems were compiled by the research team with the intent that they would be used in conjunction with standard plans for steel-and-concrete mod- ular systems. As such, these specifications for rapid replace- ment focus heavily on means and methods required for rapid construction with prefabricated modular systems and are part of the ABC Toolkit. Task 13 focuses on the development of technical training materials suitable for a one-day course on ABC to be deployed by the National Highway Institute. Task 13 will run concur- rently with Phase IV activities and is not addressed in this report. Introduction to the Final report This Final Report, prepared in accordance with Task 14 require- ments for this project, documents the findings of Tasks 1 through 12. It contains four chapters and eight appendices. Chapter 1 gives a review of the problem statement, the research objective, and the scope of study. Chapter 2 describes the research tasks and the findings of the literature search, sur- vey, and focus group meetings. The 16 ABC design concepts
7developed by the R04 team from the Phase I investigations are described in Chapter 2 with concept sketches and photo- graphs. Chapter 3 contains the results of the engineering and constructability evaluations of the ABC concepts detailed in Chapter 2, as well as a short list of concepts that could be advanced to the ABC design and implementation phase. Chapter 4 introduces the ABC Toolkit developed in the R04 Project, combined with an overview of innovative project delivery and contracting provisions for ABC. Appendix A contains the literature search and ABC case studies compiled by the R04 team. Appendix B summarizes the surveys and focus group findings. Appendix C is the UHPC Lab Testing Report. Appendix D is the report on the construction of the first field demonstration project in Iowa. Appendix E is composed of the ABC standard plans and Appendix F provides ABC sample design calculations. Appen- dices G and H include the recommended LRFD design and construction specifications, respectively.
