Innovative Bridge Designs for Rapid Renewal (2014)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1This report documents and presents the results of SHRP 2 Renewal Project R04, Innovative Bridge Designs for Rapid Renewal, to develop standardized approaches to designing and con- structing complete bridge systems for rapid renewals. Bridge deterioration and the need for replacement continue to be ongoing problems in the United States. Accelerated bridge construc- tion (ABC) techniques have the potential to minimize traffic disruptions during bridge renewals, to promote traffic and worker safety, and to improve the overall quality and durability of bridges. Accelerated bridge construction entails prefabricating as many bridge components as feasible. Minimizing road closures and traffic disruptions is a key objective of ABC. For ABC systems to be viable and see greater acceptance, savings in construction time should be clearly demon- strated. Successful use of prefabricated elements to accelerate construction requires careful eval- uation of the requirements for the bridge, site constraints, and an unbiased review of total costs and benefits. Accelerated bridge construction applications in the United States have developed two different approaches: accelerated construction of bridges in place using prefabricated systems and the use of bridge movement technology and equipment to transfer a completed bridge from an off- alignment location to its final position. Rapid construction of bridges in place offers the promise of limited closures, possibly for days or weeks, during complete construction of a bridge. This type of construction traditionally relies on extensive prefabrication of bridge elements, including substructure and superstructure components, and the use of cranes to install these elements into their final locations. An alternative to rapid construction in place is the use of preassembled bridges, completed at off-alignment locations and then moved by various methods using tech- niques such as lateral sliding, rolling, and skidding; incremental launching; and movement and placement using SPMTs (self-propelled modular transporters) into the final locations. A key objective of this project is to identify impediments and obstacles to greater use of ABC and to seek solutions to overcome them. Focus group meetings and owner surveys identified several factors that have contributed to the slow adoption of ABC in the United States. Despite life-cycle cost savings and the gradual lowering of costs, departments of transportation are hesi- tant to use ABC techniques because of their higher initial costs. Another great impediment to rapid construction is the slow process of custom engineering every solution. Rather than custom solutions, pre-engineered modular systems configured for conventional construction equipment could promote more widespread use of ABC through reduced costs and increased familiarity of these systems among owners, contractors, and designers. An objective of the SHRP 2 R04 project was to develop “standardized approaches to designing and constructing complete bridge systems for rapid renewals.” 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. This project takes the approach that for ABC to be successful, ABC designs should allow maximum opportunities for Executive Summary

2the general contractor to do its own prefabrication, as there is reluctance among contractors to outsource much work to precasters. In this regard, the R04 team has determined that ABC sys- tems should be • As light as possible, • As simple as possible, and • As simple to erect as possible. To get the maximum advantage possible from the speed of on-site construction with prefab- ricated bridge installations, consideration should be given to using complete prefabricated bridge systems, including foundations and substructures. In many cases, foundation and sub- structure construction is the most costly and time-consuming part of constructing a bridge. This project provides design standards for complete prefabricated bridge systems, including super- structure and substructure systems and foundation strategies for shallow and deep foundation systems in the context of ABC projects. A key objective of this project is to identify impediments and obstacles to greater use of ABC and seek solutions to overcome them. These challenges can be met and successfully addressed if owners, designers, and contractors innovate incrementally and collaboratively. Building on pre- vious experience and constantly pushing the envelope will result in continued successes. Project R04 involved three distinct phases performed over a period of 4 years. Phase I, consist- ing of Tasks 1 through 5, was completed in November 2009. In this phase, the team collected extensive data on ABC projects and identified current impediments and challenges to 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 subjected to critical evaluations in Phase II to identify concepts that could be advanced to stan- dard plans in Phase III. Work on Phase III commenced on January 1, 2011, and was completed in March 2012. A synopsis of project activities follows. The literature review consisted of gathering published data and reviewing innovative design and construction concepts that involved many project examples demonstrating different approaches to ABC. Sixteen ABC design concepts developed in the Phase I investigations included new concepts or adaptations of existing concepts that are proposed as solutions to various ABC problems. ABC design concepts have been classified into five tiers on the basis of 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: Significant reduction of overall project schedule by months or years. The work in Phase II incrementally winnowed the collected findings and ABC concepts from Phase I through screening and further evaluation. Phase II consisted of an engineering and con- structability evaluation of the concepts, as well as identification of obstacles to implementation of various Phase I concepts. These evaluations provided recommended ABC concepts and tech- niques that could be advanced to standard plans and field trials. Phase II proposed a short list of concepts that could be advanced to design standards and the implementation phase. From this short list, standard plans were developed for the most useful technologies that could be deployed on a large scale in bridge replacement applications. They included complete prefabricated mod- ular systems as outlined here: • Precast modular abutment systems 44 Integral abutments; and 44 Semi-integral abutments.

3• 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. Typical designs for superstructure and substructure modules have been grouped into the fol- lowing span ranges: • 40 ft ≤ span ≤ 70 ft; • 70 ft ≤ span ≤ 100 ft; and • 100 ft ≤ span ≤ 130 ft. To assist the owners and engineers with implementation of ABC, a goal was established to develop a set of standard conceptual details demonstrating the possibilities and limits of ABC erection technologies. Guidelines were also provided for conventional erection of ABC systems by using cranes. The erection concepts presented in the drawings were intended to assist the owner, the designer, and the contractor in selecting suitable erection equipment for the handling and assembly of prefabricated modular systems. Another task entailed identifying any shortcom- ings in the current AASHTO LRFD Bridge Design Specifications that may limit their use for ABC designs and making recommendations for addressing such limitations. The primary deliverable was recommended specification language for ABC systems, suitable for future inclusion in the LRFD Bridge Design Specifications. 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. Investigations of joint types and material options have identified full moment connection 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. The properties of UHPC make it possible to create small- width, full-depth closure pour connections between modular components. These connections may be significantly reduced in size as compared with conventional concrete construction prac- tice and could include greatly simplified reinforcement designs. A lab testing program was car- ried out at Iowa State University in Phase III of this project to further evaluate the performance of UHPC in ABC applications. The tests evaluated the strength, serviceability, and constructabil- ity of both longitudinal and transverse UHPC joints. The first ABC demonstration project under SHRP 2 Project R04 was completed in Phase III in late 2011. The project consisted of replacing the bridge located on US-6 over Keg Creek in Pottawattamie County, Iowa. The replacement structure is a three-span steel/precast modular bridge with precast bridge approaches. The principal objective of the project was to demolish and replace the existing bridge within the 14-day ABC period by using ABC standard plans developed in this project. A daylong Highways for LIFE (HfL) workshop, including a site visit, occurred during the critical accelerated bridge construction period and provided an opportunity to disseminate information to bridge owners from around the country. The workshop high- lighted the innovative design and construction features advanced by this project.