When the Interstate Highway System network was being built, the routes were mostly new facilities, and managing traffic through the construction zones was not a concern. Majority of those routes today are heavily congested and the cost to maintain traffic control through a work zone can vary anywhere from 10% in rural areas to 40% in urban areas of the total construction cost. In some high-mobility routes and lifeline networks, total closure to traffic flow during reconstruction for long duration is not feasible nor can it be tolerated. Then a facility owner is required to provide temporary detour route and/ or bridge, which increases the total project cost. In consideration of the added expenses to constructing
and they are in the critical path and control the construction schedule. When one considers the series of sequential work stages in building a bridge, that is, foundation, substructure, superstructure, and parapet, it requires several months to construct even a simple bridge. The use of prefabricated bridge elements and systems (PBES) built off the critical path enables a contractor to erect bridges in a matter of hours as opposed to months. The prefabricated elements or systems fabricated in a shop-controlled environment provide owners with much higher-quality products that last longer and cost less over the life cycle of these bridges.
7.2.1 Objectives of ABC
The main objectives of ABC to accelerated project delivery are the following: • To reduce the impact on delays to the traveling public
• To produce high-quality and durable products fabricated in shop-controlled environment • To enhance the work zone safety by minimizing exposure to both the motorists and construction
workers by reducing the amount of time it takes to complete a project
• To reduce the overall construction schedule to a fraction of the amount of time normally needed on-site
7.2.2 ABC Bridges Are Covered under the AASHTO LRFD Specifications
Bridges designed under the ABC are governed by the American Association of State Highway and Transportation Officials (AASHTO) Load Resistance Factor Design (LRFD) Specifications (AASHTO 2010a). Bridges erected using ABC techniques and materials used for the bridge elements are governed by the LRFD Construction Specifications (AASHTO 2010b). Roles and responsibilities for bridge own- ers, designers, contractors, and manufacturers are defined in these specifications.
7.2.3 Prefabricated Bridge Technology Enables Rapid Construction
During a 2004-U.S. sponsored technology scanning tour to Europe and Japan, a group of American engi- neers and the author have reported on several replacement bridges in urban areas that were erected in a matter of hours and reopened for traffic use after short weekend closures. The key factor in the success- ful implementation of ABC is the innovative use of PBES with its components fitting together like an erector set. This idea eliminates as much as possible the time-dependent related activities on-site when compared with the conventional construction method. For example, the sequence for constructing a concrete bridge begins with the foundation, then the footing, to be followed by the substructure (pier column and pier caps) and finally the superstructure (girder and deck) with the superimposed loads (parapets, sidewalks, and accessories), being the last elements to complete a bridge. And this is not all of it. For with each element, a contractor has to execute more sequential activities, that is, building the formwork, laying the reinforcing steel, pouring concrete, curing concrete from 7 to 14 days, stripping the formwork, and moving up to the next element or phase of work. Conventional bridge construction
traffic disruption, improve work zone safety, and minimize disruption to the environment. The use of PBES improves constructability using heavy lift equipment to quickly erect partial or completed bridge system. The use of PBES also offers higher-quality products because they are manufactured under con- trolled conditions and brought to the construction site ready for installation. When standard compo- nents are to be developed, PBES can lower production costs and will result in lowering the overall and life cycle costs. These sought-after benefits were reported by the 2004 technology scan team members on several projects successfully implemented in Japan and Europe.
ABC can enhance safety through the construction zones for both workers and the traveling public. Each year, the FHWA reported the number of highway deaths caused by traffic crashes within construc- tion work zones and the following is taken from their Work Zone Safety Fact Sheet: “Work zone safety is a growing roadway safety concern. In 2008, there were 720 work zone fatalities; this figure represents 2% of all roadway fatalities for the year. Over four out of every five-work zone fatalities were motorists. In addition, there are over 40,000 injuries in work zones” (FHWA 2011a).
7.2.5 Accelerating Project Delivery Has Become a National Initiative
The concept of accelerating the project delivery was first presented by the Transportation Research Board (TRB) in conjunction with FHWA and the AASHTO, Technology Implementation Group (AASHTO- TIG). Following the completion of two pilot workshops, one in Indiana and one in Pennsylvania, the originating task force, A5T60, passed the concept off to FHWA and TIG to further develop accelerating project delivery. The AASHTO-TIG team did a great job compiling the initial database consisting of design and construction details of projects using PBES. The database formed the basis for the posted information through the FHWA Web site at http://www.fhwa.dot.gov/bridge/.
In the early days of deploying ABC, FHWA undertook a two-prong process and helped several states deploy accelerated construction technology in their projects. The process involved deploying a team of highly experienced technical experts in numerous disciplines and working with the state agency goal own- ers to scope the project from conception through construction. This process aims at collapsing the time frames in various tasks that affect the project readiness before traffic flow is interrupted for construction staging. The second process focused on collapsing the bridge construction time frame. Once it is identified in the critical path, either PBES or prefabricated modular systems are used to quickly erect the structures.
The speed in which a bridge project can be delivered in a matter of hours is incredible and unheard of until the turn of the twenty-first century. The Utah Department of Transportation (UDOT) has been specifying ABC project delivery schedule as a standard requirement for their bridge replacement proj- ects after they have had great success in accelerating the I-15 corridor reconstruction that required replacing more than 140 bridges in Salt Lake City. Once again, they have delivered an impressive record of over a hundred ABC bridges over the past 4 years. Utah demonstrated that the total construction cost for ABC projects is becoming equal or less than conventional practice. Massachusetts DOT is following suit and advertised 152 construction projects with a combined construction budget valued at $1.013 billion in 2011 (MADOT 2011).
7.2.6 Definition of ABC
The official definition given to ABC has been published by FHWA. Some state DOTs have their own. Here are two definitions that captured some common processes, goals, and elements of ABC:
The FHWA (2011b) defines ABC as the use of innovative planning, design, materials, and con- struction methods to specifically reduce the onsite construction time and mobility impacts that occur when building new bridges or replacing and rehabilitating existing bridges.
The author worked with a team and developed a definition for the Oregon DOT ABC approach as a process that incorporates innovative technologies, contracting methods, design and construc- tion techniques and/or prefabricated elements and systems, to minimize impacts to the traveling public, local community and environment.
This means that any ABC method that utilizes prefabricated bridge elements combines elements into systems or moves a complete bridge span to quickly deliver a project and reopens the highway to traffic is acceptable. The timescale for acceleration can be a small fraction of the conventional construction delivery schedule or it can be as short as a matter of hours or over a weekend.
The FHWA has two time metrics for ABC—on-site construction time and mobility impact time. The on-site construction time is the period of time from when a contractor alters the project site location until all construction-related activity is removed. This includes, but is not limited to, the removal of maintenance of traffic, materials, equipment, and personnel. The mobility impact time is any period of time the traffic flow of the transportation network is reduced due to on-site construction activities. This metric further categorizes into five tiers:
• Tier 1: Traffic impacts within 1–24 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
A common reason to use ABC is to reduce the traffic impacts through the construction work zones or to avoid long detours. The traffic flow in the transportation network can be directly impacted by the disruptions caused by on-site construction-related activities. Most of past projects that provided incen- tives/disincentives for early completion were based on the time delay costs to mobility.
7.3 Decision-Making Frameworks
It is no mystery how a bridge replacement project shows up on the statewide transportation improvement plan or commonly known as STIP. Suffice to say that generally a bridge project is being programmed for replacement based on its structural deficiency or functionally obsolescence, freight mobility, and route priority with input from several stakeholders. When required by an emergency, which is becoming quite common in recent years, due to natural or man-made disasters (e.g., damage caused by earthquake,