CHAPTER 1

Introduction

This chapter provides essential context for the synthesis, including a topic overview, the objectives of the synthesis, and details on the project’s scope and methodology. It outlines the content that will be covered to address the study’s scope and highlights any key issues discussed. Additionally, the chapter defines terms used throughout the report and explains its structure.

Background

Between 1992 and 2015, departments of transportation (DOTs) decommissioned 31,803 bridges in the United States, an average of 1,272 bridges per year (Bektas and Albughdadi 2020). Some bridge replacement projects present unique challenges, such as location restrictions, mobility impacts, distinct design and geometry features, or environmental constraints. DOTs must evaluate various construction strategies and techniques for these complex scenarios, considering multiple factors in their decision-making processes. As these strategies evolve, documenting current practices, available guidance, and the lessons learned from past complex bridge replacements is essential to support DOTs in addressing future challenges and needs in similar projects.

Synthesis Objective

This synthesis documents the practices and decision-making processes used by DOTs for bridge replacements in complex scenarios. In this context, complex scenarios refer to replacements on critical arteries or remote roadways that require intricate and, at times, costly strategies and construction techniques. These projects must balance maintaining mobility, ensuring work zone safety, achieving construction quality, adhering to geometric constraints, managing material availability, mitigating environmental impacts, and staying within budgetary and schedule limits.

Synthesis Scope and Approach

Specific topics addressed in this synthesis include the following:

• Construction strategies and techniques DOTs use to construct bridge replacements;
• Factors and constraints DOTs consider when choosing the appropriate bridge replacement construction strategies and techniques; and
• Written policies, rubrics, guidelines, metrics, and tools DOTs use for bridge replacement decision-making in complex scenarios.

Information was gathered through a literature review, a survey of the DOTs, and interviews with selected DOTs to develop case examples. The synthesis is organized under the following chapters:

Literature Review

Due to the limited resources available for decision-making in complex bridge replacement scenarios, this synthesis includes a literature review of guidance documents from DOTs, FHWA, and NCHRP projects. Relevant documents were identified through the Transportation Research Information Documentation (TRID) database, supplemented by internet searches and DOT survey responses. The review revealed that while resources exist on general bridge replacement guidelines, construction techniques, procurement, and project delivery, there is a lack of specific documentation addressing methods and decision-making strategies for complex bridge scenarios. Key guidance documents on bridge design, construction, project development, alternative project delivery [APD; e.g., accelerated bridge construction (ABC)], alternative contracting methods [ACM; e.g., design-build (D-B)], and DOT bridge manuals were identified as most relevant to the scope.

Survey

The survey questionnaire was developed and distributed to the voting members of the AASHTO Committee on Bridges and Structures (COBS) in all 52 DOTs (50 state DOTs and those of Puerto Rico and Washington, DC). The majority of AASHTO COBS voting members are state bridge engineers. As illustrated in Figure 1-1, 47 DOTs participated in the survey (a 90% response rate). The results are summarized in Chapter 3. The survey and responses are included in Appendix A and Appendix B, respectively.

Case Example Interviews

Case examples from six DOTs (California DOT, Colorado DOT, Massachusetts DOT, Texas DOT, Washington State DOT, and Wisconsin DOT) were developed to illustrate in more detail the strategies, decision-making, and project delivery processes that DOTs use for complex bridge replacement scenarios (Figure 1-2). Responses from the survey and the findings from the literature review were used to identify DOTs that indicated the use of unique strategies or methods in the multiple-choice questions, DOTs with guidelines and experience with different replacement strategies or project delivery methods (PDMs), and agencies with unique buy-in strategies for complex bridge replacement projects. Then, among these DOTs, respondents willing to participate in a case study were identified, ensuring all four AASHTO regions were represented.

Summary of Findings

The synthesis’s key findings are summarized, highlighting observations on the current state of practice, identifying knowledge gaps, and offering suggestions for additional research. These insights provide a comprehensive overview of the current practice and potential areas for further guidance. This information is presented in Chapter 5.

Terminology

Words, definitions, and acronyms that are frequently used in this report, and which readers may not be familiar with or may prefer to have clarified, are provided in this section. These terms are essential for understanding the context, processes, and concepts discussed throughout the report. By offering clear and concise explanations, this section aims to ensure a consistent

understanding of the terminology used in the discussion of bridge replacement practices and decision-making in complex scenarios.

• Accelerated Bridge Construction (ABC) – “Accelerated Bridge Construction (ABC) involves utilizing innovative planning, design, materials, and construction techniques to safely and cost-effectively minimize the on-site construction time required for building new bridges or replacing and rehabilitating existing ones. ABC is commonly employed to reduce traffic disruptions, ensure the safety of travelers, and maintain the flow of the transportation network. Additionally, ABC addresses site constructability challenges, such as lengthy detours, expensive temporary structures, remote locations, and limited construction windows, offering practical and economical alternatives to traditional construction methods” (Culmo et al. 2011).
• Alternative Contracting Methods (ACMs) – “Contracting methods—including design-build, construction manager/general contractor, and alternative technical concepts—to accelerate project delivery, encourage the deployment of innovation, and minimize unforeseen delays and cost overruns” (D’Angelo et al. 2019).
• Alternative Delivery Method (ADM) – “A wide array of methods used by public agencies to deliver transportation project improvements. These methods include construction manager/general contractor, design-build, design-build-operate-maintain, design-build-finance, design-build-finance-operate-maintain, fee services, long-term lease concessions, and operations and maintenance. Also known as alternative project delivery” (D’Angelo et al. 2019).
• Alternative Project Delivery (APD) – “A wide array of methods used by public agencies to deliver transportation project improvements. These methods include construction manager/general contractor, design-build, design-build-operate-maintain, design-build-finance, design-build-finance-operate-maintain, fee services, long-term lease concessions, and operations and maintenance” (FHWA 2018). Also known as alternative delivery method.
• Bridge Bundling – “A defined set (or bundle) of bridges that are planned for preservation/preventive maintenance, rehabilitation, or replacement in a timely and efficient manner through a series of bridge bundling contracts with the support of various funding options and/or partnerships that may include a program completion time frame” (D’Angelo et al. 2019).
• Construction Manager/General Contractor (CM/GC) – “The agency procures professional services on a qualifications or best-value basis from a construction manager during the design phase to offer suggestions on innovations, cost and schedule savings, and constructability issues. Upon completion of the design or individual design packages, the contractor and agency negotiate a price for the construction contract (often verified by an independent cost estimator), and then the construction manager acts as a general contractor to complete construction. The contract can employ a guaranteed maximum price administered on a cost-reimbursable basis, unit price, or lump-sum contract” (FHWA 2018)
• Design-Build (D-B) – “A project delivery method that combines two, usually separate services into a single contract. With D-B procurements, agencies execute a single, fixed-fee contract (lump sum) for both architectural/engineering services and construction. The D-B entity—also known as a constructor—may be a single firm, a consortium, a joint venture, or other organization assembled for a particular project. D-B has been implemented using various procurement approaches, including qualified low bid and best value” (FHWA 2018).
• Design-Bid-Build (D-B-B) – “The traditional delivery method where the agency contracts separately for design and construction services, the bid is based on complete (100 percent) plans and specifications, and design and construction occur sequentially. D-B-B is typically a unit-priced contract, but it can also include lump-sum items” (FHWA 2018).
• Design-Build-Finance (DBF) – “A project delivery method where procurement is a single contract awarded for the design, construction, and full or partial financing of a facility. Responsibility for the long-term maintenance and operation of the facility remains with the project sponsor but could be included in a separate agreement. This approach takes advantage of the

• efficiencies of the design-build approach and also allows the project sponsor to defer financing either completely or partially during the construction period” (D’Angelo et al. 2019).
• Horizontal Skidding or Sliding (also known as bridge slide) – “The lateral sliding or skidding method is a technique used for moving and installing large bridge systems. In this method, the new bridge is constructed parallel to its final location on a temporary support frame equipped with rails. The bridge can then be moved transversely to its intended position using cables or hydraulic systems. This method also allows for minor vertical adjustments to be made to the bridge” (Culmo et al. 2011).
• Indefinite Delivery and Indefinite Quantity (ID/IQ) – “The ID/IQ method of contracting allows a project owner to procure an unknown quantity of supplies or services for a fixed time. As described in FHWA’s [interim final rule] IFR, 85 FR 72919 (Nov. 16, 2020), government agencies use this method when they cannot determine, above a specified minimum, the precise quantities of supplies or services that they will require during the contract period. Contracting agencies use other names for these and similar types of contracts, including [job order contracting] JOC contracts, master contracts, on-call contracts, area-wide contracts, continuing contracts, design-build push-button contracts, push-button contracts, stand-by contracts, and task order contracts” (FHWA 2022).
• Public-Private Partnership (P3) – “A contractual agreement between a public agency and a private entity that allows for greater private participation in the delivery of a transportation project. P3s include any contractual arrangement in which the private sector takes on more risk. P3 goals may vary from raising funds from the lease of an existing facility (brownfield) to constructing a brand-new facility (greenfield). P3s do not necessarily involve toll facilities. P3s traditionally include variations of design-build with one or more operate, maintain, and/or finance components [e.g., design-build-operate, design-build-finance-operate, design-build-finance-operate-maintain (DBFOM), availability-payment concession, and DBFOM concession] and could include other delivery methods such as construction manager/general contractor alliancing” (D’Angelo et al. 2019).
• Procurement Method – “The means used to select a vendor (contractor, designer, or other service). These include low bid, best value, and qualifications-based selection. Other less common methods include adjusted low bid, sole source, and emergency selection” (D’Angelo et al. 2019).
• Project Delivery Method (PDM) – “The comprehensive process used by an agency to deliver a project, which includes planning, programming, design, construction, and consideration of required operations and maintenance. These methods include design-bid-build, indefinite delivery/indefinite quantity, design-build (D-B), and public-private partnerships (P3s). P3s include D-B with operate, maintain, and/or financing components, e.g., design-build-operate, design-build-finance-operate, design-build-operate-maintain, and design-build-finance-operate-maintain” (D’Angelo et al. 2019).
• Progressive Design-Build (PDB) – “A variation of design-build that facilitates involvement of the design-build team during the earliest stages of the agency’s project development, ensuring they are part of the project team developing design solutions” (D’Angelo et al. 2019).
• Self-Propelled Modular Transporters (SPMTs) – “Self-Propelled Modular Transporters (SPMTs) are high-capacity, highly maneuverable transport trailers used in ABC. These transporters are self-propelled, meaning they do not require an external tractor to move them; instead, they utilize an onboard hydraulic power pack connected to hydraulic drive motors on several axles. The “modular” aspect of SPMTs refers to their ability to be connected both longitudinally and transversely to form larger transporters, with configurations often described in terms of ‘lines’ of wheel sets” (Culmo et al. 2011).