Practices for Ensuring the Smoothness of Concrete Bridge Decks (2022)

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3   This chapter describes the background information related to this study, the scope of the study, the study approach, the terminology used in the synthesis, and the organization of the synthesis. Background The ride quality of roads and bridge decks is important to users of the highway system. State Departments of Transportation (DOTs) use the International Roughness Index (IRI), which is a parameter to judge ride quality and to monitor the roughness level of state highway systems. Research studies have shown that IRI is related to the ride quality experienced by road users (Sayers and Karamihas 1998). The profile data of the pavement collected with an inertial profiler are needed to compute the IRI. In the 1970s, the National Bridge Inspection Standards (NBIS) were implemented to establish a unified method of collecting data on public highway bridges (Markow and Hyman 2009). State DOTs are required to perform biennial inspec tions of all public highway bridges. State DOTs must submit these data annually to the FHWA, which compiles them into the National Bridge Inventory (NBI) database. The NBI has enabled the FHWA to monitor bridge conditions and performance nationally, identify bridge improvement needs, and establish criteria for federal bridge funding for bridge projects (Markow and Hyman 2009). Although the condition of the bridge deck is a data element included in the NBI database, the roughness of the bridge deck or of the approach slabs is not a data element in this database. State DOTs keep track of the roughness of their highway network by collecting profile data on both wheelpaths of a travel lane, using an inertial profiler and then computing an IRI value from the collected data for each wheelpath. The average of the left and right wheelpath IRI values is referred to as the Mean IRI (MIRI), and is used to judge the ride quality. The MIRI values are stored in a state DOT’s pavement management system (PMS), typically at 0.1-mi. intervals. State DOTs use the MIRI data to evaluate the roughness of the pavement network, to identify projects for rehabilitation, and for budgeting purposes. The Federal Highway Administration has a requirement that state DOTs must annually submit to the Highway Performance Monitoring System (HPMS) MIRI data for the following roadways in their state (FHWA 2016): • National Highway System (NHS) roads, • Non-NHS freeways, expressways, and principal arterials, and • HPMS sections that are located on rural minor arterials. C H A P T E R 1 Introduction

4 Practices for Ensuring the Smoothness of Concrete Bridge Decks The MIRI data that are submitted can include the MIRI of bridge decks, but the segments that contain a bridge must be identified by a separate code. The MIRI data submitted to the HPMS are used to assess the condition of the nation’s highways by the FHWA and are summarized in a document called Highway Statistics that shows the quantity of miles associated with various MIRI levels (FHWA 2019). If a state submitted the MIRI of the bridge deck, that information is included in the mileage summaries. However, the MIRI of bridges is not included separately in the Highway Statistics document. Therefore, there is no national database or document that contains information about the roughness of bridge decks in the United States. It is well known that bridge decks and/or pavement-bridge interfaces have a high roughness that affects the ride quality experienced by highway users (Schleppi 2003). Overall, when travel- ing on a highway network, higher roughness is felt by highway users at bridges and pavement- bridge interfaces when compared to the roughness on pavements (Schleppi 2003). Rough bridge decks and rough pavement-bridge interfaces can result in • Reduced user satisfaction of the ride quality, • Safety issues related to controlling the vehicle, • Decreased life of the structure due to higher dynamic loads applied by vehicles, • Increased vehicle-user cost due to wear and tear of vehicles, and • Increased freight cost resulting from damage to goods. Ride quality of bridge decks and ride quality at pavement-bridge interfaces have not received the attention that the ride quality of pavements has received. The reason for this may be that the ride quality of bridge decks and approach slabs is not a data element included in the HPMS or the NBI database. In order to achieve a smooth bridge deck during construction, a specification is needed for the smoothness of the bridge deck. This specification needs to describe a method or a ride-quality index to assess the smoothness of the bridge deck that reflects the ride quality experienced by highway users. In order to construct smooth roads, many state DOTs specify the required smoothness level of a road in terms of the IRI. Many state DOTs apply a negative pay adjustment if the final paved surface is rougher than the specified threshold and a positive pay adjustment when the surface is smoother than the specified level. Scope and Approach of the Study There is a lack of information on procedures used by state DOTs to ensure that smooth bridge decks are constructed, on procedures that are followed by state DOTs to monitor the rough- ness of bridges in their highway network, and on procedures that are followed by state DOTs to maintain the smoothness of bridge decks over their life. The objective of this study was to document the state of the practice for concrete bridge decks followed by state DOTs in the United States for the following items: • Methods used to evaluate the smoothness of the bridge deck when constructed. • Procedures used to track the roughness of bridge decks over time. • Procedures used to maintain the smoothness of bridge decks over their life. This study was limited to concrete bridge decks. In some cases, an asphalt concrete (AC) over- lay is placed on the concrete bridge deck when the bridge deck has deteriorated. However, this study did not address practices followed by state DOTs for bridge decks that are being overlaid with AC.

Introduction 5   A survey of state DOTs in the United States was performed to gather information on the fol- lowing topics related to the smoothness of bridge decks when they are constructed: • Equipment used to assess or measure the smoothness. • The metric used to assess the smoothness. • The threshold of the metric used for construction acceptance. • Differences in methods used to assess smoothness based on the length of the bridge. • Procedures to detect localized roughness. • Use of pay adjustment factors for smoothness. During the survey, information was also gathered on practices that are followed by state DOTs related to monitoring of the roughness of the bridge deck and maintenance of smooth- ness of bridges decks. Information about the following items was gathered during the survey: • If data on the roughness of bridge decks obtained from network level surveys are stored in a database. • If the roughness data are stored, the limits of the bridge for which roughness data are stored (i.e., bridge deck only or bridge deck and approach slabs). • If the roughness data are stored, whether the progression of roughness of bridge decks is monitored. • If the roughness data are stored, whether the roughness of a bridge deck is included in the decision trees for the maintenance or rehabilitation of the bridge deck. • The type of maintenance or rehabilitation activities that are used for maintaining the smooth- ness of the bridge deck. The study also included the following: • Performing a literature review to gather background information related to roughness of bridge decks, equipment used to measure the smoothness of bridge decks, methods and ride quality indices that are used to assess the smoothness of bridge decks, and past studies that have been performed on bridge roughness. • Conducting interviews with six state DOTs to gather detailed information on the specification they use to ensure that smooth bridge decks are constructed. This information is presented as case examples in this synthesis. Appendix A includes the survey that was developed for this study. This survey was sent to the DOTs in all 50 states and the District of Columbia. The survey was sent to many of the state DOT representatives in the states that are participating in the Transportation Pooled Fund study TPF 5(063), Improving the Quality of Highway Profile Measurement. For the other states, the survey was sent to a person identified in the DOT who was a bridge engineer and a member of an American Association of State Highway and Transportation Officials committee or to other targeted individuals that work in the area of ride quality. The survey was conducted through a web-based program. As reflected in Appendix B, 39 state DOTs responded to the survey, which represents a response rate of 76%. State DOTs were selected to conduct interviews such that they represented DOTs where different equipment types were used to collect data to judge the smoothness of the bridge deck. Terminology In this synthesis, the terms “smoothness” as well as “roughness” are used. The term roughness implies a lack of smoothness. The term smoothness is typically used instead of roughness when addressing the ride quality of a newly constructed bridge deck.

6 Practices for Ensuring the Smoothness of Concrete Bridge Decks The definitions of the following key terms used in this synthesis are presented in this section and are specific to the context of this synthesis: • Blanking Band: A band having a specified width that is placed on the profile collected by a profilograph when computing the Profile Index (PI). A zero blanking band refers to a refer- ence line that is placed on the profile collected by a profilograph when computing the PI. • Certified Profiler: An inertial profiler that has demonstrated it can meet a repeatability and an accuracy criterion based on a specified threshold. • Certified Operator: An operator who has been certified by some agency as proficient in per- forming the following activities on the equipment that collects smoothness data—calibration of components in the equipment, performing calibration checks on the equipment, and oper- ating the equipment to collect data. In addition, the operator has demonstrated the ability to analyze the data collected by the equipment. • Contractor: Company that has been awarded a bridge construction project. • Department of Transportation (DOT): The agency that is responsible for the state-maintained highways and bridges in the state. • International Roughness Index (IRI): A statistic used to denote the amount of roughness in a longitudinal profile that is computed from the data collected by an inertial profiler. • Inertial Profiler: A vehicle that is equipped with an inertial profiling system that comprises height sensors, accelerometers, a distance measuring system, and a computer, which can pro- duce the longitudinal profile of a paved surface. • Localized Roughness: A location on a paved surface that has a high roughness level compared to the adjacent paved areas, which causes a poor ride quality. • Longitudinal Profile: According to AASHTO R57-14, “The vertical deviations of the pavement surface taken along a line in the direction of travel referenced to a horizontal datum.” • Mean IRI (MIRI): The average of the IRI values that are obtained for the left and the right wheelpaths. • Profile Index (PI): A statistic used to determine the amount of roughness in a measured longi- tudinal profile, which is computed from the data collected by a profilograph. • Profilograph: A device that has multiple wheels at either end of a truss or a beam with an additional wheel at the center that is used to measure the profile of a paved surface. A statistic called PI is computed from the collected data. • Rolling Straightedge: A rolling straightedge consists of a wheel or two wheels at each end of a beam, with another wheel at the center. The center wheel measures the deviations at the center of the beam with respect to the datum established by the wheels at the two ends of the beam. • Roughness: According to ASTM E867-06, “The deviation of a surface from a true planar sur- face with characteristic dimensions that affect vehicle dynamics, ride quality, dynamic loads, and drainage.” • Straightedge: A straightedge consists of a metal beam that is placed on a paved surface to evaluate the distance from the bottom of the straightedge to the top of the paved surface. Organization of the Synthesis This synthesis is organized into the following chapters and sections: • Chapter 1—Introduction. This chapter indicates the background information, scope and the study approach, terminology, and the organization of the synthesis. • Chapter 2—Literature Review. This chapter presents the information gathered from the litera- ture review. The following topics are addressed in this chapter: federal reporting requirements for bridges, bridge management systems (BMS), bridge preservation programs, differential settlement at the bridge-road interface, equipment used to measure the smoothness of bridges

Introduction 7   after construction, ride quality indices that are used as a metric to indicate the smoothness of bridges, and past studies that have been performed related to bridge roughness. • Chapter 3—State of the Practice. This chapter presents the information from the survey on practices that are followed by state DOTs to assess the smoothness of bridges after they are constructed; storage of roughness data on bridges that are collected during network-level surveys and their use; and maintenance and rehabilitation activities that are performed on the bridge deck to address roughness. • Chapter 4—Case Examples. This chapter presents the information obtained from interviews with personnel from six state DOTs that describe the details of the specification used by the DOT in each state to assess the smoothness of the bridge deck after construction. • Chapter 5—Summary of Findings. This chapter presents a summary of findings from the study, gaps in knowledge, and suggestions for future research. • References and Abbreviations and Acronyms. • Appendices. Appendix A includes the survey that was sent to the state DOTs, and Appendix B summarizes the responses to the survey received from the state DOTs.