bluuebunny/crossref_metadata_2025 huggingface dataset:
Corridor Approaches to Integrating Transportation and Land Use
Authors: Rooney Kathleen , Savage Karen , Rue Harrison , Toth Gary , Venner Marie
Published: December 2010

Transportation agencies nationwide are under pressure to help address a wider range of transportation issues than ever before in the United States. Many of them extend beyond traditional state department of transportation (DOT) activities and span of control. There is an interconnection between transportation and land use that the public and local decision makers do not often see. Yet the public frequently holds DOTs responsible for solving transportation problems resulting from local and regional land use decisions and preferred development patterns. The objective of this research is to identify and explore successful innovations in integrating transportation and land use planning for transportation corridors, with a focus on practices that could be transferred to other locations. A case study approach was used to identify projects that integrated, rather than merely linked, land use and transportation planning and decision making. This paper summarizes six case studies: Chicago Metropolitan Agency for Planning, Illinois; Envision Utah and the Mountain View Environmental Impact Statement, Utah; Gateway Route 1, Maine; NJFIT: Future in Transportation, New Jersey; UnJAM 2025 and Places29, Virginia; and MetroVision and Blueprint Denver, Colorado. The paper also analyzes practices and lessons learned, highlighting common themes among the case studies.
From Academia to Application
Authors: Bernardin Vincent L. , Conger Michael
Published: December 2010

This paper presents an overview of a new architecture for travel demand forecasting models. The new hybrid accessibility-based models are neither traditional trip-based models nor standard activity-based simulation models. Instead, they are a blend of aggregate and disaggregate component models offering much of the sensitivity typical of activity-based models but with more modest development and application costs. This paper presents results from the first full application of the new model design. It documents the experience of the Knoxville (Tennessee) Regional Transportation Planning Organization from the data collection and visioning stage to the stage of investing time and resources to develop the new model. Ultimately, some basic comparisons are made between the new hybrid model and the previous trip-based model. Some key innovations in the new model design are highlighted, making special note of added sensitivity to planning and policy variables. The paper also reports findings related to the effects of residence location on travelers' willingness to travel and the effect of psychological barriers such as river crossings and county lines on stop location choice.
Changing Assignment Algorithms
Authors: Florian Michael , He Shuguang
Published: December 2010

The mainstay method of equilibrium assignment methods is based on adaptation of the linear approximation algorithm. Practically all commercial software packages for transportation planning offer a version of this algorithm. In the early days of personal computing, when random-access memory (RAM) was limited, this method was the most appropriate one to use because it requires little intermediate storage. As personal computers became more powerful and RAM became plentiful, the drawbacks of the linear approximation method became evident to practitioners. A measure of convergence is the relative gap, which measures the relative difference between total travel time and total travel time on the shortest paths. Relative gaps of less than 10–4 are difficult to reach with this method. Alternative assignment methods, based on algorithms that have better convergence rates, are known and can obtain finer solutions. Changing to new algorithms would appear to be a trivial task; however, it is not the case. The issues related to changing assignment algorithms pertain to the uniqueness of equilibrium paths, flows, and times. Examples of the expected changes in results for both standard multiclass assignments and for one complex model, which is equilibrated with feedback procedures, are presented. An adaptation of the projected gradient with path flows is used to represent the modern algorithms, which can reach relative gaps of 10–6 or better. Differences in relevant results are relatively small. Nevertheless, practitioners are careful to reproduce results and may face a challenge to accept slightly different results with a faster converging algorithm.
Accelerated Procedure of Multiclass Highway Traffic Assignment for Maryland Statewide Transportation Model
Authors: Ye Xin
Published: December 2010

The Maryland Statewide Transportation Model (MSTM) under development contains 20 user classes in the highway assignment procedure, including three types of autos: single-occupancy vehicles (SOV), high-occupancy vehicles (HOV) with two passengers, and HOV with three or more passengers classified by five income levels: commercial vehicle, median trucks, heavy trucks, regional autos, and regional trucks. A comprehensive disaggregation of user classes aids in capturing differences in how the transportation network is used. For example, SOV drivers are not allowed to use HOV lanes; trucks cannot be driven on truck-prohibited lanes; drivers at various income levels make different decisions about using toll roads because of their different values of time. However, a large number of user classes impose substantial computational burden on the procedure of multiclass highway assignment. If the conventional algorithm is used, the time consumption for this procedure is approximately proportional to the total number of user classes. In this study, a novel algorithm proposed by Robert Dial in 2006 is used to transfer min-path trees from one user class to another in the procedure of multiclass traffic assignment. This algorithm made it possible to speed up the highway assignment procedure of MSTM by a factor of 5.87.
Modeling Framework for Evaluating Sensitivity of Airline Schedules to Airport Congestion Pricing
Authors: Hassan Ahmed , Abdelghany Khaled , Abdelghany Ahmed
Published: December 2010

This paper presents a modeling framework for evaluating the sensitivity of airline schedules to the congestion pricing of airports. The framework allows airport agencies and aviation management authorities to examine the effectiveness of airport pricing schemes in reducing flight delays at congested airports. The framework replicates airlines' schedule planning decisions in a free market as it considers the effect of applying time-varying landing fees and associated delay externalities. The framework adopts the concept of Wardrop's network equilibrium as the basis for modeling competition among air carriers. A hypothetical airline network with two competing air carriers is used to illustrate the capabilities of the developed framework. The results of the conducted experiments show the importance of considering the network effect in developing effective pricing strategies.
Estimation of Flight Delay Costs for U.S. Domestic Air Passengers
Authors: Baik Hojong , Li Tao , Chintapudi Naveen K.
Published: December 2010

Evaluating the economic value of flight delays has always been a keen interest of research groups as well as of federal agencies such as the U.S. Department of Transportation and FAA. However, because of the complexity of the question as well as the incompleteness of available data sets, the estimation of flight delay costs is considered a challenging task in practice. This paper presents a method for estimating domestic air passengers' delay costs incurred by flight delays in U.S. airports. A unique feature of the method is that the costs incurred by flight delays relative to the original flight schedules are imposed at passengers' final destination airports. The underlying assumption of this idea is that the opportunity costs (incurred from compromised business opportunities or personal affairs due to the delayed flights) happen at the destination airports, not at the transfer airports. To reflect the variability of flight delays, both average and 95th percentile flight delays are calculated at each airport and applied to estimate corresponding delay costs. In 2007, total domestic passenger delay cost was estimated at $5.2 billion and $8.7 billion for, respectively, average and 95th percentile gate arrival delays. Assumptions, data sets, and results from this study are summarized and compared with those from previous studies.
Automated Measurement of Wait Times at Airport Security
Authors: Bullock Darcy M. , Haseman Ross , Wasson Jason S. , Spitler Robert
Published: December 2010

An anonymous Bluetooth tracking system was deployed at the new Indianapolis International Airport in Indiana from May 8 to June 2, 2009, to measure the time for passengers (a) to move from the nonsterile side of the airport (presecurity), (b) to clear the security screening checkpoint, and (c) to enter the walkway to Concourse B on the sterile side. The maximum passenger transit time between these checkpoints was observed on Monday mornings at approximately 0600, when it could take passengers up to 20 min to transit the security queue and screening and to walk to Concourse B. Depending on the day of the week, this approach was demonstrated to sample between 5% and 6.8% of passengers. This modest sample size provides a more robust measurement of screening times than the current system of manually distributing time-stamped cards as passengers enter the queue and collecting them where passengers pass through the magnetometer. Furthermore, because the final passenger reference point used in this study is on the sterile concourse, it captures the time associated with passengers repackaging their belongings and redonning their shoes. The data from this pilot study suggest the feasibility of using an automated system to provide quantitative information to managers for more effective allocation of scarce resources, as well as providing the traveling public with necessary information about the amount of time they should allocate for transiting the security screening process. The paper concludes by suggesting that additional pilot studies should be performed at several airports with alternative checkpoint configurations to develop a consensus on best practices for locating sensors to measure passage times at airport security screening.
True Multimodalism for Mitigating Airport Congestion
Authors: Janic Milan
Published: December 2010

Continuous long-term growth of air transportation has created congestion and aircraft–flight delays at many large airports. In general, the most common long-term measure for managing and mitigating the congestion and delays at these airports has included building new airside and landside infrastructure capacity. Particularly in Europe, an additional measure has implied the transformation of some large airports into multimodal transport nodes, thus enabling other surface transport modes to take over more substantially a portion of the excessive airport demand. This has usually meant inclusion of these airports into conventional rail networks, high-speed rail (HSR) networks, or both. This paper deals with an analysis and assessment of the savings of airline and passenger delays and related costs of substituting comparable HSR services at a large congested airport for some short-haul flights. For such a purpose, the deterministic queuing model for quantifying these savings is developed. The model is applied to a large congested European airport with the use of the what-if scenario approach.
Macroscopic Tool for Measuring Delay Performance in National Airspace System
Authors: Zhang Yu , Nayak Nagesh
Published: December 2010

Airline delays lead to a tremendous loss of time and resources and cost billions of dollars every year in the United States. To explore solutions for reducing delay, it is essential to understand factors causing flight delays and also the network impact of delays at one airport in the National Airspace System (NAS). For air transportation planning and policy purposes, this study concentrates on providing answers from a macroscopic point of view without being distracted by volatile operational details. A set of multivariate equations is proposed to model daily average arrival delay at one airport, and another for the rest of the NAS. The model for the single airport considers independent variables such as deterministic arrival queuing delay, delay at other airports in the NAS, adverse weather (convective and local), and different demand management regimes. The model for the rest of the NAS considers arrival delay as a function of deterministic arrival queuing delay, arrival delay at the single airport, adverse weather (convective and local), and other factors. Observation of the interactions between these two models shows that they can be regressed with an econometric technique: two-stage least squares. This macroscopic framework of delay impact analysis can be used to investigate the network effect of capacity improvement or new demand management strategies at a single airport. Hypothetical scenarios are generated and the systemwide delay reduction is calculated. This is a powerful decision support tool for stakeholders to use in deciding how to allocate resources optimally and to reduce delays.
Flight Delay Propagation Impact on Strategic Air Traffic Flow Management
Authors: Churchill Andrew M. , Lovell David J. , Ball Michael O.
Published: December 2010

Despite recent decreases in air traffic, congestion is still at higher levels than it was several years ago. Because of this congestion and expected increases in traffic, strategic planning for daily operations in the air traffic system has taken on an increasingly important role. Weather typically has a strong influence in developing such plans, as it leads to degraded airport and airspace capacity, which in turn causes delays. However, many reported delays are induced by these initial effects. Thus, it is essential to understand the scope and impact of propagation of flight delays in a strategic setting. In this paper, delay propagation is examined over several years in spatial and temporal terms. Two models, each incorporating different levels of fidelity and flexibility, are applied in an effort to examine this phenomenon. The first model tracks individual aircraft as they operate several flights and explicitly separates the new delay from the propagated delay. The second model operates at a higher level by relating earlier and later delays at several airports. Results identifying the various impacts of delay propagation are reported for several airports and scenarios, and recommendations are made for incorporating these models and their output into strategic planning efforts.
Regional Cooperation, Coordination, and Communication between Airports during Disasters
Authors: Smith James Fielding
Published: December 2010

Regional cooperation, coordination, and communication between airports can promote preparedness and continuity of operations during disasters. Interviews at 20 U.S. airports led to workshops in South Florida, New England, and Minnesota, in which representatives of airports, airlines, local responders, state agencies, and federal agencies discussed needs, opportunities, and barriers to increased regional cooperation, coordination, and communication. Qualitative analysis of the discussions led to a number of recommendations. Increased regional cooperation, coordination, and communication between airports and between regional groups of airports and other responding or regulatory agencies are highly desirable goals. Different regions of the country have different methods in place, but none is fully optimized. Interstate mutual aid between airports has different issues from intrastate aid arrangements. Intrastate arrangements may need new state legislation to provide liability coverage and reimbursement. Airports in New England and the Midwest seem interested in the airport Disaster Operations Group (DOG) approach. In Florida, the Florida Emergency Management Agency already provides strong intrastate coordination between counties and local agencies; in New England, the primary interest is interstate. A yet-unformed national umbrella organization could coordinate the regional DOGs and serve as the Emergency Management Assistance Compact's aviation coordination function. The Transportation Security Administration, the Centers for Disease Control and Prevention, and FAA have current initiatives that will assist airports during disasters. FAA's Advisory Circular 150/5200-31C opens an opportunity to expand regional airport cooperation and airport–community preparedness. This study makes 11 specific recommendations to improve regional cooperation among airports during disasters.
Using Online Data to Explore Competitive Airline Pricing Policies
Authors: Mumbower Stacey , Garrow Laurie A.
Published: December 2010

Since the mid-2000s, the airline industry has seen volatile fuel prices, a record number of carriers ending service, and a merger between two major airlines. In a time of such turmoil in the industry, it is increasingly important to understand the relationship between airline consolidation and competitive pricing policies, because this relationship directly affects the formation of new airline policies associated with competition policy (antitrust), deregulation, and mergers. However, there is a lack of consensus about market concentration and its influence on airfares, mainly because of data limitations of past research. Given the emergence of online booking engines, there is a new opportunity to collect detailed fare data. This project uses disaggregate online airfare data to study the relationship between market concentration and pricing policies. The data set includes 62 markets that cover a broad range of market structures. A case study approach is used to analyze the data. Using disaggregate fare data, this study finds low price dispersion can be associated with both low and high levels of market concentration. As the day of departure approaches, price dispersion is observed to increase or decrease, depending on the market. Additionally, peak and off-peak periods demonstrate different pricing strategies. Markets with codeshares sometimes exhibit unusually high price dispersion.
Hybrid System Model of Air Traffic Controller Cognition
Authors: Huang Haomiao , Tomlin Claire J.
Published: December 2010

Increased automation in air traffic control has many benefits, but to incorporate advanced automation tools safely and effectively requires careful analysis of their impact on human controllers. The literature on cognitive psychology and human factors has produced many qualitative models that describe the cognitive processes of controllers as well as a variety of computational models that attempt to reproduce the way controllers make decisions. The work presented here uses these results to form a novel hybrid system framework for modeling human cognition and describes a model of air traffic controller cognition based on this framework. The thought process is modeled as a set of critical variables that represent the human controller's picture of a given air traffic situation, with the evolution of these variables described by a set of hybrid dynamics where the discrete variables correspond to different thought processes and cognitive tasks. The primary contribution of this paper is to place the cognitive model within the formal mathematical framework of hybrid systems theory, allowing verification and online estimation and control with the tools of hybrid systems.
Understanding Nonfiscal Barriers to Airport Development and Exploring Federal Policy Solutions
Authors: Favarulo Daniel
Published: December 2010

Airport development projects are vulnerable to an array of nonfiscal challenges that can significantly delay or prevent projects. Through a survey of 20 airports, this research paper identifies important nonfiscal barriers to airport development and analyzes their characteristics and potential effects on the development process. In addition, a thorough literature review as well as meetings with industry professionals and FAA staff was used to explore resulting challenges and examine potential federal policy solutions. Research findings have revealed that community opposition, political opposition, airport stakeholder opposition, land availability, and environmental requirements are the most frequent nonfiscal challenges to airport development. These nonfiscal challenges have resulted in a lengthy and highly complex process in which runway expansion projects take a significant amount of time to complete. The impact on the national aviation system warrants a serious commitment by the federal government to address these nonfiscal challenges. Specifically, the federal government needs to tackle these obstacles more aggressively by expanding programs and reforming policies. By acquiring a better understanding of the nonfiscal challenges to airport development and exploring federal policy solutions, aviation system planners can move closer to achieving capacity, safety, and environmental goals.
Effects of Cross-Frame Placement and Skew on Distortion-Induced Fatigue in Steel Bridges
Authors: Hartman Amanda S. , Hassel Heidi L. , Adams Chris A. , Bennett Caroline R. , Matamoros Adolfo B. , Rolfe Stanley T.
Published: December 2010

Because of detailing practices common before the mid-1980s, many bridges are highly susceptible to distortion-induced fatigue. This research explored the influence of cross-frame placement and skew angle in bridges subject to distortion-induced fatigue. Forty high-resolution, three-dimensional finite element analyses of a bridge with multiple cross-frame and skew configurations were performed to examine the relationships between skew angle, cross-frame placement, and stresses on distortion-induced fatigue susceptibility. Bridges with skew angles of 0°, 20°, and 40° and cross-frames spaced at 4.58 m (15 ft) and 9.15 m (30 ft) were investigated. Cross-frame configurations examined included staggered perpendicular to the girder line as well as parallel to the support skew. The analyses found maximum stresses in the web-gap occurred in positive moment regions but not necessarily in regions of highest differential deflection. In configurations with cross-frames placed parallel to the skew angle, maximum stress demand was in the top web-gap but it was in the bottom web-gap region when cross-frames were staggered. Increased spacing between cross-frames correlated with slightly increased maximum web-gap stresses for parallel-to-skew cross-frame arrangements and decreased maximum web-gap stresses for perpendicular-to-girder line cross-frame arrangements. Skew angle had a minimal effect on web-gap stresses in the bridge studied.
Development of a Technique to Improve Fatigue Lives of Crack-Stop Holes in Steel Bridges
Authors: Crain Josh S. , Simmons Gary G. , Bennett Caroline R. , Barrett-Gonzalez Ron , Matamoros Adolfo B. , Rolfe Stanley T.
Published: December 2010

A common technique to prevent the propagation of fatigue cracks in bridge girders is to drill crack-stop holes at crack tips. Stress concentrations at the crack tips are reduced and fatigue life of the bridge is extended. The size of the crack-stop hole needed to prevent further crack growth is determined by using known material properties and relationships developed through experimentation. However, these equations often result in a crack-stop hole diameter larger than can be practically drilled; physical limitations force crack-stop holes to be undersized in the field. To improve effectiveness of undersized holes to that of full-sized holes, a method is needed to strengthen undersized crack-stop holes. This study investigated the potential of a technique to improve the fatigue life of undersized, crack-stop holes. It uses piezoelectric actuators operated at ultrasonic frequencies to convert electrical signals into mechanical work. The technique produced residual compressive stresses of the same order of magnitude as those produced by static cold expansion. A suite of finite element models was created to quantify and characterize the residual stresses surrounding the cold-expanded, undersized, crack-stop holes. Results were compared with analyses in the literature.
Adjustment of Load and Resistance Factor Design Live Load Factors Using Recent Weigh-in-Motion Data
Authors: Sivakumar Bala , Ghosn Michel , Moses Fred
Published: December 2010

Traffic loads on bridges exhibit significant variations regionally, from state to state, and from site to site. Accounting for actual live loads in the bridge design process is important to improving the overall reliability and safety of bridges. In some cases, the code-specified live loads may underestimate traffic loading on a bridge. The current load and resistance factor design (LRFD) live load calibration is based on a biased sample of truck weights collected as part of an Ontario, Canada, truck weight survey conducted in 1975. In the past 35 years, truck traffic has significantly increased in volume and weight, which may necessitate adjusting the LRFD live load factors in certain cases on the basis of current truck traffic conditions. Although the quality and quantity of traffic data being collected by highway agencies has improved since 1975, it has not been used to update the bridge design loads. NCHRP Project 12–76 was initiated in 2006 to develop a set of protocols and methodologies using recent truck traffic data to update live loads for LRFD bridge design. Various levels of complexity are available using the site-specific truck weight and traffic data to calibrate live load models. One simplified calibration approach focuses on the lifetime maximum live load for updating the live load model or the load factor for current traffic conditions. Another, more robust, reliability-based approach for calibration is proposed in the protocols. The models are applicable for the design of bridge members, for both ultimate capacity and cyclic fatigue, and are implementable for both main structural members and the design of bridge decks.
Introduction to Rehabilitation of Bridges
Authors: Gutarra Louise Delgado
Published: December 2010

Many countries are giving increasing importance to rehabilitating structures, because replacing them is wasteful. There are few standardized methods and procedures to evaluate and rehabilitate an existing structure, however. Peru decided to use the manual load and resistance factor rating (LRFR), because Peruvian bridge structural designs have long used AASHTO specifications. In Peru, the LRFR manual is being applied cautiously in the evaluation of existing bridges. An application of the new standards for the Ochape Bridge located in the northeast of the country is illustrated. This information includes monitoring, reinforcement, and retrofit process control through the final stage. Peruvian engineers should be encouraged to share experiences in the assessment, rehabilitation, and reinforcement of existing bridges and thus enable Peru to refine and apply the LRFR manual according to local conditions.
Characterization of High Early-Strength, Self-Consolidating Concrete for Design of Pretensioned Bridge Elements
Authors: Kim Young Hoon , Trejo David , Hueste Mary Beth D.
Published: December 2010

Self-consolidating concrete (SCC) is an innovative construction material that can be placed into forms without mechanical vibration. Precast, prestressed concrete plants require that the concrete used to fabricate their structural members attain high early strength. High early-strength SCC could provide significant value for precast plants. However, the high early-strength SCC mixture constituents, proportions, and construction may affect the hardened properties, and SCC may not provide the same performance as conventional concrete. SCC and conventional concrete mixture proportions designed for precast, prestressed bridge elements were evaluated to characterize the associated mechanical properties, shear characteristics, bond characteristics, and creep. To assess the applicability of SCC in prestressed girder systems, four full-scale girder–deck systems containing conventional concrete and SCC precast girders were fabricated and tested. Results from this research indicate that the AASHTO Load and Resistance Factor Design Specifications can be used to estimate the mechanical properties of high early-strength SCC. With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for SCC girders with a compressive strength greater than 10 ksi (69 MPa). Bridge girder–deck systems containing relatively small (Texas Type A) girders containing high early-strength SCC exhibited similar flexural performance as bridge girder–deck systems with girders containing conventional concrete. Results indicate that the AASHTO equations for computing the nominal moment capacity, strand transfer length, and strand development length may be used for SCC girder–deck systems similar to those tested in this study.
Innovative Applications of Precast Concrete to Complex Bridge Projects in Colorado
Authors: Reese Gregg A.
Published: December 2010

Several recent urban bridge projects with long spans and complex geometry have been designed and built with a variety of innovative applications of precast concrete girder and deck slab construction. Concrete U-girders, cast in both curved and straight segments, are spliced and posttensioned to create a new alternative approach to complex bridge construction. The U-girder has created a cross section that can be cast in curved sections. Combining this development with spliced, posttensioned construction has created a new design option for complex interchange projects. The success of these projects, which are all in service, clearly demonstrates that commercially precast concrete products can be used to construct cost-effective, complex, long-span structures in high-profile applications where aesthetics and urban geometrics are a significant design consideration.
Moving Substrate in an Ephemeral Stream
Authors: Herrmann George R. , Cleveland Theodore G.
Published: December 2010

A case study concerns a small bridge site in an arid area where ongoing inhibition of the transport of bed load sediment has caused chronic problems and maintenance issues for many years. The crossing of Guadalupe Arroyo by US-62-180 exhibits many unusual and important characteristics that are seldom seen in one place. Guadalupe Arroyo is an ephemeral stream in a very arid area. The stream originates high on the east slopes of the Guadalupe Mountains of Texas, where the watershed is subject to rainfall generated by orographic lift. The stream traverses several miles of arid land and ultimately disappears into a dry lake. It is subject to severe flash flooding because of the slope and orographic effects of the mountains, and it apparently transports large amounts of widely graded material (silt to boulder sized). A bridge across this stream was constructed for US-62-180 in 1959. Since that construction, the stream has exhibited symptoms of instability in the reach around the bridge, manifesting as chronic, severe aggradation accompanied by widening, avulsion, and bank erosion. Evidence exists of large magnitude transport of very large particles on a regular basis, to the extent of requiring protection of the piles from boulder impacts. Maintenance forces have continually removed accumulated bed material from the bridge opening and the reach immediately upstream. A large lens of bed material has accumulated upstream and extends approximately 1,000 ft (305 m) from the bridge. This site presents a rare opportunity to study an extreme case of the inadvertent inhibition of the transport of bed material in an ephemeral desert stream by the construction of an otherwise ordinary and innocuous highway bridge.
Resonant Sensors for Detecting Corrosion in Concrete Bridges
Authors: Yousef Ali Abu , Pasupathy Praveenkumar , Wood Sharon L. , Neikirk Dean P.
Published: December 2010

A passive sensor platform was developed to detect the onset of corrosion in concrete bridge decks. The term “passive” is used to describe the sensors because they do not include onboard processing capabilities or sources of power. The sensors are powered and interrogated in a wireless manner by measuring the impedance through an external reader coil, which is magnetically coupled to resonant circuits within the sensor. The sensors are designed to be embedded in a concrete bridge during construction and interrogated periodically over its service life. Reinforced concrete slabs were subjected to long-term exposure tests to demonstrate the reliability of the prototype sensors. The middle region of each slab was exposed to alternating moisture cycles with saltwater. Sensors in this region indicated that threshold amounts of corrosion occurred, whereas sensors located in regions that were not exposed to saltwater indicated the absence of corrosion. At the conclusion of the tests, the sensor readings were confirmed by removing the concrete cover and examining the condition of the embedded reinforcement. One flaw in the initial design of the sensors, however, was that the transducing element (a corroding steel wire) passed through the epoxy potting that protected the circuit components. This configuration provided a pathway for contaminants to infiltrate the sensors, causing corrosion. To improve the durability of the passive sensors, a new configuration is being developed in which the corroding element is physically isolated from the resonant circuits within the sensor.
Thermographic Imaging of Subsurface Deterioration in Concrete Bridges
Authors: Washer Glenn , Bolleni Naveen , Fenwick Richard
Published: December 2010

The deterioration of concrete bridge components due to corrosion presents a significant challenge for bridge owners worldwide. Deterioration commonly develops at the level of embedded reinforcing steel because of the expansion of corrosion products and resulting stresses in the concrete. As a result, deterioration cannot be detected with visual inspection until it has progressed sufficiently to be manifest in spalling or advanced deterioration of the concrete. This paper presents the results of a study to develop thermal imaging (infrared imaging) for detection of subsurface deterioration. This nondestructive evaluation technique detects delamination on the basis of resulting perturbations in the heat transfer characteristics of the concrete, which are manifest as variations in surface temperature. The technique has the advantage of being applied from a distance and thus reduces access and traffic control requirements. However, it depends on certain environmental conditions to achieve thermal gradients in the concrete needed to detect subsurface deterioration. This study explored the effects of environmental parameters on the detectability of delamination in concrete. Specifically, the effects of diurnal temperature changes on the detection of damage in the soffit area of bridges are reported. Experimental studies and field testing were conducted. This paper focuses on guideline requirements developed through the research for the effective application of the technology in the field and describes experience with application of the technology for the detection of deterioration in a typical highway bridge.
Using Geophones for Nondestructive Evaluation of Full-Scale Bridges
Authors: Ragland William S. , Penumadu Dayakar , Williams Richard T.
Published: December 2010

Nondestructive damage identification for civil engineering structures has received the attention of many researchers over the past several years. Vibration-based damage detection is a nondestructive structural health-monitoring approach that focuses on changes in the dynamic characteristics of a structure as indicators of damage. All vibration-based damage detection techniques require high signal-to-noise vibration data for analysis; thus the sensors used to measure vibrations are an important consideration. The objective of this study is to demonstrate the use of inexpensive geophones for determining the modal parameters of bridges to be used with vibration-based damage detection techniques. A geophone is a velocity transducer commonly used by seismologists for subsurface exploration. Researchers typically use accelerometers to measure bridge vibrations. However, compared with geophones, accelerometers are relatively expensive, have lower sensitivity, and require additional electronics for signal conditioning. To validate the use of geophones for modal parameter identification, a simple beam experiment was conducted, and the results were compared with theoretical values and a finite element model. Modal parameters identified from a full-scale bridge test are presented, and the effects of parapet rails and temperature change on the bridge's modal parameters are discussed. For successful implementation of the proposed methodology in a remote, wireless approach, a solar-powered, cell phone modem–based data acquisition system is demonstrated. This study makes an important contribution because the cost of the sensors needed for implementation of vibration-based damage detection on a large scale is substantially reduced with the use of high-sensitivity geophones.
Mass Stabilization for Environmentally Sensitive Projects in Florida
Authors: Garbin Ed , Mann Joseph A.
Published: December 2010

US-1 is a two-lane highway and the main route to and from the Florida Keys. A hurricane preparedness and public safety plan included the Florida Department of Transportation's replacement of the drawbridge over Jewfish Creek with a fixed bridge and widening of the roadway north of the bridge. Before construction, the widening program included mass stabilization to improve the soft underlying soils, which consisted of 5 ft of granular fill placed over 10 to 15 ft of soft organic silt overlying limestone. The bridge approach embankments reached up to 20 ft in height. Safety was critical because the work took place adjacent to an active highway. The entire project was environmentally sensitive and required attention to spoil controls because the work was performed adjacent to water and wildlife. In another environmentally sensitive area, a new two-lane bridge was planned for construction on driven piling over a waterway in Port Everglades, Florida. The subsurface consisted of 3 to 4 ft of sand followed by 8 to 10 ft of peat, then limestone. The peat layer was unsuitable to support the mechanically stabilized earth (MSE) walls planned for the abutments. A mass stabilization program was conducted to improve the bearing capacity and limit settlement and to ensure global stability of the MSE walls. Considerations included the existing condition of soils contaminated by petroleum hydrocarbon and environmentally sensitive adjacent properties, including a manatee mating area. The mass stabilization construction methods and procedures, design considerations, quality control, equipment, and performance monitoring of these two environmentally sensitive bridge projects are discussed.
Assessment of Washington Avenue Bridge across the Mississippi River in Minneapolis, Minnesota, for Central Corridor Light Rail Transit
Authors: Milius John , Roy Sougata
Published: December 2010

Retrofit of the iconic Washington Avenue Bridge is proposed for the incorporation of light rail over the Mississippi River, a critical link in the 11-mi Central Corridor Light Rail Transit (CCLRT) Project connecting St. Paul and Minneapolis, Minnesota. The structure is a unique double-decker bridge carrying an upper-level pedestrian deck with an enclosed walkway and a lower-level vehicular deck with two roadway lanes in each direction. The CCLRT Project proposes to replace one roadway lane in each direction to accommodate the light rail transit. Considered nonredundant and fracture-critical, the existing superstructure consists of dual girder-floorbeam-stringer-type framing with two noncomposite and independent reinforced concrete decks. The retrofit proposes the installation of four new longitudinal trusses constructed within the existing superstructure cross section and a new full-width composite deck. Designed to match the stiffness of the existing girders, the new trusses effectively convert the existing dual two-girder system into an eight “girder” composite superstructure. Built in 1965, the bridge incorporated innovations new to the bridge industry at the time of original construction, namely, the use of high-strength quenched and tempered steel. Advanced analysis of the structure was performed to meet the following project goals: (a) provide a functional structure for its proposed usage including light rail, (b) provide a redundant superstructure, (c) provide a structural system reliable against fatigue and fracture, and (d) provide a structure that meets load and resistance factor design criteria for a 75-year design life.
Renovation of Structural Health Monitoring System for Seohae Bridge, Seoul, South Korea
Authors: Gil Heungbae , Park Jongchil , Cho Junsang , Jung Gyungja
Published: December 2010

After years of research and development, the structural health monitoring system for the Seohae Bridge was installed in 2000 in South Korea. This steel–concrete composite cable-stayed bridge has a main span of 470 m. To monitor the long-term structural behavior and anomalies of the bridge, the system was composed of hundreds of sensors, including accelerometers, anemometers, and strain gauges. These sensors were installed on critical elements of the bridge, such as the stay cables, a stiffening girder, and the main pylons. After the development and stabilization phase, which lasted almost a year, the system has been successfully operated and has helped in understanding the structural characteristics and long-term behavior of the bridge. After more than 9 years of operation, however, the system started to show signs of aging and deterioration. Some gauges and sensors have worn out and have become malfunctioning. To fix these problems and upgrade the system, the renovation work was planned and carried out with a budget estimated at US$2 million. The main goals of the renovation work were to optimize sensor deployments, improve graphical user interfaces, and deploy state-of-the-art sensors and technologies. Although the number and types of sensors were minimized, a monitoring system based on a global navigational satellite system was newly installed to monitor deformation and geometry change of the bridge.
Continuous Remote Monitoring of Structural Health for Life Extension of Uplift Bearing Assembly on Large Cantilever Truss Bridge
Authors: Kosnik David E. , Hopwood Theodore , Kotowsky Mathew P. , Corr David J. , Marron Daniel R.
Published: December 2010

A situation on a large cantilever through-truss bridge, the John F. Kennedy Memorial Bridge, which carries I-65 over the Ohio River at Louisville, Kentucky, provides significant opportunities for applying innovative health monitoring techniques to transportation infrastructure. One of four anchor bolts restraining an uplift bearing at one end of the bridge fractured as a result of corrosion fatigue; the fracture led to concerns about the continuing safety and serviceability of the compromised bearing assembly. Short- and long-term instrument-based monitoring systems were deployed on the bearing assembly to (a) characterize the behavior of the damaged bearing and its intact counterparts, (b) quantify the load transfer due to the retrofit, and (c) monitor the performance of the retrofit continuously for the long term. The monitoring strategy has been successful on all counts; in particular, during Part 3 the system detected a significant shifting of loads that was later confirmed to correspond to fracture of a threaded rod that had been used to replace the failed anchor bolt; this result showed the utility of continuous remote monitoring in detecting failures between inspections. This paper describes the instrumentation plan and strategies for data acquisition, communication, and autonomous operation used on the bridge. The data and implications for management decisions are also discussed.
Delaware's Indian River Inlet Bridge
Authors: Shenton Harry W. , Carson Patrick D. , Chajes Michael J. , O'shea Dennis , Kursinsky Craig
Published: December 2010

Plagued by a serious scour problem, the existing bridge over the Indian River Inlet in Sussex County, Delaware, will be replaced by a 1,750-ft cable-stayed bridge. The new bridge is being constructed under a design–build contract by the team of Skanska and AECOM. The bridge is due to open in summer 2011. As part of this project, a comprehensive structural monitoring system has been designed and will be installed on the bridge to aid in the long-term maintenance and operation of this significant structure. The concept and the design of the monitoring system were proposed by the Center for Innovative Bridge Engineering, University of Delaware. The system has been designed with the intent of providing quantitative data on the long-term performance of the bridge, which can be used to augment the traditional inspection program. The all-fiber-optic system will include 119 embedded and surface-mounted sensors that will measure strain in the deck and pylons; accelerations on the deck, pylons, and cables; deck inclination; chloride penetration in the deck; temperature; and wind speed and direction. Slow, gradual trends resulting from thermal effects and environmental factors will be captured by the monitor data, readings taken on the hour, every hour. Bridge response under intense live loads, such as heavy vehicles and high winds, will be recorded as event data. A series of baseline readings and diagnostic tests will be conducted once the bridge is completed and will be used for future comparisons. The paper presents an overview of the monitoring system and the monitoring program, a description of the way the data will be used, and the owner's perspective.
Constructability Considerations in Selection and Design of Drilled Shaft Foundations for Bridges
Authors: Brown Dan
Published: December 2010

The great strength and ductility of drilled shaft foundations can be used to advantage on bridge projects in circumstances that favor their construction. However, drilled shaft construction methods contain risks of construction difficulties that must be addressed in the selection and design of drilled shafts. Some aspects of design and specification of drilled shaft foundations that can lead to constructability problems are described, and practical solutions that may satisfy the structural design requirements and lead to improved economy and reliability are offered. Many constructability problems relate to concrete specifications, congested reinforcement, splices, and construction of the column–shaft connection. The extent of the potential issues and the range of effective solutions often are dictated by the construction methods needed to accommodate the specific ground conditions at the site.