bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of a Container-on-Barge Network Along the Texas Gulf Coast
Authors: Bomba Michael S. , Harrison Robert
Published: April 2007

Freight volumes in Texas and throughout the world have been increasing as a result of growing national economies and international trade. The use of intermodal containers to transport this freight presents the opportunity for a more efficient transportation system. Using barges to carry containers could diminish roadway congestion, reduce fuel consumption and emissions, increase shipper options, and expand the reach of smaller ports. Although a number of benefits could be realized from container-on-barge (COB) service, the feasibility of a COB network along the Texas Gulf Coast remains less clear. At present, the likelihood of a COB network is slight because the hindrances are daunting: the lack of infrastructure and equipment; inadequate distribution of population along the Texas Gulf Coast; only a few navigable inland waterways, with none serving a major population center outside Houston; transport times that are incompatible with many manufacturers’ needs; a history of failed attempts for COB companies; intense competition from railways; unclear costs for serving ports without container infrastructure; and a limited number of participants due to restrictions of the Jones Act. Opportunities may exist, however, for a COB operation to exploit the substantial amount of industrial activity along the Texas Gulf Coast and the inefficiencies in the existing supply chain. Growing U.S. trade with Mexico might also offer some possibilities for COB services, but the recent trend has been toward Texas receiving a diminishing share of the value and weight of containerized commodities being moved from Mexico.
Development of an Inland Marine Transportation Risk Management Information System
Authors: Dobbins James P. , Abkowitz Mark D.
Published: April 2007

Historically, inland marine transportation has been one of the most efficient and reliable modes of commercial freight transportation. However, hazardous material shipments have become more common on inland waterways, creating concerns about the dissemination of shipment information to land-based emergency responders immediately following an incident. Marine transportation accidents have demonstrated that a spill involving hazardous materials near a major urban area can have devastating consequences. For these reasons a prototypical decision support system for inland marine transportation risk management has been developed. The system is designed to support real-time response as well as planning decisions such as risk resource allocation and evaluation of potential response strategies. It can be applied to barge accidents as well as counterterrorism planning activities. The system is based on the integration of geographic information systems (GIS), database management systems, Global Positioning Systems, and the Internet. In the event of an incident, this system enables en route responders to view incident details via an Internet GIS map service. The map service contains data that describe land use, population, and dispersion results for air and surface water at downstream intakes. To illustrate system capability, a recent accident is re-created to show how the response could have been improved with system access. A case study showing planning applications is also provided.
Innovative Transshipment Technologies: Implementation in Seaports and Barge Terminals
Authors: Ballis Athanasios , Stathopoulos Antony
Published: April 2007

The industry as well as the European Commission has launched a number of initiatives that, when brought to fruition, will raise the level of competitiveness of seagoing and inland waterway transport modes. These initiatives include the development of new technologies for the achievement of better vessel turnaround times and faster cargo flows. The scope of this work is to present the innovative concepts and technologies (in pilot, study, or even conceptual phase) that have been investigated for implementation in European seaports and barge terminals. The presentation includes a technical description of each system, identifying its structural elements and stressing its unique characteristics. Finally, a decision table is formulated to assist selection based on a number of criteria—loading unit type, productivity, throughput, compatibility with existing transshipment forms, automation level, and implementation stage.
Ship Safety Issues Involving Elderly or Disabled Passengers
Authors: Marin-Lamellet Claude , Minguy Jean-Luc
Published: April 2007

The aim of the Investigation into the Employment of Handicapped Persons in the Maritime Industry (the HANDIAMI project funded by the European Commission DG VII Task 38 Waterborne Transport) is to produce a number of concrete recommendations concerning the safety (evacuation procedures) of passengers on board car ferries who are elderly or have disabilities, and the accessibility available to them. A discussion is presented on issues concerning the main differences between high-speed and traditional ferries and the safety management of passengers in an emergency situation. There is a concentration on how an evacuation of elderly or disabled passengers is carried out. The approach used was based on focus groups, interviews, and observations. That led to a cross analysis of ship equipment and passengers’ functional abilities to highlight situations in which the crew will have to help compensate. Results are presented in tables that identify the independent relationship between functional disabilities and the ship’s infrastructure. The study undertaken showed that the safe evacuation of elderly and disabled passengers can be achieved through coordination of design, deployments, and training. Means of evacuation should be considered at the concept design stage, deployments should include representative sample populations including elderly and disabled passengers, and dedicated staff should be trained to specifically meet the needs of these passengers and to provide for their safe evacuation.
Application of Advisory Committee Recommendations on Passenger Vessel Access: Case Study
Authors: Chapman David S.
Published: April 2007

Passenger vessel access by people with disabilities will be facilitated by new standards developed by the U.S. Access Board under the Americans with Disabilities Act. The board has been assisted by the Passenger Vessel Access Advisory Committee (PVAAC), an assembly of representatives from the community of people with disabilities and the passenger vessel industry. PVAAC provided recommendations to the board in the form of guidelines for the design, new construction, and alteration of passenger vessels. Its December 2000 report addressed accessibility issues such as onboard and on–off accessible routes, emergency egress and alarms, toilet facilities, lodging, vehicle parking, and employee areas. PVAAC recommendations will be applied to an existing 1,000-passenger, 100-vehicle ferry vessel; and commentary will be provided on the resulting implications for ferry design, new construction, and alterations. The purpose is to further awareness of accessibility issues in passenger vessel design, new construction, and alterations; to highlight areas of opportunity for technology-assisted solutions; and to challenge the design community to develop workable and cost-effective solutions. PVAAC recommendations focus primarily on mid- to large-size passenger vessels (carrying more than 150 passengers), including vessels with overnight accommodations such as cruise liners and coastal excursion vessels. They also address smaller vessels, typically including types such as dinner cruise boats, whale watcher and fishing head boats, and small passenger-only ferries. A sampling of those recommendations will be addressed in addition to recommendations applied to the 1,000-passenger ferry.
Fast Vehicle Ferries for the Alaska Marine Highway System
Authors: Smith Gary , Van Slyke Robert J. , Harford Ken
Published: April 2007

For more than 40 years the Alaska Marine Highway System has maintained and operated a vehicle-ferry service that provides critical transportation needs throughout coastal regions of Alaska. It is now implementing plans to markedly improve ferry service in southeast Alaska and Prince William Sound. High-speed roll on/roll-off (ro-ro) ferries, or fast vehicle ferries, are an important part of these improvements. Such ferries have been used successfully in other areas of the world, but this is the first U.S. application of fast ferries for year-round ro-ro service. Why speed is important to economic improvements in Alaska transportation is discussed, some critical features of the fast vehicle ferry design are outlined, and insight into the decision-making process to date is provided.
Determining Critical Arcs for Collecting Real-Time Travel Information
Authors: Yang Baiyu , Miller-Hooks Elise
Published: April 2007

The problem explored is that of selecting a fixed number of arcs, representing a subset of the network arcs, referred to as information critical arcs (ICAs), which will be instrumented to collect real-time information, such as travel times, from a transportation network. The objective is to select the ICAs such that the greatest benefit (e.g., in relieving traffic congestion or providing optimal real-time path strategies for onboard route guidance) will be derived. A mathematical formulation of the problem of selecting the ICAs is given. Since the problem as described in this formulation is proved to be NP-hard (which infers that the problem belongs to a class of problems for which there is no known polynomial time solution), a heuristic is proposed, referred to as the critical arc set (CAS) heuristic, for solving the problem. Numerical experiments are conducted on the Texas highway network for assessing the ICAs selected by the CAS heuristic in the context of providing real-time path strategies. The experimental results indicate that for this network, good real-time path strategies can be obtained by instrumenting a fairly small number of the network arcs when the arcs are chosen by the CAS heuristic.
Internodal Delay Issues in Long-Range, Adaptive Traffic Forecasts
Authors: Horowitz Alan J.
Published: April 2007

Five mechanisms are examined by which traffic-controlled intersections can interact within a long-range traffic forecast, and the computational implications of each are explored. These mechanisms apply to networks that can adapt to changing travel behaviors over a long period of time. One mechanism relates to user-optimal equilibrium traffic assignment, which is a prerequisite for the remaining four: the chopping of traffic streams by signals, the smoothing of traffic streams by signs or meters, progressive signalization, and deployment of newly warranted traffic control devices. The inclusion of nodal interactions in traffic forecasts can substantially improve the precision of traffic forecasts but may require a very large increase in computational effort.
Dynamic Truckload Truck Routing and Scheduling in Oversaturated Demand Situations
Authors: Kim Yongjin , Mahmassani Hani S. , Jaillet Patrick
Published: April 2007

The problem considered is dynamic online truckload routing and scheduling with time windows operating in oversaturated conditions, that is, when the demand for service exceeds the system’s average capacity. The relationship between computation time and the solution quality, measured by system efficiency and response time, is discussed. A dynamic operation process for implementing various algorithms and procedures is described, with the aim of fully utilizing computational resources without wasting available time between successive demand requests. In addition, particularly when demand arrival rates result in oversaturated system conditions, application of intelligent acceptance and filtering decision procedures that consider system status and demand characteristics can result in significant operational benefits. Simulation experiments conducted to evaluate the relative performance of the proposed approaches confirm the existence of significant improvement potential in terms of both system efficiency and response time over previous approaches.
Uncoupled Method for Equilibrium-Based Linear Path Flow Estimator for Origin-Destination Trip Matrices
Authors: Nie Yu , Lee Der-Horng
Published: April 2007

Recently, models of the path flow estimator, in which origin–destination (O-D) matrices are determined according to the solutions of path flows, have been adopted for O-D matrix estimation with the equilibrium assignment assumption. This research suggests that the linear path flow estimator can be solved independently by employing the K-shortest-paths ranking algorithm. This intuitive and simple mechanism finds the user-equilibrium (UE) path columns and a simplex decomposition that specifies the most likely O-D trip matrix. A modified version of the K-shortest-paths ranking algorithm is presented to guarantee that all cyclic-free path columns satisfying the UE condition are recognized. The proposed method uncouples the conventional equilibrium-based O-D estimation model, in which the reproduction of the equilibrium flow pattern and the estimation of the O-D matrix are executed simultaneously and iteratively, into two simple individual problems. The uncoupled approach allocates flows directly onto the path that has been ensured as one of the optimal paths. The excess computational overhead, such as the repeated shortest-path search and redundant column operations brought by the column generation method, is thus avoided. According to the computational results, the presented approach is capable of reproducing the UE flow pattern perfectly while obtaining a substantially accurate O-D matrix with fewer iterations consumed.
Link- and Path-Based Traffic Assignment Algorithms: Computational and Statistical Study
Authors: Lee Der-Horng , Nie Yu , Chen Anthony , Leow Yuen Chau
Published: April 2007

The computational performance of five algorithms for the traffic assignment problem (TAP) is compared with that of mid- to large-scale randomly generated grid networks. The applied procedures include the Frank-Wolfe, PARTAN, gradient projection, restricted simplicial decomposition, and disaggregate simplicial decomposition algorithms. A statistical analysis is performed to determine the relative importance of various properties (network size, congestion level, solution accuracy, zone-node ratio) of the traffic assignment problem for the five selected algorithms. Regression models, which measure central processing unit time and number of iterations consumed by each algorithm using various factors and their combinations, are derived to provide a quantitative evaluation. Ultimately, the findings of this research will be useful in guiding transportation professionals to choose suitable solution algorithms and to predict the resulting algorithm performance in TAPs.
Analytical Dynamic Traffic Assignment Model with Probabilistic Travel Times and Perceptions
Authors: Liu Henry X. , Ban Xuegang , Ran Bin , Mirchandani Pitu
Published: April 2007

Dynamic traffic assignment (DTA) has been a topic of substantial research during the past decade. Although DTA is gradually maturing, many aspects still need improvement, especially regarding its formulation and solution capabilities under the transportation environment affected by advanced transportation management and information systems. It is necessary to develop a set of DTA models to acknowledge the fact that the traffic network itself is probabilistic and uncertain, and different classes of travelers respond differently under an uncertain environment given different levels of traffic information. The aim of this research is to advance the state of the art in DTA modeling in the sense that the proposed model captures the travelers’ decision making among discrete choices in a probabilistic and uncertain environment, in which both probabilistic travel times and random perception errors that are specific to individual travelers are considered. Travelers’ route choices are assumed to be made with the objective of minimizing perceived disutilities at each time. These perceived disutilities depend on the distribution of the variable route travel times, the distribution of individual perception errors, and the individual traveler’s risk-taking nature at each time instant. The integrated DTA model is formulated through a variational inequality approach. Subsequently, the solution algorithm for the formulation is discussed, and experimental results are given to verify the correctness of solutions obtained.
Schedule-Based Path-Finding Algorithms for Transit Trip-Planning Systems
Authors: Huang Ruihong , Peng Zhong-Ren
Published: April 2007

Many existing methods for transit assignment and path finding do not support schedule coordination in network search or optimization processes. Other methods do not provide adequate performance that meets the demands for Internet trip-planning applications. Two schedule-based path-finding algorithms (forward search and backward search) are presented for the transit network, in which schedule coordination is an inherent feature. The forward-search algorithm finds the optimal path from an origin to a destination with a planned departure time, and the backward-search algorithm finds the optimal path for an expected arrival time at the destination. In addition, a non-schedule-based minimal-transfer-path algorithm for the transit network is also developed, which is capable of accommodating more path optimization criteria for sophisticated path finding. Facilitated by a uniquely designed network structure based on a geographic information system and an objectoriented data model, these algorithms demonstrated good performance in path finding on a dynamic transit network. These algorithms have been implemented in an Internet transit trip-planning system in the city of Waukesha, Wisconsin.
Heuristic Algorithms for Solving Hazardous Materials Logistical Problems
Authors: Zografos K. G. , Androutsopoulos K. G.
Published: April 2007

Consideration of risk as a criterion for selecting hazardous materials distribution routes contributes substantially to the reduction of accident probability and the severity of accident impacts. Moreover, optimum deployment of emergency response units ensures an immediate response to a hazardous materials accident and consequently contributes significantly to the reduction of accident impacts. Vehicle routing and emergency response facility location are two of the most frequently faced logistical decisions in hazardous materials distribution management and emergency response planning, respectively. In particular, hazardous materials transportation can be defined as a bi-objective vehicle routing problem with time windows since risk minimization accompanies cost minimization in the objective function. Furthermore, the emergency response unit location problem aims at locating a set of response units to minimize the total response time and distribute the emergency response workload equally among them. The complexity of these two problems causes a heavy computational burden for their solution, especially in cases of large-scale distribution networks. Two new heuristic algorithms are presented for solution of the bi-objective vehicle routing and scheduling problem and the emergency response facility location problem. The algorithm for the hazardous materials routing problem was applied to several benchmark problems and provided results superior to those of other competing algorithms. The algorithm for the emergency response problem was applied to several case studies and provided near-optimal solutions.
Emergence of Private Advanced Traveler Information System Providers and Their Effect on Traffic Network Performance
Authors: Oh Jun-Seok , Jayakrishnan R.
Published: April 2007

The emergence of supply-side competition in the advanced traveler information system (ATIS) industry and marketability of private ATIS service are examined. An architectural model in which the ATIS companies collect network information from their subscribers while providing them with real-time traffic information is described. A simulation study on competition and cooperation among multiple private and public information agencies follows. This study focuses on analyzing the interaction among information agencies and the effect of this interaction on traffic system performance.
Diagnostic Methodology for the Detection of Safety Problems at Intersections
Authors: Kononov Jake , Janson Bruce N.
Published: April 2007

There is an established consensus among traffic safety researchers that a nonlinear relationship exists between traffic exposure and safety. This relationship is reflected by the safety performance functions (SPFs) calibrated for various classes of roads and intersections. One of the main uses of SPFs is to identify locations with potential for accident reduction. While this application is certainly important, the use of SPFs provides no information related to the nature of the accident occurrence. Without being able to relate accident frequency and severity to roadway geometrics, traffic control devices, roadside features, roadway condition, driver behavior, or vehicle type, it is not possible to develop effective countermeasures. A methodology was developed to provide guidance in diagnostics of safety problems, recognition of accident patterns, and development of appropriate countermeasures. Considering that traffic accidents can be viewed as random Bernoulli trials, it is possible to detect deviation from the statistical process by computing observed cumulative probability for each of the accident characteristics. Detection of an accident pattern at an intersection suggests the presence of an element in the roadway environment that triggered a deviation from a random statistical process in the direction of reduced safety. Identification of such an element always provides a critical clue to accident causality.
Artificial Neural Networks and Logit Models for Traffic Safety Analysis of Toll Plazas
Authors: Abdelwahab Hassan T. , Abdel-Aty Mohamed A.
Published: April 2007

Little research has been conducted to evaluate the traffic safety of toll plazas and the impact of electronic toll collection (ETC) systems on highway safety, but analyses indicate that toll plazas do contribute to traffic accidents. Traffic safety issues related to toll plazas and ETC systems were studied using the 1999 and 2000 toll plaza traffic accident reports of the Central Florida expressway system. The analysis focused on accident location with respect to the plaza structure (before, at, after plaza) and driver injury severity (no injury, possible, evident, severe injuries). Two well-known artificial neural network (ANN) paradigms were investigated: the Multi-Layer Perceptron and Radial Basis Functions neural networks. The performance of ANN was compared with calibrated logit models. Modeling results showed that vehicles equipped with ETC devices, especially medium/heavy-duty trucks, have higher risk of being involved in accidents at the toll plaza structure. Also, main-line toll plazas have a higher percentage of accident occurrence upstream of the toll plaza. In terms of driver injury severity, ETC users have a higher chance of being injured when involved in an accident. Older drivers tend to have higher risk of experiencing more severe injuries than younger drivers. Female drivers have a higher chance of experiencing a severe injury than do male drivers.
Injury Severity Analysis with Variable and Correlated Thresholds: Ordered Mixed Logit Formulation
Authors: Srinivasan Karthik K.
Published: April 2007

An ordered mixed logit (OML) formulation is proposed to model injury severity, given a crash. The proposed formulation extends the ordered probit/logit models by accommodating variable, random, and correlated injury severity thresholds associated with various severity levels. The proposed model is calibrated using a sample from the 1996 National Automotive Sampling System General Estimates System data set. Chi-square tests indicate that the more general OML formulation provides a statistically superior representation of observed injury severity data than corresponding ordered logit models. Model results indicate that injury severity thresholds vary systematically depending on individual, traffic, crash-related, and vehicle characteristics. Further, significant unobserved variability in thresholds is found, and the thresholds are correlated within a given individual. The results suggest drastically increased chances of fatal injury due to certain factors including tripped rollovers and injuries sustained by moped riders. These findings suggest that targeting these drivers, behaviors, and conditions with suitable countermeasures including education, enforcement, or curfews is likely to result in substantial safety benefits. The model and results have important implications for developing effective safety countermeasures and more accurate assessment of their impacts.
Fractal Analysis of Track Geometry Data
Authors: Hyslip James P.
Published: April 2007

An ongoing FRA-sponsored research project at the University of Massachusetts has been exploring the use of fractal analysis of track geometry data for indicating track geometry condition, planning maintenance, and evaluating the cause of substructure-related problems. Results indicate that fractal analysis is able to provide unique numerical values (fractal dimensions) that characterize railway track geometry patterns, can discern different orders of roughness within track geometry data, and is effective for maintenance management by providing independent fractal parameters for trend analysis and geometry deterioration assessment. Fractal theory is discussed, and the usefulness of fractal analysis for quantifying railroad geometry data is demonstrated by highlighting key aspects of the research results. The relationship between track structure conditions and fractal dimensions for use in maintenance planning and condition evaluation is also discussed.
Corrosion of Reinforcing Steel in Drilled Shafts with Construction Flaws
Authors: Sarhan Hazem A. , O’Neill Michael W. , Simon Philip D.
Published: April 2007

The construction process for drilled shafts sometimes introduces structural flaws such as voids or soil inclusions within the shaft. In that case, the reinforcing steel loses concrete cover and comes in contact with the surrounding soil medium, which creates a favorable environment for corrosion. Corrosion of steel inside concrete, as well as in soil media, has been investigated in the literature. However, the specific case of steel passing through different media (concrete and soil) simultaneously has received little attention. The results of an experimental program designed to investigate the effect of two different media of substantially different pH values on the rate of corrosion of steel reinforcement in sand and clay soils and with different anode-to-cathode-area ratios are presented. Preliminary results suggest that galvanic currents driven by dissimilar media could increase the corrosion rate of exposed steel by 3.3 to 5.6 times, particularly in environments with otherwise low corrosion potential.
Filter Paper Technique for Measuring Total Soil Suction
Authors: Likos William J. , Lu Ning
Published: April 2007

An experimental program was conducted to investigate the noncontact filter paper technique for total suction testing. Calibration curves for seven different batches of Whatman #42 filter paper were obtained to evaluate the variation in the calibration characteristics from one batch of paper to another. Additional tests using salt solutions for controlling suction were conducted to evaluate the measurement uncertainty as a function of suction magnitude. Calibration curves for the various papers varied significantly from batch to batch. This variation can be as much as 11% for filter paper water content, which results in a potential measurement error as high as 92% for suction. Scatter in the measurements appeared to increase with decreasing total suction. At relatively high values of suction (32 000 kPa), the standard deviation for five independent measurements was as much as 11.6% of the mean. At relatively low values (270 kPa), the deviation appeared to increase to 23.2% of the mean. One hundred measurements over a wide range of values for an expansive clayey soil confirmed the observation that the scatter in the measurements increases as total suction decreases.
Measured Effects of Liquid Soil Stabilizers on Engineering Properties of Clay
Authors: Rauch Alan F. , Harmon Jacqueline S. , Katz Lynn E. , Liljestrand Howard M.
Published: April 2007

Stabilization of pavement subgrade soils and base materials has traditionally relied on treatment with lime, cement, and sometimes fly ash. Marketed as alternatives to these conventional bulk soil stabilizers, a variety of concentrated liquid chemical products are sold by several companies. Most transportation agencies, however, are hesitant to specify these nontraditional liquid stabilizers without reliable data to support vendor claims of product effectiveness. Standard laboratory soil tests were conducted to measure changes in the engineering properties of five clay soils when treated with three liquid chemical products. The tests involved three reference clays (kaolinite, illite, montmorillonite), two high-plasticity natural clays, and three representative liquid stabilizers (ionic, polymer, enzyme types). Tests were conducted on untreated control soil samples and on samples treated with each product at the suppliers’ recommended application rates. All of the test specimens were prepared in accordance with a specified 10-step protocol that allowed objective comparisons of the test results. Each treated and untreated soil was characterized in terms of the Atterberg limits, compacted unit weight, one-dimensional free swell potential, and undrained triaxial shear strength. Given some variation in the test samples, the test results did not show consistent, significant changes in the properties of these soils as a result of treatment with these three products. Higher application rates might yield more favorable results. Clearly, independent laboratory evaluations with project-specific soils are warranted before the use of these proprietary liquid stabilizers in the field.
Feasibility of Geosynthetic Inclusion for Reducing Swelling of Expansive Soils
Authors: Vessely Mark J. , Wu Jonathan T. H.
Published: April 2007

The feasibility of geosynthetic inclusion for reducing swelling of expansive soils was studied by performing laboratory soil-geosynthetic swell tests on an expansive soil. The test specimen measures 12 × 12 × 12 in., with a sheet of geosynthetic embedded horizontally at the midheight of the soil. To prepare the test specimen, the soil was first compacted, in 1-in. lifts, inside a wooden mold to the prescribed density and moisture content. The soil was then allowed to swell subject to wetting by soil suction. The vertical and lateral deformations of the specimen were monitored throughout the test. To assess the effect of geosynthetic inclusion, a test without geosynthetic inclusion was performed in otherwise identical conditions for comparison purposes. The test method and test results are described. On the basis of the test results, the feasibility of geosynthetic inclusion for reducing swelling of expansive soils in practical applications is addressed.
Stabilizing Fine-Grained Soils by Phosphate Electrogrouting
Authors: Alshawabkeh Akram N. , Sheahan Thomas C.
Published: April 2007

The results of a laboratory study demonstrate the significant potential of electrogrouting, a new method for stabilizing soft soils with relatively low hydraulic conductivity. The experiments reported show that migration of stabilizing ions through soil pore fluid under applied direct current (dc) electric fields can be substantial. The method can achieve a more stable soil (i.e., less compressibility and higher shear strength, among other property improvements) without causing significant volume changes. In the experiments reported, the effect of stabilizing Boston Blue Clay (BBC) samples using phosphate ions was investigated. Initially, batch tests were conducted by mixing BBC samples with specific volumes of phosphoric acid solutions prepared at different concentrations. An increase of as much as 280% over the initial strength was achieved at the highest concentration of the acid used (10% of concentrated phosphoric acid solution). From the success of these batch tests, electrogrouting experiments were conducted by placing the soil in special treatment cells and applying a constant voltage gradient for 2 weeks. Electrogrouting the BBC under 1 V/cm dc is 15 times faster than is injection under a unit hydraulic gradient and produced increases in shear strength across the soil, with the greatest strength gain (160% of the initial shear strength) occurring in the soil section near the cathode (negatively charged probe). Additional results show the effects of electrogrouting on soil compressibility. A detailed review is given of the considerations necessary to implement the electrogrouting method in the field.
Stabilization of Silty Sand with Nontraditional Additives
Authors: Santoni Rosa L. , Tingle Jeb S. , Webster Steve L.
Published: April 2007

A laboratory experiment was conducted to evaluate the stabilization of a silty- sand (SM) material with nontraditional chemical or liquid stabilizers. SM soil specimens were mixed with various stabilization products and compacted using a gyratory compaction machine to approximate ASTM D1557 moisture—density compaction. Each specimen was subjected to wet and dry testing following the designated cure period. Twelve nontraditional stabilizers were evaluated in this experiment, including acids, enzymes, lignosulfonates, petroleum emulsions, polymers, and tree resins. Additional specimens were stabilized with an asphalt emulsion, cement, and lime to provide a comparison with traditional stabilizers under the same mixing, compaction, and curing conditions. The analysis of the test data consisted of determining the average strength, in terms of sustained load, of three replicate specimens of each mixture. The average strength of the three replicates of each additive was compared with the average strength results of the remaining nontraditional additives, the traditional stabilization results, and a series of control specimens that were not stabilized. The results of the experiment indicate increased strength of some nontraditionally stabilized specimens compared with that of both the control series and the traditional stabilization alternatives. Other nontraditional stabilizers did not demonstrate significantly increased strength compared with the control series for the conditions of the experiment. Many of the stabilized specimens were highly moisture susceptible, indicating the potential for poor performance when they are exposed to adverse environmental conditions, whereas a few specimens demonstrated excellent performance when exposed to moisture. Specific product categories are recommended for stabilizing SM soils.
Effects of Gradation, Composition, and Degree of Compaction on the Mechanical Characteristics of Recycled Unbound Materials
Authors: Molenaar André A. A. , van Niekerk Andres A.
Published: April 2007

Recycling is a hot topic in the Netherlands. This implies also the recycling of waste resulting from the demolition of buildings and civil engineering structures. Since the late 1970s, reuse of old concrete and masonry as base course materials for roads is common practice in the Netherlands. Although such materials have been successfully used for more than two decades now, relatively little information is available on the effects of factors such as gradation, composition, and others. Knowledge about these factors is required, because the quality of the recycled materials varies from location to location and is fairly difficult to control. To gain this knowledge, a large research program was started at the Delft University of Technology into the behavior of unbound base course materials made from recycled concrete and masonry rubble in relation to factors such as gradation, composition, and others. The results indicate that indeed such factors have an influence on the mechanical characteristics. However, it is shown that the degree of compaction (DOC) is the most important of the influence factors. This is an important result for practice, because the DOC is far easier to realize and to control than are factors such as gradation and composition. The results have shown that good-quality road bases can be built from recycled concrete and masonry rubble.
Effects of Particle and Mix Characteristics on Performance of Some Granular Materials
Authors: Cheung Lam Wah , Dawson Andrew R.
Published: April 2007

Three types of aggregate—a dolomitic limestone, a granodiorite, and a gravel—were studied to investigate the relationship between the particle properties and their performance in terms of strength, elastic behavior, and resistance to permanent deformation. Particles of each material were assessed for their geometry at both coarse and fine scales. This was quantified using several different measures including particle shape, roughness factor, roundness, sphericity, surface friction characteristics, and angularity. Laboratory tests, using a large shear box (300 × 300 mm) and a large (280-mm-diameter) repeated-load triaxial apparatus, were carried out to understand the significance of the geometry of the particles as well as of their surface friction characteristics and the effect of grading and of compaction. Roundness and angularity are considered to be the major factors affecting ultimate shear strength and permanent deformation. The degree of compaction and consequent density also has a great effect on the shear strength and resistance to permanent deformation. However, an increase in surface friction and surface roughness tends to improve the resilient shear stiffness. A pavement trial on the three aggregates, 300 mm thick over a subgrade, was constructed. Subsequent trafficking indicated that the limestone and the granodiorite performed significantly better than the gravel. It confirms that high roundness and low angularity have a much greater impact on performance than does surface friction when rutting is the chief distress mechanism.
Wavelet-Based Three-Dimensional Descriptors of Aggregate Particles
Authors: Kim Hyoungkwan , Haas Carl T. , Rauch Alan F. , Browne Craig
Published: April 2007

Morphological characteristics of stone aggregates, including particle shape, angularity, and surface texture, have a significant impact on the performance of hot-mix asphalt materials. To accurately identify and quantify these critical aggregate characteristics, well-defined particle descriptors are essential. Moreover, because a large number of irregular particles must be assessed to adequately characterize an aggregate material, descriptors that can be quantified with automated machines are preferred. In processing true three-dimensional (3-D) data from a laser scanner, wavelet-based 3-D particle descriptors are proposed as a way to characterize individual stone particles. Aided by the multiresolution analysis feature of the wavelet transform, these descriptors provide a generalized, comprehensive, and objective way of describing aggregates. This approach was implemented in conjunction with an automated laser-profiling device built for rapidly characterizing the size and shape properties of aggregate samples. Tests with this equipment have produced data that show strong correlations between the wavelet-based particle descriptors and visual perceptions of the aggregate morphological properties. These results demonstrate that the wavelet-based approach is a promising method for quantifying these important aggregate properties.
Quantification of Coarse Aggregate Angularity Based on Image Analysis
Authors: Rao Chetana , Tutumluer Erol , Kim In Tai
Published: April 2007

Aggregate angularity affects the shear strength properties of asphalt concrete and granular base layers in pavements. It also improves aggregate interlock and load transfer properties of jointed concrete pavements. The development of a quantifiable index based on image analysis to characterize the angularity of coarse aggregate used in pavement layers is described. The new angularity index (AI) was developed as part of the University of Illinois Aggregate Image Analyzer, and the procedure was calibrated for two aggregate samples, rounded gravel and crushed stone, which possess the two extremes of particle angularity. A statistical study demonstrated that the AI computation technique is not only able to distinguish crushed stone from gravel but also is robust enough to give similar AI values regardless of the particle size and orientation. Furthermore, the crushed stone and gravel samples together with a 50–50 blend of the two samples by weight were tested for shear strength under triaxial loading conditions. The AI value computed for these samples could be correlated to the angle of internal friction and thus the shear strength properties of the samples. The AI distributions of representative aggregate samples from Illinois, crushed gravel, limestone, and dolomite, were also computed. The newly developed index has also demonstrated the capability to distinguish between crushed stone and crushed gravel samples. With this AI value as a measure of aggregate angularity, pavement engineers can objectively quantify the influence of aggregate angularity on asphalt concrete, portland cement concrete, and granular mix performance and thereby establish meaningful criteria relating aggregate properties to performance indicators.
Factors Affecting Air Traffic Controller Workload: Multivariate Analysis Based on Simulation Modeling of Controller Workload
Authors: Majumdar Arnab , Ochieng Washington Y.
Published: April 2007

Airspace capacity in a high-density air traffic network is determined by controller workload. Controller workload is primarily affected by the features of the air traffic and air traffic control (ATC) sector. Factors that affect controller workload are examined by, first, a review of the literature on this subject and then a multivariate analysis of the data obtained from simulations of a model of air traffic controller workload. This model, the European Airspace Model (EAM), has been widely used in European airspace planning. The results from simulations of five very different areas of European airspace are analyzed. In particular, the results of principal components analysis and factor analysis provide a valuable insight into the aircraft profile factors affecting controller workload.
Runoff Control in Porous Pavements
Authors: Ranieri Vittorio
Published: April 2007

A runoff model from porous pavements is presented that links the hydraulic conductivity ( kD) of porous pavement with the geometric characteristics of the road section and rainfall intensity ( I). The theoretical model has been tested in the laboratory with an original device that simulates rainfall on porous pavements and, at the same time, measures the depth of water over the impervious layer during the seepage motion. Based on the experimental data, a useful chart for porous pavement design is also presented. For every inclination ( i) of the impervious layer, the graph provides the value of the nondimensional ratio Hmax/L between the maximum depth ( Hmax) of the water table over the impervious layer and the length ( L) of the seepage path, in the function of the nondimensional ratio 4 I/k between rainfall intensity ( I) and permeability ( k). Data provided with this graph could improve porous pavement design (e.g., to assess the minimum thickness of an open-graded friction course needed to avoid surface runoff) usually based only on mechanical resistance determinations. If the chart is not used, to ensure the best flow conditions, the relation i2> 4I/k should be always verified.
Micromechanical Analysis of Viscoelastic Properties of Asphalt Concretes
Authors: Papagiannakis A. T. , Abbas A. , Masad E.
Published: April 2007

A methodology for relating the microstructure of asphalt concretes to their viscoelastic behavior is described. Imaging techniques are used to capture the asphalt concrete microstructure, and the finite element method (FEM) is used to model its stress-strain behavior in the time domain. Aggregates are modeled as linear elastic, and the binder is modeled through mechanistic models as either linear viscoelastic or nonlinear viscoelastic. The binder viscoelastic properties are input into the FEM algorithm by two methods: a built-in viscoelastic function and a user-specified material characterization subroutine. The latter handles non-linearity in an iterative piecewise linear fashion, whereby the mechanistic binder model parameters are updated as a function of the strain level. For each strain level, mechanistic models are fitted to describe binder viscoelastic behavior based on dynamic shear rheometer data. The two approaches used for specifying binder viscoelastic properties into the FEM algorithm were verified by comparing binder response predictions with direct measurements. Finally, the asphalt concrete micro-structure model was verified by comparing FEM predictions of dynamic shear modulus and phase angle with measurements obtained by using a Superpave® shear tester.
Application of Digital Image Correlation Method to Mechanical Testing of Asphalt-Aggregate Mixtures
Authors: Seo Youngguk , Kim Y. , Witczak Matthew W. , Bonaquist Ramon
Published: April 2007

The digital image correlation (DIC) method, a noncontact, full-field displacement measurement technique, has been applied to mechanical testing of asphalt concrete. A single couple charged device camera acquires images of an area of interest from a specimen in the undeformed and deformed states. These images are correlated to determine deformations, and advanced mathematical procedures are applied to these deformations to calculate strains. To verify the DIC measurements, vertical displacements for the middle and bottom sections of a specimen subjected to monotonic tension are compared with conventional linear variable differential transformer measurements. A series of DIC images captured during the monotonic and cyclic tests visualizes the evolution of the failure zone (i.e., the fracture process zone) at the crack tip. Also, it is demonstrated that the full-field measurement and post-processing nature of DIC allows a more accurate determination of the stress-strain behavior of the fracture process zone. The applicability of this method to a cylindrical specimen with a curved surface is also investigated by testing a 75-mm-diameter cylindrical specimen. Finally, the DIC method is extended to cyclic testing of asphalt mixtures with the aid of a synchronized image acquisition technique.
Identification and Forecasting of Key Commodities for Virginia
Authors: Brogan James J. , Brich Stephen C. , Demetsky Michael J.
Published: April 2007

County-level commodity flow data were commercially procured to describe freight flows into, out of, within, and through Virginia. With the use of these data, Virginia’s key commodities were identified and their flows were assigned to county-level origin–destination tables. Predictive equations of freight-generation and -attraction relationships for each of Virginia’s 15 key commodities were developed. Explanatory variables were investigated and defined, including sources. A strategy for developing regression equations using a series of weighted regressions was developed using a series of robust and stepwise regressions to minimize the effects of outliers. For each key commodity with a two-digit Standard Transportation Commodity Classification code, a set of generation and attraction equations was developed, including relationships for nonoutliers, first-order outliers, and second-order outliers. In addition, several socioeconomic variables were identified that significantly affect freight generation and attraction within Virginia. It was concluded that robust regression is an appropriate tool for modeling freight generation, especially when outliers are present in the data set.