bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Analysis of Robustness of Centralized and Distributed Network Route Control Systems in Incident Situations
Authors: Hawas Yaser E. , Mahmassani Hani S.
Published: August 2018

A procedure for providing real-time route guidance in congested vehicular traffic networks is described. The control procedure, implementable in a decentralized scheme, envisions a set of distributed local controllers in the network in which every controller can extract only limited information from detectors. The assignment logic is driven by informed local search procedures and heuristics. A simulation-assignment model was developed and used to assess the effectiveness and robustness of the procedure in dealing with normal as well as incident traffic conditions. A comparative study was undertaken to gauge the performance of the distributed control structure against a benchmark scenario of the time-dependent system-optimal logic in a centralized architecture. The assessment was conducted under various operational scenarios of different incident links, durations, and severity. The findings of the simulation-based experiments indicated that the distributed scheme is more robust than the centralized time-dependent scheme under incident conditions.
Dynamic Estimation and Prediction of Freeway O-D Matrices with Route Switching Considerations and Time-Dependent Model Parameters
Authors: Madanat Samer M. , Hu Shou-Ren , Krogmeier James V.
Published: August 2018

An enhanced Kalman Filtering algorithm for the dynamic estimation and prediction of freeway origin-and-destination (O-D) matrices is presented. The effects of traffic congestion and traffic diversion information on the O-D distribution pattern are explicitly captured through a behavioral model of route switching. Moreover, in view of the time-varying nature of traffic variables, the proposed algorithm updates the model parameters by using on-line traffic measurements. Preliminary simulation results demonstrate the importance of using time-dependent model parameters and accounting for the effect of traffic information in the estimation and prediction of dynamic freeway O-D demands.
Walking Distances to and from Light-Rail Transit Stations
Authors: O'Sullivan Sean , Morrall John
Published: August 2018

A quantifiable basis for developing design guidelines for pedestrian access to light-rail transit (LRT) stations is provided for planners based on observations in Calgary, Canada. Calgary's LRT system, which began operations in 1981, has been operating for long enough for walking patterns to and from its stations to become established. Interviews were conducted with 1,800 peak-hour LRT users about the origins and destinations of their LRT trips. Those who walked to or from a station were asked to point out on a map their approximate origins or destinations. The distances were then measured off the maps. Walking distance guidelines were developed for central business district (CBD), transfer and local stations. Catchment area maps were produced, and the relationship between reported walking time and measured walking distance was calculated. Also compared are the walking distances at LRT stations and the walking distances at bus stops. The research strongly indicates that people walk farther to reach an LRT station than a bus stop. Using bus walking standards would result in an underestimate of LRT walking distances by about half. For the city of Calgary the average walking distance to suburban stations is 649 m with a 75th-percentile distance of 840 m. At CBD stations the average walking distance is 326 m and the 75th-percentile distance is 419 m.
Field Studies of Pedestrian Walking Speed and Start-Up Time
Authors: Knoblauch Richard L. , Pietrucha Martin T. , Nitzburg Marsha
Published: August 2018

Today's traffic environment is not well adapted to the needs of the older pedestrian. Unfortunately, except in the case of children, little is known about the characteristics and behavior of pedestrians. Although the simple fact that older pedestrians walk more slowly than younger ones is easily supported by field data, existing data on walking speeds and start-up time (i.e., the time from the onset of a Walk signal until the pedestrian steps off the curb) have many shortcomings. A series of field studies was conducted to quantify the walking speed and start-up time of pedestrians of various ages under different conditions. Sixteen crosswalks in four urban areas were studied. Data were collected on walking speeds and start-up times relative to site and environmental factors, including street width, posted speed, curb height, grade, number of vehicle travel lanes, signal cycle length, pedestrian-signal type, street functional classification, crosswalk type, and channelization. Data on a subject group of pedestrians who appeared to be 65 years of age or older and a control group of pedestrians under age 65 were collected. Results indicate a broad range of walking speeds among pedestrians. The 15th-percentile walking speed for younger pedestrians (ages 14 to 64) was 1.25 m/sec (4.09 ft/sec); for older pedestrians (ages 65 and over) it was 0.97 m/sec (3.19 ft/sec). For design purposes values of 1.22 m/sec (4 ft/sec) for younger pedestrians and 0.91 m/sec (3 ft/sec) for older pedestrians are appropriate. Results also indicated that walking rates are influenced by a variety of factors, including the functional classification and vehicle volumes on the street being crossed, the street width, weather conditions, the number of pedestrians crossing in a group, the signal cycle length, the timing of the various pedestrian-signal phases, whether right turn on red is allowed, pedestrian signals, medians, curb cuts, crosswalk markings, stop lines, and on-street parking. However, for each of these factors, the effect on crossing speeds, although statistically significant, is not meaningful for design.
Analysis of Pedestrian Conflicts with Left-Turning Traffic
Authors: Lord Dominique
Published: August 2018

The interaction between pedestrians and left-turning vehicles at signalized intersections are examined using the traffic conflict technique. Paramount was a comparison of the safety of left turns at two types intersections: T-intersections and X-intersections (cross-intersections). Previous research has indicated that T-intersections are more dangerous to pedestrians. In preparation for the comparison several traffic conflict definitions and their applications to pedestrians were evaluated. Use of a laptop computer for data collection was tested. Eight sites taken from intersections in Hamilton, Ontario, Canada, were selected. A conflict recording methodology was developed for T-intersections and X-intersections that consisted of recording data at various times along the paths of pedestrians and left-turning vehicles, and recording traffic conflicts. Two computer programs were written for the data collection process: one for vehicles and one for pedestrians. Several statistical tests to relate traffic conflicts and the expected number of accidents were performed. These tests indicate that a positive correlation between traffic conflicts and expected number of accidents exists; they also suggest that T-intersections have a higher traffic conflict rate than X-intersections.
Pedestrian Crash Types: 1990s Update
Authors: Stutts Jane C. , Hunter William W. , Pein Wayne E.
Published: August 2018

A report is given on an application of the NHTSA pedestrian crash-typing system for categorizing pedestrian–motor-vehicle crashes according to the specific sequence of events leading up to individual crashes. Results are based on a recent sample of over 5,000 pedestrian crashes drawn from six states and reported by police. Over 80 percent of the pedestrian crashes fell into the following crash type categories: vehicle turn or merge (9.8 percent), intersection dash (7.2 percent), driver violation at intersection (5.1 percent), other intersection (10.1 percent), midblock dart or dash (13.3 percent), other midblock (13.1 percent), not in roadway and waiting to cross (8.6 percent), walking along roadway (7.9 percent), and backing vehicle (6.9 percent). These crash types were found to vary according to the characteristics of the pedestrian and factors of the location, environment, and roadway. The process of typing pedestrian crashes can be a valuable tool at both the state and local level for developing more highly effective countermeasures to reduce the annual toll of nearly 100,000 pedestrians killed and injured in traffic crashes.
Factors Influencing Nondiscretionary Work Trips by Bicycle Determined from 1990 U.S. Census Metropolitan Statistical Area Data
Authors: Baltes Michael R.
Published: August 2018

An extensive range of factors that may have some influence on the selection of the bicycle as the mode for work trips is explored using data from metropolitan statistical areas (MSAs) extracted from the 1990 U.S. census. Only data extractable from the census were used for analysis. The sample included 100 percent of MSAs in the United States. Regression analysis was used to provide insight into the contributory factors. The dependent variable used in the analysis was the percentage of the modal split captured by bicycle for work trips in each MSA. The findings from the analysis indicated that levels of bicycling vary greatly from metropolitan area to metropolitan area within the United States. MSAs with relatively high levels of nondiscretionary bicycling appear to have urban densities that promote shorter trips, relatively temperate year-round climates, and a large proportion of students, particularly college students. The strongest finding reinforces what is already well known about nondiscretionary travel by bicycle: commuting to work by bicycle is a behavior most prevalent in MSAs that have unique communities within their statistical boundaries, such as universities or colleges. According to 1990 U.S. census data, this unique type of MSA has the highest levels of bicycling.
Mechanistic-Empirical Flexible Pavement Design: An Overview
Authors: Thompson Marshall R.
Published: August 2018

Activities associated with the development of the revised AASHTO Guide for the Design of Pavement Structures (1986 edition) prompted the AASHTO Joint Task Force on Pavements (JTFOP) recommendation to immediately initiate research with the objective of developing mechanistic pavement analysis and design procedures suitable for use in future versions of the AASHTO guide. The mechanistic-empirical (M-E) principles and concepts stated in the AASHTO guide were included in the NCHRP 1-26 (Calibrated Mechanistic Structural Analysis Procedures for Pavements) project statement. It was not the purpose of NCHRP Project 1-26 to devote significant effort to develop new technology but to assess, evaluate, and apply available M-E technology. Thus, the proposed processes and procedures were based on the best demonstrated available technology. NCHRP Project 1-26 has been completed and the comprehensive reports are available. M-E flexible pavement design is a reality. Some state highway agencies (Kentucky and Illinois) have already established M-E design procedures for new pavements. M-E flexible pavement design procedures have also been developed by industry groups (Shell, Asphalt Institute, and Mobil). The AASHTO JTFOP continues to support and promote the development of M-E procedures for pavement thickness design and is facilitating movement toward an M-E procedure. The successful and wide-scale implementation of M-E pavement design procedures will require cooperating and interacting with various agencies and groups (state highway agencies, AASHTO—particularly the AASHTO JTFOP, FHWA—particularly the Pavement Division and Office of Engineering, and many material and paving association industry groups). It is not an easy process, but it is an achievable goal.
Overview of South African Mechanistic Pavement Design Method
Authors: Theyse H. L. , De Beer M. , Rust F. C.
Published: August 2018

A historical overview of the South African mechanistic pavement design method, from its development in the early 1970s to the present, is presented. Material characterization, structural analysis, and pavement life prediction are discussed, and stiffness values are suggested for a range of materials in the absence of measured values. The modes of failure for these material types include the fatigue of asphalt material, deformation of granular material, crushing and effective fatigue of lightly cemented material, and deformation of selected and subgrade material. The critical parameters and transfer functions for these material types and modes of failure are discussed and included in the pavement life prediction process.
Updating Pavement Design Procedures for New York State
Authors: Chen Hong-Jer , Bendaña Luis Julian , McAuliffe Dan E. , Gemme Raymond L.
Published: August 2018

New York's effort in adapting concepts from AASHTO's pavement design guide as a basis for a revised state design procedure for thickness of new and reconstructed pavements is summarized. The rationale for this revised procedure was to design more durable pavements and reduce life-cycle costs. New York's past pavement design practice and the background for the revisions are briefly described. A sensitivity analysis was conducted to identify how AASHTO design variables affect pavement thickness. Past performance of selected New York pavements was also studied. The rationale is discussed for determination of appropriate design variables, based on the sensitivity analysis, performance studies, and reviews of past and current practice. Also described is the justification of other design features, such as 50-year design life, granular subgrade, permeable base, edge drains, shorter slabs, maximum and minimum pavement thicknesses, and new dowel and tie-bar designs. Development and implementation of New York's new AASHTO-based thickness design procedure are major steps toward accomplishing the goals of building longer-lasting pavements and reducing life-cycle costs.
VEROAD: A Viscoelastic Multilayer Computer Program
Authors: Hopman P. C.
Published: August 2018

The mathematical principles and derivation of a linear viscoelastic multilayer computer program are described. The principles of the derivation apply equally to conventional linear elastic programs. The practical consequences of the viscous material properties for the mathematical derivation have been solved by Fourier transformation; another mathematical consequence is that complex calculus was inevitable. The program is called VEROAD, (viscoelastic road analysis Delft). The program's primary extension is that the analyzed material can be vis-coelastic. Consequences of this extension are numerous: calculation from physical material properties of quantities such as time-dependent displacements, stresses and strains, permanent deformations, and dissipated energies is made possible. All these quantities depend on velocity of traffic, which is explicitly included in the calculations. The material model assumes the bulk modulus to be elastic and the shear modulus to be viscoelastic. The latter follows Burger's model. For illustrative purposes some mechanical analyses of asphaltic road structures are carried out, with emphasis on the distribution of stresses, strains, (permanent) deformations, and dissipated energies.
Attempt at Resilient Modulus Modeling Using Artificial Neural Networks
Authors: Tutumluer Erol , Meier Roger W.
Published: August 2018

The pitfalls inherent in the indiscriminate application of artificial neural networks to numerical modeling problems are illustrated. An example is used of an apparently successful (but ultimately unsuccessful) attempt at training a neural network constitutive model for computing the resilient modulus of gravels as a function of stress state and various material properties. Issues such as the quantity and quality of data needed to successfully train a neural network are explored, and the importance of an independent test set to verify network performance is examined.
Normal Stresses in a Granular Material under Falling Weight Deflectometer Loading
Authors: Ullidtz P. , Askegaard V. , Sjølin F. O.
Published: August 2018

The vertical normal stress under a falling weight deflectometer (FWD) was measured in a sand. The material had more than 90 percent falling within the sand fraction from 60 μm to 2 mm. The stress was measured with three different transducers. All transducers were installed at a depth of 280 mm. The sand was uniform to a depth of 700 mm and at a distance of 600 mm to either side of the centerline. An FWD was used to exert a known vertical force on the surface of the sand, using a loading plate 300 mm in diameter. The average stress under the plate was about 300 kPa. All the loads were imposed in the centerline of the three gauges, but at different horizontal distances from FWD to transducers. An integration of the measured stress on the plane of the transducers results in a force 10 to 14 percent larger than the peak force exerted by the FWD. The measured force is thus reasonably close to the actual force. When the measured stress is compared with the stress predicted using Boussinesq's equation for an elastic half-space, a very large difference is observed. At the centerline of the load, the measured stress is about twice the theoretical value. This difference cannot be explained by variation in material characteristics, including nonlinearity, or by dynamic effects.
Statistical Analyses of Temperature and Moisture Effects on Pavement Structural Properties Based on Seasonal Monitoring Data
Authors: Ali Hesham A. , Lopez Aramis
Published: August 2018

In light of the data collected under the Seasonal Monitoring Program of the Long-Term Pavement Performance Program, the relationship between climatic factors and pavement structural properties is investigated. Using deflection data collected at a seasonal site over the course of 1 year, layer elastic moduli are backcalculated. The correlations between pavement structural properties (represented by layer elastic moduli) and climatic factors (represented by pavement temperature and moisture conditions) are studied using a series of statistical analyses. Bivariate analysis is used to evaluate linear association between pairs of variables. Principal components analysis is used to identify principal constructs of the system. Multiple regression is used to calibrate linear models. Numerical optimization is used to calibrate nonlinear models that correlate backcalculated layer moduli to pavement temperature. The latter models are then used to derive a temperature correction algorithm of backcalculated asphalt concrete elastic modulus.
Application of Artificial Neural Networks to Concrete Pavement Joint Evaluation
Authors: Ioannides Anastasios M. , Alexander Don R. , Hammons Michael I. , Davis Craig M.
Published: August 2018

Application of the principles of dimensional analysis has recently led to the development of a robust method for assessing the deflection and stress load transfer efficiencies of concrete pavement joints and for backcalculating joint parameters. The new method eliminates the need to make a priori assumptions since pertinent inputs can now be experimentally determined using the falling weight deflectometer. A data base has been generated using numerical integration of Westergaard-type integrals and has been used to train a backpropagation neural network algorithm for joint evaluation. The resulting computer program is simple, efficient, and precise and can be used on site for immediate results. Its predictions are verified by comparisons with closed-form and finite-element solutions pertaining to data collected at three major civilian airports in the United States, including the new Denver International Airport. Also discussed is the role of dimensional analysis in the generation of the training set for a neural network. It is demonstrated that significant savings can be achieved through reduction of the dimensionality of the problem, which could be reinvested in broadening the range of applicability of the neural network. Comparison of neural network predictions with those from conventional regression analysis and from direct interpolation illustrates the benefits of data generation on the basis of fundamental principles of mechanics.
Application of Stochastic Finite-Element Method to Deflection Analysis of Pavement Structures
Authors: Parvini Mehdi , Stolle Dieter F. E.
Published: August 2018

The effect of random variations in layer properties of a pavement-subgrade system on surface deflections is investigated. This is done by using a stochastic finite-element framework based on the perturbation method. The Taylor's expansion scheme is used. The variations of the surface deflections are related to the variations of layer moduli via a coefficient matrix, thereby allowing an investigation of the sensitivity of measured deflections to the variation of pavement and subgrade moduli. The analyses confirm that surface deflections are not very sensitive to variations of modulus within the pavement structure. Using the Boussinesq-Odemark approximation, it is concluded that, for the sample problem analyzed, the effect of higher-order terms on variation estimates of displacement is negligible when the coefficient of variation of subgrade modulus is less than 15 percent. The effect of inertia on the coefficient of variation of displacement due to variations in layer moduli is also briefly addressed. It is demonstrated that the variation in displacement under the load is sensitive to both the loading frequency and the equivalent mass of the pavement-subgrade system, particularly in the vicinity of the natural frequency of the system.
Comparison of Simplified Elastostatic and Elastodynamic Models for Falling Weight Deflectometer Data Interpretation
Authors: Stolle Dieter F. E.
Published: August 2018

The characterization of pavements and subgrades by interpreting falling weight deflectometer data is discussed. Two backcalculation strategies—one based on an approximate elastostatic model and the other on dynamic impedance for a two-layered pavement subgrade system—are presented and applied to data collected along experimental pavement sections. Both strategies characterize the structural integrity of a pavement by equivalent asphalt thickness and the stiffness of the subgrade by effective subgrade modulus. It is indicated that, although both procedures predict similar trends, the values of the system parameters differ, particularly the equivalent asphalt thickness. The net pavement-subgrade stiffness predicted using dynamic impedance was found to be consistently higher than that obtained with the elastostatic model for the data studied. The capability of dynamic impedance to identify variations of in situ conditions along a section of roadway is also demonstrated.
Elementalistic and Holistic Views for Evaluation and Design of Structure Movement Systems
Authors: Burke Martin P.
Published: August 2018

In the evaluation and design of structure movement systems (bridge joints, bearings, flexible members, flexible supports, etc.), numerous errors are made by bridge designers who appear to have used and depended on a primarily elementalistic approach to structure design. By means of representative examples, it is demonstrated that bridge designers should supplement the elementalistic approach with a comprehensive or holistic approach. This dual approach to design will help ensure that structure movement systems will be suitably configured and coordinated to facilitate all anticipated short- and long-term movements and deformations.
New Safety-Based Checking Procedure for Overloads on Highway Bridges
Authors: Fu Gongkang , Hag-Elsafi Osman
Published: August 2018

Overweight trucks exceeding legal weight limits are seen crossing highway bridges. Many states adopt the AASHTO rating concept with or without an overstress criterion to check overweight permits for bridge evaluation. However, the basis of these overstress criteria has not been well documented, and the AASHTO load-rating concept is not intended to be applicable to overweight truck traffic. The development of a new overload-permit checking procedure for bridge evaluation, in the format of load and resistance factors and based on relatively uniform bridge safety, is presented. Annual and trip overload permits for nondivisible loads are covered. This procedure may be included in bridge evaluation codes for overload checking.
Strength Degradation of Existing Bridge Columns under Seismic Loading
Authors: Jaradat Omar A. , McLean David I. , Marsh M. Lee
Published: August 2018

The strength and degradation behavior of reinforced concrete bridge columns under seismic loading were investigated. Experimental tests were conducted on four reduced-scale column specimens that incorporated deficiencies selected to be representative of those present in existing bridges designed before 1971. The columns were fixed against rotation at both the top and bottom, resulting in a transfer of shear forces through the column even after the lower hinging region lost its flexural capacity. The specimens were subjected to increasing levels of cycled inelastic displacements under constant axial load. The focus of the study was to characterize the load and displacement capacities present in older columns for purposes of seismic assessment and retrofit design. Flexure-dominated failures occurred in three of the specimens. A rapid degradation in flexural strength was observed at the bottom hinging regions of the tested columns because of the presence of lap splices and poor confinement. Top hinging regions that did not have lap splices exhibited degradation in flexural capacities at higher displacement ductilities because of eventual longitudinal bar buckling. In the fourth specimen, flexural yielding was initially observed at both the top and bottom of the column, but this was followed by an eventual brittle shear failure. Various procedures for assessing flexural and shear behaviors were compared with the observed experimental results.
Dynamic Characteristics of Tsing Ma Suspension Bridge
Authors: Au Siu Kui , Mickleborough Neil , Roschke Paul N.
Published: August 2018

Numerical simulation was carried out to determine the dynamic properties of the Tsing Ma Suspension Bridge. Both the structure as a whole and individual subcomponents were modeled. Classical analytical solutions for simplified models from the available literature were compared with the results obtained from a finite-element code. Quantitative results for static deflection, natural frequencies, and mode shapes were compared with analytical solutions from linear theory. Out-of-plane modes were shown to be dominant. For in-plane antisymmetric and symmetric bending modes, in which the suspension cable and bridge deck vibrate in the same direction, the natural frequency of the main span of the bridge is determined to be approximately equal to the square root of the sum of the squares of the frequencies of the cable and bridge deck.
Measurement of Truck Load on Bridges in Detroit, Michigan, Area
Authors: Kim Sangjin , Sokolik Andrej F. , Nowak Andrzej S.
Published: August 2018

The objective of the study was to determine the actual truck loads on selected bridges in the Detroit, Michigan, area. Seven representative bridges were selected. The measurements were taken by using a weigh-in-motion system. For each measured truck, the record included vehicle speed, axle spacing, and axle loads. The variation in the accuracy of the gross vehicle weight (GVW) measurement was estimated to be ±5 percent and that of the axle weights was estimated to be ±20 percent for most types of trucks. Selected bridges were instrumented, and measurements were taken for 2 or 3 consecutive days. There was a considerable variation in traffic volumes and the weights of trucks, even within a given geographic area. The estimated average daily truck traffic varied from 500 to 1,500 in one direction. The maximum observed truck weights varied from 360 kN (81 kip) to 1100 kN (250 kip). The maximum observed axle weights varied from 90 kN (20 kip) to 225 kN (50 kip). The percentage of trucks exceeding the legal limits in Michigan varied depending on the road. The heaviest GVWs and axle weights were observed on Interstate highways. The largest percentage of overloaded trucks was observed for 11-axle vehicles. The maximum lane moments and shears from the trucks varied between 0.6 and 2.0 times AASHTO load and resistance factor design values. It was found that there are similarities in GVW and lane moment distributions.
Interpretation of Buried Pipe Test: Small-Diameter Pipe in Ohio University Facility
Authors: Brachman R. W. I. , Moore I. D. , Rowe R. K.
Published: August 2018

Two- and three-dimensional finite-element analyses were used to examine the response of a small-diameter leachate collection pipe tested at Ohio University. The influence of the cell boundaries was examined, and the implications of the loading system were investigated. The state of stress in the soil around the cell was studied, and its influence on the expected soil and pipe responses was evaluated. Comparisons between the pipe response induced in the test cell and that which was expected to occur in a real field installation were also made. It was found that nonuniform vertical and horizontal stress distributions different from those expected in real field installations developed in the test cell. This presents various difficulties associated with interpreting loading as an equivalent height of fill. At low load levels in the test cell the granular backfill adjacent to the pipe yielded as local bending developed under the rigid platform used to apply pressure to the ground surface. The decreased lateral support altered the mode of pipe deflection. At high load levels the response in the test cell was governed by soil failure, producing conditions not expected in a landfill environment.
Field Tests of Buried Pipe Installation Procedures
Authors: Webb Mark C. , McGrath Timothy J. , Selig Ernest T.
Published: August 2018

Full-scale field tests to evaluate pipe-soil interaction during backfilling were conducted on the campus of the University of Massachusetts at Amherst. The program consisted of 14 tests, with each test including concrete, plastic, and metal sections. In addition to pipe type, installation variables included in situ soil conditions, trench width, backfill material including controlled low-strength flowable material, haunching effort, and compaction methods. Test trenches were excavated under undisturbed in situ soil conditions. Eleven installations were conducted with 900-mm (inside diameter) pipe, and three installations were conducted with 1500-mm (inside diameter) pipe. Pipe and soil behavior was monitored during backfilling. Measurements included pipe shape, pipe strains, pipe-soil interface pressures, soil density, soil stresses, and soil strains. The pipes were buried to a cover depth of 1.2 m and were then excavated to inspect the pipe bedding and haunches. The results indicated significant variations in pipe behavior caused by installation practices. The rammer compactor produced greater backfill density than did the vibratory plate compactor with the same number of coverages and produced higher residual lateral soil stresses that contributed to better overall pipe performance during backfilling. The silty sand backfill tripled the peaking deflection during sidefill compaction compared with that with angular crushed rock backfill, but the former was more sensitive to deviations from good installation practice. Backfill compaction in the region from the spring line to 30 degrees below the spring line has a significant positive effect in mitigating poor bedding and haunching conditions. Pipe tests with controlled low-strength material for backfill performed very well.
Construction of Stone Matrix Asphalt Section at Edwards Air Force Base
Authors: Shoenberger James E.
Published: August 2018

In February 1993, the U.S. Air Force Civil Engineering Support Agency asked the U.S. Army Engineer Waterways Experiment Station to provide technical assistance for construction of a stone matrix asphalt (SMA) pavement demonstration project at Edwards Air Force Base (AFB). In August 1993, approximately 0.8 km (0.5 mi) of SMA pavement was placed on a road at Edwards AFB. The SMA mixture contained crushed stone, natural sand, fly ash, cellulose fiber, and an AR-4000 asphalt cement. The following summer, it was reported that excessive amounts of bleeding had occurred in all wheelpaths. An inspection in August 1994 confirmed this finding, and it was noted that the bleeding was worse near the intersections. The SMA mixture apparently contained too much asphalt cement. Several factors contributed to the bleeding: (a) the SMA mixture as designed contained too many fines, especially in passing the No. 4 sieve, compared with current guidance from the National Asphalt Paving Association and others; (b) the void content of the mixture may have been inadequate; and (c) samples obtained from the in-place pavement had a finer grading and higher asphalt content than specified. The bleeding has caused concern; however, no maintenance has been performed on the SMA pavement and no measurable rutting has occurred in the wheelpaths.
Performance-Based Mix Design and Field Quality Control for Asphalt-Aggregate Overlays
Authors: Sousa Jorge B. , Way George , Harvey John T.
Published: August 2018

In its continuing effort to improve pavement technology, the Arizona Department of Transportation evaluated the use of the repetitive simple shear test at constant height and flexural bending beam test as part of the mix design and field quality assurance process. The results of the efforts, conducted to design and place an overlay on a test section, indicated that those tests and associated analysis procedures are feasible and implementable for routine use.
Variability Analysis of Hot-Mix Asphalt Concrete Containing High Percentage of Reclaimed Asphalt Pavement
Authors: Solaimanian Mansour , Tahmoressi Maghsoud
Published: August 2018

A research project was undertaken to evaluate the production and construction variability of hot-mix asphalt concrete (HMAC) containing large quantities of recycled asphalt pavement (RAP) material. Four construction projects were selected. Two of the projects used 35 percent RAP material, while the other two used 40 and 50 percent RAP, respectively. The projects differed in size with total hot-mix ranging from 12,000 to 30,000 tons. In all cases, dedicated RAP stockpiles were used. A series of tests were performed at both the hot-mix plant laboratory and the University of Texas (UT) asphalt laboratory. The tests at the plant included extraction, gradation, and asphalt content using nuclear gauge. A number of specimens were also compacted and shipped to the Texas Department of Transportation Materials and Tests Division for Hveem stability testing. Asphalt recovery, penetration, and viscosity tests for both HMAC and RAP were conducted at the UT laboratory. Each day, four sublots were sampled. The results obtained from the tests were analyzed. The gradation and asphalt content deviations, air voids, penetrations and viscosities, and stabilities were included in the analysis. Pay adjustment factors were determined for gradation and asphalt content deviation, as well as for air voids. In general, these high-percentage RAP projects indicated higher variability than a typical HMAC project without RAP. The gradations of plant-produced mixtures were finer than the job mix formula target gradations, possibly because of aggregate crushing during the milling operation.
Study of Longitudinal-Joint Construction Techniques in Hot-Mix Asphalt Pavements
Authors: Kandhal Prithvi S. , Mallick Rajib B.
Published: August 2018

There is a need to identify suitable longitudinal-joint construction techniques for multilane, hot-mix asphalt pavements that can minimize or eliminate cracking at the joint and raveling adjacent to the joint. It is believed that the longitudinal cracks result primarily from the density gradient that is usually encountered across the joint. This density gradient can be attributed to low density at the unconfined edge when the first lane is paved and relatively high density at the confined edge when the adjacent lane is paved. Seven different longitudinal-joint construction techniques were used on I-25 in Colorado in 1994, including various rolling procedures to compact the joint, provision of a vertical face with a cutting wheel, and use of rubberized asphalt tack coat on the face of the unconfined edge. Two longitudinal-joint construction techniques were used on I-79 in Pennsylvania in 1994: the conventional technique (control) and the New Jersey–type wedge joint. The latter technique uses a 3:1 taper at the unconfined edge of the first lane. The face of the taper is heated with an infrared heater before the adjacent lane is placed. Pavement cores were taken on the joint and 305 mm (1 ft) away from the joint for density measurements in all experimental test sections. Different techniques for joint construction have been ranked on the basis of statistical analysis of all density data. Various joints were also evaluated visually by teams of at least four engineers in June 1995. The performance, or ranking, of the joints in both Colorado and Pennsylvania projects after one winter seems to have been influenced by the overall density at the joint. The joints with high densities indicate better performance than those with relatively low densities. These rankings may change in the future on the basis of the long-term performance as measured by cracking and raveling.
Wisconsin Department of Transportation's Asphaltic Pavement Warranties
Authors: Shober Stephen F. , Whited Gary C. , McMullen Kevin W.
Published: August 2018

The Wisconsin Department of Transportation (WisDOT), the Wisconsin Asphalt Pavement Association, and FHWA have joined together to develop a comprehensive warranty specification that can be incorporated into highway construction contracts for asphaltic concrete pavements. The warranty specification is expected to reduce WisDOT's project delivery costs, lower total project construction costs, enable contractors to use innovative construction methods and materials, and result in equal or greater quality construction. The development of Wisconsin's warranty specification is briefly discussed, and the unique features of the warranty specification are outlined, including the warranty period, bonding requirements, pavement performance characteristics, performance thresholds, pavement evaluation methods, required pavement remedial actions, and use of a conflict-resolution team. The specification has been used successfully to bid and construct three highway projects in Wisconsin. WisDOT has evaluated projected costs over 5 years to determine the impact of warranties on total costs. Other types of projects that may be suitable for use of warranties have been identified and several will be tried in 1996. Distress evaluations from the first year indicate that the warranty projects yield a good ride, no significant rutting, and low distress. No distress thresholds were exceeded, thus no remedial actions (warranty work) are required after 1 year.
Current Initiatives in Quality Asphaltic Pavement Construction: The Wisconsin Experience
Authors: Schmitt Robert L. , Whited Gary C. , Waelti Gerald J. , Hanna Awad S. , Russell Jeffrey S. , Bahia Hussain U.
Published: August 2018

The Wisconsin asphalt-paving industry is undertaking several initiatives to continually improve the construction of asphalt pavements through a quality management program and two piloted specifications. The quality management program provides contractors and the Wisconsin Department of Transportation (WisDOT) with structured process control and quality assurance for hot-mix asphalt paving projects. A warranted pavement specification, piloted on three projects during 1995, warranties the pavement for 5 years and allows greater flexibility for contractors during construction. A statistically based nuclear-density specification will be piloted in 1996 to provide density-process control and quality assurance using nuclear density gauges. These initiatives are moving toward the goal of performance-based construction and are possible with a commitment to quality from WisDOT and contractors, including members of the Wisconsin Asphalt Pavement Association. Members of the industry are combining resources and restructuring to develop and implement methods to improve the quality and performance of hot-mix asphalt pavements. Focus is placed on mutual development of solutions to various problems encountered by the industry.
Evaluation of Superpave Gyratory Compaction of Hot-Mix Asphalt
Authors: Brown E. R. , Hanson D. I. , Mallick Rajib B.
Published: August 2018

To achieve 4.0 percent air voids in laboratory-compacted hot-mix asphalt with the Superpave gyratory compactor, different gyration levels are currently specified in the Superpave manual, each applicable to a particular combination of traffic and maximum pavement temperature. Two 1-year-old and four 2-year-old in-place densities were compared to those obtained from Superpave compaction of laboratory-prepared specimens and from compaction of reheated plant-produced mixtures. The gyration numbers corresponding to in-place density fell below 100 for all the mixes. At similar gyration levels, density of compacted, reheated, and laboratory-prepared specimens indicated an average difference of about 1 percent. Current data show that the Ndesign, Ninitial, and Nmax gyration levels may be too high, at least for lower traffic. Evaluation of the currently specified Ndesign values will be refined when the 3-year in-place density data become available.
Effect of Concrete Mix Consolidation on Joint Faulting and Load Transfer Efficiency
Authors: Hossain Mustaque , Wojakowski John B.
Published: August 2018

Six jointed reinforced concrete pavement and one jointed plain concrete pavement test sections on US-69 in Miami County, Kansas, constructed in 1979 have been surveyed annually for faulting for the past 9 years. Falling weight deflectometer tests were conducted in 1995 to assess the load transfer efficiency of the joints. The results show that, in general, as the original concrete density increases due to improved consolidation, the rate of increase of the joint fault depth decreases at doweled joints at a given pavement age. The occurrence of joint faulting is much more severe when load transfer devices are not present; this was observed even for the pavement section built on a nonerodible subbase. Improved consolidation sometimes appeared to help improve load transfer, resulting in a lower rate of faulting. Thus, the mandatory density requirement of 98 percent rodded unit weight, which has been in effect since 1980, has undoubtedly led to better joint performance for concrete pavements in Kansas.
Full-Scale Test of High Early Strength Bonded Concrete Overlay Design and Construction Methods
Authors: Delatte Norbert J. , Fowler David W. , McCullough B. Frank
Published: August 2018

For rehabilitation of concrete pavements, resurfacing with a bonded concrete overlay (BCO) may provide significantly longer life and reduced maintenance costs. Two important issues are bonding and rapid reopening of resurfaced sections. The project objectives were to determine a method of constructing a BCO under extreme weather conditions in El Paso, Texas, that would ensure early opening to traffic and achieve design requirements for long-term performance, and to investigate methods of detecting and mapping delaminations nondestructively. A BCO test slab that was designed and constructed for a full-scale test of feasible design and construction alternatives is reported. The month of June was selected for the test because severe environmental conditions were expected. The experimental variables encompassed in eight test sections were reinforcement of concrete (plain, polypropylene fiber–reinforced, and steel fiber–reinforced), use of shear connectors (nails and anchors), reinforcement, surface preparation, and day or night construction. A weather station was used to record air temperature, relative humidity, and wind speed. By combining these data with concrete temperatures, evaporation rates could be calculated. Several nondestructive testing methods were used to attempt to detect and map delaminations. The results developed from the test are presented in terms of observations during construction, weather and slab temperatures, coring and pull-off testing, delamination detection, cracking, and slab loading. Recommendations are made for construction and quality control of BCOs for early opening to traffic.
Noise Characteristics of Pavement Surface Texture in Wisconsin
Authors: Kuemmel David A. , Jaeckel John R. , Satanovsky Alexander , Shober Stephen F. , Dobersek Mitzi M.
Published: August 2018

Twelve portland cement concrete pavement (PCCP) test sections were constructed to compare with standard PCCP and asphaltic concrete pavement (ACP) to quantify the effects of the pavement surface texture on noise, safety, and winter maintenance. Asphalt pavements studied included a Strategic Highway Research Program asphalt, stone matrix asphalt (SMA), and Wisconsin standard asphalt. A dependency between the pavement textures and their noise characteristics was observed. Noise measurements indicated that uniformly transverse tined PCCP created dominant noise frequencies that were audible adjacent to the road and inside the test vehicles. Careful design and construction of transversely tined PCCP can reduce tire-road noise. No significant acoustical advantages of open-graded asphalts over the standard dense asphalt were found. The results of this research are preliminary and have not yet been approved by the Wisconsin Department of Transportation Council on Research.
Lateral Sliding of Multispan Steel Bridges
Authors: Anderson W. Victor , Trenkler Ferdinand
Published: August 2018

As the urban infrastructure in the cities around the world becomes more complex and congested, engineers are more often required to design and construct major structures under severely constrained physical and environmental conditions. To deal with these constraints, an increasing number of projects in recent years have involved the construction and subsequent sliding of bridges, including the lateral sliding of major, multispan steel bridges. Because multispan continuous steel bridges are relatively lightweight, robust, and resistant to any possible inadvertent damage from major sliding operations, they are particularly well-suited to dealing with the constraints in a cost-effective manner. Several such projects have been completed in Europe, the United States, Canada, Japan, and elsewhere in the world. These and other related steel bridge projects are described that have successfully used complex, computer-controlled, multitrack lateral bridge slides.