bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic Evaluation of Test Data from Long-Term Pavement Performance Jointed Plain Concrete Pavement Test Sections
Authors: Jane Jiang Y. , Tayabji Shiraz D.
Published: April 2007

Over the years, pavement engineers have attempted to develop rational mechanistic-empirical (M-E) methods for predicting pavement performance. In fact, the next version of AASHTO’s Guide for Design of Pavements is planned to be mechanistically based. Many M-E procedures have been developed on the basis of a combination of laboratory test data, theory, and limited field verification. Therefore, it is important to validate and calibrate these procedures using additional data from in-service pavements. The Long-Term Pavement Performance (LTPP) program data provide the means to evaluate and improve these models. A study was conducted to assess the performance of some of the existing concrete pavement M-E-based distress prediction procedures when used in conjunction with the data being collected as part of the LTPP program. Fatigue cracking damage was estimated using the NCHRP 1–26 approach and compared with observed fatigue damage at 52 GPS-3 test sections. It was shown that the LTPP data can be used successfully to develop better insight into pavement behavior and to improve pavement performance.
Three-Dimensional Finite Element Study on Effects of Nonlinear Temperature Gradients in Concrete Pavements
Authors: Pane Ivindra , Hansen Will , Mohamed Ashraf R.
Published: April 2007

A three-dimensional (3D) finite element (FE) model is developed to investigate whether the condition of plane sections remaining plane exists in concrete pavements subjected to nonlinear temperature gradients. This model is utilized to validate the analytical method proposed by Mohamed and Hansen. The 3D brick element is chosen so that the plane section condition is not imposed in the model, as compared with the model using the flat plate element. Furthermore, the possibility of loss of contact between the pavement slab and the subgrade is studied. The condition of full contact is investigated for a nonlinear temperature gradient that produces the maximum tensile stress in the slab according to the data used. Two slab lengths and two radii of relative stiffness are considered. It is found that plane sections remain plane for the entire slab except for a region very close to the free edges, which also establishes the boundary where solutions by Mohamed and Hansen are applicable. In both cases of the contact condition, the 3D FE model predicts no loss of contact between the slab and the subgrade.
Numerical Modeling of Continuously Reinforced Concrete Pavement Subjected to Environmental Loads
Authors: Kim Seong-Min , Won Mooncheol , Frank McCullough B.
Published: April 2007

Continuously reinforced concrete pavement (CRCP) performance depends on, among other factors, the characteristics of early developing cracks caused by environmental loads. The primary objective is to evaluate effects of design, materials, and construction variables on the characteristics of cracks in CRCP when subjected to environmental loads. A mechanistic model is developed using finite element formulations. Concrete and longitudinal steel are discretized using the plane strain and the frame elements, respectively. Various bond stress and slip models between concrete and longitudinal steel and between concrete and the underlying layers are developed using the spring elements. The creep effect is also included using the effective modulus method. CRCP responses from the model vary depending on the concrete and steel bond-slip models. An accurate bond-slip model needs to be investigated further by experiments to increase the accuracy of the mechanistic model. Concrete creep has beneficial effects on CRCP responses. The thermal coefficient of concrete has significant effects on CRCP responses. Using concrete with a low thermal coefficient will improve CRCP performance. Longitudinal steel variables—the amount of steel, bar diameter, and steel location—are important design variables that influence CRCP behavior. For given environmental conditions, an optimum steel design can be developed using the model developed.
Study on Thermal Stresses in Continuously Reinforced Concrete Pavement
Authors: Nishizawa Tatsuo , Shimeno Shigeru , Komatsubara Akinori , Koyanagawa Masashi
Published: April 2007

In the structural design of continuously reinforced concrete pavement (CRCP), thermal stresses should be properly taken into account. Thermal strains and temperatures in concrete slabs were measured on test sections of CRCP. Measured strains were divided into axial, curling, and nonlinear components, and each component was examined. It was found that the curling component is predominant in terms of transverse stress, which is important in the structural design. However, the maximum thermal stress is reduced by 25 percent because of the nonlinear component. On the basis of the results, a procedure for estimating the thermal stress in CRCP was proposed.
Asphalt-Treated Permeable Base: Laboratory Testing, Performance, and Predictions
Authors: Harvey J. , Tsai B. , Long F. , Hung D.
Published: April 2007

Flexible pavements containing a thin asphalt-treated permeable base (ATPB) layer have been used in California for more than 15 years. The original philosophy upon which use of ATPB is based, the implementation of that philosophy, and observations regarding its effectiveness are examined. Laboratory tests for resilient modulus of ATPB are presented for the as-compacted state, after 3 and 10 days of soaking, and after repetitive loading in the as-compacted and saturated states. The results indicate a loss of stiffness after soaking, and failure caused by stripping and loss of cohesion between the aggregates when subjected to repetitive loading while saturated. The lab test results were used in simulations of fatigue life for pavements with and without ATPB. The results indicate that predicted pavement fatigue lives are improved when ATPB is included in the pavement structure as compared with when aggregate base alone is used, but the improvement diminishes if water damage occurs in the ATPB. Recommendations are made regarding future use of ATPB in flexible pavements.
AYMA: Mechanistic Probabilistic System To Evaluate Flexible Pavement Performance
Authors: Ayres Manuel , Witczak Matthew W.
Published: April 2007

A new rational mechanistic model for analysis and design of flexible pavement systems has been developed. Furthermore, a fundamental probabilistic approach was incorporated into this system to account for the uncertainty of material and environmental conditions. The system was integrated in a user-friendly Windows program with a variety of user-selected options that include widely used models and those recently developed in the Strategic Highway Research Program project. Three basic types of distress can be investigated separately or all together, including fatigue cracking, permanent deformation, and low-temperature cracking. The mechanistic approach makes use of the JULEA layered elastic analysis program to obtain pavement response. The system provides optional deterministic and probabilistic solutions, accounts for aging and temperature effects over the asphalt materials, variable interface friction, multiple wheel loads, and user-selected locations for analysis. Tabular and graphical results provide expected distress values for each month as well as their variability, probability of failure, and assessment of the overall reliability of the pavement relative to each type of distress for a user-selected failure criterion. Only the load-associated module of AYMA is presented; a separate work describes the low-temperature cracking analysis.
Evaluation of Mechanistic-Empirical Performance Prediction Models for Flexible Pavements
Authors: Ali Hesham A. , Tayabji Shiraz D.
Published: April 2007

In recognition of the potential of mechanistic-empirical (M-E) methods in analyzing pavements and predicting their performance, pavement engineers around the country have been advocating the movement toward M-E design methods. In fact, the next AASHTO Guide for Design of Pavement Structures is planned to be mechanistically based. Since many of the performance models used in the M-E methods are laboratory-derived, it is important to validate these models using data from in-service pavements. The Long-Term Pavement Performance (LTPP) program data provide the means to evaluate and improve these models. The fatigue and rutting performances of LTPP flexible pavements were predicted using some well-known M-E models, given the loading and environmental conditions of these pavements. The predicted performances were then compared with actual fatigue cracking and rutting observed in these pavements. Although more data are required to arrive at a more conclusive evaluation, fatigue cracking models appeared to be consistent with observations, whereas rutting models showed poor agreement with the observed rutting. Continuous functions that relate fatigue cracking to fatigue damage were developed.
Development of Mechanistic-Empirical Pavement Design in Minnesota
Authors: Timm David , Birgisson Bjorn , Newcomb David
Published: April 2007

The next AASHTO guide on pavement design will encourage a broader use of mechanistic-empirical (M-E) approaches. While M-E design is conceptually straightforward, the development and implementation of such a procedure are somewhat more complicated. The development of an M-E design procedure at the University of Minnesota, in conjunction with the Minnesota Department of Transportation, is described. Specifically, issues concerning mechanistic computer models, material characterization, load configuration, pavement life equations, accumulating damage, and seasonal variations in material properties are discussed. Each of these components fits into the proposed M-E design procedure for Minnesota but is entirely compartmentalized. For example, as better computer models are developed, they may simply be inserted into the design method to yield more accurate pavement response predictions. Material characterization, in terms of modulus, will rely on falling-weight deflectometer and laboratory data. Additionally, backcalculated values from the Minnesota Road Research Project will aid in determining the seasonal variation of moduli. The abundance of weigh-in-motion data will allow for more accurate load characterization in terms of load spectra rather than load equivalency. Pavement life equations to predict fatigue and rutting in conjunction with Miner’s hypothesis of accumulating damage are continually being refined to match observed performance in Minnesota. Ultimately, a computer program that incorporates the proposed M-E design method into a user-friendly Windows environment will be developed.
Potential Safety Cost-Effectiveness of Treating Rutted Pavements
Authors: Start Marc R. , Kim Jeong , Berg William D.
Published: April 2007

Pavement rutting is a problem that has unknown consequences from a safety-based point of view. It is assumed that the wheelpath fills with water in wet-weather situations, thus increasing the potential for a vehicle to hydroplane. A study was conducted to quantify how pavement rutting affects accident rates and to evaluate possible safety-based guidelines for the treatment of pavement rutting. Rut depth, traffic volumes, and accident databases maintained by the Wisconsin Department of Transportation for undivided rural highways were then analyzed to identify statistical trends and relationships. Accidents were categorized as rut-related if the prevailing conditions could be potentially associated with the occurrence of hydroplaning. Rut depth measurements were average values for both directions of 1.8-km (1.1-mi) segments and represent the average elevation difference between the tire paths and the high point between them. The results of the statistical analyses indicated that the defined rut-related accident rate begins to increase at a significantly greater rate as rut depths exceed 7.6 mm (0.3 in.). The cost-effectiveness of potential accident reductions associated with reductions in the relative amount of rutted pavement was also evaluated.
Mechanics of Small Utility Cuts in Urban Street Pavements: Implications for Restoration
Authors: Humphrey Mewburn H. , Parker Neville A.
Published: April 2007

The results of a three-dimensional finite element analysis of the impacts of small utility cuts in urban street pavements are presented. The analysis was restricted to flexible pavements for cuts of the order of 915 mm (3 ft) square. Using ANSYS Solid 45 Version 5.2 on a one-eighth area, the excavation process was simulated using a stress relief approach, in which the material was assumed to be removed in successive layers. Starting with gravity loading on the uncut model, the element stress results from the previous removal were used to compute the new effective confining stresses of the respective layers. The in situ material properties were typical of flexible pavements in an urban street. The analysis presented a clear picture of the magnitude and extent of the distress induced on the pavement structure below and surrounding the cut. The analysis also showed how the restraining action of the asphalt layer is reflected in its arching up from heave and granular material thrusting, causing tension at the bottom and compression at the top. The results suggested that for unsupported depths of up to 1524 mm (5 ft), material distress may extend approximately 1068 mm (3.5 ft) into the pavement structure. Implications for methodology and economics of restoration are discussed, including determination of optimum cutback and recompaction of the affected area of pavement.
Relationships Among Rate-Dependent Stiffnesses of Asphalt Concrete Using Laboratory and Field Test Methods
Authors: Sias Daniel Jo , Richard Kim Y.
Published: April 2007

As the application of nondestructive testing on pavements in service becomes more frequent, it is increasingly important to relate the resulting stiffnesses to those from laboratory test methods. The relationship among stiffnesses measured from five test methods currently used for asphalt concrete is addressed: creep compliance, complex modulus, impact resonance, falling weight deflectometer, and surface wave. Established relationships from linear viscoelastic theory are used to relate stiffnesses, including a comparison of creep stiffness, S( t), and relaxation modulus, E( t), calculated from creep compliance, D( t). Using laboratory and field measured stiffnesses, a linear relationship was discovered between stiffness and frequency on a log-log scale.
Short-Loading-Time Stiffness from Creep, Resilient Modulus, and Strength Tests Using Superpave Indirect Tension Test
Authors: Roque Reynaldo , Buttlar William G. , Ruth Byron E. , Dickison Stephen W.
Published: April 2007

The Superpave indirect tension (IDT) system was modified to determine the short-loading-time stiffness of asphalt mixtures from resilient modulus, creep, and strength tests. The idea was not only to provide a more accurate method to determine the resilient modulus, but also to determine whether reasonable measures of short-loading-time stiffness could be obtained from tests that provide other properties and thereby minimize the amount of testing needed to characterize asphalt mixtures. It was found that even when evaluated at very short loading times, the stiffnesses determined from the different tests were significantly different. Detailed evaluation indicated that the differences can be explained by the differences in loading rates between the tests. In general, stiffnesses from the different tests all appeared to be reasonable and followed the same trend. However, since the rheological behavior of asphalts and mixtures varies, stiffnesses from different tests were not directly related. Therefore, although the interpretation methods developed in this study for creep and strength tests appear to provide a reasonable alternative to the resilient or dynamic modulus, the short-loading-time stiffnesses determined from these tests are not directly comparable with the resilient or dynamic modulus or with each other. The work illustrates the sensitivity of stiffness to relatively small changes in loading rate and other variables, which emphasizes the need to precisely define load pattern, load level, and data interpretation methods to determine asphalt mixture stiffness at short loading times.
Effects of Aging on Viscoelastic Properties of Asphalt-Aggregate Mixtures
Authors: Sias Daniel Jo , Richard Kim Y. , Lee Hyun-Jong
Published: April 2007

The effects of aging on asphalt-aggregate mixtures is a topic that has been gaining attention in recent years. Of special interest is how the fatigue performance of asphalt concrete mixtures changes with time because of changing material properties. The fatigue performance of a mixture is related to its viscoelastic material properties. An investigation of the effects of aging on viscoelastic properties of an asphalt-aggregate mixture, such as creep compliance, relaxation modulus, dynamic modulus, and phase angle, is discussed in this paper. The framework for including the effect of aging in an existing uniaxial constitutive model is established, and the applicability of Schapery’s elastic-viscoelastic correspondence principle to aged mixtures is validated.
Reference Standards for Use with Indirect Tension Test
Authors: Christensen Donald W. , Mehta Yusuf A.
Published: April 2007

The purpose of this paper is to describe the fabrication, calibration, and use of high-density polyethylene (HDPE) reference standards for the indirect tension (IDT) creep test, which was developed during the Strategic Highway Research Program and is one of the standard Superpave mixture tests now under further development and implementation. The use of reference standards in conjunction with the IDT test will help to achieve rapid and effective implementation of this promising test method. An IDT reference standard is useful in three ways: as a final step in a thorough calibration of the IDT system, for rapid verification of the IDT test system between calibrations, and as a tool for training engineers and technicians in proper execution of the test. In this study, HDPE specimens were calibrated using the IDT creep test. During this calibration, statistical methods were used to verify that the HDPE was homogenous, linear, and isotropic. The calibration was then confirmed using companion specimens of the HDPE machined for testing by using the bending beam rheometer (BBR). It was concluded that useful IDT reference standards can be machined of HDPE and that these specimens can be calibrated using repeated testing on the IDT, with further confidence provided through verification of the calibration using BBR specimens. Companion BBR specimens are also potentially useful for detecting any long-term changes in the properties of the HDPE reference standards.
Effect of Aggregate Gradation on Fatigue Life of Asphalt Concrete Mixes
Authors: Sousa Jorge B. , Pais Jorge C. , Prates Manuel , Barros Rui , Langlois Pierre , Leclerc Anne-Marie
Published: April 2007

Four-point bending fatigue tests following the Strategic Highway Research Program (SHRP) M009 test protocol were executed to investigate to what extent gradation has an effect on fatigue performance of asphalt aggregate mixes. Gradations and mixes were selected that would satisfy all volumetric Superpave designs passing below the restricted zone. Other mixes were prepared with gradations passing through and above the restricted zone. The measured fatigue lives of 130 actual laboratory tests were compared with predictions by the Shell, Asphalt Institute, and SHRP-A003A fatigue-predictive equations.
Evaluation of Ability of Superpave Shear Tester To Differentiate Between Mixtures with Different Aggregate Sizes
Authors: Romero Pedro , Mogawer Walaa S.
Published: April 2007

A study was conducted to determine whether the results from the Superpave shear tester (SST) could measure the effect of nominal maximum aggregate size on rutting susceptibility of asphalt mixtures without the need of a model. Four mixtures were analyzed using direct measurements from the SST. Two of the mixtures were prepared with AC-5 asphalt cement and nominal maximum aggregate sizes of 19.0 mm and 37.5 mm. The other two were prepared with AC-20 asphalt cement and the same two gradations. The results were analyzed statistically and compared with the performance of the respective mixtures tested by the FHWA Accelerated Loading Facility (ALF). The specimens were compacted to a target air voids of 7 percent using the Superpave gyratory compactor. The testing sequence consisted of performing the simple shear at constant height (SSCH) test followed by the frequency sweep at constant height (FSCH) test at 40°C and 58°C. These temperatures were chosen because they represent, respectively, the highest temperature used in Superpave complete analysis and the target pavement temperature at 20 mm depth used in the ALF tests. After the SSCH and FSCH tests, the repeated shear at constant height (RSCH) test was performed on all samples at 40°C. The ALF provided a significant decrease in rutting susceptibility with increase in aggregate size; however, the SST was unable to separate mixtures with the same binders and the two different nominal maximum aggregate sizes.
Determining Gyratory Compaction Characteristics Using Servopac Gyratory Compactor
Authors: Butcher Mike
Published: April 2007

Investigations are reported on that were carried out by Transport SA initially into the effects of the major parameters (gyratory angle, vertical stress, and gyratory speed) on the density of specimens compacted using the new Australian gyratory compactor, the Servopac. More recent investigations were carried out into the benefits of measuring shear resistance during the compaction process. Australian Standard AS 1289.2.2 for asphalt gyratory compaction was formulated as a result of investigations during the early 1990s using the first Australian gyratory compactor, the Gyropac, and this standard is now part of asphalt contract specifications for a number of state road authorities. The more versatile and accurate Servopac is seen as a technological advance on the Gyropac, and its ability to quickly modify critical gyratory parameters has enabled these studies to be carried out more efficiently. The voids and cycle precision and how tolerances affect these parameters were evaluated over a wide range of angles, vertical pressures, and rotation, with findings indicating that gyratory angle and vertical pressure settings are critical. Rotation speed was found to be a noncritical parameter. Subsequent investigations into shear resistance measurements, however, have indicated the potential for new windows to be opened for their use in characterization of asphalt mixes. This new approach hinges around maximum shear resistance and the rate of change of voids at the maximum shear stress position and the probability that gyratory settings may not be so critical when looked at in this way.
Evaluation of Stripping for Asphalt Concrete Mixtures Using Accelerated Testing Methods
Authors: Pan Changlin , White Thomas D.
Published: April 2007

A laboratory study was conducted to determine the water sensitivity and rutting potential of asphalt mixtures. The two major tests included in the study were AASHTO T-283 and a laboratory wheel tracking device. AASHTO T-283 has been adopted in the Superpave system for evaluating mixture-stripping potential. The laboratory wheel tracking device was designed and fabricated to represent conditions associated with stripping, that is, moisture, high temperature, and a moving wheel load. Tests can be conducted with a hot and wet or a hot and dry environment. The objective of the study was to evaluate factors influencing bituminous mixture stripping potential. The laboratory wheel tests can simulate mixture stripping conditions as well as pavement loadings. Rutting potential with and without stripping in hot-wet and in hot-dry environments, respectively, can be determined independently. The difference in rutting for the two environmental conditions indicates the magnitude of rutting associated with stripping. Test results show the potential for the wheel tracking device to evaluate the rutting and stripping of asphalt mixtures under various temperature and moisture conditions. In a comparison of two Indiana No. 11 surface mixtures, limestone and dolomite, the limestone mix has a lower susceptibility to rutting than that of the dolomite mix at 50 and 60°C. Moisture damage was shown to occur over a range of temperatures from room temperature to 60°C.
Calculating Air Voids at Specified Number of Gyrations in Superpave Gyratory Compactor
Authors: Vavrik William R. , Carpenter Samuel H.
Published: April 2007

The Superpave volumetric mix design is based on compaction of mixtures to Nmax revolutions, yielding approximately 2 percent air voids, and then back-calculating the properties of the mixture at N design revolutions, which is the specified number of revolutions at which the sample should achieve 4 percent air voids. It has been shown, both in mixture design and in field quality control testing, that this back-calculation procedure is not always accurate for determining the number of gyrations that give 4 percent air voids in the compacted sample. The current back-calculation procedure is examined in this paper, and the observed inaccuracy in the current method is shown in both quality control/quality assurance (QC/QA) and the mixture design procedures. Also examined is an alternative method that has been shown to be more accurate in predicting the number of gyrations at which a mixture reaches a given air void level. This study recommends a method that gives higher accuracy in determining the number of gyrations at which a mixture reaches 4 percent air voids. A diverse group of mixtures, each having different properties, was examined, and an improved method for predicting the number of gyrations to accurately produce 4 percent air voids in the compacted mixture was determined.
Simulation of Human Movement for Ergonomic Design on Numerical Mock-Up
Authors: Verriest Jean-Pierre
Published: April 2007

In the field of computer-aided vehicle design, it is important to simulate the activity of the future end user in order to evaluate the product being designed on the basis of ergonomic criteria such as ingress/egress, encumbering, control reach, control maneuverability, and visibility. This can be done with a computerized graphical mannequin. Some of the problems related to this question are reviewed and a method of mannequin manipulation for posture simulation is presented. In this method, the postures and movements implied by the use of the product being designed are generated from position and orientation constraints assigned by the user to various body parts. An inverse geometric algorithm then computes a set of angles satisfying the geometric constraints. The algorithm is based on a functional segmentation of the human body into autonomous mobile segments, organized in a tree-like structure and able to cooperate in order to solve an inverse geometric problem. The resolution strategy is based on an action plan, decomposing the global constraint problem into local subproblems handled by the segments and taking into account priority levels of action attributed to the segments. Some examples of postures obtained with this method related to the use of an automobile are presented.
Evolving Model for Studying Driver-Vehicle System Performance in Longitudinal Control of Headway
Authors: Fancher Paul S. , Bareket Zevi
Published: April 2007

A model for studying and evaluating the performance of drivers in controlling headway situations is currently being used to better understand how a driver’s perception of headway range and its rate of change in time (range rate) influence the performance of the driver-vehicle system in freeway driving situations. The model is based upon ideas derived from vehicle dynamics, control theory, and human factors research. It is an interpretive model in the sense that results obtained during real driving are processed to evaluate the parameter values and functional relationships used in the model. In this way, the model evolves as new data and information become available and as calculated results are interpreted and understood.
Interactive Highway Safety Design Model: Issues Related to Driver Modeling
Authors: Levison William H.
Published: April 2007

The Federal Highway Administration has undertaken a multiyear project to develop the Interactive Highway Safety Design Model (IHSDM), which is a set of software tools to analyze candidate highway geometric designs from a safety standpoint. The IHSDM is envisioned to contain five analysis tools or “modules”: (1) policy review, (2) design consistency, (3) accident analysis, (4) traffic analysis, and (5) driver/vehicle analysis. The structure of the driver/vehicle module is reviewed, with emphasis on the driver component. Modeling issues regarding decision and control are discussed. Major issues include (1) perceptual and decision processes in planning speed and path profiles during curve approach and curve negotiation, and (2) nonlinear versus linear aspects of control.
Visual Information Processing: Perception, Decision, Response Triplet
Authors: Demirarslan Hasan , Chan Yupo , Vidulich Michael
Published: April 2007

In performing critical tasks, the reaction time of the decision maker may mean the difference between safety and hazard. While different people have different risk-taking behavior, the process by which they react to a stimulus is fundamentally similar. The process involves perception, decision, and response. Thus, the decision maker sees an outside stimulus, processes the information and arrives at a yes or no decision, and then takes the necessary physical steps to implement the decision. For example, a driver sees the onset of a yellow light, makes up his or her mind about stopping or running for the light, and accordingly steps on the brake or the gas pedal. We refer to perception, decision, and response as the fundamental “triplet” underlying any human performance in a simple or complex environment. Unless this triplet is understood, other behavioral models cannot be constructed with confidence. By observing the percentage of drivers that run for a light and stop for a light, the authors have shown that one can separately measure the perception, decision, and response times in terms of probability distributions. The proposed approach is illustrated for drivers at an intersection through a series of experiments. Preliminary results point to its applicability toward other human tasks, such as landing an aircraft.
End-Result Specifications for Warranted Asphalt Pavements
Authors: Zaghloul Sameh , Saeed Nasser A. , Al Jassim Ali , Rafi Ahmed M.
Published: April 2007

Long-term pavement performance is highly dependent on its initial condition. High initial roughness leads to higher maintenance and rehabilitation costs, to shorter service life, and to significant reduction in riding quality. A performance-based specification applicable for new and rehabilitated warranted pavements is developed and presented here. The primary purpose of this specification is control of the initial longitudinal roughness of pavements, which will lead to smoother pavements and hence satisfactory long-term performance. In this specification, pavement roughness is measured by using Class I or calibrated Class II profilometers, such as infrared and laser profilometers. Tests are performed on each asphalt layer before the next layer is constructed. Three criteria are considered in the specification: surface tolerance, roughness indices, and repeated waves. It should be noted that this specification focuses on the functional performance of pavements and does not directly address their structural performances. A user-friendly software is developed to implement this specification. The software is capable of simulating straightedge inspections, calculating roughness statistics, and performing frequency analyses, such as power spectral analysis. With the software, a pavement section can be evaluated, tested, and analyzed in few minutes. Highway agencies as well as contractors will benefit from implementing this specification. Highway agencies will benefit by being able to achieve the goal of having safe, smooth, and economic pavements, and contractors will benefit by reducing maintenance cost during maintenance and warranty periods. Also, contractors will get quick results and meaningful feedback to the paving operation. A payment structure, including bonus payments for extended service lives, is included in the specification. This payment structure is based on the long-term effects of the initial roughness on the pavement life-cycle costs. The bonus program will encourage contractors to achieve higher levels of quality.
Mitigating the Adverse Impacts of the Dallas North Central Expressway Construction on Businesses
Authors: Harrison Rob , Waldman Benjamin
Published: April 2007

Reconstruction of the Dallas North Central Expressway is one of the largest construction projects undertaken by the Texas Department of Transportation. The $450 million, 18-km highway and light-rail corridor is being stage constructed under heavy commuting and Interstate traffic and a variety of strategies have been undertaken to mitigate the adverse impacts on traffic flow and businesses. The findings of various surveys conducted to evaluate the effectiveness of the business mitigation policies, including the impact on sales and access of business sales data reported to the state comptroller, an examination of multitenant occupancy rates for office space in the catchment area, and an analysis of businesses that either closed or opened are reported here. Somewhat surprisingly, more businesses opened than closed during construction. Recommendations are made on which policies can be utilized in other metropolitan areas of Texas and the United States.
Public Information Activities To Mitigate the Impacts of Closing San Francisco’s Central Freeway
Authors: Billheimer John W. , McNally Juliet , Sibley Doug , Robbins Gerald
Published: April 2007

San Francisco’s Central Freeway, which carried 93,000 commuters a day over Market Street into the Hayes Valley/Western Addition neighborhood, was shut down on August 25, 1996, so the freeway’s upper deck could be demolished as a first step in improving the seismic safety of the structure. Anticipating disastrous traffic tie-ups, local newspapers characterized the construction period in advance as “six months of traffic hell.” In an effort to mitigate the effects of the closure, the California Department of Transportation and the city of San Francisco developed a mitigation plan and implemented a wideranging public information program that included direct mailings of brochures detailing alternative travel patterns to commuters observed using the freeway. On the first day after the closure, the media braced for disaster and sent reporters to cover the expected traffic jams. When none occurred, the absence of backups became news, and politicians questioned whether the freeway was really needed. Commuters had heeded the advice of the public information campaign and spread themselves over enough routes and modes to avert large-scale delays. However, the diverted traffic brought additional congestion, delays, and potentially more accidents to the city streets in the vicinity of the freeway. The traffic patterns before and after closure are documented here, and the effectiveness of the public information program in influencing these patterns is assessed.
Neuronet-Based Approach for Assessing Liquefaction Potential of Soils
Authors: Eldin Ali Hossam , Najjar Yacoub M.
Published: April 2007

A backpropagation artificial neural network (ANN) algorithm with one hidden layer was used as a new numerical approach to characterize the soil liquefaction potential. For this purpose, 61 field data sets representing various earthquake sites from around the world were used. To develop the most accurate prediction model for liquefaction potential, alternating combinations of input parameters were used during the training and testing phases of the developed network. The accuracy of the designed network was validated against an additional 44 records not used previously in either the network training or testing stages. The prediction accuracy of the neural network approach–based model is compared with predictions obtained by using fuzzy logic and statistically based approaches. Overall, the ANN model outperformed all other investigated approaches.
Deformation of Embankments Due to Liquefaction During 1994 Northridge Earthquake
Authors: Bardet J.P. , Davis C.A.
Published: April 2007

The 1994 Northridge and 1971 San Fernando earthquakes subjected the Lower and Upper San Fernando Dams of the Van Norman Complex in the San Fernando Valley, California, to strong near-source ground motions. In 1994, these earth dams, which were out of service and retained only a few meters of water, extensively cracked and settled because of liquefaction of their hydraulic fill. The Lower San Fernando Dam moved more than 15 cm upstream as the hydraulic fill liquefied beneath its upstream slope. The Upper San Fernando Dam moved even more, and it deformed in a complex three-dimensional pattern. The responses of the Lower and Upper San Fernando Dams during the 1994 Northridge earthquake, although less significant than in 1971, provided the geotechnical engineering community with two useful case histories.
Centrifuge Testing of Remediation of Liquefaction at Bridge Sites
Authors: Balakrishnan A. , Kutter B.L. , Idriss I.M.
Published: April 2007

Five centrifuge models were tested to begin to quantify the effectiveness of liquefaction remediation techniques and to optimize the required volume of soil to be treated to reduce liquefaction consequences to a tolerable level. Detailed models of a bridge site including a river channel, flood plains, and bridge abutments were tested in the large centrifuge at the University of California, Davis. The models consisted of a deep, level, liquefiable sand layer overlain by a sloping, less-permeable clay layer with a free face at the river channel. Densification of a limited region of sand and in-ground water barriers were evaluated as possible remediation treatments. While spinning at a centrifugal acceleration of 30 g, the base of each model was shaken with realistic earthquake base motions. Base motions, pore pressures in the treated and untreated zones, profiles of ground deformations, settlements, and lateral sliding are compared. Settlements were controlled satisfactorily, but lateral sliding of the surface clay layer was not adequately controlled by the limited remedial treatments.
Ground Modification for Mitigation of Liquefaction
Authors: Welsh Joseph P. , Hussin James D. , Baez Juan I.
Published: April 2007

On the basis of proven success of mitigation of liquefaction by ground modification, transportation and other projects increasingly are being protected by these technologies. The concept of liquefaction and the various ground improvement methods currently in use for liquefaction mitigation are discussed. Case histories of ground modification techniques used for the in situ improvement of potentially liquefiable soils are cited.
Differential Settlements and Inelastic Response in Steel Bridge Beams
Authors: Hearn George , Nordheim Knut
Published: April 2007

A proposed method for mitigation of pavement faults at bridge abutments (the “bump at the end of the bridge”) is the use of shallow foundations. Abutments on shallow foundations are expected to settle compatibly with embankments and thus to minimize pavement faults. Allowing bridge abutments to settle may reduce faults, but it creates a demand for tolerance of different settlement in bridge superstructures. Current guidelines for tolerable differential settlement of bridges are empirical only, and the application of elastic analysis of bridge superstructures to determine tolerance of settlement has not produced satisfactory results. Inelastic analysis of steel bridge beams was applied to the computation of tolerable differential settlement. Tests of inelastic rotation capacity of steel beams were reviewed and compared with the results of inelastic analyses. A model of tolerable inelastic rotation capacity in steel beams is proposed.
Pile Forces in Integral Abutment Bridges Subjected to Truck Loads
Authors: Mourad Shehab , Tabsh Sami W.
Published: April 2007

Interest in the use of integral bridges has increased in recent years because of their economy, reliability, and strength. However, most of the published research on integral bridges has been concerned with determination of the thermal effect, creep analysis, and seismic behavior. Few studies on live load analysis of integral abutment bridges have been carried out. The pile load behavior of integral abutments supporting composite steel superstructures subjected to gravity loads is investigated. The applied loading is composed of one or more side-by-side HS20-44 trucks. The finite element method is used to analyze the three-dimensional bridge system and determine forces in the piles. A parametric study is performed to obtain the effects of the number of trucks and their location, superstructure geometry, pile spacing and stiffness, pile connection type, and wingwall length on the pile loads. A simple, approximate procedure for computing pile loads is developed on the basis of the findings of the finite element analysis. The results indicate that the abutment-wingwall system does not behave as a rigid block as in the conventional case of a footing on flexible piles. Also, the generated bending moment in the piles caused by gravity load is significant and cannot be neglected in design.
Application of Anchored Geosynthetic Systems for In Situ Slope Stabilization of Fine-Grained Soils
Authors: Vitton Stanley J. , Harris Wendell W. , Frank Whitman M. , Liang Robert Y.
Published: April 2007

The use of anchored geosynthetic systems (AGS) was proposed by Koerner et al. for the stabilization of slopes at or near their failure state. AGS provides in-situ stabilization of soil slopes by combining a surface-deployed geosynthetic with an anchoring system of driven reinforcing rods similar to soil nailing. Installation of the system involves tensioning a geosynthetic over a slope’s surface by driving anchors through the geosynthetic at a given spacing and distance. By tensioning the geosynthetic over the slope’s surface, a compressive load is applied to the slope. Benefits of AGS are described to include the following: ( a) increased soil strength due to soil compression, including increased compressive loading on potential failure surfaces; ( b) soil reinforcement through soil nailing; ( c) halt of soil creep; ( d) erosion control; and ( e) long-term soil consolidation. Following installation of the AGS and 1 year of monitoring, it was found that the anchored geosynthetic system provided only some of the reported benefits and in general did not function as an active stabilization system. This was in part because the system could not provide and maintain loading on the geosynthetic. The geosynthetic, however, did tension when slope movement occurred, preventing the slope from failing. Thus, the system functioned more as a passive restraint system and appeared to function well over the monitoring period.
Quality Control for Pile Foundations Using Nondestructive Testing: Case Studies in Taiwan
Authors: Lin San-Shyan , Hoe Eric
Published: April 2007

A study was conducted in Taiwan of the quality control of drilled shafts using nondestructive testing. Ultrasonic borehole logging used for borehole quality control is introduced. Experiences from incorporation of nondestructive test methods into contract documents during the design phase, the use of a specification for acceptance of a pile during construction, and remedial measures are discussed. Three projects on quality control of drilled piles using nondestructive tests are evaluated. Interpretation based on the test results used to reach a decision for acceptance or rejection of a pile is discussed for the case studies.
Assessing Reliability of Drilled Shaft Integrity Testing
Authors: Davis Allen G.
Published: April 2007

The reliability of an engineering system can be described as the degree of confidence in the system performing as it is designed or intended to do. This can be assessed by a purely subjective, “gut feeling” reaction from the engineer making judgments based on the test results, or it can be expressed mathematically by considering the reliability of individual system components, together with their relative effects on the performance of the total system. Nondestructive testing (NDT), when used in the quality control of drilled shafts, can be viewed from two extremes: either NDT helps engineers confirm that their design and intended performance criteria are being met, or NDT checks that the contractor has supplied the owner with the product for which the owner has paid (material quality, minimal geometric requirements, etc.). NDT methods currently available are more suited to the first scenario (performance specification). This is supported by analysis of the parameters controlling NDT results and by experience in the United States and in the rest of the world.
Using Dynamic Pile Testing To Evaluate Quality and Verify Capacity of Driven Piles
Authors: Walton Phillip A. , Borg Stephen L.
Published: April 2007

Pile testing using a pile driving analyzer is a nondestructive method of evaluating the support capacity provided by the soil to a pile. The New York State Department of Transportation’s (NYSDOT) approach to incorporating this testing procedure into a project is discussed from design into construction. Specification and contractural responsibilities are addressed, as are typical applications of the test method. By judiciously using dynamic pile testing, NYSDOT is able to cost-effectively link the design process to construction. Informed decisions are possible regarding the field performance of driven piles with respect to pile-soil support capacity, hammer operation, driving stress, damage to piles during driving, and verification of assumptions made for wave equation analysis of piles.
Evaluation of the Massachusetts Motorist Assistance Program: Assessment of Congestion and Air Quality Impacts
Authors: Stamatiadis Chronis , Gartner Nathan H. , Winn James , Bond Russell
Published: April 2007

A motorist assistance program has been operating in Massachusetts since 1995 to assist stranded motorists on selected freeway routes during the morning and evening peak periods. The program covers 21 major routes throughout the state, with one van, fully equipped to handle the majority of incidents encountered assigned to each route. To evaluate the program’s effectiveness a comprehensive analysis of a set of performance measures was carried out. The analysis consisted of simulating the program’s impact on each route category for all time periods and incident types. Benefit to cost ratios were calculated for each route and for the program as a whole. The program’s benefits far exceed the costs: the average value of the benefit to cost ratio is 19:1, whereas the values for the different routes range from 3:1 to 58:1. Overall, the program provides significant benefits in terms of reduction of travel time, fuel consumption, and emission of pollutants. The analysis results were also used to design an improved operations scheme on the routes that are served.