Turner Fairbank Highway Research Center
Turner Fairbank Highway Research Center
Mensching D.J.,Turner Fairbank Highway Research Center |
Rowe G.M.,Abatech Inc. |
Sias Daniel J.,University of New Hampshire
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2016
Low temperature cracking is a critical distress form and is heavily influenced by the relaxation and strength capabilities of the material. These properties are related to the stiffness through principles of viscoelasticity. Recently, there is elevated pressure on decisions made by pavement and materials engineers to produce the longest lasting, most resourceful pavement systems possible to optimize monetary and non-renewable resource usage. The primary objectives of this study are to: 1) assess the value of a parameter which can describe low temperature cracking resistance by using dynamic modulus (|E∗|) and phase angle (δ) of the mixture and laboratory-measured performance; 2) present shape parameters of a mixture master curve that are directly related to the relaxation spectra, which is expected to play a pivotal role in low temperature distress resistance with aging; 3) define failure lines in Black Space which correspond with laboratory-measured performance and operate under a well-understood basis reinforced by the literature; and 4) provide agencies with a tool to aid in the movement towards a performance-based mixture design, acceptance, or rehabilitation decision-making system. An analysis of the mixture master curve is done to establish parameters which describe the relaxation spectra and aging potential of materials. A mixture-based Black Space parameter is presented based on results from the |E∗| master curve construction and the thermal stress restrained specimen test. This approach holds promise, but must be calibrated with a robust database before serious implementation considerations are made. Future work will look to determine a common stiffness condition to better define the failure threshold and to identify possible alternatives to the modified Glover-Rowe Junction used in this study. Further evaluation is also needed to optimize the temperature-frequency combination of the Black Space parameter itself and ensure a condition is specified that can be captured by test equipment an owner agency or contractor may possess as part of a performance-based specification framework. © 2016 Taylor & Francis.
Wu K.-F.,National Chiao Tung University |
Thor C.P.,Turner Fairbank Highway Research Center
Transportation Research Record | Year: 2015
Many factors are associated with crash risk, but their contribution to the progression of a crash is often unclear. Research on and understanding of the crash sequence are needed. One of the advantages of studying crash sequence is to identify the causative chain of crashes and, subsequently, the identification of effective countermeasures that may feasibly mitigate crash risk. An analogy to epidemiological studies is particularly useful: although researchers confirm that many factors are associated with an increase in the probability of myocardial infarction, there is still a need to research the disease process, the physiological process that promotes disease growth, and the possible interventions to treat or even prevent the disease. This study used data from the Integrated Vehicle-Based Safety System program. Two freeway rear-end events, including one crash and one near crash, with similar crash sequences were studied. The crash sequences of the two events were as follows: (a) the drivers maintained a temporal headway of less than 1 s at the beginning; (b) the traffic flow conditions were likely to cause misjudgments by the drivers and result in glances in inappropriate directions; (c) when the drivers were distracted, the leading vehicle decelerated; (d) the drivers did not decelerate accordingly and had their feet on the accelerator pedal; and (e) one event resulted in a crash and the other in a near crash. This study highlighted an approach for comparing and dissecting the differences in the crash sequence that led to the different outcomes.
Adams M.T.,Turner Fairbank Highway Research Center |
Nicks J.E.,Turner Fairbank Highway Research Center
Geotechnical Special Publication | Year: 2017
This paper presents a conceptual framework for prospective owners of mechanically stabilized earth (MSE) walls to assess and manage the risk of their project. The proposed framework is based on information about the causes of failure for MSE walls. The format of this assessment is centered on the principles of risk management necessary to meet the objectives of an owner or agency. The intent of the assessment is to manage the effects of uncertainty and poor practice centered on the main factors associated with MSE wall failures: soil type, design, communication, water, and construction. The assessment first establishes a relative consequence, or impact of failure, valued against the project requirements, cost, and significance, followed by determining the likelihood of an event based on the level of practice leading to uncertainty that could cause poor serviceability or failure. The assessment attempts to guide the owner towards best practices while also providing them with fundamental information to identify, analyze, and prioritize risk necessary to make informed decisions on the course of a wall project with respect to economics (cost), requirements, and performance. © ASCE.
Wang D.,Turner Fairbank Highway Research Center |
Roesler J.R.,University of Illinois at Urbana - Champaign
International Journal of Pavement Engineering | Year: 2014
This paper presents an analytical solution for prediction of the one-dimensional (1D) time-dependent temperature profile in a multi-layered rigid pavement system. Temperature at any depth in a rigid pavement system can be estimated by using the proposed solution with limited input data, such as pavement layer thicknesses, material thermal properties, measured air temperatures and solar radiation intensities. This temperature prediction problem is modelled as a boundary value problem governed by the classic heat conduction equations, and the air temperatures and solar radiation intensities are considered in the surface boundary condition. Interpolatory trigonometric polynomials, based on the discrete least squares approximation method, are used to fit the measured air temperatures and solar radiation intensities during the time period of interest. The solution technique employs the complex variable approach along with the separation of variables method. A FORTRAN program was coded to implement the proposed 1D analytical solution. Field model validation demonstrates that the proposed solution generates reasonable temperature profile in the concrete slab for a four-layered rigid pavement system during two different time periods of the year. © 2012 Taylor and Francis.
Li X.-J.,Turner Fairbank Highway Research Center |
Marasteanu M.O.,University of Minnesota
Proceedings of the Society for Experimental Mechanics, Inc. | Year: 2010
This work presents a repeatable semi circular bending (SCB) fracture test to evaluate the low temperature fracture resistance of asphalt mixture. The fracture resistance of six asphalt mixtures, which represent a combination of factors such as binder type, binder modifier, aggregate type, and air voids, and two testing conditions of loading rate and initial notch length, was evaluated by performing SCB fracture tests at three low temperatures. Fracture energy was calculated from the experimental data. Experimental results indicated strong dependence of the low temperature fracture resistance on the test temperature. Experimental plots and low coefficient of variation (COV) values from three replicates show a satisfactory repeatability from the test. The results of the analysis showed that fracture resistance of asphalt mixtures is significantly affected by type of aggregate and air void content. Experimental results, also confirmed the significance of binder grade and modifier type with relation to cracking resistance of asphalt mixtures. Analysis of result also indicated that both the loading rate and initial notch length had significant effect on the fracture energy at the highest test temperature, whereas the effect was strongly diluted at the two lower temperatures. No clear trend was found with the fracture peak load from either the effect of loading rate or notch length. © Society for Experimental Mechanics 2009.
Li X.,Turner Fairbank Highway Research Center |
Marasteanu M.,University of Minnesota
Engineering Fracture Mechanics | Year: 2010
The fracture process zone (FPZ) is a key factor to mechanistically characterize material fracture. This study investigates the FPZ of asphalt mixture at low temperature. The fracture process under a semi-circular bend (SCB) test of seven asphalt mixtures that represent a combination of different factors was monitored using an acoustic (AE) system with eight piezoelectric sensors. The size of FPZ was estimated by locating micro-cracks that correspond to 95% AE energy before peak load in the vicinity of the initial crack tip. The experimental data illustrates the significant influence of test temperature on the behavior of the asphalt mixture. Comparison results showed that the size of the FPZ significantly depends on air voids and aggregate type, but is less depend on the asphalt content. It was found that at a very low temperature, different loading rates produced very close FPZ, both for the width and length. No obvious difference was observed on the width of the FPZ for the three different initial notch lengths, whereas the length of the FPZ was found significantly increases with the decrease of the notch length. The size of FPZ was also numerically estimated for one case with the cohesive zone model (CZM) calibrated by experimental data from the same SCB test. The FPZ size obtained with both methods agrees reasonably with each other. © 2010 Elsevier Ltd.
Park E.S.,Texas A&M University |
Carlson P.J.,Texas A&M University |
Porter R.J.,University of Utah |
Andersen C.K.,Turner Fairbank Highway Research Center
Accident Analysis and Prevention | Year: 2012
Although it is generally expected that wider lines will have a positive effect on vehicle safety, there have not been any convincing evidence based on the crash data analysis, partly because of the lack of relevant data. In this paper, the safety effect of wider edge lines was examined by analyzing crash frequency data for road segments with and without wider edge lines. The data from three states, Kansas, Michigan, and Illinois, have been analyzed. Because of different nature of data from each state, a different statistical analysis approach was employed for each state: an empirical Bayes, before-after analysis of Kansas data, an interrupted time series design and generalized linear segmented regression analysis of Michigan data, and a cross sectional analysis of Illinois data. Although it is well-known that causation is hard to establish based on observational studies, the results from three extensive statistical analyses all point to the same findings. The consistent findings lend support to the positive safety effects of wider edge lines installed on rural, two-lane highways. © 2012 Elsevier Ltd. All rights reserved.
Xue W.,Virginia Polytechnic Institute and State University |
Weaver E.,Turner Fairbank Highway Research Center
Transportation Research Record | Year: 2011
FHWA conducted controlled loading tests on the US-23 test road in hot weather conditions in Ohio. The tests used four tire types in both dual and wide-base configurations, which were fitted on a single unit two-axle truck, maintaining a constant gross vehicle weight. Two pavement sections, one 8 in. (200 mm) and one 4 in. (100 mm) thick, were instrumented with strain gauge rosettes oriented vertically to measure strain traces induced from the passing wheel loads at three speeds and tire inflation pressures. Pavement temperature was monitored with depth during testing as well as wheel track offset distance from the strain sensors. Because of time constraints, only the sensors in the plane parallel to the direction of loading were analyzed, and response data were compared only with linear elastic pavement response models. The as-measured data were processed and evaluated for all rosettes oriented in the direction of loading. Stress relaxation modulus data were used to adjust the pavement modulus to a common temperature and loading time so all measured data could be compared at the same loading conditions. The WinLEA linear elastic model was used to determine the relationship of structural modulus to strain. Lateral offset distributions were determined from measured data to adjust all strains to the offset where maximum strain response is observed in the as-measured data. The adjustments were then applied to the as-measured strain data to make consistent comparisons between tires. Three of the four tire configurations produce nearly equivalent pavement response, which was attributed to similarities between the tire footprint widths.
Chen L.,Professional Service Industries Inc. |
Graybeal B.A.,Turner Fairbank Highway Research Center
Journal of Bridge Engineering | Year: 2012
The concrete-damaged plasticity (CDP) model with proposed material properties replicated the observed deflection and strain responses of three experimentally tested I-girders and was determined to be consistent for different spans under both flexural and shear tests. In this study, the CDP model was further tested in modeling the behaviors of a prestressed second-generation ultrahigh-performance concrete (UHPC) pi-girder. The computational aspects include discussion of the various parameters that influenced the accuracy of the model and investigation of the scenarios regarding the limits that are useful for further optimization of the girder. The CDP model was reconfirmed to be consistent and reliable in replicating the observed structural response of both the UHPC pi-girder and a modified structural configuration referred to as the "UHPC pi-girder-with-joint. " The finite-element analysis modeling techniques developed herein are expected to be valuable in the future development of additional UHPC structural components. © 2012 American Society of Civil Engineers.
Li X.,Turner Fairbank Highway Research Center |
Gibson N.,U.S. Federal Highway Administration
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2013
This study investigated the feasibility of performing dynamic modulus and fatigue performance tests using reduced scale specimens in an Asphalt Mixture Performance Tester. Ten different mixtures were characterized which had different nominal maximum aggregate sizes and were laboratory prepared or field cored from accelerated pavement test sections. Indirect tension dynamic modulus was included in the characterization of the field cored materials. An aspect ratio for 38 mm diameter specimens was recommended based on an exploratory portion of the study. The experimental results show that the modulus of the small scale specimens can be quite similar to the full size specimens and tends to be slightly softer at high temperature and low reduced frequencies. Phase angle is more comparable and, when different, tends to be slightly higher for the small scale specimens. Data analysis comparing the full size and small scale specimens revealed two out of three data quality indicators from small size dynamic modulus are as good as that of full size dynamic modulus. The third quality indicator was worse for about one third of the data points, but the majority of tests satisfied recommended values. The fatigue test results showed the modulus reduction at failure and endurance limit are comparable between full size and small scale specimens. There was no consistent trend where small scale was larger or smaller than full scale specimens in fatigue resistance and the ranking was mostly preserved between the two sized specimens. Overall, the small scale approach is very promising which can allow the field-compacted fatigue and stiffness characteristics of pavements to be assessed. The applications of this research are field validation of cracking tests, performance based quality assurance and forensic investigations. © 2013 Taylor & Francis.