Impacts of Climatic Regions and Design Factors on the Condition and Distress of Specific Pavement Test Sections in the Long-Term Pavement Performance Program

2016 ◽  
Vol 2590 (1) ◽  
pp. 113-121
Author(s):  
Gopikrishna Musunuru ◽  
Gilbert Baladi ◽  
Tyler Dawson ◽  
Michael Prohaska ◽  
Kyle Thomas
Keyword(s):  
Pavement Performance ◽  
Climatic Regions ◽  
Design Factors

Calibration of Performance Models for Jointed Plain Concrete Pavements Using Long-Term Pavement Performance Database

1998 ◽  
Vol 1629 (1) ◽  
pp. 108-116 ◽  
Author(s):  
Marcelo Bustos ◽  
Hernáan E. De Solminihac ◽  
Michael I. Darter ◽  
Andres Caroca ◽  
Juan Pablo Covarrubias
Keyword(s):  
Plain Concrete ◽  
Pavement Performance ◽  
Concrete Pavements ◽  
Performance Models ◽  
Climatic Regions ◽  
Transverse Cracking ◽  
Global Calibration ◽  
Regional Factors

A methodology for calibrating performance models for jointed plain concrete pavements (JPCP) is presented; it is based on statistical analysis of data from the Long-Term Pavement Performance (LTPP) database. The methodology provides calibration factors to pavements in four climatic regions (dry-freeze, dry-nonfreeze, wet-freeze, and wet-nonfreeze) for the JPCP performance models in HDM-4: joint faulting, transverse cracking, joint spalling, and roughness. The procedure allows calculation of global calibration factors, which does not affect significantly the quality of the prediction compared with the quality achieved through the use of regional factors.

Use of Long-Term Pavement Performance Data to Develop Traffic Defaults in Support of Mechanistic-Empirical Pavement Design Procedures

2003 ◽  
Vol 1855 (1) ◽  
pp. 176-182 ◽  
Author(s):  
Weng On Tam ◽  
Harold Von Quintus
Keyword(s):  
Pavement Design ◽  
Vehicle Classification ◽  
Pavement Performance ◽  
Traffic Data ◽  
Design Procedures ◽  
Load Spectra ◽  
State Highway ◽  
Pavement Structures ◽  
Empirical Design

Traffic data are a key element for the design and analysis of pavement structures. Automatic vehicle-classification and weigh-in-motion (WIM) data are collected by most state highway agencies for various purposes that include pavement design. Equivalent single-axle loads have had widespread use for pavement design. However, procedures being developed under NCHRP require the use of axle-load spectra. The Long-Term Pavement Performance database contains a wealth of traffic data and was selected to develop traffic defaults in support of NCHRP 1-37A as well as other mechanistic-empirical design procedures. Automated vehicle-classification data were used to develop defaults that account for the distribution of truck volumes by class. Analyses also were conducted to determine direction and lane-distribution factors. WIM data were used to develop defaults to account for the axle-weight distributions and number of axles per vehicle for each truck type. The results of these analyses led to the establishment of traffic defaults for use in mechanistic-empirical design procedures.

Comprehensive Evaluation of Rutting of Warm-Mix Asphalt Utilizing Long-Term Pavement Performance Specific Pavement Studies

2020 ◽  
Vol 2674 (7) ◽  
pp. 272-283 ◽  
Author(s):  
Biswajit K. Bairgi ◽  
A.S.M. Asifur Rahman ◽  
Rafiqul A. Tarefder ◽  
Matias M. Mendez Larrain
Keyword(s):  
Comprehensive Evaluation ◽  
Field Investigation ◽  
Warm Mix Asphalt ◽  
Pavement Performance ◽  
Laboratory Evaluation ◽  
Production Temperature ◽  
Wheel Tracking Test ◽  
Modified Binder ◽  
Wheel Tracking

Warm-mix asphalt (WMA) technologies allow binder softening for compaction benefits. Lower production temperature also causes reduced short-term aging in WMA. Considering the long-term implication of the reduced aging and binder softening, WMA is being questioned about its rutting characteristics. As such, this study evaluates different WMA technologies for rutting characteristics in comparison to traditional hot-mix asphalt (HMA) through laboratory and field investigation. The study utilized the long-term pavement performance (LTPP) project in the state of New Mexico called Specific Pavement Study-10 (SPS-10), which was designed to evaluate the WMA performances. The LTPP SPS-10 section includes: (i) control HMA, (ii) foaming, (iii) Evotherm, (iv) Cecabase 1, and (v) Cecabase 2 mixtures. Cecabase 2 mixture consists of a polymer-modified binder (PG 70-28+), whereas other mixtures consist of PG 70-28 binder. The aggregate type, properties, and gradations are the same in all the sections. Laboratory evaluation of rutting was conducted through the Hamburg wheel tracking test. Long-term field rutting was evaluated through Mandli’s pavement profile scanner, a laser-based distress evaluation technology. The study found that WMA with foaming, Evotherm, or Cecabase shows slightly higher rutting compared with the control HMA; however, all the sections satisfied laboratory and field rutting criteria. The use of a polymer-modified binder in WMA significantly improves the rutting characteristics.

Seed Modulus Generation Algorithm for Backcalculation of Flexible Pavement Moduli

2005 ◽  
Vol 1905 (1) ◽  
pp. 117-127 ◽  
Author(s):  
T. F. Fwa ◽  
Thakur Swapna Rani
Keyword(s):  
Closed Form ◽  
Flexible Pavements ◽  
Flexible Pavement ◽  
Pavement Performance ◽  
Program Performance ◽  
Generation Algorithm ◽  
User Input ◽  
Pavement Structures ◽  
Performance Project

The seed moduli chosen for backcalculation analysis of multilayer flexible pavements can have significant impacts on the performance of backcalculation software and, sometimes, the final solutions of the backcalculated moduli. Practically all backcalculation programs provide internally generated seed moduli for backcalculation analysis. However, as the internally generated seed moduli do not always produce satisfactory results, the use of user-input seed moduli is generally encouraged. With the aim of providing useful guidance in the choice of seed moduli, a seed modulus generation algorithm, 2L-BACK, for multilayer flexible pavements based on a closed-form modulus backcalculation solution for two-layer flexible pavement structures was developed. The proposed algorithm does not require any subjective judgment by the user. An evaluation analysis of the effectiveness of the proposed procedure is presented by the use of two types of backcalculation software, MICHBACK and EVERCALC, and is based on measured and computed data for flexible pavement segments from the Long-Term Pavement Performance project. A comparison was made of the backcalculation program performance and the computed moduli of solutions obtained from internally generated seed moduli and those obtained from seed moduli generated by the proposed algorithm. It was found that the proposed seed modulus generation algorithm led to enhanced program performance of MICHBACK with respect to convergence characteristics and the accuracies of the backcalculated solutions. In comparison, the corresponding improvements for the case of EVERCALC were less. The proposed seed modulus generation algorithm does not suffer from the location and pavement type transferability constraints of most regression-based seed modulus generation methods. The results of the study suggest that the algorithm can be effectively incorporated into backcalculation software for multilayer flexible pavements.

scholarly journals The Current Dietary Risk Assessment of Chemicals in Food Underestimates the Actual Risk

2019 ◽  
Vol 73 (10) ◽  
pp. 832-834
Author(s):  
Jürg A. Zarn ◽  
H. Christoph Geiser
Keyword(s):  
Daily Intake ◽  
Added Value ◽  
Toxic Substances ◽  
Dietary Risk ◽  
Short And Long Term ◽  
Exposure Levels ◽  
Design Factors ◽  
Dietary Risk Assessment ◽  
Long Term Studies

Dietary risk assessments (DRA) help determine safe exposure levels of toxic substances in food. Of these, Acceptable Daily Intake (ADI), derived from No Observed Adverse Effect Levels (NOAEL) of long-term toxicity studies, is compared to exposure estimates using lifetime-averaged food intakes. These estimates ignore intermittent high exposures exceeding the ADI; toxic effects of such exposures are considered irrelevant, on the assumption that toxic potency increases with exposure duration, which would be reflected by decreasing NOAELs. However, our statistical analysis of thousands of animal toxicology studies shows that NOAELs after short- and long-term exposure are similar if study design factors are considered. Thus, the short- and long-term potency effects of chemicals are similar. Hence, a short-term toxic effect is generally ignored in current DRA. It accounts for lifetime-averaged but not intermittent high food intakes and, therefore, must be revised. Additionally, there is no added value of long-term studies for ADI derivation.

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