Evaluation of Mechanistic-Empirical Performance Prediction Models for Flexible Pavements

1998 ◽  
Vol 1629 (1) ◽  
pp. 169-180 ◽  
Author(s):  
Hesham A. Ali ◽  
Shiraz D. Tayabji
Keyword(s):  
Prediction Models ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Continuous Functions ◽  
Poor Agreement ◽  
Empirical Performance ◽  
Pavement Structures ◽  
Using Data ◽  
Program Data

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.

Mechanistic-Empirical Rut Prediction Model for In-Service Pavements

2000 ◽  
Vol 1730 (1) ◽  
pp. 99-109 ◽  
Author(s):  
Hyung Bae Kim ◽  
Neeraj Buch ◽  
Dong-Yeob Park
Keyword(s):  
Prediction Model ◽  
Prediction Models ◽  
Flexible Pavements ◽  
Proposed Model ◽  
Major Mode ◽  
Global Positioning ◽  
Pavement Engineering ◽  
Using Data ◽  
Consistency Properties

Rutting is a major mode of failure in flexible pavements. Development of accurate predictive rut performance models is an ongoing pursuit of the pavement engineering community. This has resulted in a plethora of rut prediction models ranging from purely mechanistic to empirical. Presented is the development of a mechanistic-empirical rut prediction model that uses data from 39 in-service flexible pavements from Michigan. The proposed model accounts for the rut contribution of the subgrade, subbase, base, and asphalt concrete layers. The model addresses inventory-type variables like pavement cross section, ambient temperature, and asphalt consistency properties. The applicability of the model was validated by using data from 24 Long-Term Pavement Performance–Global Positioning System (GPS) sites. For 19 of the 24 GPS sites, the predicted rut depth was within 5 mm of the measured rut depth.

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.

Mechanistic Evaluation of Test Data from Long-Term Pavement Performance Jointed Plain Concrete Pavement Test Sections

1998 ◽  
Vol 1629 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Y. Jane Jiang ◽  
Shiraz D. Tayabji
Keyword(s):  
Test Data ◽  
Additional Data ◽  
Fatigue Cracking ◽  
Plain Concrete ◽  
Concrete Pavement ◽  
Pavement Performance ◽  
Distress Prediction ◽  
Program Data ◽  
Insight Into

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.

scholarly journals Development Of A Pavement Rutting Model Using Shakedown Theory

2015 ◽  
Vol 16 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Mostapha Boulbibane ◽  
Ian F. Collins
Keyword(s):  
Flexible Pavements ◽  
Design Methods ◽  
Design Parameters ◽  
Ride Quality ◽  
Simple Relationship ◽  
Wheel Load ◽  
Premature Failure ◽  
Shakedown Theory ◽  
Pavement Structures

Abstract The rutting of flexible pavements during their exploitation is considered to be one of the main problems in UK as well as worldwide. It is a serious mode of distress alongside fatigue in bituminous pavements that may lead to premature failure, as indicated by permanent deformation or rut depth along the wheel load path, and results in early and costly rehabilitation. This kind of pavement distress makes a negative impact to the serviceability characteristics of the flexible pavement, to the residual life of pavement structure and also to the safety and ride quality for traffic. Two design methods have been used to control rutting: one to limit the vertical compressive strain on the top of subgrade and the other to limit rutting to a tolerable amount usually around “12 mm”. Although experimental data and practical experience have been introduced into these design methods through empirical parameters, there is not a simple relationship between the elastic strain and the long-term plastic behaviour of pavement materials. This paper describes a method based on the kinematic shakedown theorem for constructing a mathematical model to predict the long-term behaviour of pavement structures under the action of repeated and cyclic loadings imposed by moving traffic. This method seeks the mechanism from within a class of mechanisms that minimises the shakedown limit load for pavement structures consisting of layers of Mohr-Coulomb materials. The model differs from extant models, in that the cyclic nature of the loading on a pavement is recognised from the outset, and the current method which is based upon foundation analysis, is replaced by a procedure employing shakedown theory that features the capabilities and applications of the developed technique for assessing rutting in flexible pavements. The basic concepts are outlined together with the most recent calculations of the critical design shakedown load. The influence of the design parameters such as, the strength, stiffness and depth of the granular base-course material as well as the consequences of traffic loading (number of equivalent standard axel loads – ESAL’s) are discussed.

Clinical impact of myositis-specific autoantibodies on long-term prognosis of juvenile idiopathic inflammatory myopathies: multicentre study

Rheumatology ◽  
2021 ◽  
Author(s):  
Yuichi Yamasaki ◽  
Norimoto Kobayashi ◽  
Shinji Akioka ◽  
Kazuko Yamazaki ◽  
Shunichiro Takezaki ◽  
...  
Keyword(s):  
Matrix Protein ◽  
Multiple Drug ◽  
Idiopathic Inflammatory Myopathies ◽  
Inflammatory Myopathies ◽  
Gamma Subunits ◽  
Specific Autoantibody ◽  
Long Term Prognosis ◽  
Using Data ◽  
Drug Free

Abstract Objectives This study aimed to investigate the clinical characteristics, treatment and prognosis of juvenile idiopathic inflammatory myopathies (JIIM) in Japan for each myositis-specific autoantibody (MSA) profile. Methods A multicentre, retrospective study was conducted using data of patients with JIIM at nine paediatric rheumatology centres in Japan. Patients with MSA profiles, determined by immunoprecipitation using stored serum from the active stage, were included. Results MSA were detected in 85 of 96 cases eligible for the analyses. Over 90% of the patients in this study had one of the following three MSA types: anti-melanoma differentiation-associated protein 5 (MDA5) (n = 31), anti-transcriptional intermediary factor 1 alpha and/or gamma subunits (TIF1γ) (n = 25) and anti-nuclear matrix protein 2 (NXP2) (n = 25) antibodies. Gottron papules and periungual capillary abnormalities were the most common signs of every MSA group in the initial phase. The presence of interstitial lung disease (ILD) was the highest risk factor for patients with anti-MDA5 antibodies. Most patients were administered multiple drug therapies: glucocorticoids and MTX were administered to patients with anti-TIF1γ or anti-NXP2 antibodies. Half of the patients with anti-MDA5 antibodies received more than three medications including i.v. CYC, especially patients with ILD. Patients with anti-MDA5 antibodies were more likely to achieve drug-free remission (29 vs 21%) and less likely to relapse (26 vs 44%) than others. Conclusion Anti-MDA5 antibodies are the most common MSA type in Japan, and patients with this antibody are characterized by ILD at onset, multiple medications including i.v. CYC, drug-free remission, and a lower frequency of relapse. New therapeutic strategies are required for other MSA types.

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