Mechanistic-Empirical Approach to Assessing Relative Pavement Damage

1998 ◽  
Vol 1639 (1) ◽  
pp. 112-119 ◽  
Author(s):  
Anastasios M. Ioannides ◽  
Rohit K. Karanth ◽  
Krishnakumar Sanjeevirao
Keyword(s):  
Cross Sections ◽  
Damage Accumulation ◽  
Empirical Approach ◽  
Elastic Analysis ◽  
Analysis Tools ◽  
Equivalency Factors ◽  
Pavement Engineering ◽  
Pavement Damage ◽  
Engineering Practices ◽  
Load Equivalency Factors

The purpose of this investigation was to examine the feasibility of using conventional pavement analysis tools to derive mechanistic-empirical load equivalency factors (LEFs) applicable to wheel assemblies and pavement cross-sections not included in the AASHTO guide tables in a manner that would provide seamless continuity with current pavement engineering practices. The derivation of such LEFs was pursued on the assumption that two controversial concepts—namely, load equivalency and linear damage accumulation—were, in fact, valid. The purpose of this assumption is to investigate whether it is possible to reach reasonable conclusions for as long as no theoretically valid alternatives to these concepts are available. It was found that it is possible to reproduce with a reasonable fit the statistical/empirical LEFs found in the AASHTO guide tables, using layered elastic analysis and the fatigue relationship derived by Vesic and Saxena. Other conventional fatigue relationships yield unreliable results when compared to the AASHTO LEFs. It is also possible to derive mechanistic-empirical extensions to the AASHTO LEFs using this approach, so tire configurations and pavement cross-sections not included in the AASHTO tables of LEFs can be accommodated in a seamless and equitable manner.

Reducing Damage to Low-Volume Roads by Using Trucks with Reduced Tire Pressures

1997 ◽  
Vol 1589 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Maureen A. Kestler ◽  
Richard L. Berg ◽  
Thomas L. Moore
Keyword(s):  
Cross Sections ◽  
Design Procedure ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Tire Pressure ◽  
Low Volume Roads ◽  
Minimal Damage ◽  
Allowable Load ◽  
Low Volume ◽  
Pavement Damage

Heavy-volume highways in seasonal frost areas are designed to resist the effects of spring thaw. However, timber access roads, county roads, and other low-volume roads with thin bituminous surfaces can be quite susceptible to pavement damage during midwinter- and spring-thaw periods. To reduce damage to low-volume roads, towns, cities, and states typically either post reductions in allowable load or completely prohibit hauling during damage-susceptible periods. Associated economic impact can be significant. To evaluate the effects of tire pressure on cumulative road damage, a mechanistic pavement design procedure developed by the U.S. Army Corps of Engineers for use in seasonal frost areas was used on a matrix of tire pressures, low-volume pavement cross sections, and environmental conditions. A series of computer simulations showed ( a) trucks operating with conventional tire pressures can cause excessive damage, particularly in the form of cracking, to low-volume roads with thin bituminous surfaces during relatively short thaw periods; ( b) pavement damage could be reduced substantially by restricting hauling to trucks operating with reduced tire pressures; and ( c) there are “threshold” tire pressures under which only minimal damage occurs, even during critical spring thaw. These results could influence guidelines for hauling restrictions and, in turn, associated economics.

Performance of Superpave Mixtures Under Accelerated Load Testing

2000 ◽  
Vol 1716 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Zhong Wu ◽  
Mustaque Hossain ◽  
Andrew J. Gisi
Keyword(s):  
Fatigue Damage ◽  
Maximum Size ◽  
Fatigue Tests ◽  
Transverse Strain ◽  
Load Testing ◽  
Soil Pressure ◽  
Tire Pressure ◽  
River Sand ◽  
Equivalency Factors ◽  
Pavement Damage

The performances of two Superpave® test sections, constructed with 12.5 mm (0.5 in.) nominal maximum size Superpave mixture (SM-2A) with varying percentages of river sand at the Kansas Accelerated Testing Laboratory (K-ATL), are described. A 150-kN (34-kip) tandem axle with dual wheels and 620-kPa (90-psi) tire pressure was used for loading. After 10,000 repetitions, the sections were loaded by 160-kN (36-kip), 150-kN (34-kip), and 144-kN (32.5-kip) tandem axles and 98-kN (22-kip), 90-kN (20-kip), and 80-kN (18-kip) single axles, for estimating relative pavement damage due to different axle loads and configurations. Critical pavement responses were measured on each test section with the transverse strain gauges and soil pressure cells under both K-ATL tandem axle and falling weight deflectomter (FWD) loads. The pavement responses were also estimated from a multilayer elastic analysis program, ELSYM5. Laboratory fatigue tests were conducted on the SM-2A beams. Fatigue and rutting damage analyses were then conducted. The results indicated very little fatigue damage on these sections. The Superpave mixtures appeared to be less susceptible to fatigue damage, presumably due to better aggregate structure and higher binder content than the traditional asphalt mixtures. Rutting on the section with 15 percent river sand was mainly due to consolidation of the SM-2A and/or other layers since no significant flow of the Superpave mixture was evident. The AASHTO load equivalency factors were found to be much higher than those calculated in this study.

scholarly journals Load equivalency factors for off-road trucks

2019 ◽  
Vol 72 (4) ◽  
pp. 601-608
Author(s):  
Taciano Oliveira da Silva ◽  
Sérgio Leandro Scher Dias Neto ◽  
Heraldo Nunes Pitanga ◽  
Marcela Luiza Pelegrini Guimarães
Keyword(s):  
Equivalency Factors ◽  
Load Equivalency Factors

Imaging in Periodontology

2010 ◽  
pp. 204-236
Author(s):  
O. Nackaerts
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
3D Visualization ◽  
The Elderly ◽  
Diagnostic Tools ◽  
Periodontal Tissues ◽  
Analysis Tools ◽  
2D And 3D ◽  
2D Images

Periodontal disease is the most common oral disorder in the elderly population. Early detection of bony and soft tissue support changes is therefore crucial in relation to the prevention of tooth loss and/or the patient’s general health. Unfortunately, the current diagnostic tools for accurate assessment of this periodontal status have shown several limitations. Most image analysis tools are based on 2D images, while bone remodelling is a 3D process. At present, Cone Beam Computed Tomography (CBCT) has become a powerful diagnostic tool in dentistry. This chapter will bring an overview of 2D and 3D visualization methods of the periodontal tissues and their pathologic manifestations like infrabony craters and furcation involvements. The diagnostic use of 2D radiographic projections, image filtering and subtraction will be compared to the use of 3D cross-sections and the image analysis tools for 3D visualization and/or follow-up of bony changes.

scholarly journals Determination of load equivalency factors by statistical analysis of weigh-in-motion data

2016 ◽  
Vol 11 (4) ◽  
pp. 251-258 ◽  
Author(s):  
Zoltán Soós ◽  
Csaba Tóth ◽  
Dávid Bóka
Keyword(s):  
Pavement Design ◽  
Border Crossings ◽  
Design Data ◽  
Vehicle Class ◽  
Motion Data ◽  
Weigh In Motion ◽  
Equivalency Factors ◽  
False Result ◽  
One Year ◽  
Load Equivalency Factors

The load equivalency factors for pavement design currently in use by the Hungarian standard have been developed using Weigh-in-Motion data obtained during the first few years of operations after installing some 30 measuring sites in Hungary in 1996. In the past years, and currently, data is collected mainly at the border crossings of the country, however the data is used only for law enforcement purposes, and no comprehensive statistical analyses have been done. To develop actual load equivalency factors for the use in pavement design, data of one year was collected and statistical methods were applied. An algorithm was used to help managing the multimodal distribution of axle loads in mathematical perspectives. Monte-Carlo methods were applied to determine the factors for each heavy vehicle type and eventually for each vehicle class used by the current Hungarian pavement design manual. The calculated factors are considerably different from the current ones, indicating that the pavement design may lead to a false result. Furthermore, there are three vehicle types suggested to be incorporated into the standard due to their high occurrence.

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