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This study evaluated the optimum location of a reinforcement layer to maximize the efficiency of the reinforcement inclusion in an unpaved road section. The analyses are used to investigate the optimum location of the reinforcement layer within the aggregate base course (ABC) layer, and provide a possible reason for the improvement in performance. A series of three-dimensional finite element method analyses was performed, and the strain and stress response of a reinforced unpaved road section with two different ABC thicknesses was evaluated. The analyses were conducted under cyclic loading with three different radii of the circular loaded area. The embedded depth of reinforcement was varied within the ABC layer. Results indicate that regardless of ABC layer thickness, the surface deformation is minimized when the reinforcement is embedded at a depth equal to half of the radius of the loaded area (D = 0.5r). A higher tension force is mobilized in the reinforcement element when it is placed at D = 0.5r. It is also shown that the required thickness of ABC is reduced when the reinforcement layer is implemented at the depth at which the maximum vertical strain occurs. Depending on the thickness of the ABC layer, the finite element analysis results indicate that the reinforcement layer could be ineffectual if it is placed at the interface between the ABC and the subgrade layer as is traditionally the case. Key words: reinforcement, geosynthetics, unpaved, location, finite element. Cette etude a evalue l'emplacement optimal d'une couche de renforcement pour maximiser l'efficacite de l'inclusion de renforcement dans la section d'une route non asphaltee. Les analyses sont utilisees pour etudier l'emplacement optimal de la couche de renforcement a l'interieur de la couche de base d'agregats (ABC), et expliquer les raisons possibles pour l'amelioration de la performance. Une serie d'analyses d'elements finis en trois dimensions ont ete effectuees, et la reponse a la contrainte et a la deformation d'une section de route non revetue avec deux differentes epaisseurs ABC a ete evaluee. Les analyses ont ete realisees sous chargement cyclique avec trois rayons differents de la surface chargee circulaire. La profondeur enfouie de renforcement a ete modifiee a l'interieur de la couche ABC. Les resultats ont indique que, quelle que soit l'epaisseur de la couche ABC, la deformation de surface est reduite lorsque le renforcement est enfoui a une profondeur egale a la moitie du rayon de la zone chargee (D = 0,5r). Une plus grande force de tension est mobilisee dans l'element de renforcement lorsqu'il est place a D = 0,5r. Il est egalement montre que l'epaisseur requise d'ABC est reduite lorsque la couche de renforcement est mise en reuvre a la profondeur a laquelle la deformation verticale maximale se produit. En fonction de l'epaisseur de la couche ABC, les resultats des analyses par elements finis ont indique que la couche de sous fondation pourrait etre inefficace si elle est placee a l'interface entre l'ABC et la plate-forme de la couche de sous fondation comme il est traditionnellement le cas. [Traduit par la Redaction] Mots-cles: renforcement, geosynthetiques, emplacement, non pave, element fini., Introduction Over the years, many studies have been performed to investigate the deformation behavior of the reinforced unpaved road. These included small-scale and large-scale laboratory testing and full-scale field tests [...]

Northern jurisdictions implement spring load restrictions (SLRs) on low volume roads to minimize damage during spring thaw. For this study, SLRs are applied when the thawing front depth reaches 300 mm. Spring load restrictions should be removed when the pavement structure is completely thawed and the stiffness is sufficiently restored. Thawing and freezing index and thermal numerical modelling-based SLR methods are compared. The methods were first calibrated using air temperatures and measured freezing and thawing depths from two instrumented pavement sections in northern Ontario. The calibrated methods were then tested by predicting SLR application and complete thawing for the two sites for spring 2010. Comparisons with measurements show that both methods are able to predict SLR application within several days for both sites, but were off in excess of one month for complete pavement thawing. This study indicates that a calibrated thawing-index based method is most conducive for regional scale application of SLRs. Key words: spring load restrictions, thermal numerical modelling, thawing index, freezing index, thermistors, frost and thaw depths, predictions, comparisons with measurements. Les autorites legislatives nordiques appliquent des restrictions de charges au printemps sur les routes a faible volume afin de minimiser les dommages durant le degel du printemps. Pour la presente etude, les restrictions de charges sont appliquees lorsque la profondeur de degel atteint 300 mm. Ces restrictions devraient etre retirees lorsque la structure de la chaussee est completement degelee et que la rigidite est suffisamment restauree. L'indice de gel-degel ainsi que des methodes thermiques de restrictions de charges basees sur des modeles sont comparees. Les methodes ont tout d'abord ete etalonnees en prenant des temperatures de l' air et des profondeurs mesurees de gel et de degel provenant de deux sections de chaussee instrumentees du nord de l'Ontario. Les methodes etalonnees ont ensuite ete testees en predisant l'application des restrictions de charges au printemps et le degel complet pour les deux sites au printemps 2010. Les comparaisons avec les mesures montrent que les deux methodes peuvent predire l'application de restrictions de charges au printemps a quelques jours pres pour les deux sites, mais elles depassaient de plus d'un mois le degel complet de la chaussee. Cette etude indique qu'une methode etalonnee basee sur un indice de degel est la plus propice a l'application des restrictions de charges au printemps a l' echelle regionale. Mots-cles : restrictions de charges au printemps, modelisation thermique numerique, indice de degel, indice de gel, thermistors, profondeurs de gel et de degel, previsions, comparaisons avec les mesures. [Traduit par la Redaction], Introduction In northern climates frost penetrates into a pavement structure over the winter months. The depth of frost penetration depends on climatic conditions, including air temperatures, precipitation, wind speed, and [...]

Rutting, due to permanent deformations of unbound materials, is one of the principal damage modes of low traffic pavements. Flexible pavement design methods remain empirical; they do not take into account the inelastic behavior of pavement materials and do not predict the rutting under cyclic loading. A finite-element program, based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings, has been used to estimate the permanent deformations of unbound granular materials subjected to traffic loading. Based on repeated load triaxial tests, a general procedure has been developed for the determination of the material parameters of the constitutive model. Finally, the results of a finite-element modeling of the long-term behavior of a flexible pavement with the simplified method are presented and compared to the results of a full-scale flexible pavement experiment performed by Laboratoire Central des Ponts et Chaussees. Finally, the calculation of the rut depth evolution with time is carried out. DOI: 10.1061/(ASCE)EM.1943-7889.0000165 CE Database subject headings: Elastoplasticity; Triaxial tests; Full-scale tests; Highways and roads; Predictions. Author keywords: Elastoplasticity; Elastic shakedown; Plastic shakedown; Repeated load triaxial tests; Full-scale experiment.

An important element of achieving quality in a road network is the control of vehicle vibration due to pavement roughness and road irregularities. Scientific literature and international standards suggest that we evaluate these phenomena by measuring the whole body vibration (WBV) on the road user, but, for the practical aims of road engineering, this expression has to be related to road unevenness indexes, especially the most common one (the international roughness index, IRI). This index, in turn, is obtained from measured pavement geometric data using a conventional model of a mechanical system representing part of a vehicle. To better investigate the problem of user comfort, more complex models and analyses are needed. In this paper, a model of a real and common vehicle is presented and used, after a calibration process, to perform many dynamic simulations. The obtained results, in terms of weighted vertical acceleration ([a.sub.wz], that is, the WBV index, according to ISO standard), show good correlations ([R.sup.2] from 0.75 to 0.93, depending on vehicle speed) with the IRI values of the examined road sections. On the basis of this correlation, authors propose threshold values for both vibration and roughness indexes; these thresholds could be used for road users' comfort evaluation and adopted in technical standards. DOI: 10.1061/(ASCE)TE.1943-5436.0000143 CE Database subject headings: Surface roughness: Pavements; Deterioration: Surveys; Highways and roads; Vibration. Author keywords: Road roughness; Pavement deterioration; Surveys; Highways; Comfort limits.

In order to study the dynamic response of an asphalt road, a dynamic model of the road under a moving load is proposed, in which the viscoelastic characteristics of the base and pavement are all considered, the pavement is regarded as an infinite beam on a Kelvin viscoelastic base. By using Green's functions, Laplace transforms, and Fourier transforms, the analytical solution in transient is deduced. As the viscosity of the pavement is included in the model, the analytical solution can be used to investigate more of the factors that affect the dynamic response, such as vehicle speed, temperature, and road material properties. Using this analytical solution, some numerical calculations are given to illustrate the effects of vehicles' speeds and different damping on the deflection with the displacement. DOI: 10.1061/(ASCE)0733-9399(2010)136:2(168) CE Database subject headings: Moving loads; Viscoelasticity; Pavements; Transient response. Author keywords: Moving load; Viscouselastic base; Viscouselastic pavement; Transient response; Analysis solution.

Wetting depth in a slope is an important indicator to properly evaluate the rainfall-induced slope instability. This rainfall infiltration has potential to induce shallow slope failures. It is necessary to characterize the field infiltration and movement of the wetting front due to a natural rainfall. To monitor important infiltration characteristics of a field slope, a compacted roadside slope in an express highway (South Korea) was instrumented to measure variations of matric suction and water content. The monitored variations of matric suction and water content in vegetated and nonvegetated areas are discussed. The pattern of field infiltration by severe rainfall storms is also compared with the estimation results obtained by widely used ID infiltration models. The Chu model, by considering the ponding and run-off at each time interval, showed a good agreement with the field measurements. DOI: 10.1061/(ASCE)GT.1943-5606.0000160 CE Database subject headings: Unsaturated soils; Slope stability; Rainfall; Infiltration; Highways and roads. Author keywords: Unsaturated slope; Natural rainfall; Rainfall infiltration; Wetting front depth.

The aims of the presentation are to discuss the efficiency of the different methods for friction control of winter roads on the safety and accessibility due to climatic conditions, to show that the climate should be an important factor in selecting the strategies for winter maintenance and to establish climatic parameters that may be helpful in making those decisions. The analyses are based on Swedish data assembled by VTI on road accidents involving fatalities and severe injuries, road surface conditions and climate. The accident and the road condition recordings are compared to self-defined climatic parameters, which describe the severity, stability and instability of the winter climate in the regions investigated. The parameters are assumed to describe whether salting or sanding is favorable/unfavorable for friction control. The results of the analyses show that the effect of salting is substantial for improving accessibility. Generally the number of winter accidents resulting in fatalities and severe injuries is lower on the salted road network compared to the unsalted road network in the southern and central parts of Sweden. However, in the northern region, with very cold winters, the number of winter accidents is highest on the salted road network. The data also indicates that the highest accident numbers are found when the proportion of vehicle mileage on snow and ice in the winters varies within 30-40%. The paper recommends that salting should be avoided in areas and in periods when the frequency of road surface temperatures below -8[degrees]C exceeds 20%. In such climates the warm-wetted sand method is probably more favorable for friction control. Warm-wetted sand is also favorable on roads with traffic less than average annual daily traffic 2,000 and in periods with stable winter conditions. DOI: 10.1061/(ASCE)0887-381X(2009)23:4(113) CE Database subject headings: Highways and roads; Maintenance; Cold weather operation; Parameters.

A multiplatform simulation of a highway overcrossing bridge is introduced where the embankments, abutments, and pile groups are modeled in a powerful finite-element (FE) package with nonlinear soil material model while the bridge is modeled in another FE package that excels in fiber-based frame analysis. The Meloland Road Overcrossing Bridge, which is heavily instrumented, is selected as a reference analysis model due to the existence of measured data. The components as well as the integrated system are verified through comparison with previous studies and measured data. The stiffness of abutments and pile foundations are evaluated by three-dimensional finite-element analysis and compared with those from previous investigations. The analytical models of abutments and foundations are combined with the structural model using the multiplatform analysis framework, UI-SimCor. The dynamic properties of the model for multiplatform analysis are compared with those evaluated from system identification techniques using recorded ground motion. Finally, response history analyses are conducted with recorded free-field ground motion. The analysis results are in very good agreement with measured response showing the promising potential of multiplatform dynamic simulation. DOI: 10.1061/(ASCE)0733-9445(2008)134:4(651) CE Database subject headings: Seismic analysis; Roads; Simulation; Computer software; Bridges, highway.

The tyre to road contact friction is one of the most important properties when it comes to manoeuvrability of ground vehicles and information, to driver and vehicle, is of vital importance in critical situations. Different characteristics of different friction estimation methods make it hard to determine and compare performance of estimators. This article is an attempt to define and evaluate the performance of tyre to road friction estimators. The objective of the performance evaluation is to define and grade the performance of estimators based on all sorts of approaches and combinations of these. The result may be used in the context of benchmarking as well as a tool in the development process of the estimator. The test methods and metrics presented are illustrated with a comparative study of three different estimation approaches.

Byline: Peter Mucka, Oldrich Kropac This paper describes the statistical properties of the pure random component of longitudinal road profile. The individual obstacles were removed from the road profile by median filtering approach. A total of 25,830 test sections records from the long-term pavement performance (LTPP) programme were analysed. The differences between asphalt concrete (AC) and cement concrete (CC) wearing courses were outlined. The comparison was shown on statistics (mean, median, standard deviation values) and probability density functions (PDFs) of contemporary used road indices (international roughness index (IRI), road elevation variance, power spectrum density (PSD) parameters in one-, two- and three-wavelength bands, etc.). The simulation study revealed the marked influence of obstacles on the road indices. The spectral properties of the pure random part were quantified.