1,721,108 research outputs found
Development of semi-mechanistic roughness performance model by computer simulation edited by Farad Khosrowshahi , London november 2002.
No full textThe development of pavement performance models is a critical component of a multi-year analysis within a pavement management system (PMS).The paper describes an empirical-mechanistic roughness progression model, as function of loads, climate conditions, structural layout, overall construction quality and material properties that has been implemented in a computer program. The analysis is performed by dividing the road section into 0.30 m long sub-sections. Material properties and layers thickness’ variations are described through a second order autoregressive process and assigned to each sub-section. A starting profile is randomly assigned to road section basing on construction specifications. The computer simulation is performed through an step-by-step process; during each time step the program calculates the dynamic loads, the stress and the permanent deformation induced by 16 types of heavy vehicles in each sub-section, according to 8 daily climatic conditions (every three hours). At the end of the step, the total rutting and the degradation of asphalt modulus due to fatigue cracking is calculated for each sub-section, the profile is updated and the IRI index of the road section is evaluated. Roughness deterioration curves derived in such manner highlight that daily temperature variations seems to play a critical role in the evaluation of roughness and rutting progression. Furthermore, a comparison with curves developed through empirical models proposed by world bank has shown a fairly good agreement
An energy-based approach to predict skid-resistance progression
No full textThe assessment of the evolution of skid resistance and texture of surface pavement plays a key role in a modern Pavement Management System. However, the problem can not be straightforwardly tackled since different factors (e.g. material related, environmental, traffic related, etc) affecting the skid resistance and macro-texture progression can be detected. Therefore, empirical models derived from experimental measures have been developed in the past. Actually, following skid resistance and macro-texture measurements carried out within a 5-6 year long period on a specific road section, regression curves are usually derived as a function of cumulated traffic. The main drawback of this approach is related to its effectiveness being strictly dependent on the context in which the expression has been derived and to the extended monitoring period required.
In this paper, a different methodology for the development of skid resistance empirical deterioration model has been proposed. According to this methodology, the surface damage induced by traffic is related to the dissipated frictional energy of the tribological system describing the tire-road interface. Basing on this approach, within a very few period, skid resistance measurements have to be carried out on several road sections in which similar bituminous mixes of different age have been laid. Making use of a suitable equivalency criterion for damage induced by vehicles, it becomes possible to effectively describe the deterioration state of a specific bituminous mix as a function of cumulated damage induced by the traffic and of mix properties
Predicting roughness progression of asphalt pavements by empirical-mechanistic model
No full textThe evaluation of road roughness progression represents one of the most important issue of modern pavement design and management. The roughness deterioration models developed so far, are often based on an empirical approach. Usually, an extensive long-term measurement campaign on a wide range of pavement sections is needed to calibrate such complex regression models and additional difficulties occur in collecting data on overlay roughness evolution. Furthermore, empirical models are unable to take into account new pavement materials performance. Empirical-mechanistic approach could partly solve these problems allowing the development of deterioration models by numerical simulations.
In this paper an empirical-mechanistic model, implemented in a computer software, is described in order to simulate the progression of pavement roughness as function of loads, climate, structural configuration, overall construction quality and material properties. The analysis is performed by dividing the road section into 0.250.33 m long sub-sections. Material properties and layer thickness are assigned to the sub-section through a autoregressive process and non linear elastic behaviour of granular materials is taken into account. The simulation is performed through an iterative process according to which, within each computational step, the program calculates pavement stress-strain level and permanent deformation induced by dynamic loads, for 16 different types of axes and 8 daily climatic condition in each sub-section. At the end of step the total rutting is computed in each sub-section, the profile is updated and the IRI index of the road section is evaluated. The model has been used to simulate roughness progression and a preliminary parametric analysis has been performed whose results are briefly illustrated
Interazione dinamica tra veicoli e profilo della superficie stradale: applicazione allo studio delle vibrazioni indotte dal traffico veicolare
No full textThe problem of road traffic induced vibrations is gaining wider attention among people and transport engineers as vibrations transmitted by vehicular traffic are often considered to be liable for minor damages
and for nuisance in building close to major road section in urban areas.
Among the different mitigation approaches,
the use of an anti-vibrating pavement seems the most feasible, in view of the various economic and functional constraints on site.
Early examples of anti-vibrating pavements in Italy date back to the beginning of the seventies when Colonnetti designed the first anti-vibrating road superstructure in order to mitigate the vibration level in Villa Farnesina induced by traffic traveling along the LungoTevere road. Analysis of the
scarce literature related to these road superstructures has highlighted that the effectiveness of a particular solution seems to be mainly verified by means of an experimental approach, theoretical models developed are often very rough and simple; furthermore, the design of pavement in view of its serviceability, is often neglected.
Following these remarks, a new methodological approach to the design of an anti-vibrating pavement is proposed, according to this which, several pavement layouts have been initially checked against conventional pave-ment design criteria and afterwards their effectiveness in attenuating vibration has been evaluated by means of an “ad hoc” mathematical model that can be conceptually divided into two main sub-models: a vibration generation model and a propagation model.
In the generation sub-model the dynamic
interaction between heavy vehicle and road surface irregularity is tackled.
Vehicle is represented by means of a discrete dynamic system (a typical “half car”, four-degree-of freedom model), whereas the road profile is described in a deterministic manner. Input parameters in this phase are: vehicle speed, vehicle inertial and mechanical properties, and road profile.
Output of this phase are the time histories
of dynamic overloads transmitted by the front and rear axle to the road surface.
In the propagation sub-model the transmission of vibration induced by the heavy vehicles up to a specific distance from the source is analyzed by means of a three-dimensional FEM
model
A for new methodology stochastic modelling of pay factors in hot-mix asphalt pavements
No full textSince 1990 several research projects developing any pay-adjustment (PA) procedure for implementing performance related specification (PRS) in hot-mix Asphalt (HMA) pavement construction have been issued. Previous studies proved that an approach based on life-cycle cost analysis and Monte Carlo simulation was an effective way to develop rational pay-adjustment procedures. However, the PRS systems developed so far had some significant weaknesses in the modelling of the variability of materials and construction (M&C) characteristics with corresponding PA. Furthermore they are mainly based on an empirical approach rather than on a mechanistic one. A new approach to model M&C variability in PRS systems, based on beta distribution, is introduced and a new stochastic method for pay-adjustment evaluation is developed. These criteria were embedded in a mechanistic system framework based on life-cycle cost analysis and Monte Carlo simulation. The model has been recently applied to a real case study and results are reported and analysed in this paperwork
Evaluation of pavement-oriented countermeasures to mitigate traffic induced vibrations in urban areas
No full textThe problem of road traffic induced vibrations is gaining wider attention among people and transport engineers as vibrations transmitted by vehicular traffic are often considered to be liable for minor damages and for nuisance in building close to major road section in urban areas. This complex topic that can be usually split in several phases: generation of vibrations, transmission through pavement layer and underlying soils, and reception in the building. Among the different mitigation approaches, the use of an anti-vibrating pavement seems the most feasible, in view of the various economic and functional constraints on site. In this paper a methodological approach for the design of an anti-vibrating pavement is proposed. Several pavement layouts have been initially checked against conventional pavement design criteria and afterwards their effectiveness in attenuating vibration has been evaluated by means of an “ad hoc” mathematical model. Results of numerical simulations seems to indicate that the attenuation properties are greatly affected by on-site soils, although the asphaltic concrete pavements examined show a moderate efficiency in reducing vibration level
Integrated performance indicator in urban road infrastructure management
No full textThe management of the road sector today is based on goals and results. In urban areas goals are defined in the transport policy set by local government, and the most common objectives in these policies are: accessibility for all users (i.e. vehicles, pedestrian cycle, etc.), safety, environment, transport quality and mobility, asset development and improvement.
Decision support system ought to be used for defining and prioritizing different maintenance/improvement activities, in order to ensure the fulfilment of the pre-defined goals. These processes are based on indicators, which measure the effectiveness of the maintenance activities respect to the pre-defined objectives. As matter of fact substantial efforts have been made to define and develop suitable and relevant performance indicators in the past decade.
In this study the lessons learned from this findings are used in order to develop a set of performance indicators for management of urban road pavement. An holistic approach is used in developing the framework of indicators, that is hierarchical (articulated in three levels), fully integrated (conversion from technical to key indicators), target oriented (fits the specific target that needs to be measured), and based on measured road attributes. The present paper illustrates the overall framework focusing on methods and criteria used in the development of environmental indicators dealing with relevant issues such as traffic induced noise and vibration. A case study is also presented in order to demonstrate the effectiveness of the framework proposed
Individuazione delle sezioni omogenee attraverso modelli lineari con variazioni strutturali multiple
No full textRegardless of analysis and optimisation criteria, Pavement Management Systems require a preliminary evaluation of road condition data in order to detect homogeneous sections. At present, different approaches have been proposed but none of these seems to be effective with regards to all pavement state parameters. In this paper a new criterion for the detection of homogeneous sections based on time series analysis through linear models with multiple structural changes is illustrated. The effectiveness of this criterion has been verified through the analysis of a case study related to skid resistance measurements made by SCRIM device within which a comparison between the different approaches derived from literature has been performed
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