Tesi sul tema "International Roughness Index (IRI)"

Engineers of off-road equipment, on-road vehicles, pavement, and tires must assess the roughness of a terrain surface for the design of their products. The International Roughness Index (IRI), a standardized means of assessing longitudinal road roughness, quantifies roughness based on the average suspension travel for a particular vehicle at a prescribed speed. The Discrete Roughness Index (DRI) developed in this work address fundamental limitations of the IRI. Specifically, the DRI is calculated for each discretely measured location along a terrain surface and is applicable to vehicles traveling at varying speeds and using parameters other than the Golden Quarter-Car on which the IRI is based. The development of the DRI begins with a consistent discretization of the terrain surface, vehicle response, and the IRI. Next the Fractional Response Coefficient is developed, the properties of which are critical in the development of the DRI. The DRI is developed and its properties are discussed through theory and simulation of the ASTM E1926-08 profile. One important property of the average DRI is that it converges to the IRI as the distance between sampled points becomes smaller, for the particular case when the Golden Quarter-Car model is simulated at 80 kph. The DRI is not an alternative to the standard IRI, therefore, but a widely applicable roughness measure of which the standard IRI is a single specialized application.
Master of Science

In the field of vehicle durability, many individuals are focusing on methods for better replicating the durability a user will experience throughout the typical design lifespan of a vehicle (e.g., 100,000 miles). To estimate user durability a means of understand the types of damaging events and driving styles of uses must be understood. The difficulty with accurately estimating customer usage is, firstly, there is a large pool of possible roads for a user to drive along, for example, there are over 4 million miles of public roads in the United States, alone [1]. In addition, while measurements of these surfaces could be collected it would be impractical for two reasons, the first is the financial and extreme time burden this would take. Second, when collecting measurements of a road surface only the current state of a road surface can be measured, thus as a road deteriorates or is repaved the measurements collected would no longer be an accurate representation of the road. It should be mentioned that even, if all of the road surfaces were measured performing simulation and analysis of all of these road surfaces would be computationally intensive. Instead, it would be beneficial if select events that account for a significant portion of the damage a vehicle experiences can be identified. These damaging events could then be used in more complex vehicle simulation models and as input and validation of proving ground and laboratory durability testing. The objective of this research is to provide a means for improved estimation of vehicle durability, specifically a means for identifying, characterizing, and grouping unique separable damaging events from a road profile measurement. In order to achieve this objective a measure that can be used to identify separate damaging events from a road profile is developed. This measure is defined as Localized Pseudo Damage (LPD), which identifies the amount of damage each individual road excitation makes to the total accumulated damage for a single load path in a vehicle system. LPD is defined as a damage density to minimize the effect of measurement spacing on the resulting metric. The developed LPD measure is causal in that the value of LPD at a location is not affected by any future locations. In addition, for a singular event (e.g., impulse or step) in the absences of other excitations, the LPD value at the singular event location is equivalent to the total pseudo damage divided by the step size at the location. Once a measure of pseudo damage density is known at multiple locations along a road profile for multiple load paths of interest, then separable damaging events can be identified. To identify separable damaging events the activity of the vehicle system must be considered because separate damaging events can only occur when a region of inactivity is present across all load paths. Subsequently, an optimization problem is formed to determine the optimal active regions to maintain. The cost function associated with the optimization problem is defined to minimize the cost (number of locations maintained in damaging events) and maximize the benefit (the amount of pseudo damage maintained). Lastly, a statistical test is developed to assess if separate damaging events can be considered to be from the same general class of events based on their damage characteristics. The developed assessment methods establish the similarity between two more separable damaging events based on application specific user defined inputs. In the development, two example similarity metrics are defined. The first similarity metric is in terms of distance and the second is in terms of likelihood (probability). The developed statistical analysis uses the current state-of-the-art in clustering algorithms to allow for multiple damaging events to be identified and grouped together.
Doctor of Philosophy
In the automotive field determining the level of damage a typical production vehicle experiences over its lifetime has always been a desirable criterion to identify. This criterion is commonly referred to as customer usage. By understanding the typical customer usage of a vehicle over the lifetime of a vehicle, automotive engineers are able to improve the design of vehicle components. The issue with defining customer usage is that there are millions of miles of roads that a customer can travel on and millions of customers that all have unique driving characteristics. While it is possible to collect measurements of these road surfaces to use in further vehicle simulations, it is not feasible both from a financial and time perspective. In addition, the simulation and analysis of all road surfaces would be computationally intensive. However, if select damaging events (regions of the road surface that excessively contribute to accumulated damage) are identified, then they can be used in more complex vehicle durability analyses with lower computational efforts. In conventional damage analysis a total amount of accumulated damage is established for a known road surface. The issue with defining damage this way is that unique events which likely contributed a large amount of the accumulated damage cannot be identified. The first objective of this research is to define damage as a function of the vehicle's location along a road surface. Then, unique and separable damaging events can be identified and separated from sections of the road that do not significantly contribute to the accumulated damage. After defining this measure, an optimization problem is developed to identify damaging events based on maximizing the benefit (amount of damage accounted for in damaging events) and minimizing the cost (amount of road surface retained). Unique and separable damaging events are identified by solving this optimization problem. While the optimization problem identifies unique, separable damaging events, it is likely that some damaging events contain similar characteristics to each other. When performing additional durability analysis, it would be beneficial to form connections between similar damaging events to allow for analysis to be performed based on groups of events. To identify damaging events with similar characteristics, a statistical analysis is developed as the last contribution of this work. By combining this analysis with current state-of-the-art clustering algorithms and user provided definitions based on applications, similar damaging events are able to be grouped together.

This dissertation is compiled of the findings of several phases of a detailed research study that was aimed at investigating the Skid Resistance phenomenon. In the first phase of the dissertation research a study was performed to evaluate the different factors that influence frictional measurements obtained using the Dynamic Friction Tester (DFT). A temperature calibration factor that would account for temperature effects on DFT readings and IFI computations was developed. In addition, other variables that also affect the friction measurements obtained using the DFT are identified. In the next phase of the dissertation research the effect of pavement roughness on the Skid Resistance was investigated. The variation of the normal load and its nonlinear relation to SN was used to explain lower SN values measured on relatively rougher surfaces. The feasibility of using the International Roughness Index (IRI) and the Dynamic Load Coefficient (DLC) as predictors of the reduction in SN due to pavement roughness was also investigated. In the final phase of the dissertation research an in-depth investigation was carried out to better understand the principles underlying the concept of the International Friction Index (IFI), and specifically the role played by the Speed Constant ( Sp) parameter in the IFI computations. The parameter Sp dictates the speed variation of the wet friction measurements taken on a given pavement surface. The results of the current investigation suggest the revision of the procedure for computation of the Sp parameter to incorporate device specific properties. Furthermore, the incorporation of vehicle characteristics in the Sp parameter computations would help address a well known deficiency of the IFI, which is the inconsistent FR60 (predicted friction at 60 km/h) obtained from the friction values measured at two different slip speeds on the same surface. This study also showed that the modification of the Sp parameter reduces significantly the slip speed dependency of the device calibration parameters A and B. Finally, a modified IFI procedure that incorporates device specific slip conditions is presented. The modified IFI procedure showed consistently better predictive capability than the conventional ASTM procedure on all the different devices considered in this study.

Pavement roughness has been found to have an effect on the coefficient of friction measured with the Locked-Wheel Skid Tester (LWT) with measured friction decreasing as the long wave roughness of the pavement increases. However, the current pavement friction standardization model adopted by the American Society for Testing and Materials (ASTM), to compute the International Friction Index (IFI), does not account for this effect. In other words, it had been previously assumed that the IFI's speed constant (SP), which defines the gradient of the pavement friction versus speed relationship, is an invariant for any pavement with a given mean profile depth (MPD), regardless of its roughness. This study was conducted to quantify the effect of pavement roughness on the IFI's speed constant. The first phase of this study consisted of theoretical modeling of the LWT using a two-degree of freedom vibration system. The model parameters were calibrated to match the measured natural frequencies of the LWT. The calibrated model was able to predict the normal load variation during actual LWT tests to a reasonable accuracy. Furthermore, by assuming a previously developed skid number (SN) versus normal load relationship, even the friction profile of the LWT during an actual test was predicted reasonably accurately. Because the skid number (SN) versus normal load relationship had been developed previously using rigorous protocol, a new method that is more practical and convenient was prescribed in this work. This study concluded that higher pavement long-wave roughness decreases the value of the SP compared to a pavement with identical MPD but lower roughness. Finally, the magnitude of the loss of friction was found to be governed by the non-linear skid number versus normal load characteristics of a pavement.

The subject of the master thesis is to verify the possibility of application of geodetic methods to determine longitudinal and transverse pavement surface roughnesses. Geodetic techniques are compared to techniques specified in ČSN 73 6175. Subject of testing is absolute and relative accuracy of altitude measurement and accuracy of roughness parameter determination. As a result, the graphic interpretation of these parameters and deviations from reference values are presented in the current document. Practical use of the surveying methods is evaluated based on the application of the above mentioned techniques and the results of accuracy analysis.

Research was performed to analyze the performance of the crack, seat, and overlay (CS&O) roadway rehabilitation technique in the Central Coast and Northern regions of California. This technique was evaluated through literature review to determine the state of practice and their conclusions. California highway sections rehabilitated using CS&O were selected for evaluation based on age and location. Pavement distresses and traffic data for these sections were collected and analyzed. Prior to beginning analysis this data was checked for errors, outliers, and omissions. The analysis consisted of checking the data for correlations among distresses and regions. The focus of this research is to develop performance prediction models for pavement distresses in CS&O sections. Using data collected from Caltrans’ Pavement Condition Reporting Software, performance models were developed based on dependent (distress) variables: alligator cracking, transverse cracking, longitudinal cracking, and International Roughness Index (IRI). And independent (explanatory) variables: age, traffic in the form of equivalent single axle load (ESAL), thickness of hot mix asphalt (HMA), thickness of Portland Cement Concrete (PCC), and cumulative traffic in the form of cumulative ESAL. Prediction models were then analyzed for preciseness and sensitivity to the variables included in each model.

Devido à grande predominÃncia do modal de transporte rodoviÃrio no Brasil, se faz cada vez mais necessÃrio um controle sobre as aÃÃes de manutenÃÃo e de conservaÃÃo das rodovias. Para isso, muitos ÃrgÃos rodoviÃrios adotam modernos sistemas informatizados, que à o caso do DER/CE, que utiliza o SIGMA (Sistema Integrado de GestÃo da ManutenÃÃo). O sistema, atravÃs do subsistema SGP (Sistema de GerÃncia de Pavimentos), possui um vasto banco de dados relativos à condiÃÃo das rodovias, que à alimentado com dados provenientes de levantamentos de campo, que trazem, periodicamente, informaÃÃes atualizadas da condiÃÃo das rodovias estaduais. Estes dados sÃo adquiridos utilizando metodologias definidas pela equipe tÃcnica do DER/CE, baseadas em procedimentos normalizados, sendo os principais: o levantamento de irregularidade longitudinal (IRI) e o Levantamento Visual ContÃnuo (LVC). O primeiro avalia o conforto ao rolamento e o segundo registra os defeitos de superfÃcie das rodovias. Esta pesquisa apresenta uma anÃlise comparativa entre dados de LVC e de IRI, avaliando a evoluÃÃo das quantidades de defeitos e do IRI e as metodologias e os equipamentos envolvidos nos levantamentos. Apresenta, ainda, uma tentativa de compreensÃo da evoluÃÃo dos parÃmetros medidos pelo LVC ao longo de oito anos. Espera-se que, com a contribuiÃÃo desta pesquisa, as metodologias e os dados relativos à condiÃÃo das rodovias sejam analisados considerando as limitaÃÃes encontradas e que sejam sempre adotados o equipamento e o procedimento mais apropriados.
Due to the large predominance of the transportation by highways in Brazil, it is necessary to control the actions related to maintenance and conservation of the roads. With this purpose, institutions make use of modern computational systems, such as the DER/CE, which uses the ISMA (Integrated System of Maintenance Administration). The referred system, using the subsystem PMS (Pavement Management System), has a large database related to the roads condition, filled with data provided by surveys that bring periodically up to date information of the state roads. These data are acquired by using methodologies defined by the technical staff of the DER/CE, based on the following normalized procedures: Visual Continuous Survey (LVC) and International Roughness Index Survey (IRI). The first one evaluates the comfort of the traffic rolling and the second registers the surface distresses of the roads. This research presents a comparative analysis between LVC and IRI data, evaluating the evolution of the distresses and the methodologies and equipments involved in the procedures. It is expected that, with the contribution of this research, the methodologies and road related data be analyzed considering the limitations of the equipments and procedures.

Previous studies show that pavement condition properties are significant factors to enhance road safety and riding experience, and pavements with low quality might have inadequate performance in terms of safety and riding experience. Pavement Management System (PMS) databases include pavement properties for each segment of the road collected by the agencies. Understanding the impact of road characteristics on crash frequency is a key step to prevent crashes. Whereas other studies analyzed the effect of different characteristics such as International Roughness Index (IRI), Rutting Depth (RD), Annual Average Daily Traffic (AADT), this thesis analyzed the effect of Critical Condition Index (CCI) on crash frequency, in addition to the other factors identified in previous studies. Other characteristics such as Percentage of Heavy Vehicles, Road Surface Condition, Road Lighting Condition, and Driver Conditions are taken into the consideration. The scope of the study is the interstate highway system in Fairfax County, Virginia. Negative Binomial, Least Square and Nominal Logistic Models were developed, showing that the CCI value is a significant factor to predict the number of crashes, and that it has different effect for different values of AADT. The result of this study is a substantial step towards developing an integrated transportation control and infrastructure management framework.
Master of Science
Many factors cause crashes in the roads. Although there is a common sense that road characteristics such as asphalt quality are important in terms of road safety, there are few studies that scientifically prove that statement. In addition, asphalt maintenance decisions making process is mainly based on cost benefit optimization, and traffic safety is not considered at the process. The purpose of this study is to analyze crashes and road characteristics related to each crash to understand the effect of those characteristics on crash frequency, and eventually, to build a model to predict the number of crashes at each part of the road. The model can help transportation agencies to have a better understanding in terms of safety consequences of their infrastructure management plans. The scope of this study is the highway interstate system in Northern Virginia. Results suggest that pavement condition has a significant impact on crash frequency.

Road damage identification is still largely based on visual inspection methods and profilometer data. Visual inspection methods heavily rely on expert knowledge which is often very subjective. They also result in traffic flow interference due to the need for redirection of traffic to alternative routes during inspection. In addition to this, accurate high-speed profilometers, such as scanning vehicles, are extremely expensive often requiring strong economic justifications for their acquisition. The low-cost profilometers are very slow, typically operating at or less than walking speeds, causing their use to be labour-intensive if applied to large networks.This study aims at developing a road damage identification methodology for both paved and unpaved roads based on modelling the road-vehicle interaction system with an artificial neural network. The artificial neural network is created and trained with vehicle acceleration data as inputs and road profiles as targets. Then the trained neural network is consequently used for reconstruction of road profiles upon simulating it with vertical vehicle accelerations. The simulation process is very fast and can often be completed in a very short time thus making it possible to implement the methodology in real-time. Three case studies were used to demonstrate the feasibility of the methodology and the results on field tests carried out on mine vehicles with crudely measured road profiles showed a majority of the tested roads were reconstructed to within a fitting accuracy of less than 40% at a correlation level of greater than 55% which in this study was found to be practically acceptable considering the limitations imposed by the sizes of the haul trucks and their tyres as well as the quality of the road profiles and lack of control in the vehicle operation.
Thesis (PhD)--University of Pretoria, 2015.
Mechanical and Aeronautical Engineering
Unrestricted

碩士
國立中央大學
土木工程學系
102
Taiwan's National Highway plays an important role in Taiwan's transportation, through a series of north-south and east-west road networks, it is convenient to go to anywhere. From this we can see the highway road quality is a project that always need to be concerned.How to enhance the pavement quality of National Highway, will be the main subject of this study.The understanding, analysis and maintenance decision of highways, are the main topics of this thesis. In order to improve the comfort index of National Highway.In this study, we first understand the examination part of National Highway.Like road testing items and methods. And because the need of study,we need to organize the relevant information of National Highway road comfort index and survey processes. With the survey and analysis processes,is beneficial to maintain and enhance the comfort quality of National Highway. With a great amount of data, arrange and analysed with in different level, and find the relationship between their performance and budget. From the sorted results, we can find the reasonable and objective fund that should be used. and in the final analysis,we also added the safety index to make a comprehensive consideration and evaluation to make this study complete. After analyzing survey relevant information, information feedback mechanism is also developing in this study through the concept of pavement management system,and develop a pavement management system for National Highway .With the record of maintenance funding each year, We can estimate a more objective and reasonable budget.

碩士
國立臺北科技大學
土木與防災研究所
101
The sign of a city’s progress is the quality of the roads. More people live and visit New Taipei City after it’s upgraded, which leads more demand of tourist and economic development and transportation. As the result, the load of road is getting heavier and easier to be damaged. The quality and safety of traffic is deeply affected by then. This is why we need to start the project of the perfection of roads: to renovate, leveling and improve the quality of the roads in the city, and make New Taipei City a more friendly environment. The most direct experience for people on the road is how smooth the roads are. More complaints are followed by the worse of the road condition. Which affect the administration efficiency of the local government the most. In order to improve the public transportation quality, the most important achievement of New Taipei City are: perfection of the road surface, brightness of lights and fluency of water. The perfection of the road surface is the top target among these three. This research aims at roads that were completed under the project: New Taipei City Government promoting Road Improvement Work. In 2012, it applied IRI examination method and statistical analysis to analyze and compare road flatness rate. The result shows that IRI statistics at between 3m/km to 5m/km; average of 4.69m/km before the project, and 2m/km to 4m/km; average of 3.14m/km after the project.. This means the IRI ratio is on the downside. There is an obvious improvement of smoothing the road surface after this project was implemented. Here we provide the suggestions and strategy management plan of the post- project of “pavement smoothness project”. We also expect to last the efficiency of the surface quality so as to increase the period of road usage and the comfort of driving.

碩士
淡江大學
土木工程研究所
83
Pavement maintenance management must contain two kinds of evaluation, the structural evaluation (e.g. strength and capacity) and the functional evaluation (e.g. roughness, distress and skid resistance). Proper decisions for pavement maintenance and rehabilitation rely on adequate information of evaluations. While the structural evaluation has been the primary interest of engineers and researchers, there is an ergent need of research study on the functional evaluation as well as the establishment of domestic pavement serviceability index in Taiwan. Since roughness is the major factor that contributes to pavement serviceability, and the lack of roughness related research study in Taiwan, this study was then initiated. The major purpose of this research was to review roughness related literature, evaluate and compare current roughness measuring equipments, introduce the theory and derivation of of international roughness index (IRI), conduct a field roughness measurement experiment using rod and level and the high-speed profilometer, compute the IRI from elevation data, and finally develop regression models of Maysmeter Output (MO), root mean square acceleration (RMSA) and the IRI. The conclusions summarized from this study include : 1. the inertia type surface dynamic profilometer is most suitable for pavement maintenance management purpose in Taiwan, 2. the field measurements and computation of the IRI proved that it is applicable in Taiwan, and 3. the regression models developed from this study could be utilized to convert current roughness indices to the IRI when processing the roughness data.

碩士
國立臺灣科技大學
營建工程系
105
With the development of the social economy, the people demands of transportation is growing day by day, to satisfy citizen's desire, government actively promoting lots of transport infrastructure. Now the internal urban road is approach to saturation and reach the conversion from construction to management, face so many road isnʼt an easy job, so that's why management is so important. In this research, the Evolutionary International Roughness Index Inference Model used the influence factors of pavement to predict the IRI change between two years. Through a precise prediction of IRI, the management unit can’t arrange road section update and funds distribution of city road. This research established the Evolutionary International Roughness Index Inference Model by learning the historical cases. First, the related references was collected and then the influence diagram and the filter diagram were used to figure out the influence factors of pavement. The next step is to combine them to International Roughness Index(IRI). Furthermore, the input and the output variables were identified to establish the database of historical cases which is the base of the model. Second, the Symbiotic Organisms Search - Least Squares Support Machine (SOS-LSSVM) was applied to the model as its main core in order to discover the relationship between the input (influence factors ) , and the output variables(Estimate the IRI changes between two years) which can be combine with last year IRI then you can get this year IRI. According to the result management unit can decide the priority of road maintance and calculate the expense. The obtained results show that this research can provide a highly accurate and stable forecasting. By comparing the results with other Artificial Intelligence (AI) methods, it is confirmed that Evolutionary International Roughness Index Inference Model is useful way to control road situation.