Tires are the most influential component of the vehicle as they constitute the only contact between the vehicle and the road and have to generate and transmit forces necessary for the driver to control the vehicle. Hydroplaning is a phenomenon which occurs when a layer of water builds up between the tires of a vehicle and the road surface which leads to loss of traction that prevents the vehicle from responding to control inputs such as steering, braking or acceleration. It has become an extremely important factor in the automotive and tire industry to study the factors affecting vehicle hydroplaning. Nearly 10-20% of road fatalities are caused by lack of traction on wet surfaces. The tire tread pattern, load, inflation pressure, slip and camber angles influence hydroplaning to a great extent. Finite Element Analysis, although computationally expensive, provides an excellent way to study such Fluid Structure Interactions (FSI) between the tire-water-road surfaces. Abaqus FSI CEL approach has been used to study tire traction with various vehicle configurations. The tire force data obtained from the Finite Element simulations is used to develop a full vehicle hydroplaning model by integrating the relevant outputs with the commercially available vehicle dynamics simulation software, CarSim. / Master of Science

A curva de transição apresenta um raio de curvatura variando de um valor infinito no fim da tangente até um valor igual ao raio da curva circular no final da curva de transição. Nos projetos rodoviários, o tipo de curva mais utilizado é a clotóide, pois esta corresponde à trajetória descrita pelo veículo, com uma velocidade constante e o volante girando com velocidade angular constante. Consequentemente, é uma situação em que não requer esforço do motorista, proporciona uma trajetória mais natural e um aumento/redução da aceleração radial de um veículo de forma gradual. O presente trabalho admite que o comprimento desejável da espiral de transição em rodovias rurais e urbanas, baseado na recomendação da AASHTO (2011), é igual à distância correspondente a um tempo de percurso de 2 segundos ao longo da via à velocidade de projeto. É recomendável que o comprimento considerado como desejável seja suficiente para se realizar a transição da superelevação, e por outro lado, deve ser menor que o comprimento crítico de hidroplanagem, ou seja, comprimento a partir do qual o veículo passa a perder contato do pneu/pavimento em uma pista coberta com lâmina dágua, a uma velocidade crítica. Visto que os manuais brasileiros não introduzem a hidroplanagem como um dos fatores considerados para estabelecer estes comprimentos, pretende-se desenvolver uma ferramenta de trabalho que auxilia na determinação do comprimento desejável da espiral de transição, possibilitando uma análise do risco de ocorrência do fenômeno da hidroplanagem. No estudo de caso, são calculados comprimentos da espiral de transição de três curvas, onde serão feitas também simulações com diferentes parâmetros para analisar as situações críticas de hidroplanagem. Os resultados obtidos demonstram que comprimentos muito longos da espiral de transição, combinado com uma declividade longitudinal muito baixa pode aumentar o risco de hidroplanagem. / The transition curve has a radius of curvature varying from infinity at the end of the tangent to a value equal to the radius of the circular arc at the end of the transition curve. In highway design, clothoid is the most commonly used spiral type because it corresponds to the path described by the vehicle, with a constant speed and the less need for steering. Consequently, it\'s a situation that doesn\'t require driver effort, providing a more natural path and a gradual increase / reduction of the centrifugal force of a vehicle. Based on AASHTO (2011)\'s recommendation, this study establishes that the desired length of the spiral transition in highways and streets is equal to the distance traveled in 2 seconds in the design speed. It\'s recommended that the spiral length considered as desirable is sufficient to perform the superelevation runoff and on the other hand, should be shorter than the critical length of hydroplaning, in other words, it\'s a phenomenon caused by the increase of the water film above the contact pressure of tire and road. Since the manuals do not introduce hydroplaning as one of the criteria considered in establishing these lengths, a tool will be developed to define the desirable spiral length, allowing an analysis of the risk of hydroplaning. In the study, the lengths of three spiral transition curves are calculated; furthermore simulations with different parameters of these three curves are also calculated to analyze critical situations of hydroplaning. The results demonstrate that longer lengths of spiral transition combined with lower grades may increase the risk of hydroplaning.

A curva de transição apresenta um raio de curvatura variando de um valor infinito no fim da tangente até um valor igual ao raio da curva circular no final da curva de transição. Nos projetos rodoviários, o tipo de curva mais utilizado é a clotóide, pois esta corresponde à trajetória descrita pelo veículo, com uma velocidade constante e o volante girando com velocidade angular constante. Consequentemente, é uma situação em que não requer esforço do motorista, proporciona uma trajetória mais natural e um aumento/redução da aceleração radial de um veículo de forma gradual. O presente trabalho admite que o comprimento desejável da espiral de transição em rodovias rurais e urbanas, baseado na recomendação da AASHTO (2011), é igual à distância correspondente a um tempo de percurso de 2 segundos ao longo da via à velocidade de projeto. É recomendável que o comprimento considerado como desejável seja suficiente para se realizar a transição da superelevação, e por outro lado, deve ser menor que o comprimento crítico de hidroplanagem, ou seja, comprimento a partir do qual o veículo passa a perder contato do pneu/pavimento em uma pista coberta com lâmina dágua, a uma velocidade crítica. Visto que os manuais brasileiros não introduzem a hidroplanagem como um dos fatores considerados para estabelecer estes comprimentos, pretende-se desenvolver uma ferramenta de trabalho que auxilia na determinação do comprimento desejável da espiral de transição, possibilitando uma análise do risco de ocorrência do fenômeno da hidroplanagem. No estudo de caso, são calculados comprimentos da espiral de transição de três curvas, onde serão feitas também simulações com diferentes parâmetros para analisar as situações críticas de hidroplanagem. Os resultados obtidos demonstram que comprimentos muito longos da espiral de transição, combinado com uma declividade longitudinal muito baixa pode aumentar o risco de hidroplanagem. / The transition curve has a radius of curvature varying from infinity at the end of the tangent to a value equal to the radius of the circular arc at the end of the transition curve. In highway design, clothoid is the most commonly used spiral type because it corresponds to the path described by the vehicle, with a constant speed and the less need for steering. Consequently, it\'s a situation that doesn\'t require driver effort, providing a more natural path and a gradual increase / reduction of the centrifugal force of a vehicle. Based on AASHTO (2011)\'s recommendation, this study establishes that the desired length of the spiral transition in highways and streets is equal to the distance traveled in 2 seconds in the design speed. It\'s recommended that the spiral length considered as desirable is sufficient to perform the superelevation runoff and on the other hand, should be shorter than the critical length of hydroplaning, in other words, it\'s a phenomenon caused by the increase of the water film above the contact pressure of tire and road. Since the manuals do not introduce hydroplaning as one of the criteria considered in establishing these lengths, a tool will be developed to define the desirable spiral length, allowing an analysis of the risk of hydroplaning. In the study, the lengths of three spiral transition curves are calculated; furthermore simulations with different parameters of these three curves are also calculated to analyze critical situations of hydroplaning. The results demonstrate that longer lengths of spiral transition combined with lower grades may increase the risk of hydroplaning.

Hydroplaning is a phenomenon that occurs when a layer of water between the tire and pavement pushes the tire upward. The tire detaches from the pavement, preventing it from providing sufficient forces and moments for the vehicle to respond to driver control inputs such as breaking, accelerating and steering. This work is mainly focused on the tire and its interaction with the pavement to address hydroplaning. Before using a full-scale tire model, interactions of the tread block with a specific surface is studied. To do so, several mechanical tests such as uniaxial, biaxial, planar (shear), and DMA are conducted to predict the hyper-viscoelastic properties of the rubber. Using multi-scale modeling techniques, the friction coefficient between the tire and pavement, for wet conditions, is characterized via developing 2D and 3D model representing the rubber tread interacting with the rough surface. Using a tire model that is validated based on results found in the literature as well as in-house experimental data, fluid-structure interaction (FSI) between the tire-water-road surfaces are investigated through two approaches. In the first approach, the coupled Eulerian-Lagrangian (CEL) formulation was used. The drawback associated with the CEL method is the laminar assumption that the behavior of the fluid at length scales smaller than the smallest element size is not captured. To improve the simulation results, in the second approach, an FSI model incorporating finite-element methods and the Navier-Stokes equations for a two-phase flow of water and air, and the shear stress transport k-ω turbulence model, was developed and validated, improving the prediction of real hydroplaning scenarios. The improved FSI model was applied to hydroplaning speed and cornering force scenarios. In addition, tire contact patch length was calculated using the developed FSI model and was compared to the results obtained from the intelligent tire. / Doctor of Philosophy / Hydroplaning is a phenomenon that occurs when a layer of water between the tire and pavement pushes the tire upward. The tire detaches from the pavement, preventing it from providing sufficient forces and moments for the vehicle to respond to driver control inputs such as breaking, accelerating and steering. Hydroplaning as well as low skid resistance are considered as the main factors leading to traffic accidents. This work is mainly focused on the tire and its interaction with the pavement to address hydroplaning. Different factors involve in the hydroplaning phenomenon such as water film thickness, tire pressure, tire tread pattern, tire tread depth, vehicle speed and pavement texture. Before using a full-scale tire model, interactions of the tire tread with a specific surface is studied. To do so, several mechanical tests are conducted to predict the hyper-viscoelastic properties of the rubber. Using a single scale methodology is not capable to obtain the sufficient information regarding the effect of roughness on the friction. As a result, using multi-scale modeling techniques, the friction coefficient between the tire and pavement, for wet conditions, is characterized via developing 2D and 3D model representing the rubber tread interacting with the rough surface. Since in the hydroplaning problem, a solid structure and a fluid domain are in interaction, such a problem considered as a fluid-structure interaction (FSI) problem. In this work, the FSI between the tire-water-road surfaces are investigated through two approaches. To improve the simulation results, an FSI model incorporating finite-element methods and the Navier-Stokes equations for a two-phase flow of water and air, and the shear stress transport k-ω turbulence model, was developed and validated, improving the prediction of real hydroplaning scenarios. In addition, tire contact patch length was calculated using the developed FSI model and was compared to the results obtained from the intelligent tire.

A aquaplanagem é um fenômeno que pode ocasionar riscos de acidentes em pistas rodoviárias e que consiste na perda de aderência entre os pneus de um veículo e a superfície do pavimento, em decorrência da presença de uma película de água com certa espessura que impede o contato entre ambos, situação essa que pode ser gerada em condições de precipitações pluviométricas de intensidades relativamente elevadas. De uma forma geral tal fenômeno é desconsiderado em normas, manuais e especificações para projetos rodoviários, tanto no Brasil como no Exterior. O presente trabalho tem como objetivo básico a proposição de um procedimento metodológico que permita a identificação de trechos de traçados rodoviários nos quais tal fenômeno possa ocorrer, seja na fase de elaboração de projetos, seja no processo de avaliação das condições de segurança de pistas existentes. O procedimento proposto foi estruturado com base na análise dos principais modelos de previsão de risco de aquaplanagem levantados durante a revisão bibliográfica, bem como em uma extensiva análise das principais variáveis que influenciam esse fenômeno. Com o propósito de avaliar a adequabilidade do procedimento proposto foi elaborado um estudo de caso considerando as características geométricas e dados pluviométricos relativos a determinada extensão do Trecho Leste do Rodoanel de São Paulo. Em tal estudo de caso foram apresentadas proposições de soluções alternativas de mitigação de risco para os trechos identificados como locais com possibilidade de ocorrência de aquaplanagem. / Hydroplaning is a phenomenon that can result in hazard risk on highways, its occurrence is defined by an absence of adherence between the tire and the pavement caused by the presence of a water film of a certain depth that hinder the contact between those surfaces, it\'s occurrence is related to high rainfall intensity situations. Usually highway design manuals, standards and criteria don\'t consider the occurrence of this phenomenon, in Brazil or abroad. The present work has the object of proposing a methodological procedure that allows for the identification of highway segments that are subject to hydroplaning, during its design or during the evaluation of its security conditions. The proposed procedure was based on the analysis of the hydroplaning prediction models studied during the bibliography review, as well as in an extensive analysis of the main variables influencing its occurrence. For the evaluation of the proposed procedure, a case study was conducted with the east portion of the \"Rodoanel Mario Covas\" geometric characteristics and pluviometry data. In this study some risk mitigation proposals were evaluated for the extensions on which were identified the possibility of hydroplaning occurrence.

A aquaplanagem é um fenômeno que pode ocasionar riscos de acidentes em pistas rodoviárias e que consiste na perda de aderência entre os pneus de um veículo e a superfície do pavimento, em decorrência da presença de uma película de água com certa espessura que impede o contato entre ambos, situação essa que pode ser gerada em condições de precipitações pluviométricas de intensidades relativamente elevadas. De uma forma geral tal fenômeno é desconsiderado em normas, manuais e especificações para projetos rodoviários, tanto no Brasil como no Exterior. O presente trabalho tem como objetivo básico a proposição de um procedimento metodológico que permita a identificação de trechos de traçados rodoviários nos quais tal fenômeno possa ocorrer, seja na fase de elaboração de projetos, seja no processo de avaliação das condições de segurança de pistas existentes. O procedimento proposto foi estruturado com base na análise dos principais modelos de previsão de risco de aquaplanagem levantados durante a revisão bibliográfica, bem como em uma extensiva análise das principais variáveis que influenciam esse fenômeno. Com o propósito de avaliar a adequabilidade do procedimento proposto foi elaborado um estudo de caso considerando as características geométricas e dados pluviométricos relativos a determinada extensão do Trecho Leste do Rodoanel de São Paulo. Em tal estudo de caso foram apresentadas proposições de soluções alternativas de mitigação de risco para os trechos identificados como locais com possibilidade de ocorrência de aquaplanagem. / Hydroplaning is a phenomenon that can result in hazard risk on highways, its occurrence is defined by an absence of adherence between the tire and the pavement caused by the presence of a water film of a certain depth that hinder the contact between those surfaces, it\'s occurrence is related to high rainfall intensity situations. Usually highway design manuals, standards and criteria don\'t consider the occurrence of this phenomenon, in Brazil or abroad. The present work has the object of proposing a methodological procedure that allows for the identification of highway segments that are subject to hydroplaning, during its design or during the evaluation of its security conditions. The proposed procedure was based on the analysis of the hydroplaning prediction models studied during the bibliography review, as well as in an extensive analysis of the main variables influencing its occurrence. For the evaluation of the proposed procedure, a case study was conducted with the east portion of the \"Rodoanel Mario Covas\" geometric characteristics and pluviometry data. In this study some risk mitigation proposals were evaluated for the extensions on which were identified the possibility of hydroplaning occurrence.

Crashes on wet pavements are responsible for 25% of all crashes and 13.5% of fatal crashes in the US (Harwood et al. 1988). This number represents a significant portion of all crashes. Current methods used by the Department of Transportations (DOTs) are based on wet over dry ratios and simplified approaches to estimate hydroplaning speeds. A fraction of all wet crashes is hydroplaning; although they are related, the difference between a "wet crash" and "hydroplaning" is a wet-crash hydrodynamic-based severity scale is less compared to hydroplaning where the driver loses control. This dissertation presents a new conceptual framework design to reduce wet- and hydroplaning-related crashes by identifying locations with a high risk of crashes using systemic, data-driven, risk-based approaches and available data. The first method is a robust systemic approach to identify areas with a high risk of wet crashes using a negative binomial regression to quantify the relationship between wet to dry ratio (WDR), traffic, and road characteristics. Results indicate that the estimates are more reliable than current methods of WDR used by DOTs. Two significant parameters are grade difference and its absolute value. The second method is a simplified approach to identify areas with a high risk of wet crashes with only crash counts by applying a spatial multiresolution analysis (SMA). Results indicate that SMA performs better than current hazardous-road segments identification (HRSI) methods based on crash counts by consistently identifying sites during several years for selected 0.1 km sections. A third method is a novel systemic approach to identify locations with a high risk of hydroplaning through a new risk-measuring parameter named performance margin, which considers road geometry, environmental condition, vehicle characteristics, and operational conditions. The performance margin can replace the traditional parameter of interest of hydroplaning speed. The hydroplaning risk depends on more factors than those identified in previous research that focuses solely on tire inflation pressure, tire footprint area, or wheel load. The braking and tire-tread parameters significantly affected the performance margin. Highway engineers now incorporate an enhanced tool for hydroplaning risk estimation that allows systemic analysis. Finally, a critical review was conducted to identify existing solutions to reduce the high potential of skidding or hydroplaning on wet pavement. The recommended strategies to help mitigate skidding and hydroplaning are presented to help in the decision process and resource allocation. Geometric design optimization provides a permanent impact on pavement runoff characteristics that reduces the water accumulation and water thickness on the lanes. Road surface modification provides a temporary impact on practical performance and non-engineering measures. / Doctor of Philosophy / Crashes on wet pavements are responsible for 25% of all crashes and 13.5% of fatal crashes in the US (Harwood et al. 1988). This number represents a significant portion of all crashes. Current procedures used by DOTs to identify locations with a high number of wet crashes and hydroplaning are too simple and might not represent actual risk. A fraction of all wet crashes is hydroplaning, although they are related to the difference between a "wet crash" and "hydroplaning" is a wet crash water-vehicle interaction is less compared to hydroplaning where the driver loses control. This dissertation presents a new procedure to evaluate the road network to identify locations with a high risk of wet crashes and hydroplaning. The risk estimation process uses data collected in the field to determine the risk at a particular location and, depending on the available data a transportation agency uses, will be the approach to apply. The first statistical method estimates the frequency of wet crashes at a location. This estimate is developed by using a statistical model, negative binomial regression. This model measures the frequency of dry crashes, wet crashes, traffic, and road characteristics to determine the total number of wet crashes at a location. Results indicate that this option is more reliable than the current methods used by DOTs. They divide the number of wet crashes by the number of dry crashes. Two elements identified to influence the results are the difference in road grade and its absolute value. The second statistical method to estimate wet crashes considers crash counts by applying a statistical process, spatial multiresolution analysis (SMA). Results indicate that SMA performs better than current processes based only on the crash counts. This option can identify the high-risk location for different years, called consistency. The more consistent the method is, the more accurate is the results. A third statistical method is a novel way to estimate hydroplaning risk. Hydroplaning risk is currently based on finding the maximum speed before hydroplaning occurs. A vehicle's performance related to the water-film thickness provides an estimation method developed by (Gallaway et al. 1971), which includes rainfall intensities, road characteristics, vehicle characteristics, and operating conditions. The hydroplaning risk depends on more aspects than tire inflation pressure, tire footprint area, or vehicle load on the wheel. The braking and tire tread affect the performance margin. Highway engineers can use this improved hydroplaning risk-estimation tool to analyze the road network. Finally, a critical review showed the available solutions to reduce the probability of having a wet crash or hydroplaning on wet pavement. The recommended strategies to mitigate wet crashes and hydroplaning provide information to allocate resources based on proven, practical strategies. Road geometry design can be optimized to remove water from the road. This geometry is a permanent modification of pavement characteristics to reduce water accumulation and water thickness on the road. Road surface treatments and non-engineering measures provide temporary measures to improve vehicle performance or driver operation.

<p>Aquaplaning accidents are relatively rare, but could have fatal effects. The task of this master’s thesis is to use data from the Laser Road Surface Tester to detect road sections with risk of aquaplaning. </p><p>A three-dimensional model based on data from road surface measurements is created using MATLAB (version 6.1). From this general geometrical model of the road, a pond model is produced from which the theoretical risk ponds are detected. A risk pond indication table is fur-ther created. </p><p>The pond model seems to work well assuming that the data from the road model is correct. Determining limits for depth and length of risk ponds can be made directly by the user. MATLAB code is reasonably easy to understand and this leaves great opportunities for changing different parameters in a simple way. </p><p>Supplementary research is needed to further improve the risk pond detection model. Collecting data at smaller intervals and with more measurement points would be desirable for achieving better correlation with reality. In a future perspective, it would be wise to port the code to another programming language and this could make the computations faster.</p>

Aquaplaning accidents are relatively rare, but could have fatal effects. The task of this master’s thesis is to use data from the Laser Road Surface Tester to detect road sections with risk of aquaplaning. A three-dimensional model based on data from road surface measurements is created using MATLAB (version 6.1). From this general geometrical model of the road, a pond model is produced from which the theoretical risk ponds are detected. A risk pond indication table is fur-ther created. The pond model seems to work well assuming that the data from the road model is correct. Determining limits for depth and length of risk ponds can be made directly by the user. MATLAB code is reasonably easy to understand and this leaves great opportunities for changing different parameters in a simple way. Supplementary research is needed to further improve the risk pond detection model. Collecting data at smaller intervals and with more measurement points would be desirable for achieving better correlation with reality. In a future perspective, it would be wise to port the code to another programming language and this could make the computations faster.