Hyperelastic Modeling of Wide-Base Tire and Prediction of Its Contact Stresses

Description of tire model development using the finite element (FE) method is presented. Three-dimensional tire-pavement contact stresses were predicted for braking, traction, and free rolling using the FE method. Measured load-deflection curves, contact area, and contact stresses were used for model outcome validation. Slide-velocity-dependent friction and accurate input regarding geometry and material properties were considered. The developed tire model, which helped in studying contact stresses variation in each direction, was used to explain the various phenomena taking place at the tire-pavement interface during straight-line rolling. The analysis matrix includes nine rolling conditions and various loads, tire inflation pressures, and speeds. Vertical contact stresses were not significantly affected by speed or slip ratio; however, contact stresses were greatly modified along the in-plane directions by rolling conditions. Analytical expressions were introduced to represent vertical and longitudinal contact stresses for full braking and full traction. Formulas are presented for low speed and full braking, which are relevant for roadway intersections design

Concrete Pavement Blowup Considering Generalized Boundary Conditions

An analytical expression for static stability of a rectangular slab with two simply supported and two elastically restrained edges is presented. The linear elastic isotropic slab can represent a rigid pavement resting on an elastic foundation and loaded by a uniform in-plane axial load per unit length along the edges. The partially restrained edges are connected to the ground by translational and rotational elastic springs; an appropriate magnitude of the springs can capture classical boundary conditions such as free, simply supported, and clamped edges. Results from classical boundary conditions and a finite-element model were used to validate the proposed stability equation. The generalized boundary conditions were found to change the critical load by a factor of two and greatly affected the first buckling mode shape of a typical concrete pavement. The critical load was not sensitive to the slab’s geometry if the length was four times longer than the width, but this was not the case for small aspect ratios. Finally, the translational spring was found to be a defining factor in determining the influence of the other variables on the critical load

Contact Phenomenon of Free-Rolling Wide-Base Tires: Effect of Speed and Temperature

The finite-element method was used to quantify the effect of temperature and speed on contact area, deflection, and three-dimensional contact stresses of a free-rolling wide-base tire. The tire model comprised material properties identified in the laboratory and/or provided by the tire manufacturer (hyperviscoelastic rubber and linear elastic reinforcement) and accurate geometry. The model was validated using measured deflection and contact area. The analysis matrix consisted of 81 cases resulting from a combination of three loads, tire-inflation pressures, speeds, and temperatures. Four criteria were used to compare contact stresses: range, average, root-mean-square error, and coefficient of determination. Speed and temperature influence the contact area more than deflection. Longitudinal contact stresses were the most affected, followed by transverse contact stresses. In general, under constant load and tire-inflation pressure, the influence of temperature was more significant on the considered output variables than the effect of speed

Semicoupled Modeling of Interaction between Deformable Tires and Pavements

The interaction between deformable tires and pavements was studied using finite-element modeling and a semicoupled approach. Three finite-element models were used: (1) a hyperelastic tire rolling on an infinitely rigid surface; (2) a three-dimensional pavement model; and (3) a hyperelastic tire rolling on a deformable viscoelastic body. The tire and pavement models have been successfully compared with experimental measurements. Tire interaction with a rigid surface provided contact stresses to excite the pavement model, and results of the pavement model defined the boundary conditions of the tire rolling on the deformable body. After that, the pavement loaded with the contact stresses from the tire interacting with the deformable body was run. This study focuses on issues related to pavement damage (tire–pavement contact stresses and critical pavement responses) and lifecycle assessment (rolling resistance). Transverse contact stresses were the most affected by pavement deformation, which translated into impact on the maximum vertical strain and the maximum shear strain in the asphalt concrete layer. The tire moving on a deformable body showed that the thin pavement created a higher rolling resistance force than thick pavements. In addition, dissipation-based and deflection-based approaches for calculating pavement contribution to rolling resistance were equivalent. Finally, for the range of values considered, changes in tire inflation pressure affected the rolling resistance force more than changes in applied load

Tire-Pavement Interaction Modeling: Hyperelastic Tire and Elastic Pavement

The interaction between deformable tire and pavement was studied using the validated finite element model; the full understanding of tire–pavement contact has implications for pavement damage prediction and pavement life-cycle assessment (fuel consumption estimation). The tire’s rubber and reinforcement were considered hyperelastic and linear elastic, respectively, with material constants obtained from the tire manufacturer (rubber) and laboratory testing (reinforcement). On the other hand, the pavement was assumed linear elastic supported by linear elastic springs. This assumption was made as a first step to examine the impact of using a deformable-on-deformable tire–pavement system to predict energy in the tire and contact stresses. The effect of the pavement stiffness on contact area, tire deflection, three-dimensional contact stresses, surface deflection, internal energy of the tire and its components, the work performed by the contact forces, and dissipation caused by friction was also studied. The elastic modulus of the pavement affected the contact area, while the elastic constants of the springs were more relevant for tire deflection. In addition, stiffness of the pavement had a varying effect on each component of the three-dimensional contact stresses: vertical contact stresses remained almost constant and longitudinal ones were the most affected. The symmetry of the surface deflection decreased and the friction dissipation increased 10.2% as the elastic modulus changed from the smallest to the highest value. Finally, the work performed by the vertical contact forces was significantly higher than by the in-plane loads, and the stiffness of the pavement affected rolling resistance force, which is related to fuel consumption

Closed-Form Solution for Curling Responses in Rigid Pavements

Closed-form expressions for calculating stresses and displacements of partially restrained concrete pavement caused by a linear temperature gradient are presented. Translational and rotational linear elastic springs along the slab edges defined the partial restraint. In addition to plate theory behavior, the model assumes linear elastic concrete and an infinitely long slab resting on a Winkler foundation. The solutions of curling stresses and displacements were validated using the finite-element (FE) method and quantified the effect of semirigid connections, slab and foundation material properties, and slab thickness and width on them. Rotational and translational restraints, which can be related to joint condition in concrete pavement, had significant influence on the magnitude and location of maximum curling stresses and deflections. In addition, Westergaard analysis, a particular case of the proposed solution when there is no restriction along the slab’s edges, resulted into the largest deflections at the center of the slab and the lowest maximum curling stresses. Adjustment factors that convert the theoretical findings from an infinitely long slab to a square slab are proposed

Efecto de las condiciones de curado del hormigón en su comportamiento frente a ciclos hielo-deshielo

El objetivo de este trabajo es relacionar las condiciones de curado del hormigón y la adición de un inclusor de aire, con los daños producidos por los ciclos hielo-deshielo en hormigones curados con baja humedad y alta temperatura. Para ello se ha realizado una campaña experimental sobre probetas de hormigón curadas en condiciones extremas reales “in situ” de humedad y temperatura con y sin aire ocluido sometida a ciclo de hielo deshielo. El trabajo presenta la correlación de la evaluación del comportamiento mecánico del hormigón sometido a ciclos hielo-deshielo frente al grado de hidratación del hormigón y el volumen y tamaños de los poros. De los resultados obtenidos se concluye que las probetas sin aireante muestran un deterioro de sus propiedades mecánicas tras el ensayo de hielo-deshielo. Sin embargo, la inclusión de aire beneficia el comportamiento del hormigón frente a los ciclos hielo-deshielo, de modo que incluso mejoran sus propiedades mecánicas tras el ensayo. Este comportamiento anómalo se explica porque el proceso de hidratación del cemento continúa durante los ensayos hielo-deshielo, cerrando la red porosa. Este aspecto se ha podido confirmar con los ensayos de ATD y TG realizado

Evaluación del Deterioro del Hormigón Sometido a Ciclos de Hielo-Deshielo.

Una de las causas principales de la degradación del hormigón en regiones frías es el efecto provocado por los ciclos hielo-deshielo. La transición del hielo al deshielo está acompañada por cambios dimensionales y cambio de la tensión interna y pudiendo causar la pérdida de la capacidad resistente del hormigón. El objetivo de este trabajo es relacionar la dosificación y las condiciones de curado del hormigón con los daños producidos por los ciclos de hielo-deshielo. El trabajo presenta la evaluación del deterioro de las probetas de hormigón mediante medidas de velocidad ultra sónicas, haciendo un estudio comparativo con la pérdida de peso, la variación de longitud y la evaluación de las propiedades mecánicas (resultados antes y después los ciclos). De los resultados obtenidos se concluye que las medidas ultrasónicas predicen adecuadamente el deterioro de los hormigones debido al efecto de los ciclos hielo-deshielo, anticipándose a las medidas obtenidas de pérdida de peso y cambios de longitud

Effect of the curing conditions of concrete on the behaviour under freeze-thaw cycles

The aim of this work is to relate the curing conditions of concrete and the addition of an air-entraining admixture with the damage caused by freeze–thaw cycles. In countries with a continental climate, the curing of concrete in summer is performed under climatic conditions of high temperature and low humidity, and during the winter the concrete suffers conditions of freeze–thaw, often accompanied by the use of de-icing salts. This paper shows the experimental results of the behaviour of concrete specimens cured under climatic summer conditions (high temperature and low humidity) and then subjected to freeze–thaw cycles. Curing of the specimens includes conditions of good and bad practice in relation to wetting and protection of the concrete. It also examines the effectiveness of using an air-entraining admixture in both cases. The experimental programme includes an evaluation of the mechanical properties of the concrete, the study of the cement hydration and the measurement of the volume and pore sizes of the concrete. These tests were performed before and after the application of the freeze–thaw cycles. The results obtained showed that the specimens without air-entraining admixture show a deterioration of mechanical properties after the freeze–thaw test. However, the inclusion of air bubbles benefits the behaviour of concrete against freeze–thaw cycles so even better mechanical properties after the test were observed. This anomalous behaviour is because the cement hydration process continues over the freeze–thaw tests, closing the pore structure. This aspect has been confirmed with the DTA and TG tests performe

Influencia de las condiciones de curado en el comportamiento del hormigón sometido a ciclos hielo-deshielo

Una de las causas principales de la degradación del hormigón en regiones frías es el efecto provocado por los ciclos hielo-deshielo. La transición del hielo al deshielo está acompañada por cambios dimensionales y cambio de la tensión interna y pudiendo causar la pérdida de la capacidad resistente del hormigón. El objetivo de este trabajo es relacionar la dosificación y las condiciones de curado del hormigón con los daños producidos por los ciclos de hielo-deshielo. El trabajo presenta la evaluación del deterioro de las probetas de hormigón mediante medidas de velocidad ultrasónicas, haciendo un estudio comparativo con la pérdida de peso, la variación de longitud y la evaluación de las propiedades mecánicas (resultados antes y después los ciclos). De los resultados obtenidos se concluye que las medidas ultrasónicas predicen adecuadamente el deterioro de los hormigones debido al efecto de los ciclos hielo-deshielo, anticipándose a las medidas obtenidas de pérdida de peso y cambios de longitud. - One of the main causes of the degradation of concrete in cold regions is the effect caused by the freezing-thawing cycles. The transition from the freezing to thawing is accompanied by dimensional changes and change of the internal stress and this can diminish the strength of concrete. The objective of this work is to relate the dosage and the curing of concrete on the damage caused by freezing-thawing cycles. The work provides an assessment of the deterioration of the concrete samples through ultrasonic speed, making a statistical comparison with the loss of weight variation in length and evaluation of mechanical properties (results before and after cycling). From the results it is concluded that the ultrasonic adequately predicts the deterioration of the concrete by the effects of the freezing-thawing cycles, anticipating the loss of weight and length changes