arXiv subjects

Ziyad Ghaouche

Publications and source records attributed to Ziyad Ghaouche.

6 recordsLinked to original sources

arXiv2013

Performance Analysis and Optimization of Dowels in Jointed Concrete Floors

This study examines the performance of traditional round dowels in concrete floors and attempts to optimize the design of dowels through Finite Element (FE) analysis. A new type of Double-Tapered Round (DTR) dowels is proposed, and the performance of DTR dowels is compared to that of traditional cylindrical dowels. Linear Elastic (LE) analysis are performed in Abaqus (v-6.11) order to identify the optimized geometry of DTR dowels that would achieve (1) highest load transfer across adjacent slabs through shear action, and (2) lowest bearing stresses on the concrete. LE analyses are complemented by nonlinear FE analysis. The Riks method available in Abaqus/Standard, coupled with the Concrete Damaged Plasticity (CDP) model is used to simulate the degradation of concrete surrounding both DTR the traditional cylindrical dowels. Results obtained show that the use of DTR dowels can reduce bearing stresses at the face of the joint by as much 2.2 times as compared to traditional cylindrical dowels. While adequate load-transfer is a crucial part for the proper performance pavement structures, the load-transfer capacity of DTR dowels was more effective over cylindrical dowels by as far as 116%. In the inelastic range, even after significant concrete degradation and steel yielding, DTR dowels maintained a higher load-transfer capacity than traditional cylindrical dowels, and also presented lower amounts of differential deflections across concrete floors. Finally, damage in the concrete matrix below the dowel was relatively more confined for the case of DTR dowels, as compared to traditional cylindrical dowels.

physics.gen-ph↗

arXiv2013

Finite Element Investigation of the Deterioration of Doweled Rigid Pavements

The purpose of this study is to describe the failure of concrete around dowel bars in jointed rigid pavements, and the resulting effect on the pavement performance. In fact, under repetitive vehicle loading, concrete in contact with the dowel bar deteriorates, particularly at the joint face. The degradation of concrete around the dowel negatively affects the latter's performance in terms of transferring wheel loads through vertical shear action. In this context, a nonlinear 3D Finite Element analysis was performed using the commercial FE code Abaqus (v-6.11). The FE model was validated with classical analytical solutions of shear and moment along the dowel. A concrete damaged plasticity model was used for the PCC slab to model the degradation of concrete matrix around the dowels under incremental loading. Results obtained show, among other things, that the degradation of concrete matrix around the dowel was found to initiate at the face of the joint and propagate towards the interior of the dowel. Also, results obtained confirmed the decrease in load transfer capability of the dowels as the PCC matrix deteriorates. The central dowels under the wheel load lost a significant portion of their load-transfer capacity as the PCC matrix around them deteriorated, while dowels farther away from the wheel load became more engaged in load transfer.

physics.gen-ph↗

arXiv2012

3D Finite Element Analysis of HMA Overlay Mix Design to Control Reflective Cracking

This study examines the effectiveness of HMA overlay design strategies for the purpose of controlling the development of reflective cracking. A parametric study was conducted using a 3D Finite Element (FE) model of a rigid pavement section including Linear Viscoelastic (LVE) material properties for the Hot Mix Asphalt (HMA) overlay and non-uniform tire-pavement contact stresses. Several asphalt mixtures were tested in the surface, intermediate, and leveling course of the HMA overlay. Results obtained show that no benefits can be anticipated by using either Polymer-Modified (PM) or Dense-Graded (DG) mixtures instead of Standard Binder (SB) mixtures in the surface or intermediate course. For the leveling course, the use of a PM asphalt binder was found beneficial in terms of mitigating reflective cracking. As compared to the SB mix, the use of PM asphalt mixture in the leveling course reduced the level of longitudinal tensile stress at the bottom of the HMA overlay above the PCC joint by approximately 30%.

cs.CE↗

arXiv2012

Strain Response of Hot-Mix Asphalt Overlays for Bottom-Up Reflective Cracking

This paper examines the strain response of typical HMA overlays above jointed PCC slabs prone to bottom-up reflective cracking. The occurrence of reflective cracking under the combined effect of traffic and environmental loading significantly reduces the design life of the HMA overlays and can lead to its premature failure. In this context, viscoelastic material properties combined with cyclic vehicle loadings and pavement temperature distribution were implemented in a series of FE models in order to study the evolution of horizontal tensile and shear strains at the bottom of the HMA overlay. The effect of several design parameters, such as subbase and subgrade moduli, vehicle speed, overlay thickness, and temperature condition, on the horizontal and shear strain response was investigated. Results obtained show that the rate of horizontal and shear strain increase at the bottom of the HMA overlay drop with higher vehicle speed, higher subgrade modulus, and higher subbase modulus. Moreover, the rate of horizontal strain accumulation increases with higher overlay thickness. Although initial strain values were higher at positive pavement temperature distributions, the corresponding rate of strain increase were higher at negative pavement temperatures. Finally, an extrapolation of the strain history curve for various pavement design parameters was used to estimate the number of cycles for bottom-up crack initiation.

physics.gen-ph↗

arXiv2012

Effect of PCC Joint Skew on Reflective Cracking in HMA Overlays

Reflective cracking is a relatively premature distress that occurs in HMA materials overlaying cracked and jointed underlying pavements. The high concentration of stresses and strains in the vicinity of the discontinuity of the old pavement causes the cracks to reflect into the newly placed HMA overlay. While it is a common practice to use skewed transverse joints in rigid pavements to improve the latter's performance, the impact of such a practice on the cracking of a potential HMA overlay has not been examined so far. In this context, this study investigates the effect of using skewed transverse joints in rigid pavements on reflective cracking development in the HMA overlay. Advanced three-dimensional Finite Element models including viscoelastic material properties for the HMA overlay, 3D beam modeling of dowel bars, non-uniform tire-pavement contact stresses, friction interfaces, and infinite boundary elements were constructed for both normal and skewed transverse joints using ABAQUS v-6.11. The potential for reflective cracking was monitored through the fracture mechanics J-integral parameter. Results obtained show, among other things, that the practice of skewing transverse joints increases the potential for reflective cracking development in the asphalt concrete overlay.

physics.gen-ph↗

arXiv2012

Numerical Investigation of Design Strategies to Achieve Long-Life Pavements

Increasing the HMA base thickness and modifying the HMA mixture properties to improve the resistance to fatigue cracking are among the most popular methods for achieving long-lasting pavements. Such methods are based on the idea of reducing the tensile strain at the bottom of the HMA layer below the Fatigue Endurance Limit (FEL), a level of strain below which no cumulative damage occurs to the HMA mixture. This study investigates the effectiveness of several design strategies involved in long-life, perpetual pavement design. A 3D Finite Element model of the pavement involving a linear viscoelastic constitutive model for HMA materials and non-uniform tire contact stresses is developed using ABAQUS 6.11. The effects of asphalt base course thickness and mixture type, rich binder layer, and aggregate subbase layer are examined. Four asphalt base course mixture types, namely dense graded, polymer modified, high modulus, and standard binder, are studied as a function of the asphalt base course thickness. The results underline a better performance of the high-modulus asphalt base, as compared to the other base course mixtures. The aggregate subbase layer on top of subgrade soil showed a relatively minor effect on the longitudinal and lateral strain response at the bottom of asphalt base course. The addition of a rich binder layer at the bottom of the asphalt base course showed a significant reduction in tensile strains. Tables are provided as a guideline to assess the different alternatives in design of long-life perpetual pavements.

physics.gen-ph↗