Effect of Wide-Base Tires on Nationwide Flexible Pavement Systems: Numerical Modeling

2019

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Airport pavement structures experience heavy aircraft tire loading through a localized contact area. Distributed three-dimensionally and non-uniformly, tire-pavement contact stresses directly influence the near-surface behavior of flexible airfield pavements. The resulting high shear stress levels induced by aircraft tire loading may lead to instability through shoving or slippage cracking. As the tire turns during taxiing, the risk of near-surface damage is exacerbated. In this study, numerical modeling of an inverted pavement system and a conventional flexible pavement structure loaded with a single tire from the A-380 landing gear was developed. The analysis matrix included two tire-inflation pressures, two speeds, and rolling conditions that varied from free-rolling to two turning maneuvers. Two analysis approaches were performed: 1) use of traditional critical point strains, and 2) domain analysis, which characterizes bulk pavement behavior using multiaxial stresses and strains. The critical strains, which are used as inputs for airfield pavement design, changed negligibly under varying tire turning conditions despite the asymmetric contact stress distribution. On the other hand, domain analysis not only captured the asymmetric pavement behavior, but also identified that altering the tire movement from a free-rolling condition to turning could induce a significant increase in the potential damage.

Section: Airfield Pavement Structuresmentioning

confidence: 99%

Turning Maneuver Effect on Near-Surface Airfield Pavement Responses

2019

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“…FE modeling was used to calculate critical pavement responses. The 3D model considers appropriate material characterization for each layer in the pavement structure and accurate representation of truck loading regarding direction, magnitude, and amplitude ( 25 ). The numerical predictions of critical pavement responses were contrasted with experimental measurements to ensure model validity ( 26 ).…”

Section: Pavement Response and Damagementioning

confidence: 99%

“…Regarding material property inputs, AC layers were assumed to be linear viscoelastic, while the base layer was assumed to be orthotropic stress-dependent (for thin pavement only) and linear elastic otherwise. Details of the material property selection can be found elsewhere ( 25 ).…”

Section: Pavement Response and Damagementioning

confidence: 99%

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Impact of Wide-Base Tires on Pavements: A National Study

Hernandez

et al. 2018

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This paper summarizes a multi-year effort comparing the new-generation wide-base tires (NG-WBT) and dual-tire assembly from a holistic point of view. The tires were compared considering not only pavement damage but also environmental impact. Numerical modeling, prediction methods, experimental measurements, and life-cycle assessment were combined to provide recommendations about the use of NG-WBT. A finite element (FE) approach considering variables that are usually omitted in the conventional analysis of flexible pavement was used for modeling pavement structures combining layer thickness, material properties, tire load, tire-inflation pressure, and pavement type (interstate and low volume). A prediction tool, ICT-Wide, was developed based on an artificial neural network to obtain critical pavement responses in cases excluded from the FE analysis matrix. Based on the bottom-up fatigue cracking, permanent deformation, and international roughness index, the life-cycle energy consumption, cost, and green-house gas emissions were estimated. To make this research useful for state departments of transportation and practitioners, a modification to AASHTOware is proposed to account for NG-WBT. The revision is based on two adjustment factors, one accounting for the discrepancy between the AASHTOware approach and the FE model of this study, and the other addressing the impact of NG-WBT. Although greater pavement damage may result from NG-WBT, for the analyzed cases, the extra pavement damage may be outweighed by the environmental benefits when NG-WBT market penetration is considered.

“…FE modeling is a robust tool used by the scientific community to simulate complex problems (e.g., airfield pavement analysis). In contrast to analytical models, 3-D FE pavement modeling capabilities include multi-axial tire–pavement contact stresses, viscoelastic and nonlinear material characterization, material damping, layer interface properties, dynamic analysis, infinite boundary, and continuously moving load ( 2–5 ). All the aforementioned considerations provide a step forward in simulating a realistic loaded pavement scenario.…”

mentioning

confidence: 99%

Development of Domain Analysis to Predict Multi-Axial Flexible Airfield Pavement Responses Due to Gear and Environmental Loadings

Hernandez

2018

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Flexible pavement design procedures use maximum mechanistic strains to predict service life via empirical transfer functions. The conventional method of using predefined point locations for potential damage may not accurately represent realistic pavement scenarios. For instance, flexible airfield pavement analysis mainly considers the critical strain at the bottom of the asphalt concrete (AC), which may not characterize near-surface cracking potential. In lieu of point strains, domain analysis, a new method, accounts for the multi-axial behavior of pavements, as inherently excited by three-dimensional (3-D) and nonuniform aircraft tire–pavement contact stresses. Initially applied on highway pavements considering truck tire loading, this approach is an initial breakthrough for implementing domain analysis on flexible airfield pavements; in this study, A-380 and F-16 landing gear tire loads were considered. As anticipated, speed and temperature had significant influence on cumulative domain stress and strain ratios. The decrease in speed and increase in temperature not only increased the cumulative ratios up to 1.81, but nonlinearity of the problem became more prevalent at worst loading conditions (8 kph and 45°C). Minimal difference in ratios for F-16 cases suggests that the National Airport Pavement Test Facility pavement structure became less sensitive to conditions under low loads. Point response analysis revealed that critical strains were not significantly influenced by the tire-inflation pressure, for example, tensile strain at the bottom of the AC only increased up to 13.6% (considering 8 kph speed), whereas domain analysis quantified the increase with respect to 3-D stress or strain states.