Impact of Environment-Friendly Tires on Pavement Damage Hao Wang, PhD Assistant Professor, Dept. of CEE Rutgers, the State University of New Jersey The 14th Annual NJDOT Research Showcase 10/18/2012 Acknowledgement Illinois Center for Transportation (IDOT R59 project) TPF-5(197) Pool Fund Study: The Impact of Wide-Base Tires on Pavement Damage: A National Study Dr. Imad Al-Qadi at University of Illinois at Urbana-Champaign 1
Dual Tires: Tire Design Code Nominal tire width 250~305 mm 11R22.5; 275/80R22.5; 295/75R22.5 Wide-Base Tire Code Nominal tire width 400~460 mm 385/65R22.5; 425/65R22.5; 455/55R22.5 Tire width (in. or mm)/ tire aspect ratio (the ratio of section height to width)/ radial ply (R)/ rim diameter (in) Wide-Base Tire Characteristics Introduced to North America in 1982 Replace Dual Tires Low Profile Design Design for High-Speed Long- Distance Carrier Dual/ 275 1980 1982 2000 2002 2000 385 425 445/455 495 2
Why Wide-Base Tires NOW? Substantial savings to truck freight transportation Truck operation Increase hauling capacity (increase payload) Reduced tire cost and repair Ride and comfort Better handling and rolling stability Environmental benefit Fuel economy Reduced emission Reduced recycling impact of scrap tires Where Does the Fuel Go? aerodynamic drag mechanical losses rolling resistance At 60 mph (100 kmh), aerodynamic drag consumes approximately 40% of the fuel. Mechanical losses consume approximately 25% of the fuel. Rolling resistance accounts for approximately 35% of the fuel consumed. Using wide-base tires reduces rolling by 12% 3
Environmental Benefit Reduced gas emission Reduction of 1.1 million metric tons of carbon equivalent in 2010 (assuming current market share, 5%) Reduce recycling impact of scrap tires 72.5kg of residual materials for dual tires vs. 53.6kg for a wide-base tire assembly Impact on Road Infrastructure? Impact of Early Wide-Base Tires Early generation of wide-base tires (385/65R22.5, 425/65R22.5): Require high tire inflation pressure (790-890kPa) Smaller contact area and higher contact stresses compared to dual-tire assembly Significantly increase pavement damages compared to dual-tire assembly Damage ratios range between 1.5-2.0 for rutting and 2.0-4.3 for fatigue cracking 4
New Generation of Wide-Base Tires New generation of wide-base tires (445/50R22.5 and 455/55R22.5): 15-18% wider than the first generation New crown architecture that allows wider width Reduced normal tire pressure at high loads Impact on pavement damage Same as the old generation? Wide-base 425 and 455 Objective and Scope Compare pavement responses caused by various tire configurations Instrumentation measurements under accelerated pavement testing (APT) Advanced finite element modeling (FEM) Analyze impact of tire configuration on pavement damage mechanisms Fatigue cracking Top-down cracking Rutting in asphalt layer and subgrade 5
Accelerated Loading Facility Loading Matrix and Tire Configuration Tire Load (kn) 26, 35, 44, 53 & 62 Tire Configuration Speed (km/h) Loading Matrix Tire Pressure (kpa) 8, 16 550, 690& 760 Loaded Radius Tire Configuration Overall Diameter Tire Configuration Dual, WB 455 & WB 425 Overall Width Offset 0, 152, 305, and 457mm Tread Depth 11R22.5 488 1049 285 22 425/65R22.5 522 1130 421 18 455/55R22.5 498 1078 448 22 6
Full-Depth Pavement Test Sections Section A Section B Section D Section F (Al-Qadi, Wang, and et al. 2008) Thermocouple Strain gauge Example of Measured Strain Pulses Strain at Section D (micro) 100 80 Transverse Strain Longitudinal Strain 60 40 20 0 1.5-20 2 2.5 3 3.5-40 Time (sec) 7
Tensile Strain Ratios at Different Sections Strain Ratio wide / dual Asphalt Layer Thickness 152 254 420 Wide-base Tires Descriptive statistics Average Standard deviation 455 1.17 0.09 425 1.28 0.09 455 1.20 0.08 425 1.31 0.09 455 1.11 0.05 425 1.17 0.06 P-value for Two Sample t-test <0.01 <0.01 <0.01 Finite Element Pavement Model Used to predict pavement responses under moving tire loading 3-D Finite Element Model Tire contact stress Moving tire loading Viscoelastic asphalt layer Nonlinear crossanisotropic granular base and subgrade Interface condition (Wang and Al-Qadi 2009; 2011) 8
Critical Pavement Response Transfer Function! Strain Ratios Predicted from Modeling Strain Ratio wide / dual (wide-base 455 tire only) Asphalt Thickness Speed (km/h) Tensile strain Surface shear strain Subgrade comp. strain 152 254 420 8 1.28 0.92 1.27 80 1.35 0.86 1.32 8 1.25 0.88 1.16 80 1.30 0.82 1.15 8 1.06 0.79 1.01 80 1.05 0.74 1.13 9
Pavement Damage Analysis Pavement performance life were predicted using the new AASHTO Mechanistic-Empirical Pavement Design (MEPDG) approach Damage Ratio: the ratio of damage caused by one pass of a single axle with wide-base tires with respect to the damage caused by one pass of a 20-kip single axle with dual tires Load (kips) 16-in Wide-base 455 10-in 6-in Dual-tire Assembly 16-in 10-in 6-in 8 0.33 0.56 1.27 0.46 0.45 0.45 10 0.69 1.13 2.64 1.00 1.00 1.00 12 1.02 1.95 4.24 1.48 1.74 1.83 Summary Wide-base 455 tire causes less pavement damage compared the old generation (425) The impact of wide-base 455 tire on pavement vary with damage type and pavement structure The accurate tire-pavement interaction (contact area and stress) is essential to evaluate pavement damage caused by different tire configurations 10
Implementation / Future Research Convert truck traffic with wide-base tires to ESAL using the developed damage ratio in pavement rehabilitation (overlay thickness design) Implement appropriate load regulations and road pricing for trucking operations using wide-base tires Load Wide-base 455 Dual-tire Assembly (kn) Interstate Primary Local Interstate Primary Local 35 / / 0.14 / / / 44 / 0.01 0.83 Reference 53 0.0007 0.11 1.65 0.02 0.09 0.42 unit: $/mile based IDOT data * / means no additional cost Thank You Questions? Hao Wang hwang.cee@rutgers.edu 11