Pavement Damage Due to Different Tire and Loading Configurations on Secondary Roads
Due to the large percentage of goods moved by commercial trucks and its ever-growing freight industry, the U.S. needs innovative technologies to improve the efficiency of trucking operations and ensure continuous growth of the economy. One example of such a technology is the introduction of wide-base single tires to replace conventional dual tire systems. After more than two decades of research powered mainly by the tire industry, a new generation of wide-base tire was recently introduced. Compared to the first generation of wide-base tires, these new tires offer safety and cost-savings characteristics. Despite the significant advancements achieved through previous research projects on the impact of wide-base tires on pavements, past investigations have not evaluated the damage wide-base tires cause to low-volume secondary roads. This pavement class is widely encountered in many trucking applications, although for short distances, but the impact of the new generation of wide-base tires on these pavement structures is unclear. In addition, the static uniform loading assumption used in conventional flexible pavement design methods is inconsistent with realistic tire loading conditions and may result in erroneous pavement response and damage predictions. To address these shortcomings, this research project uses a developed three-dimensional (3-D) finite element model to predict pavement responses to loading applied by various tire configurations on secondary road pavements. This model incorporates the measured 3-D tire-pavement contact stresses, hot-mix asphalt (HMA) linear viscoelasticity, continuous moving load, and utilizes implicit dynamic analysis. The impact of wide-base tires on secondary road pavement damage was analyzed using available damage models, and the results were compared to the damage from conventional dual-tire assemblies. Findings of the study suggest that due to the different contact stress distributions at tire-pavement interface, the impact of the new generation of wide-base tire (455/55R22.5) on secondary road pavements varies when compared to the impact of the conventional dual-tire assembly.
THIN ASPHALT PAVEMENTS ON SOFT SOIL
This paper presents results of a study on the development of an integrated design and structural evaluation procedure for thin asphalt pavements. The procedure incorporates geotechnical design features, pavement design and evaluation, and the assessment of the reinforcing effect of geosynthetics in unbound road bases. The methodology uses the strain at the bottom and surface of the asphalt layer, the compressive strain at the top of the bound road base, the stress state at mid-depth of the unbound road base, the strain at the bottom of the bound road base, and the vertical compressive strains at the top sub-base and subgrade as design criteria. For the design of structural overlays, the load-carrying capacity of the pavement structure is expressed by the so-called Modified Structural Number, SNC, to circumvent the tedious procedure of backcalculation of layer stiffness moduli. An especially developed software tool called 'QUASAR' enables easy and very quick use of the multitude of equations to assess the structural condition of asphalt roads and to determine the required strengthening.
Simulation and control of hybrid renewable energy system connected to the grid
This paper presents a control and simulation of hybrid renewable energy system connected to the grid. The studied system includes a photovoltaic panel, synchronous permanent magnet generator based wind turbine, and a battery for storage energy. The PV array and wind systems are connected to the common DC bus by a boost converter. The battery is connected by a bi-directional DC/DC converter, and then integrated into the AC utility grid via a common DC/AC inverter. In order to extract the maximum energy, a simulation study has been carried out according to the meteorological conditions (wind speed and variable solar irradiance) while maintaining power quality at a satisfactory level. In order to capture the maximum power, a MPPT algorithm is applied for both wind turbine and photovoltaic panel. The modeling and simulation of the whole system has been performed under Matlab/Simulink environment. The obtained results show that the current and the voltage of grid side are sinusoidal and alternative forms, and the power injected to the grid is around the power produced by the hybrid system.