Soo-Hyung Lee

A Study on the Structural Design of Permeable Asphalt Pavement

The porous pavement system is widely considered very effective in urban street because of its various benefits on safety and environment, but the pavement thickness design system has not been established yet. In porous pavement system. rainwater penetrates to the subgrade through porous pavements layers. Porous pavements are expected to reduce or alleviate the problems caused by impermeable pavement layer such as flood damage due to heavy rain in the city, drainage load, disorder in ecosystem, and heat island. However, its structural design methods in traffic roads has not been made mainly because of not being able to consider adequately the effect of rainwater on subgrade strength. In this study, structural design method of porous pavements is suggested after considering the subgrade weakness due to rainwater and numerical mechanical analysis. It is noted that elastic modulus of subgrade is reduced by 20% as subgrade moisture content is increased by 2% at optimum moisture content in the literature review. As a result of both finite element analysis and strength loss of subgrade by the existing design method, it is necessary to increase subbase thickness about 30cm in porous pavements compared with the existing traffic road pavement system. It is similar to premium thickness of structural design of porous pavements in Japan.

An Economic Calibration Method for Fuel Consumption Model in HDM4

HDM4 developed by Worldbank is the calculation software which is widely used in estimating various costs such as highway construction cost and vehicle operating cost (VOC). The necessary data such as weather condition, traffic volume, running speed, road curvature and road gradient should be input to calculate fuel consumption in HDM4. In conventional HDM4 calibration, calibration factors are determined by the average fuel consumption which has been measured for various vehicles for long period. The vehicles which are released after the calibration factors are determined or those with new technology could be low in terms of fuel consumption. This paper has proposed a fuel consumption testing method for quick and easy determination of the calibration factors in HDM4 VOC calculation. The calibration for the fuel consumption of HDM4 is performed by measuring fuel consumption for round trips on two flat and straight roads at several steady speeds for a short period. By this calibration method the factors for driving resistance ranged from 0.13 to 0.30. Latest cars are lower than HDM4 models in terms of tractive resistance and power loss with more efficient fuel economy. Therefore, it appears that the calibration factors would further decrease over time. In case of HDM4, however, separate calibration factors are not provided for aerodynamic resistance. Therefore, it is reasonable to regard that the difference in aerodynamic resistance has been reflected to the two calibration factors.