PURPOSES : Almost every design method for airport concrete pavements considers only traffic loading and not environmental loading. This study proposes a mechanistic design method for airport concrete pavements, that considers both environmental and traffic loading simultaneously. METHODS: First, the environmental loading of concrete pavements in Korean airports was quantified. FEAFAA, a finite element analysis program for airport pavements, was used to calculate the maximum tensile stress (MTS) of the slab, caused by both environmental and traffic loadings. The factors that influence the MTS were identified via sensitivity analysis, and an MTS prediction model was developed using the statistical analysis program SPSS. The ratio of MTS to the tensile strength of slab was calculated using the prediction model. The fatigue model under the AC 150/5320-6E and AC 150/5320-6F standards of the FAA was corrected to make it suitable for the predicted stress-strength ratio. RESULTS : The MTS prediction model and corrected fatigue model were used to redesign the slab thickness and joint spacing of airport concrete pavements originally designed using the AC 150/5320-6D standard, which empirically considers traffic loading only. As a result, different slab thicknesses and joint spacings were redesigned with consideration for environmental loading, specifically the weather conditions of airports. . CONCLUSIONS: The slab thickness and joint spacing can be mechanistically designed at the same time, whereas previously, only the slab thickness was designed, and the joint spacing was determined empirically.

PURPOSES : It is well known that low temperature cracking is one of the most serious distresses on asphalt pavement, especially for northern U.S. (including Alaska), Canada and the northern part of south Korea. The risk of thermal cracking can be numerically measured by estimating thermal stress of a given asphalt mixture. This thermal stress can be computed by low temperature creep testing. Currently, in-direct tensile (IDT) mixture creep test mentioned in AASHTO specification is used for measuring low temperature creep properties of a given asphalt mixture. However, IDT requires the use of expensive testing equipment for performing the sophisticated analysis process, however, very few laboratories utilize this equipment. In this paper, a new and simple performance test (SPT) method: bending beam rheometer (BBR) mixture creep testing equipment is introduced, and the estimated experimental results were compared with those of conventional IDT tests. METHODS: Three different asphalt mixtures containing reclaimed asphalt pavement (RAP) and roofing shingles were prepared in the Korea Expressway Corporation (KEC) research laboratory. Using the BBR and IDT, the low temperature creep stiffness data were measured and subsequently computed. Using a simple power-law function, the creep stiffness data were converted into relaxation modulus, and subsequently compared. Finally, thermal stress results were computed from relaxation modulus master curve using Gaussian quadrature approach with condierations of 24 Gauss number. RESULTS: In the case of the conventional asphalt mixture, similar trends were observed when the relaxation modulus and thermal stress results were compared. In the case of RAP and Shingle added mixtures, relatively different computation results were obtained. It can be estimated that different experimental surroundings and specimen sizes affected the results. CONCLUSIONS: It can be said that the BBR mixture creep test can be a more viable approach for measuring low temperature properties of asphalt mixture compared to expensive and complex IDT testing methods. However, more extensive research and analysis are required to further verify the feasibility of the BBR mixture creep test.

Wheat is a major food source for a large proportion of the worldwide population. Wheat production is hampered by drought, cold and various diseases. Wheat germplasms contain various characteristics such as high yield, low plant height, resistance to diverse diseases and good seed quality. In this study, we evaluated agronomic traits of wheat germplasms collected from the National Plant Germplasm System (NPGS) for application of the breeding program. Total 221 wheat lines contain cultivars and landraces were provided by NPGS and USDA-ARS. The germplasms were evaluated quantitative and qualitative agronomic properties in Korea university research farm. The agronomic traits of the germplasms in each region were analysed using statistical analysis. The most of germplasms were geographically originated from America continent. The germplasms average heading date showed on May 10. The average heading date of Africa germplasms was 6 days earlier than Europe germplasms. The germplasms average plant height and spike length showed 81.7 cm and 8.6 cm, respectively. The germplasms of Europe showed 21.7 cm taller than average plant height of America continent and the germplasms of Africa showed the smallest plant height comparing with other continents. The germplasms of Asia showed taller spikere length than that of other continents. Seed color in germplasm comprises white, red and purple seed color, 24%, 75%, 1%, respectively. In addition, about 39% of the germplasms indicated lodging resistant. These results could be useful for improvement of wheat breeding program.