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 : The performance of pavements is decreased by reduced bearing capacity, deterioration, and distress due to complex loading conditions such as traffic and environmental loads. Therefore, the proper maintenance of pavements must be performed, and accurate evaluation of pavement conditions is essential. In order to improve the accuracy of the heavy weight deflectometer (HWD), which is a nondestructive evaluation method, the correlation between HWD test results and temperature factors were analyzed in this study. METHODS : The HWD test was conducted five times for one day on airport concrete pavement, and the ambient temperature, surface temperature, and slab internal temperature were collected. Since the slab internal temperature was nonlinear, it was replaced by the equivalent linear temperature difference (ELTD). The correlation between the HWD test results and each temperature factor was analyzed by the coefficient of correlation and coefficient of determination. RESULTSAND: The deflection of the slab center, mid edge, and corner, and impulse stiffness modulus (ISM) showed significantly high correlation with each temperature factor, especially the ELTD. However, the load transfer Efficiency (LTE) had very low correlation with the temperature factors. CONCLUSIONS : It is necessary to analyze the effect of aggregate interlocking on LTE according to the overall temperature changes in slabs by conducting seasonal HWD tests. It is also necessary to confirm the effect of seasonal temperature changes on deflection and ISM.

PURPOSES : Previously, airport concrete pavement was designed using only aircraft gear loading without consideration of environmental loading. In this study, a multiple-regression model was developed to predict maximum tensile stress of airport concrete pavement based on finite element analysis using both environmental and B777 aircraft gear loadings. METHODS: A finite element model of airport concrete pavement and B777 aircraft main gears were fabricated to perform finite element analysis. The geometric shape of the pavement, material properties of the layers, and the loading conditions were used as input parameters for the finite element model. The sensitivity of maximum tensile stress of a concrete slab according to the variation in each input parameter was investigated by setting the ranges of the input parameters and performing finite element analysis. Based on the sensitivity analysis results, influential factors affecting the maximum tensile stress were found to be used as independent variables of the multi regression model. The maximum tensile stresses predicted by both the multiple regression model and finite element model were compared to verify the validity of the model developed in this study. RESULTS: As a result of the finite element analysis, it was determined that the maximum tensile stress developed at the bottom of the slab edge where gear loading was applied in the case that environmental loading was small. In contrast, the maximum tensile stress developed at the top of the slab center situated between the main gears in the case that the environmental loading got larger. As a result of the sensitivity analysis and multiple regression analysis, a maximum tensile stress prediction model was developed. The independent variables used included the joint spacing, slab thickness, the equivalent linear temperature difference between the top and bottom of the slab, the maximum take-off weight of a B777 aircraft, and the composite modulus of the subgrade reaction. The model was validated by comparing the predicted maximum tensile stress to the result of the finite element analysis. CONCLUSIONS : The research shown in this paper can be utilized as a precedent study for airport concrete pavement design using environmental and aircraft gear loadings simultaneously.

PURPOSES : The purpose of this study is to analyze the magnitude of shoving of asphalt pavement by junction type between airport concrete and asphalt pavements, and to suggest a junction type to reduce shoving. METHODS : The actual pavement junction of a domestic airport, which is called airport “A”was modified by placing the bottom of the buried slab on the top surface of the subbase. A finite element model was developed that simulated three junction types: a standard section of junction proposed by the FAA (Federal Aviation Administration), an actual section of junction from airport “A”and a modified section of junction from airport“ A”. The vertical displacement of the asphalt surface caused by the horizontal displacement of the concrete pavement was investigated in the three types of junction. RESULTS: A vertical displacement of approximately 13 mm occurred for the FAA standard section under horizontal pushing of 100 mm, and a vertical displacement of approximately 55 mm occurred for the actual section of airport “A”under the same level of pushing. On the other hand, for the modified section from airport“ A”a vertical displacement of approximately 17 mm occurred under the same level of pushing, which is slightly larger than the vertical displacement of the FAA standard section. CONCLUSIONS: It was confirmed that shoving of the asphalt pavement at the junction could be reduced by placing the bottom of the buried slab on the top surface of the subbase. It was also determined that the junction type suggested in this study was more advantageous than the FAA standard section because it resists faulting by the buried slab that is connected to the concrete pavement. Faulting of the junctions caused by aircraft loading will be compared by performing finite element analysis in the following study.

In this study, proposed how to design an airport concrete pavement expansion joint considering the weather conditions and material properties. Currently, expansion joint spacing of airport concrete pavement in korea is not designed according to a clear standard, but it is designed to an empirical level. Various types of Admixture are used in concrete pavement and depending on the material characteristics or local environmental factors, there is a substantial difference in the extent and shrinkage to which the package is inflated. Significant differences are made in the extent to which the pavement expands or shrinkage depending on the material characteristics used or the local environmental factors. But, expansion joint design performed on empirical criteria cannot reflect these materials and environmental characteristics, resulting in unpredictable damage such as blow-up. To analyzing behavior of airport concrete pavement, horizontal displacement gauges, static strain gauges and thermometers are installed in the 3rd phase construction sites at Incheon International Airport. In this study, the relationship between the temperature and horizontal displacement of the concrete pavement was analyzed using the measured depth temperatures and the horizontal displacement data at the expansion joints at the Incheon airport site. The Finite Element Analysis Model of Incheon International Airport pavement was used to compare the difference between actual behavior and analytical behavior. In addition, it is proposed to design a suitable expansion joint spacing by considering the maximum expansion of concrete pavement and shrinkage caused by material expansion (e.g., ASR) and shrinkage due to water loss. This study was supported by Incheon International Airport Corporation (BEX00625).

PURPOSES: In this study, a three-dimensional nonlinear finite element analysis (FEA) model for airport concrete pavement was developed using the commercial program ABAQUS. Users can select an analysis method and set the range of input parameters to reflect actual conditions such as environmental loading.METHODS : The geometrical shape of the FEA model was chosen by considering the concrete pavement located in the third-stage construction site of Incheon International Airport. Incompatible eight-node elements were used for the FEA model. Laboratory test results for the concrete specimens fabricated at the construction site were used as material properties of the concrete slab. The material properties of the cement-treated base suggested by the Federal Aviation Administration(FAA) manual were used as those of the lean concrete subbase. In addition, preceding studies and pavement evaluation reports of Incheon International Airport were referred for the material properties of asphalt base and subgrade. The kinetic friction coefficient between the concrete slab and asphalt base acquired from a preceding study was used for the friction coefficient between the layers. A nonlinear temperature gradient according to slab depth was used as an input parameter of environmental loading, and a quasistatic method was used to analyze traffic loading. The average load transfer efficiency obtained from an Heavy falling Weight Deflectomete(HWD) test was converted to a spring constant between adjacent slabs to be used as an input parameter. The reliability of the FEA model developed in this study was verified by comparing its analysis results to those of the FEAFAA model.RESULTS : A series of analyses were performed for environmental loading, traffic loading, and combined loading by using both the model developed in this study and the FEAFAA model under the same conditions. The stresses of the concrete slab obtained by both analysis models were almost the same. An HWD test was simulated and analyzed using the FEA model developed in this study. As a result, the actual deflections at the center, mid-edge, and corner of the slab caused by the HWD loading were similar to those obtained by the analysis.CONCLUSIONS : The FEA model developed in this study was judged to be utilized sufficiently in the prediction of behavior of airport concrete pavement.

PURPOSES: This study is to compare load transfer efficiency of key joint and dowel joint for airport concrete pavement. METHODS: As AC150/5320-6D of FAA’s [Advisory Circular] was changed into AC150/5320-6E, Key joint type of rigid pavement were excluded from Construction Joints.. LTE(Load Transfer Efficiency) of dowel joint and key joint were compared by times and seasons through pavement temperature measurement, ocular investigation and HWD measurement. RESULTS: For the joint performance grade of No. 2(The second) runway of airport, 12% of poor rate was observed in key joint and 2% of poor rate in dowel joint. Poor rate of key joint was increased to 17%, if only No. 3~No. 6 slabs, which are mostly loaded from the airplanes, were applied for the study. In apron area, LTE poor rate of key joint was high in winter, and LTE poor rate of dowel joint was at least above ‘Fair’ grade. In summer, ‘Fair’ for key joint, ‘Acceptable’ for dowel joint appeared. CONCLUSIONS : As results, dowel joint was superior than key joint for LTE. Deviations of seasons and times were smaller in dowel joint’s result. And LTE in winter was lower than LTE in summer.