@article{ahn_cho_chung_2016, title={Development of a statistical analysis model to benchmark the energy use intensity of subway stations}, volume={179}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2016.06.065}, abstractNote={This paper presents an Energy Use Intensity (EUI) indicator model for energy benchmarking subway stations. Among the mass transportation systems, a subway, in terms of its rapidity, punctuality, and efficiency, has been preferred in metropolitan area and recently spotlighted as it mitigates environmental impacts to global warming. Of its several advantages, a subway’s carbon footprint is negligible, which directly contributes to energy savings. Therefore, demands of subway systems have increased. However, subway stations have rarely been included in most energy performance studies and surveys. Due to a lack of information and design complexity, most designers are not able to do optimal design practices. A statistical model was developed in this study using the benchmark process for 157 actual subway stations in Seoul, South Korea. It includes measured data, utility bills, simulation results, and regression modeling. This adjusted EUI benchmark model was developed using characteristics of subway stations and a statistical validation process. The effectiveness of the model is tested and verified by comparing between measured EUI and adjusted normalized EUI (EUInorm) of actual subway stations. This paper includes the test results of EUI indicator model to benchmark energy performance and assesses existing subway station.}, journal={APPLIED ENERGY}, author={Ahn, Jonghoon and Cho, Soolyeon and Chung, Dae Hun}, year={2016}, month={Oct}, pages={488–496} }
 @article{ahn_cote_robinson_gabr_borden_2009, title={Inverse Analysis of Plate Load Tests to Assess Subgrade Resilient Modulus}, volume={2101}, ISSN={["2169-4052"]}, DOI={10.3141/2101-13}, abstractNote={Cyclic plate load testing is commonly used to investigate subgrade response under repetitive loads. Two frameworks for performing inverse analysis are described for backcalculating resilient moduli on the basis of measured key outputs. In the first approach, an elastic modulus is back-calculated in each selected domain; in the second, selected parameters in the resilient modulus model are estimated. The axisymmetric finite element model analysis results suggest that the second approach is more robust because it allows the modulus to be distributed in the selected domain. A series of sensitivity analyses was conducted with the second approach to illustrate how the assumed properties or model geometry affects the backcalculated parameters. Discrepancies between the back-calculated parameters and their known values were observed when the distance to the boundary–-that is, the radial distance from centerline to sidewall–-was not properly assigned. When backcalculating only selected parameters in the resilient modulus equation, it is necessary to assign the other parameters carefully (i.e., from laboratory tests or references). An example analysis shows the application of the proposed approach to an actual plate load test.}, number={2101}, journal={TRANSPORTATION RESEARCH RECORD}, publisher={Transportation Research Board}, author={Ahn, Jaehun and Cote, Benjamin M. and Robinson, Brent and Gabr, Mohammed A. and Borden, Roy H.}, year={2009}, pages={110–117} }
 @article{ahn_biscontin_roesset_2009, title={Wave propagation in nonlinear one-dimensional soil model}, volume={33}, ISSN={["1096-9853"]}, DOI={10.1002/nag.724}, abstractNote={Abstract The objective of the research conducted by the authors is to explore the feasibility of determining reliable in situ values of shear modulus as a function of strain. In this paper the meaning of the material stiffness obtained from impact and harmonic excitation tests on a surface slab is discussed. A one‐dimensional discrete model with the nonlinear material stiffness is used for this purpose. When a static load is applied followed by an impact excitation, if the amplitude of the impact is very small, the measured wave velocity using the cross‐correlation indicates the wave velocity calculated from the tangent modulus corresponding to the state of stress caused by the applied static load. The duration of the impact affects the magnitude of the displacement and the particle velocity but has very little effect on the estimation of the wave velocity for the magnitudes considered herein. When a harmonic excitation is applied, the cross‐correlation of the time histories at different depths estimates a wave velocity close to the one calculated from the secant modulus in the stress–strain loop under steady‐state condition. Copyright © 2008 John Wiley & Sons, Ltd.}, number={4}, journal={INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS}, author={Ahn, J. and Biscontin, G. and Roesset, J. M.}, year={2009}, month={Mar}, pages={487–509} }
 @article{ahn_biscontin_roesset_2009, title={Wave propagation velocity under a vertically vibrated surface foundation}, volume={33}, ISSN={["0363-9061"]}, DOI={10.1002/nag.759}, abstractNote={Abstract The ultimate objective of the research conducted by the authors is to explore the feasibility of determining reliable in situ values of soil modulus as a function of strain. In field experiments, an excitation is applied on the ground surface using large‐scale shakers, and the response of the soil deposit is recorded through receivers embedded in the soil. The focus of this paper is on the simulation and observation of signals that would be recorded at the receiver locations under idealized conditions to provide guidelines on the interpretation of the field measurements. Discrete models are used to reproduce one‐dimensional and three‐dimensional geometries. When the first times of arrival are detected by receivers under the vertical impulse, they coincide with the arrival of the P wave; therefore related to the constrained modulus of the material. If one considers, on the other hand, phase differences between the motions at two receivers, the picture is far more complicated and one would obtain propagation velocities, function of frequency and measuring location, which do not correspond to either the constrained modulus or Young's modulus. It is necessary then to conduct more rigorous and complicated analyses in order to interpret the data. This paper discusses and illustrates these points. Copyright © 2008 John Wiley & Sons, Ltd.}, number={9}, journal={INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS}, author={Ahn, Jaehun and Biscontin, Giovanna and Roesset, Jose M.}, year={2009}, month={Jun}, pages={1153–1167} }