• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.482-491
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• 2009

In this study, the mechanical behavior of very soft ground that is reinforced on the surface has been investigated with the aid of a series of numerical analyses. Key material properties of each dredged soft ground, reinforcement and backfill sand mat have been parametrically estimated in the numerical analysis. Along with the result of the study previously performed, a series of in-situ loading conditions and settlement exerted by surface reinforcing operation by construction vehicles has been numerically simulated. These result have been used to evaluate the limit bearing capacity for the unreinforced and reinforced soft ground. Also, the results of the numerical analysis obtained in this research were compared with Yamanouchi's empirical correlation for the limit bearing capacity. Engineering charts listed in this paper for estimating the limit bearing capacity provide field engineers with preliminary design tool for surface reinforcement of very soft ground.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.79-88
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• 2013

$LiFePO_4$ is a promising active material (AM) suitable for use in high performance lithium-ion batteries used in automotive applications that require high current capabilities and a high degree of safety and reliability. In this study, an optimization of the electrode design parameters was performed to produce high capacity lithium-ion batteries based on $LiFePO_4$/graphite electrodes. The electrode thickness and porosity (AM density) are the two most important design parameters influencing the cell capacity. We quantified the effects of cathode thickness and porosity ($LiFePO_4$ electrode) on cell performance using a detailed one-dimensional electrochemical model. In addition, the effects of those parameters were experimentally studied through various coin cell tests. Based on the numerical and experimental results, the optimal ranges for the electrode thickness and porosity were determined to maximize the cell capacity of the $LiFePO_4$/graphite lithium-ion batteries.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.12
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• pp.858-866
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• 2012

A numerical study was performed to predict the performance of a fin-and-tube condenser. A condenser model was developed and verified by comparing the simulation results with experimental data for a R410A condenser in a residential air-conditioning system. The prediction error was 0.07% and -5.77% for the condenser capacity and pressure drop, respectively. In simulation results, the capacity and pressure drop of the condenser with even air velocity distribution were 0.67% and 12.93% higher than those with uneven distribution of air velocity. It was predicted by the model that the refrigerant distribution at the condenser inlet to the two first passes was not significantly influenced by the air distribution. The simulation results presented that the 1.49% of capacity and 64.6% of pressure drop were reduced by replacing helical microfin tubes with smooth tubes for the condenser.

• Steel and Composite Structures
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• v.33 no.4
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• pp.583-594
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• 2019

In the areas highly exposed to earthquakes, concrete-filled steel tube columns (CFSTCs) are known to provide superior structural aspects such as (i) high strength for good seismic performance (ii) high ductility (iii) enhanced energy absorption (iv) confining pressure to concrete, (v) high section modulus, etc. Numerous studies were reported on behavior of CFSTCs under axial compression loadings. This paper presents an analytical model to predict ultimate load capacity of CFSTCs with circular sections under axial load by using multivariate adaptive regression splines (MARS). MARS is a nonlinear and non-parametric regression methodology. After careful study of literature, 150 comprehensive experimental data presented in the previous studies were examined to prepare a data set and the dependent variables such as geometrical and mechanical properties of circular CFST system have been identified. Basically, MARS model establishes a relation between predictors and dependent variables. Separate regression lines can be formed through the concept of divide and conquers strategy. About 70% of the consolidated data has been used for development of model and the rest of the data has been used for validation of the model. Proper care has been taken such that the input data consists of all ranges of variables. From the studies, it is noted that the predicted ultimate axial load capacity of CFSTCs is found to match with the corresponding experimental observations of literature.

• Structural Engineering and Mechanics
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• v.83 no.2
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• pp.245-257
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• 2022

As the main lateral load resisting system in high-rise reinforced concrete structures, the mechanical performance of shear wall has a significant impact on the structure, especially for high-rise buildings. Steel corrosion has been recognized as an important factor affecting the mechanical performance and durability of the reinforced concrete structures. To investigate the effect on the seismic behaviour of corroded reinforced concrete shear wall induced by corrosion, analytical investigations and simulations were done to observe the effect of corrosion on the ultimate seismic capacity and drift capacity of shear walls. To ensure the accuracy of the simulation software, several validations were made using both non-corroded and corroded reinforced concrete shear walls based on some test results in previous literature. Thereafter, a parametric study, including 200 FE models, was done to study the influence of some critical parameters on corroded structural shear walls with boundary element. These parameters include corrosion levels, axial force ratio, aspect ratio, and concrete compressive strength. The results obtained would then be used to propose equations to predict the seismic resistance and drift capacity of shear walls with various corrosion levels.

• Smart Structures and Systems
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• v.29 no.3
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• pp.513-522
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• 2022

Due to the importance of accurate analysis of bearing capacity in civil engineering projects, this paper studies the efficiency of two novel metaheuristic-based models for this objective. To this end, black hole algorithm (BHA) and multi-verse optimizer (MVO) are synthesized with an artificial neural network (ANN) to build the proposed hybrid models. Based on the settlement of a two-layered soil (and a shallow footing) system, the stability values (SV) of 0 and 1 (indicating the stability and failure, respectively) are set as the targets. Each model predicted the SV for 901 stages. The results indicated that the BHA and MVO can increase the accuracy (i.e., the area under the receiving operating characteristic curve) of the ANN from 94.0% to 96.3 and 97.2% in analyzing the SV pattern. Moreover, the prediction accuracy rose from 93.1% to 94.4 and 95.0%. Also, a comparison between the ANN's error decreased by the BHA and MVO (7.92% vs. 18.08% in the training phase and 6.28% vs. 13.62% in the testing phase) showed that the MVO is a more efficient optimizer. Hence, the suggested MVO-ANN can be used as a reliable approach for the practical estimation of bearing capacity.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.225-238
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• 2022

In order to improve the cracking resistance of reinforced concrete and give full play to the advantages of prefabricated assembly structure in construction, prestressed reinforced concrete composite beam (PRCC) is proposed. Through the bending static test of seven I-shaped beam specimens, the bending failure modes and bearing capacity of PRCC and reinforced concrete composite beam are compared and analyzed, and the effects of prestress size, prestressed reinforcement layout and prestress application sequence on the flexural behavior of PRCC beams are studied. The results show that the cracking load and ultimate load of PRCC beams significantly increased after prestressing, and prestressed tendons can effectively control the crack development. With the increase of prestressing degree, the deformation resistance and bending stiffness of PRCC beams are increased. The application sequence of prestress has little influence on the mechanical properties of PRCC beams. The crack width, stiffness and normal section bearing capacity of PRCC beam are analyzed, and the calculated results are in good agreement with the experimental results.

• Journal of Biosystems Engineering
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• v.28 no.1
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• pp.1-10
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• 2003

A computer simulation was carried out to determinate the optimum capacity of bulk type trailer which is used as a tractor attachment. Soil physical properties. such as soil moisture content. bulk density, soil hardness and soil texture were measured in the 10 major rice production area for computer simulation. Mathematical model which include soil physical properties and vehicle factor was used for computer simulation. Most of the soil texture of the investigated area was silty loam. Soil moisture content ranged between 30 and 40% mostly. Soil bulk density was in the range of 1.500 to 1.700 kg/㎥. Soil hardness ranged between 1 to 18 kg/$\textrm{cm}^2$. Soil hardness incorporate the effects of many soil physical properties such as moisture content texture and bulk density, and so the range of soil hardness was greater than any other physical properties. The capacity of bulk type trailer was above 3000 kg$_{f}$ fer the most of the investigated area. and mostly in the range of 4000 to 6000 kg$_{f}$ depending upon the slip. But for the soft soil area such as Andong and Namyang. tractor itself had mobility problem and showed minus trailer capacity for some places. For this area. the capacity of bulk type trailer ranged between 1000 and 2000 kg$_{f}$ mostly so bulk type trailer should be designed as a small capacity compared to the other area.ared to the other area. area.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.5-15
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• 2013

The end bearing capacity of rock-socketed drilled shafts under axial loading is investigated by Hoek-cell tests and a numerical analysis. From the test results, it was found that the ultimate end bearing capacity ($q_{max}$) was influenced by pile diameter, rock mass modulus and the spacing of discontinuity. A new ultimate end bearing capacity method is proposed by taking end bearing capacity influence factors, including rock mass discontinuity, based on field data. Through comparisons with other field data, the proposed $q_{max}$ method represents a definite improvement in the prediction of ultimate end bearing capacity of rock-socketed drilled shafts.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.1021-1038
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• 2016

Considerable part of reinforced concrete building has suffered from destructive earthquakes in Turkey. This situation makes necessary to determine nonlinear behavior and seismic performance of existing RC buildings. Inelastic response of buildings to static and dynamic actions should be determined by considering both flexural plastic hinges and brittle shear hinges. However, shear capacities of members are generally neglected due to time saving issues and convergence problems and only flexural response of buildings are considered in performance assessment studies. On the other hand, recent earthquakes showed that the performance of older buildings is mostly controlled by shear capacities of members rather than flexure. Demand estimation is as important as capacity estimation for the reliable performance prediction in existing RC buildings. Demand estimation methods based on strength reduction factor (R), ductility (${\mu}$), and period (T) parameters ($R-{\mu}-T$) and damping dependent demand formulations are widely discussed and studied by various researchers. Adopted form of $R-{\mu}-T$ based demand estimation method presented in Eurocode 8 and Turkish Earthquake Code-2007 and damping based Capacity Spectrum Method presented in ATC-40 document are the typical examples of these two different approaches. In this study, eight different existing RC buildings, constructed before and after Turkish Earthquake Code-1998, are selected. Capacity curves of selected buildings are obtained with and without considering the brittle shear capacities of members. Seismic drift demands occurred in buildings are determined by using both $R-{\mu}-T$ and damping based estimation methods. Results have shown that not only capacity estimation methods but also demand estimation approaches affect the performance of buildings notably. It is concluded that including or excluding the shear capacity of members in nonlinear modeling of existing buildings significantly affects the strength and deformation capacities and hence the performance of buildings.