• Structural Engineering and Mechanics
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• v.88 no.2
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• pp.169-178
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• 2023

Lightweight aggregate concrete (LWAC) has various advantages, but it has limitations in ensuring sufficient ductility as structural members such as reinforced concrete (RC) columns due to its low confinement effect of core concrete. In particular, the confinement effect significantly decreases as the axial load increases, but studies on evaluating the ductility of RC columns at high axial loads are very limited. Therefore, this study examined the effects of concrete unit weight on the seismic performance of RC columns subjected to constant axial loads applied with different values for each specimen. The column specimens were classified into all-lightweight aggregate concrete (ALWAC), sand-lightweight aggregate concrete (SLWAC), and normal-weight concrete (NWC). The amount of transverse reinforcement was specified for all the columns to satisfy twice the minimum amount specified in the ACI 318-19 provision. Test results showed that the normalized moment capacity of the columns decreased slightly with the concrete unit weight, whereas the moment capacity of LWAC columns could be conservatively estimated based on the procedure stipulated in ACI 318-19 using an equivalent rectangular stress block. Additionally, by applying the section lamina method, the axial load level corresponding to the balanced failure decreased with the concrete unit weight. The ductility of the columns also decreased with the concrete unit weight, indicating a higher level of decline under a higher axial load level. Thus, the LWAC columns required more transverse reinforcement than their counterpart NWC columns to achieve the same ductility level. Ultimately, in order to achieve high ductility in LWAC columns subjected to an axial load of 0.5, it is recommended to design the transverse reinforcement with twice the minimum amount specified in the ACI 318-19 provision.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.6
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• pp.22-27
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• 1997

In general, the load which acts on the structure is almost independent of time in many locations. In this case. It is difficult to estimate the life with the service load history, because the structure is on the multi- axial and multi-point loading states. In this study, the service load of the excavator which is widely used in industry field was calculated using measured cylinder pressures and displacements. The fatigue life was estimated using the multi-axial and multi-point load counting method. Service load history of 4 pin joint which act independently each other is yielded by mult-axial and multi-point load counting method. The stress spectrum is yielded by superposition of the results of FEM stress analysis applied unit load. Palm- gren-Miner's cumulative Damage is 0.000804 for Von Mises equivalent stress sequence by one side fillet weld S-N curve. This result agress with Bench test results. As a result of this study, the fatigue life esti- mation using the multi-axial and multi-axial and multi-point load counting method is useful.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.226-231
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• 2016

Land Generated Waste Load Unit(LGWLU) estimation based on land use data is required to understand the impact of land use on water quality. The method of estimating LGWLU based on the monitoring data requires a lot of time and manpower. In this study, we propose a method of land pollution unit load estimation based on land use data with LP optimization. Optimization is the process to obtain the best possible optimal solution in a given condition. This study carried out optimization by using excel solver in Microsoft Excel. This study derived LGWLU of BOD, T-N, T-P in Gongju-Si and Seocheon-Gun by using the 2012 land use map made by ministry of environment based on 2010 satellite image. This study about LGWLU estimation is expected to be able to determine more clearly the water pollution caused by land use changes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1536-1541
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• 2018

For effective electricity consumption in urban railway station such as peak load shaving, it is important to know each electrical load pattern by various usage. The total electricity consumption in the urban railway substation is already measured in Korea, but the electricity consumption for each usage is not measured. The author proposed the deep learning method to estimate the electrical load pattern for each usage in the urban railway substation with public data such as weather data. GRU (gated recurrent unit), a variation on the LSTM (long short-term memory), was used, which aims to solve the vanishing gradient problem of standard a RNN (recursive neural networks). The optimal model was found and the estimation results with that were assessed.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.363-370
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• 2010

Load forecasting has always been essential to the operation and planning of power systems in deregulated electricity markets. Various methods have been proposed for load forecasting, and the neural network is one of the most widely accepted and used techniques. However, to obtain more accurate results, more information is needed as input variables, resulting in huge computational costs in the learning process. In this paper, to reduce training time in multi-layer perceptron-based short-term load forecasting, a graphics processing unit (GPU)-based computing method is introduced. The proposed approach is tested using the Korea electricity market historical demand data set. Results show that GPU-based computing greatly reduces computational costs.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.354-361
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• 2002

This paper propose section properties factor to generate stress history for fatigue analysis and safety inspection of steel bridge. A methodology is described for the computation of numerical stress histories in the steel truss bridge, caused by the vehicles using section properties factor. The global 3-D beam model of bridge is combined with the local shell model of selected details. Joint geometry is introduced by the local shell model. The global beam model takes the effects of joint rigidity and interaction of structural elements into account. Connection nodes in the global beam model correspond to the end cross-section centroids of the local shell model. Their displacements are interpreted as imposed deformations on the local shell model. The load cases fur the global model simulate the vertical unit force along the stringers. The load cases fer the local model are imposed unit deformations. Combining these, and applying vehicle loads, numerical stress histories are obtained. The method is illustrated by test load results of an existing bridge.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.4
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• pp.170-177
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• 2003

The electric power load during the summer peak time is strongly affected by cooling load, which decreases the preparation ratio of electricity and brings about the failure in the supply of electricity in the electric power system. The ice storage system and heat pump system etc. are used to settle this problem. In this study, the method of estimating temperature and humidity to forecast the cooling load of ice storage system is suggested. The method of forecasting the cooling load using neural network is also suggested. The daily cooling load is mainly dependent on actual temperature and humidity of the day. The simulation is started with forecasting the temperature and humidity of the following day from the past data. The cooling load is then simulated by using the forecasted temperature and humidity data obtained from the simulation. It was observed that the forecasted data were closely approached to the actual data.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.89-92
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• 1992

This paper presents an approach for thermal Unit Commitment by Lagrangian Relaxation with fuzzy technique. A proposed algorithm makes it possible to execute optimal decision making between Generation Cost and Load Demand with membership function. In order to test the validity of the proposed method, we applied to Mid-westerm utility system which has 20 thermal units. So, the usefulness of this method is verified.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.224-231
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• 2012

It is necessary to develop flow duration curve (FDC) on each unit watershed in order to analyze flow conditions in the stream for the management of Total Maximum Daily Loads (TMDLs). This study investigated a simple method to develop FDC for the general use of the curve. A simple equation for daily flow estimation was derived from the regression analysis between the 8-day interval flow data of a unit watershed and the daily flow monitoring data of an adjacent upstream region. FDC can be prepared with the calculation of daily flow by the equation for each unit watershed. An annual and a full-period FDC were drawn for each unit watershed in Guem river basin. Standard flow such as low and ordinary flow can be obtained from the annual FDC. Major percentile of flow such as 10, 25, 50, 75 or 90% can be obtained from the full-period FDC. It is considered that this simple method of developing FDC can be utilized more widely for the calculation of standard flow and the assessment of water quality in the process of TMDLs.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.2
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• pp.35-45
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• 2023

The DOR (Drainage outlet raising) in the paddy field has been suggested as one of the most important best management practices for the TMDL (Total maximum daily load) management in the technical guidelines by the NIER (National institute of environmental research). However, this method is underestimated and is not well adopted by local governments for the TMDL. The purpose of this study is to evaluate the unit load reduction equation according to the application of DOR in order to expand this equation. The original equation in the guideline was derived using the HSPF (Hydrological Simulation Program-Fortran) model for 1 year in Changnyeong. We analyzed the reduction effect of the original equation application by collecting additional long-term monitoring data from the Buan, Icheon, Iksan, and Jeonju. When comparing the reduction loads between the original equation and monitoring results, the evaluation results of the original equation were 11% of the monitoring analysis results, which was underestimated. This means that the original equation needs to be improved. For assessing the equation, the HSPF Paddy-RCH model was established according to the NI ER guideline and evaluated for applicability. The performance results of the model showed a reasonable range by the statistical criteria. Modified equations 1 and 2 were proposed based on the monitoring and modeling results. Modified equation 1 was the method of modifying the original equation's main factors, and modified equation 2 was the method of applying the non-point pollution reduction efficiency according to the rainfall class using the long-term modeling results. At the level of 58.6~64.6% of monitoring data, the difference between them could be further reduced compared to the original equation. The suggested approach will be more reasonable and practicable for decision-makers and will contribute to the TMDL management plans.