• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.293-303
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• 2010

The purpose of this study was to evaluate the influence of the methods of application of the direct analysis method, using the load amplification factor suggested by the KBC 2009 design code, for the evaluation of frame stability. For this purpose, the direct analysis method was performed for three-story-one-bay and five-story-three-bay unbraced steel frames with various notional loads, bending stiffness reductions, and factor B2s. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the influence of the applied methods. The scale of the frame, the axial load ratio, and the axial load distribution pattern were added to the main parameters to investigate the external effects. The research results showed that the influence of the methods of application of the direct analysis method is not significant in the case of the required axial strength and the application of the additional notional loads; and that the application of the factor B2 with the story stiffness concept to the direct analysis method is appropriate for the required flexural strength.

• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.27-37
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• 2024

In this study, direct algorithm-based back analysis was utilized to perform back analysis on two actual earth retaining wall fields, which was then compared with genetic algorithm-based method to evaluate the suitability of the back analysis. Additionally, in order to propose effective utilization methods of the program, the measurement data, as the input for the back analysis, was varied for each excavation step, and the applicability of the back analysis results(displacement, axial force) was examined. The research findings indicate that both direct algorithm and genetic algorithm show high applicability; however, the optimization for this program is better predicted by the direct algorithm. Moreover, in order to effectively use the back analysis program employing the direct algorithm, it was evaluated that relatively accurate prediction of the earth retaining wall behavior could be achieved by inputting measurement data from the 7th excavation step for fields with final excavation steps ranging from 8 to 11.

• Korean Journal of Construction Engineering and Management
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• v.13 no.2
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• pp.3-10
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• 2012

The current enforcement regulation of "Construction Technology Management Act" prescribes calculation standard of environmental preservation cost in construction site. According to this standard, environmental preservation cost is calculated by using the quantity-per-unit costing method or applied fixed rate on direct cost. However, when calculated by using the quantity-per-unit costing method it is few items to put in the budget according to standard of construction estimate and in the case of using the fixed rate on direct cost it is not considering various characteristics of the construction site. Therefore, it is needed a improvement plan of estimating method and management system for environmental preservation cost. In this study, it surveyed the actual state of the environmental preservation cost according to magnitude of project, site location, anti-pollution facilities and etc. over 38 road projects. The research reported in this paper environmental preservation cost was variously distributed over construction sites. Thus it needs to estimating method and management system to consider characteristics of construction site for environmental preservation cost.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1474-1480
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• 2013

This study attempted to estimate construction costs in accordance with the resource-based cost estimation (unit cost price) system by diameter for TBM method, and analyzed the direct cost and the total cost. Based on such figures, this study performed a regression analysis and proposed a model for an equation for estimating construction costs. model for the resource-based cost estimation (unit cost price) system classified by diameter for TBM method proposed by this study can be effectively applied to business planning, preliminary investigation, feasibility study, construction cost estimations in the early design stages.

• Smart Structures and Systems
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• v.29 no.2
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• pp.287-299
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• 2022

Rather than using smartphones as seismometers with designated locations and orientations, this study proposes to employ crowds' smartphones in buildings to perform fast safety assessment of buildings. The principal advantage of using crowds' smartphones is the potential to monitor the safety of millions of buildings without hardware costs, installation labor, and long-term maintenance. This study's goal is to measure the maximum interstory drift ratios during earthquake excitation using crowds' smartphones. Beacons inside the building are required to provide the location and relevant building information for the smartphones via Bluetooth. Wi-Fi Direct is employed between nearby smartphones to conduct peer-to-peer time synchronization and exchange the acceleration data measured. An algorithm to align the orientation between nearby smartphones is proposed, and the performance of the orientation alignment, interstory drift measurement, and damage level estimation are studied numerically. Finally, the proposed approach's performance is verified using large-scale shaking table tests of a scaled steel building. The results presented in this study illustrate the potential to use crowds' smartphones with the proposed approach to record building motions during earthquakes and use those data to estimate buildings' safety based on the interstory drift ratios measured.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.94-95
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• 2019

Recently, the importance of prevention has emerged for the management of construction safety accidents.. Accordingly, this study collects and quantifies various risk factors at the construction site to represent them as direct risks and to create a predictive process for prevention in advance. These risk figures can be used as comprehensive safety figures to reflect current site conditions and past accidentt cases. The prevention of industrial accidents is managed in advance through the development of applications thatt quantify and predict the risks of individuals working at construction sites. The purpose of the project is to reduce industrial accidents in the construction industry by supporting safety management of site managers and workers.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.841-844
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• 2005

Computer vision technology can be used to interpret the images captured by web cameras installed on construction sites to automatically quantify the results. This information can be used for quality control, productivity measurement and to direct construction. Steel frame construction is particularly well suited for automatic monitoring as all structural members can be viewed from a small number of camera locations, and three-dimensional computer models of steel structures are frequently available in a standard electronic format. A system is being developed that interprets the 3-D model and directs a camera to look for individual members as regular intervals to determine when each is in place and report the results. Results from a simple lab-scale system are presented along with preliminary full-scale development.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.173-180
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• 2005

The construction of a Synchronous Reluctance Motor (SynRM) is simple and also highly economical because a stator from the existing AC motor can be used. Since the synchronous inductance in the Synchronous Reluctance Motor is an element that is proportional to torque, its exact value must be experimentally or analytically found for accurate control and performance development of the motor. In this paper, direct torque control (DTC) simulation is carried out to maximize the torque of the Synchronous Reluctance Motor and the fast response characteristics with the inductance value by the Finite Element Method (FEM). The response characteristics are compared through the proposed direct torque control and torque response characteristics that are based on the existing PI Control in order to confirm the fast response features. To test the performance of the direct torque controller, the torque response is analyzed with variable speed and load condition.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.60-64
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• 2001

Recent recovery of the Korean economy drives a rapid increase in utility consumption and requires more stable utility supply and maintenance. However, power location security hardship, reinforcement of international environmental regulation and a huge cost of power plant construction have increased the burden laid on the stable supply. In addition, an efficient and flexible load management is required more than any era since an increment of the rate of increase in cooling load is expected. Therefore, according as the necessity of direct load control for cooling load during the summer in Korea was on the rise, direct load control systems by Internet communication method are constructed at five commercial buildings. Based on practical load control, this study proposes various application modes and communication methods prior to extension diffusion of direct load control hereafter.

• Structural Engineering and Mechanics
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• v.12 no.6
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• pp.633-656
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• 2001

In this paper, modal control with direct output feedback is formulated in a systematic manner for easy implementation. Its application to the seismic protection of structural systems is verified by a shaking table test, which involves a full-scale building model and an active bracing system as the control device. Two modal control cases, namely, one full-state feedback and one direct output feedback control were tested and compared. The experimental result shows that in mitigating the seismic response of building structures, modal control with direct output feedback can be as effective and efficient as that with full-state feedback control. For practical concerns, the control performance of the proposed method in the presence of sensor noise and stiffness modeling error was also investigated. The numerical result shows that although the control force may be increased, the maximum floor displacements of the controlled structure are very insensitive to sensor noise and modeling error.