• Journal of Hydrogen and New Energy
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• v.25 no.3
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• pp.297-304
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• 2014

The purpose of this study is to evaluate the experimental performance characteristics of a water-to-water geothermal heat pump featuring a vapor refrigerant injection for the production of hot water. The performance of geothermal heat pump with a vapor injection was evaluated by comparing with that of a conventional geothermal heat pump without a vapor injection. For heating operation, the geothermal heat pump with a vapor injection is superior in COP and heating capacity. The vapor injection was more effective for supplying hot water while overloading. The vapor injection was effective for the improvement of the cooling capacity. However, the vapor injection was not effective for the increasing of COP according to the increased input of a compressor. The advantage of vapor injection in water-to-water geothermal heat pump become disappeared while cooling operation with lower part loading.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.75-85
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• 2010

A new freeform structure representing "Diagrid, Cantilevered, Tilted." which has been considered not only its distinctive appearance but also the structural advantages becomes one of the trends in tall building design. Especially in the Diagrid system, loads can be distributed through bracing frame so that it can be save the materials since it has more effective in the structure behavior. But the seismic performance index such as response modification factor is not clearly defined yet. Even though the diagrid is supposed to show higher seismic performance, it is underestimated due to the lack of reliable data. In this paper the response modification factor for the diagrid system is experimentally explored.

• International Journal of Concrete Structures and Materials
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• v.10 no.sup3
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• pp.33-41
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• 2016

Ultra-high performance concrete (UHPC) is one of the most promising construction materials because it exhibits high performance, such as through high strength, high durability, and proper rheological properties. However, it has low tensile ductility compared with other normal strength grade high ductile fiber-reinforced cementitious composites. This paper presents an experimental study on the tensile behavior, including tensile ductility and crack patterns, of UHPC reinforced by hybrid steel and polyethylene fibers and incorporating plastic beads which have a very weak bond with a cementitious matrix. These beads behave as an artificial flaw under tensile loading. A series of experiments including density, compressive strength, and uniaxial tension tests were performed. Test results showed that the tensile behavior including tensile strain capacity and cracking pattern of UHPC investigated in this study can be controlled by fiber hybridization and artificial flaws.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.2009-2020
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• 2004

A parametric study of the factors controlling static and dynamic denting, as well as local stiffness, has been made on simplified panels of different sizes, curvatures, thicknesses and strengths. Analyses have been performed using the finite element method to predict dent resistance and panel stiffness. A parametric approach is used with finite element models of simplified panels. Two sizes of panels with square plan dimensions and a wide range of curvatures are analysed for several combinations of material thickness and strength, all representative of auto-motive closure panels. Analysis was performed using the implicit finite element code, LS-NIKE, and the explicit dynamic code, LS-DYNA for the static and dynamic cases, respectively. Panel dent resistance and stiffness behaviour are shown to be complex phenomena and strongly interrelated. Factors favouring improved dent resistance include increased yield strength and panel thickness. Panel stiffness also increases with thickness and with higher curvatures but decreases with size and very low curvatures. Conditions for best dynamic and static dent performance are shown to be inherently in conflict ; that is, panels with low stiffness tend to perform well under impact loading but demonstrate inferior static dent performance. Stiffer panels are prone to larger dynamic dents due to higher contact forces but exhibit good static performance through increased resistance to oil canning.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.381-384
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• 2002

The purpose of this study is to construct an Environment Database Management System (EDMS) for the Saemangeum watershed based on the linkage of Water Quality Model, i.e. QUALKO and WASP model, and GIS database to estimate water quality effectively in this area. There are two major river systems on this study area, the Mangyeong and the Dongjin rivers. Input data are automatically generated through the calculation of the pollutant loading and inflow concentration from the point and non-point sources. The developed system is composed of three different phases, such as pre-process, model performance and post-process. The Model performance is supported by the database at pre-process phase and model performance results were shown in the graphs and attribution data at post-process phase. The measured data from the Mangyeong and the Dongjin rivers are used to evaluate the applicability of EDMS. The EDMS shows higher reliability, and it is expected to contribute to the effective management and improvement of water quality modeling in the Saemangeum watershed since the system reduces complications of using a model in DOS operating environment and increases the accuracy of water quality analysis.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1928-1934
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• 2014

Induction motors are widely used due to their rugged, robust and easy to care features. Since they are heavily used in industry, testing of three phase induction motors have play a vital role. In order to determine motor equivalent circuit parameters, efficiency of motor, squirrel caged laboratory sized an induction motor test setup is prepared. It is suitable for the induction motor with the frame size of 100 and 112. A virtual Instrumentation typed engineering workbench (called as LabVIEW) software packet, is utilized as a graphical user interface program. Motor input power is measured by measuring the input voltage, current and power factor with the help of hall effect typed voltage and current transformers. Also, the output power is measured by measuring the speed and torque with the help of an encoder and torque sensor. All outputs of the voltage and current transformer, encoder and temperature, torque sensors are given to the Data Acquisition Card (DAQ) which acquires the data for processing and then the equivalent circuit parameters, efficiency, performance and loading characteristics are found out, using LabVIEW based user interface. It is suggested to use this test rig for the quality control of produced motors in industry, and an educational experiment setup in the school laboratories.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.35-54
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• 2015

The performance of a newly generated steel connection known as SidePlateTM moment connection for seismic loading and progressive collapse phenomenon has been investigated in this paper. The seismic evaluation portion of the study included a thorough study on of interstory drift angles and flexural strengths based on 2010 AISC Seismic Provisions while the acceptance criteria provided in UFC 4-023-03 guideline to resist progressive collapse must be satisfied by the rotational capacity of the connections. The results showed that the SidePlate moment connection was capable of attaining adequate rotational capacity and developing full inelastic capacity of the connecting beam. Moreover, the proposed connection demonstrated an exceptional performance for keeping away the plastic hinges from the connection and exceeding interstory drift angle of 0.06 rad with no fracture developments in beam flange groove-welded joints. The test results indicated that this type of connection had strength, stiffness and ductility to be categorized as a rigid, full-strength and ductile connection.

• Advances in concrete construction
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• v.2 no.2
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• pp.91-108
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• 2014

This paper presents a nonlinear finite element analysis (FEA) in order to investigate the flexural performance of one-way slabs strengthened by epoxy-bonded steel plates. Four point loading scheme is selectively chosen. A model is developed to implement the material constitutive relationships and non-linearity. Five Slabs were modeled in FEM software using ABAQUS. One slab was unstrengthened control slab and the others were strengthened with steel plates with varying the plate thickness and configuration. In order to verify the accuracy of the numerical model, a comparison was done between the experimental results available in the literature and the proposed equations by ACI 318-11 for the calculation of ultimate load capacities of strengthened slabs, the agreement has proven to be good and FEA attained accurate results compared with ACI code. A parametric study was also carried out to investigate the influence of thickness of steel plate, strength of epoxy layer and type of strengthening plate on the performance of plated slabs. Also, the practical and technical feasibility of splitting the steel plate in strengthening process has been taken into account. For practical use, the author recommended to use bonded steel plate as one unit rather than splitting it to parts, because this saves more effort and reduces the risk of execution errors as in the case of multiple bonded parts. Both techniques have nearly the same effect upon the performance of strengthened slabs.

• Earthquakes and Structures
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• v.14 no.5
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• pp.379-388
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• 2018

This study aims to identify the effect of both longitudinal reinforcement details and damage level on making a decision of repairing pre-damaged bridge columns using basalt fiber reinforced polymer (BFRP) jackets. Two RC bridge columns with improper details of the longitudinal and/or transverse reinforcement were tested under the effect of a constant axial load and increasing lateral cyclic loading. Test results showed that the lap-splice column exhibited an inferior performance where it showed rapid degradation of strength before achieving the theoretical strength and its deformation capacity was limited; however, quick restoration is possible through a suitable rehabilitation technique. On the other hand, expensive repair or even complete replacement could be the decision for the column with the confinement failure mode. After that, a rehabilitation technique using external BFRP jacket was adopted. Performance-based design details guaranteeing the enhancement in the inelastic performance of both damaged columns were addressed and defined. Test results of the repaired columns confirmed that both reparability and the required repairing time of damage structures are dependent on the reinforcement details at the plastic hinge zone. Furthermore, lap-splice of longitudinal reinforcement could be applied as a key design-tool controlling reparability and restorability of RC structures after massive actions.

• Steel and Composite Structures
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• v.27 no.5
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• pp.545-554
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• 2018

This study presents a novel method of improving the strength and stiffness of cold-formed steel (CFS) beams. Flexural members are primary members in most of the structures. Hence, there is an urgent need in the CFS industry to look beyond the conventional CFS beam sections and develop novel techniques to address the severe local buckling problems that exist in CFS flexural members. The primary objective of this study was to develop new CFS composite beam sections with improved structural performance and economy. This paper presents an experimental study conducted on different CFS composite beams with simply supported end conditions under four point loading. Material properties and geometric imperfections of the models were measured. The test strengths of the models are compared with the design strengths predicted by using Australian/New Zealand Standard for cold-formed steel structures. Furthermore, to ensure high precision testing, a special testing rig was also developed for testing of long span beams. The description of test models, testing rig features and test results are presented here. For better interpretation of results, a comparison of the test results with a hot rolled section is also presented. The test results have shown that the proposed CFS composite beams are promising both in terms of better structural performance as well as economy.