• Journal of the Korea Concrete Institute
• /
• v.16 no.6 s.84
• /
• pp.823-832
• /
• 2004

The purpose of this research is to investigate the flexure-shear behavior of bridge columns under seismic loads. Four full scale circular reinforced concrete columns were tested under cyclic lateral load with constant axial load. The selected test variables are aspect ratio(1.825, 2.5, 4.0), transverse steel configuration, and longitudinal steel ratio. Volumetric ratio of transverse hoop of all the columns is 0.0023 in the plastic hinge region. It corresponds to $24\%$ of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. The columns showed flexural failure or flexure-shear failure depending on the test variables. Failure behavior and seismic performance are investigated and discussed in this paper.

• Journal of the Korean Geographical Society
• /
• v.38 no.5
• /
• pp.802-821
• /
• 2003

This paper aims to illuminate how the Naturalists' concern on geography and geography education, mainly in Comenius, Rousseau, Pestalozzi who have played key roles in the development of Naturalism, has developed and how the Naturalism has influenced on the development of geography and geography education. Starting from sensual realism, the Naturalism suggested the educational principle and methods adjusting to the Nature well as exercised great influence on the formation of modem school education toward popular common education. The geography took the firm position as subject in the curriculum of the Naturalists and achieved the rationale of existence as subject in curriculum with utility to expand human experience, thanks to Naturalists. The Naturalists developed several ideas on geography teaching method such as labouring activity-centered geography teaching based on strengthening sense and experience by 'look-and-see' approach, local geography-centered geography teaching with stress the local area as the focus of direct experience and living environment, and the real thing-centered geography teaching by fieldwork. Moreover, The Naturalists had an great effect on the geographer, Karl Ritter in terms of methodology of geography.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.35 no.4
• /
• pp.747-757
• /
• 2015

The main purpose of this study is to investigate the static behavior of a horizontally curved prestressed concrete (PSC) girder. A 30m long full-scale curved PSC girder with 80.0m radius is fabricated by a portable curved form system. Deflections and concrete strains at the middle of span were measured. The obtained experimental results have been compared to those from F.E.A. analysis. When a initial crack developed, the applied load was 1.3 times the service design load and the vertical deflection at the middle of span satisfied the requirement for a live load state according to the Korea Bridge Design Specifications (2010). Also, the ductility of the full scale specimen satisfied the limit in the Specifications (2010). To verify the experimental results, a numerical F.E. analysis was carried and confirmed that the data were similar with results from the test above. The horizontally curved PSC girder fabricated on site was found to have enough strength for safety under and after construction.

• Journal of Energy Engineering
• /
• v.11 no.2
• /
• pp.130-135
• /
• 2002

Bypass air conditioning systems are divided into three types; outdoor air bypass, mixed air bypass and return air bypass system. Among bypass air conditioning systems, a return air bypass system is more effective than other two systems because it doesn't induce unconditioned outdoor air into conditioned room. The numerical study on the bypass air conditioning system shows this system can maintain indoor RH(Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. A simulator was built to compare results of a numerical experiment and those of a simulator experiment. The results of the simulator experiment was nearly same as those of the numerical experiment; when a design sensible load (the ratio of sensible load to total sensible load) was 70 percent (at this time, RSHF=0.7), indoor relative humidity (in case of both numerical experiments and simulator experiments) was maintained below 60% specified by ASHRAE STANDARD 62-1999. The bypass air conditioning system is expected to be applied to many buildings where the Percentage of latent loads or air change tate is high.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.6
• /
• pp.537-546
• /
• 2010

This research work contributed to a study for the procedure and methodology to assess the fatigue durability for a composite torque link of helicopter landing gear, which was newly developed and fabricated by the resin transfer moulding technique to interchange with metal component. The simulated load spectrum anticipated to be applied to the torque link during its operation life was generated using an advanced method of probabilistic random process, and the fatigue durability was evaluated by the strength degradation approach on the basis of material test data. The full scale fatigue test was also performed and compared with the analysis results.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.732-737
• /
• 2005

Distal 3D Real Object Duplication System(RODS) consists of 3D Scanner and Solid Freeform Fabrication System(SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and a industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer(SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. Also, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Multi-Laser Sintering(SMLS) process and 3-axis dynamic Focusing Scanner for scanning large area instead of the existing $f\theta$ lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, scan spacing. Now, this study is in progress to eveluate the effect of experimental parameters on the sintering process.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.4 s.37
• /
• pp.629-639
• /
• 1998

This paper summarizes the results of full-scale cyclic seismic performance tests on three column-tree type steel moment connections. Each test specimen consisted of a $H-600{\times}200$ beam and a $H-400{\times}400$ column of SS41 (SS400). Key parameter included was column PZ (panel zone) strength relative to beam strength. The seismic performance of specimen with stronger PZ tended to be inferior. Total plastic rotations available in the specimens ranged from 1.8 to 3.0 (% rad). The limited test results in this study seem to support the speculation that permitting PZ yielding shall be more beneficial to enhancing total plastic rotation capacity of the moment connection. Beam flange fracture across the heat affected zone and divot-type pullout of the column flange were observed in the tests. A conceptual mechanical model consistent with observed test results was also sought.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.4
• /
• pp.479-490
• /
• 2012

Flexural tests on full-scale H-shaped beams, built up from high-strength steels (HSB800 and HSA800) with a nominal tensile strength of 800 MPa, was carried out to study the effect of flange slenderness of high-strength steel on flexural strength and rotation capacity. The primary objective was to investigate the appropriateness of extrapolating current stability criteria (originally developed for ordinary steel) to high-strength steel. The performance of high-strength steel specimens was very satisfactory from the strength, but not from the rotation capacity, perspective. The inferior rotation capacity of high-strength steel beams was shown to be directly attributable to the absence of a distinct yield plateau and the high yield ratio of the material. Residual stress measurements reconfirmed that the magnitude of the residual stress is almost independent of the yield stress of the base metal.

• Journal of the Korean Society for Railway
• /
• v.13 no.2
• /
• pp.201-207
• /
• 2010

The replacement criterion of rail by accumulated passing tonnage was estimated by the bending fatigue life of rail. In order to estimate the bending fatigue life, it is basically needed to analyze bending fatigue behavior on the rail. In this study, the bending fatigue test were performed for 50kg/m and 60kg/m rails, and test specimens were distinguished by new and used rails and by the types of welded rail such as base material, thermite weld, and gas pressure weld. Also, this study analyzed the fractured surface, the position of initial crack and the bending fatigue behavior (S-N curve). Therefore, it evaluated S-N curve for welded rails according to the fracture probability. The result from this study might be used essential data in order to estimate the bending fatigue life of rail by the accumulated passing tonnage.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.3
• /
• pp.233-242
• /
• 2013

This paper reports a new beam-to-column connection that is suitable for use in the weak axis of a column. The proposed system mainly uses bolts, and it minimizes the use of welding, which is generally difficult to perform onsite. In this system, a H-shape steel beam is joined to a H-shape steel column by bolted splices at the top flange and without a scallop at the web. The structural performance of the proposed connection was verified through full-scale tests of nine specimens, taking into account the effects of the geometry and arrangement of the plate.