• Journal of Korean Society of Steel Construction
• /
• v.18 no.5
• /
• pp.525-534
• /
• 2006

Column-to-beam pinned connections can cause local moment to the web of a steel tube due to the distance of eccentricity between the row of bolts and the column flange, which possibility deteriorates the load capacity of column. In this study, a square hollow section tubular used finite element analysis of a square hollow section tubular column was carried out, and the column width and thickness, existence and non-existence of internal reinforcement, and existence and non-existence of compressive force were taken as variables to examine the load capacity deterioration of a square column caused by moment. To guarantee the reliability of the finite element results, some specimens were fabricated and tested. The yield line method was applied to suggest the strength formulas of the square tubular column to the beam pinned connections. Based on the study results, the column strength the moment of the square hollow section tubular column to the beam pined connections improved with the increase in the w to strength limitations, a no-reinforcement type of square hollow section tubular column was proposed, and if the limitation values were not satisfied, the reinforcement of the internal column was made mandatory. Therefore, the horizontal -reinforcement type considered the strength increase, and the fabrication of the square hollow section tubular column was ar column that considered its load capacity with the moment for the no-reinforcement and the horizontal-reinforcement types.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.18 no.1
• /
• pp.62-68
• /
• 2014

Purpose: After I-131 therapy, SPECT/CT is useful in identifying location of thyroid remnants and metastasis of thyroid cancers. An excessive uptake of thyroid leads to a ringing artifact in the SPECT images. The aim of this study is to investigate and suggest a proper post filters to remove ringing artifact and produce better image quality. Materials and Methods: A low-cost, customized thyroid-mimicking phantom, consisting of an acrylic bottle and a hollow sphere was used for SPECT/CT Discovery (GE Healthcare, USA). It was filled with I-131 solution. The ratio of hollow sphere to background were varied as 50:1, 200:1, 1000:1 and 4000:1. Acquired images were reconstructed by OSEM (2 iterations, 10 subsets) with and without Evolution (resolution recovery correction, GE). Three different post-filters were applied; Butterworth (cut off: 0.38 to 0.58 with intervals of 0.05), Hanning (cut off: 0.8 to 1 with intervals of 0.05) and Gaussian (FWHM: 3 to 5 with intervals of 0.5) filters. Contrast, background variability, air area variability, and full width half maximum (FWHM) were compared. Results: Higher contrasts were obtained from the SPECT images with Evolution than without Evolution. In the case of images without Evolution, image distortion such as star artifact was generated. For all sphere-to-background ratio, the Butterworth filter showed better constrasts and FWHMs than other two filters, but the ringing artifact was still generated in all studies except 50:1 and it was decreased as cutoff value was increased. The ringing artifact didn't appear with Hanning and Gaussian filters at all studies, however constrats and FWHMs with Gaussian was worse than Hanning filter. For the images having ringing artifacts, the background variability and air area variability were increased. Conclusion: In this study, we suggested that it is desirable to use Hanning filter when the ringing artifact is generated and to use Butterworth filter when ringing artifact is not generated in I-131 SPECT.

• Membrane Journal
• /
• v.21 no.2
• /
• pp.177-192
• /
• 2011

Hollow fiber membrane using CTA polymers were prepared by the phase separation method for the separation and purification of biogas and the hollow fiber gas separation membrane modules with the effective surface area of 0.17 $m^2$ were prepared. The pure gas permeation properties of membrane modules for methane, oxygen and carbon dioxide were measured. The permeance of $CO_2$ and $CH_4$were 0.46 GPU and 18.52 GPU, respectively, therefore, the high $CO_2$/$CH_4$ selectivity of 40.4 was obtained. The separation and purification test for 4 different simulated mixed gases were carried out after the pure gas test and the gas concentration and flux of the permeate at the various stage-cut were measured from the 1 stage, 2 stage, and 3 stage cascade of membrane modules. In the 1 stage test, the concentration of $CH_4$ increased as the increase of the stage-cut, while the $CH_4$ recovery efficiency ratio decreased. In the 2 stage test, the $CH_4$ recovery efficiency ratio increased compared to the 1 stage. The 3 stage test was employed to reduce the loss of $CH_4$ in biogas and the result showed less than 5% of $CH_4$ recovery loss.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.2
• /
• pp.311-318
• /
• 2002

This paper described the ultimate strength and deformation limit of welded T-joints in cold-formed square hollow sections. Previous studies showed that the strength of a T-joint still increases with increasing deformations at a ratio of branch width to chord width (${\beta}$) of below 0.8. Therefore, the strength at a certain deformation (chord flange indentation) limit can be regarded as the ultimate strength of a T-joint. The chord flange failure modes were investigated for the ratio of branch width to chord width (${\beta}$) and the ratio of chord width to chord web thickness (B/T). Experimental results including tests done by Kato proposed a deformation limit of 3%B for $16.7{\leq}B/T{\leq}41.6$ and $0.27{\leq}{\beta}{\leq}0.8$. The strength formula of CIDECT and other researchers were compared with the test results. Finally, the strength formula based on yield-line theory was proposed.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.141-159
• /
• 2016

Commonly in steel frames, steel beam and concrete slab are connected together by shear keys to work as a unit member which is called composite beam. When a composite beam is subjected to positive bending, flexural strength and stiffness of the beam can be increased due to "composite action". At the same time despite these advantages, composite action increases the strain at the beam bottom flange and it might affect beam plastic rotation capacity. This paper presents results of study on the rotation capacity of composite beam connected to Rectangular Hollow Section (RHS) column in the steel moment resisting frame buildings. Due to out-of-plane deformation of column flange, moment transfer efficiency of web connection is reduced and this results in reduction of beam plastic rotation capacity. In order to investigate the effects of width-to-thickness ratio (B/t) of RHS column on the rotation capacity of composite beam, cyclic loading tests were conducted on three full scale beam-to-column subassemblies. Detailed study on the different steel beam damages and concrete slab damages are presented. Experimental data showed the importance of this parameter of RHS column on the seismic behavior of composite beams. It is found that occurrence of severe concrete bearing crush at the face of RHS column of specimen with smaller width-to-thickness ratio resulted in considerable reduction on the rate of strain increase in the bottom flange. This behavior resulted in considerable improvement of rotation capacity of this specimen compared with composite and even bare steel beam connected to the RHS column with larger width-to-thickness ratio.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.2
• /
• pp.41-54
• /
• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to eqrthquake motions. The objective of this experimental research is to investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. Particularly for this test, constant 10 cyclic loads have been repeatedly actuated to investigate the magnitude of strength degradation for the displacement ductility factor. Important test parameters are seismic design, confinement steel ratio, axial force and load pattern. It is observed from quasi-static tests for 7 bridge piers that the seismically designed columns and the retrofitted columns show better performance than the nonseismically designed colums, i.e. about 20% higher for energy dissipation capacity and about 70% higher for curvatures.

• Economic and Environmental Geology
• /
• v.42 no.5
• /
• pp.501-507
• /
• 2009

Ordered single-walled hollow aluminogermanate (ALGE) nano-balls(NBs) and nano-tubes(NTs) have been self-assembled from the ALGE precursors having an Al/Ge ratio of 1.33 using simple pH-control. The hollow ALGE NBs with average monodisperse diameters of 5 nm and chemistry of Al/Ge=1.5~1.6 were formed through structural assembly in the ALGE solution (Al/Ge=1.33) highly basified to pH=13(Na/Al=28~30) and followed by immediate acidification to pH=9. When the basified solution(pH=13) were acidified to pH=4, ALGE S-NTs (Short-fiber nano-tubes) with diameters of 3.3 nm, 15~20 nm in length, and chemistry of Al/Ge=2.6~2.8 were successfully synthesized. Whereas the solution was basified to pH=9, and subsequently acidified to pH=4, L-NTs(Long-fiber nano-tubes) with >100 nm in length were synthesized for the first time. The self-assembly of the hollow NBs, S-NTs, and L-NTs form the ALGE precursors can be explained by the degree of $H^+$-dissociation of the -Ge-OH inner surfaces, which was controlled by amount of $Na^+$ and pH conditions of ALGE precursor solutions. This results indicate that target forms of ALGE nanomaterials can be synthesized by simple pH controls.

• Steel and Composite Structures
• /
• v.17 no.4
• /
• pp.517-533
• /
• 2014

Experimental results of 39 specimens including concrete columns, RC columns, hollow steel tube columns, concrete filled steel tubular (CFT) columns, and reinforced concrete filled steel tubular (RCFT) columns are presented. Based on the experimental results, the load-carrying capacity, confined effect, ductility, and failure mode of test columns are investigated. The effects of the main factors such as width-thickness ratio (the ratio of external diameter and wall thickness for steel tubes), concrete strength, steel tube with or without rib, and arrangement of reinforcing bars on the mechanical characteristics of columns are discussed as well. The differences between CFT and RCFT are compared. As a result, it is thought that strength, rigidity and ductility of RCFT are improved; especially strength and ductility are improved after the peak of load-displacement curve.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.3
• /
• pp.205-215
• /
• 2017

This study presents an example of conceptual design for hollow circular section multi-column tower system subjected to 10MW level wind load by introducing a method based on member utilization that examine both structural stability and economical efficiency. The basic assumptions for the proto type of a multi-column tower that can replace a single-cylinder tower were suggested and structural models were constructed following the assumptions and analyzed for identifying member forces. Based on the calculated member strengths and acting loads, the member utilization of the proposed multi-column tower structures were calculated for axial force, shear, bending and torsion and evaluaed for suitability as a wind tower. Design parameters such as steel tube dimensions, slenderness ratio, and number of floors for braces was proposed in the acceptable range of member utilization for conceptual design of multi-column wind towers.

• Membrane Journal
• /
• v.7 no.1
• /
• pp.39-47
• /
• 1997

The self-designed membrane system was tested to examine the performance of the hollow fiber type polysulfone ultrafiltration(UF) membrane for the treatment of pure water(the 3rd treated water). The molecular weight cut-off's (MWCO) of the membranes used in this study were 5, 000 and 10, 000, respectively. The recovery rate, the ratio of permeate flow rate to the feed flow rate, increased as the temperature rose. The values of MWCO obtained in this study, using 2, 000 ppm polyethylene glycol and dextran solutions with various molecular weight, showed higher values than those suggested by SKI. Based on the results of the primary experiments, the water of the Gongji-stream, in which water quality is deteriorated by the inflow of domestic wastewater, was selected for the UF membrane test. Biological oxygen demand(BOD), total solids, and turbidity of the treated water had much lower values than those of the source water. Therefore, this study confirmed the possibility of the domestic water treatment using the hollow fiber type UF membrane.