• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.3
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• pp.195-202
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• 2005

This paper presents moment-curvature analytical method of concrete filled steel tubular members considering intensity increase phenomenon by triaxial compression stress generation. For this purpose, this study considers buckling characteristics about compression department of steel members that filled up light weight and normal concrete. The analytical results are compared with the test results. Even if beam that filled up light weight concrete was calculated moment-curvature relationship easily analytically and could know that analytical results estimates as well agreed with the test results in case filled up normal concrete. In addition, the efficiency and applicabilities of the proposed moment curvature relationship algorithm are verified through conventional experimental results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.354-359
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• 2014

The objective of this study is to examine the fatigue behavior in compression of normal-weight and lightweight concrete mixtures with high volume supplementary cementitious material(SCM). The selected binder composition was 30% ordinary portland cement, 20% fly-ash, and 50% ground granulated blast-furnace slag. The targeted compressive strength of concrete was 40 MPa. For the cyclic loading, the constant maximum stress level varied to be 75%, 80%, and 90% of the static uniaxial compressive strength, whereas the constant minimum stress level was fixed at 10% of the static strength. The test results showed that fatigue life of high volume SCM lightweight concrete was lower than the companion normalweight concrete. The value of the fatigue strain at the maximum stress level intersected the descending branch of the monotonic stress-strain curve after approximately 90% of the fatigue life.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.339-345
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• 2012

Objective : The purpose of this study was to investigate the patterns and the risk factors of newly developed vertebral compression fractures (VCFs) after percutaneous vertebroplasty (PVP). Methods : We performed a retrospective review of the 244 patients treated with PVP from September 2006 to February 2011. Among these patients, we selected 49 patients with newly developed VCFs following PVP as the new VCFs group, and the remaining 195 patients as the no VCFs group. The new VCFs group was further divided into 2 groups : an adjacent fractures group and a nonadjacent fractures group. The following data were collected from the groups : age, gender, body weight/height, body mass index (BMI), bone mineral density (BMD) score of the spine and femur, level of initial fracture, restoration rate of anterior/middle vertebral height, and intradiscal cement leakage, volume of polymethylmethacrylate (PMMA). Results : Age, gender, mean body height/weight, mean BMI and volume of PMMA of each of the group are not statistically significantly associated with fractures. In comparison between the new VCFs group and the no VCFs group, lower BMD, intradiscal cement leakage and anterior vertebral height restoration were the significant predictive factors of the fracture. In addition, new VCFs occurrence at the adjacent spines was statistically significant, when the initial fracture levels were confined to the thoracolumbar junction, among the subgroups of new VCFs. Conclusion : Lower spinal BMD, the greater anterior vertebral height restoration rate and intradiscal cement leakage were confirmed as risk factors for newly formed VCFs after PVP.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.748-756
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• 2015

In this paper, we developed a miniaturized real time video compression system satisfying the military environment using ADV212 and FPGA. We present an efficient hardware design scheme for the weight reduction of the device and also a software solution to deal with noisy image signals. Experimental results show that the frame delay is reduced by a factor of 2 or 3 and the device's weight is decreased by a factor of 6 to 7. In order to prove the reliability for the military usage of this development, we examine the environmental test (MIL-STD-810G) and EMI test (MIL-STD-461F). Experimental results show that the developed system satisfies the requirements.

• Journal of the Korean Society of Clothing and Textiles
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• v.42 no.4
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• pp.612-625
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• 2018

This study designed 16 kinds of basic structure and 4 kinds of modified structure for impact protection pads with a spacer fabric shape. The pad is a structure in which hexagonal three-dimensional units, composed of a surface layer and a spacer layer, are interconnected. Designed pads were printed with flexible $NinjaFlex^{(R)}$ materials using a FDM 3D printer. The printed pads were evaluated for impact protection performance, compression properties and sensory properties. The evaluation of the impact protection performance indicated that basic structures better than CR foam material at 20cm height were DV1.5, DX1.5, DX1.0, DV1.0 and HV1.5. The evaluation of the compression properties for the five types, with good results in the impact protection performance, indicated that DV1.0, DX1.0, DV1.5, HV1.5 and DX1.5 showed good results, respectively. The sensory evaluation of DV1.0, DX1.0, and DV1.5, which with good results when considering both the impact protection performance and the compression performance, showed that DV1.0 were the best for surface, flexibility, compression and weight. Therefore, DV1.0 is shown to be the best structure for protection pads.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.631-642
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• 2010

This study is experimentally investigated for the characteristics of compression and tensile of lightweight air-trapped soils with uniform quality. Previously, EPS blocks are often used as lightweight embankment, but many problems such as the level difference and cracks caused by plastic(creep) deformation occurred in the EPS blocks. So, a new material development is urgent. By means of alternatives, lightweight air-mixed soil using in-situ soils has been developed and applied to fields. In comparison with EPS block, lightweight air-mixed soil have less creep deformation in long-time, but the strength characteristics of them are different depending on soils where they are obtained. Therefore, the quality management of them is very difficult. In this study, therefore, characteristics of lightweight air-trapped soil samples are investigated. To do this, the lightweight air-trapped soils are prepared using a manufactured sand with uniform quality. To found out the compression and tensile characteristics of lightweight air-tapped soils, unconfined compression test and splitting tensile test are conducted on the specimens prepared with different unit weight, cement-sand ratio and air-pore.

• Steel and Composite Structures
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• v.26 no.6
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• pp.719-731
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• 2018

Concrete filled steel tubular (CFST) laced columns have been widely used in high rise buildings in China. Compared to solid-web columns, this type of columns has a larger cross-section with less weight. In this paper, four concrete filled steel tubular laced columns consisting of 4 main steel-concrete tubes were tested under cyclic loading. Hysteresis and failure mechanisms were studied based on the results from the lateral cyclic loading tests. The influence of each design parameter on restoring forces was investigated, including axial compression ratio, slenderness ratio, and the size of lacing tubes. The test results show that all specimens fail in compression-bending-shear and/or compression-bending mode. Overall, the hysteresis curves appear in a full bow shape, indicating that the laced columns have a good seismic performance. The bearing capacity of the columns decreases with the increasing slenderness ratio, while increases with an increasing axial compression ratio. For the columns with a smaller axial compression ratio (< 0.3), their ductility is increased. Furthermore, with the increasing slenderness ratio, the yield displacement increases, the bending failure characteristic is more obvious, and the hysteretic loops become stouter. The results obtained from the numerical analyses were compared with the experimental results. It was found that the numerical analysis results agree well with the experimental results.

• Journal of Ocean Engineering and Technology
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• v.25 no.3
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• pp.34-39
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• 2011

This study investigated the shear and CBR characteristics of dredge soil-bottom ash-waste tire powder-mixed lightweight soil, which was developed to recycle dredged soil, bottom ash, and waste tire powder. Test specimens were prepared with various contents of waste tire powder ranging from 0 to 100% at 50% intervals by the weight of the dry dredged soil. Several series of triaxial compression tests and CBR tests were conducted. The shear strength characteristics of the lightweight soil were compared using two different shear tests (triaxial compression test and direct shear test). The experimental results indicated that the internal friction angle of the lightweight soil obtained by the direct shear tests was greater than that by the triaxial shear tests. However, the cohesion value obtained by the triaxial shear tests was greater than that by the direct shear tests. The CBR value of the lightweight soil decreased from 35% to 15% as waste tire powder content increased.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.3
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• pp.83-91
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• 2011

This study aimed to investigate the engineering and environmental characteristics of phosphogypsum-cement-soil mixtures composed of phosphogypsum, soil, and a small amount of cement was analysed on the basis of the unconfined compression test, the tensile strength test, the freezing and thawing test, the wetting and drying test, SEM and EDS analysis, XRD analysis and Leaching test. The specimens were manufactured with soil, cement and phosphogypsum. The cement contents was 10 %, and the phosphogypsum contents was 10, 20, 30, and 40 % by the weight of total dry soil. Each specimen was manufactured after curing at constant temperature and humidity room for 3, 7 and 28 days, after which the engineering characteristics of phosphogypsum-cement-soil mixtures were investigated using the unconfined compression test, the tensile strength test, the freezing and thawing test, the wetting and drying test. The basic data were presented for the application of phosphogypsum-cement-soil mixtures as construction materials. To investigate the environmental characteristics, leaching test was performed and the leaching test results were far below than of regulatory requirement of Waste Management Act in Korea. Therefore the results show that phosphogypsum is environmentally safe and can be used as construction materials in environmental aspect.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.411-415
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• 2010

A sandwich panel which is comprised of truss cores faced with solid face sheets is lightweight and multi-functional. So it is widely used to not only structural material but also heat transfer media in transportation field such as airplane, train and vessel. There are various core topologies such as pyramidal and tetrahedral truss, square honeycombs and kagome truss. The study focused on analytical approach to optimize compression and shear quality of the unit cell of PCM with pyramidal configuration. With various unit cell models which have the same core weight per unit area but different truss member angle, analytical solution for effective stress ($\bar{\sigma},\bar{\tau}$), peak stress ($\bar{\sigma}_{peak},\bar{\tau}_{peak}$) by yielding and buckling, relative density ($\bar{\rho}_c$) and effective stiffness ($\bar{E},\bar{G}$) have been computed and compared each other. With this approach, the most optimal core configuration was predicted. The result has become the efficient guidelines for the design of PCM core structure.