• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1415-1426
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• 2008

Stone columns, locally called "GCP (granular compaction pile)" can be used to improve strength and resistance against lateral movement of a foundation soil like rigid piles and piers. Also installation of such a discrete column facilitates drainage, and densifies and reinforces the soil in the sense of ground improvement. The integrity of the GCP has been indirectly controlled with the records of each batch including depth and the quantity of stone filled. An integrity testing was attempted using crosshole S-wave logging. The method is conceptionally same as the crosshole sonic logging (CSL) for drilled piers. The only and critical difference is that S-wave should be used in the logging, because P-wave velocity of the stone column is less than that of ground water. The crosshole sonic logger does not have the capability to measure S-wave propagating through the skeleton of crushed stone. An electro-mechanical source, which can generate either P- or SH-waves, and a 1-D geophone were used to measure SH-waves. Two 76mm diameter cased boreholes were installed 1 meter apart across the nominal 700mm diameter stone column. At every 10cm of depth, shear wave was measured across the stone column. One more borehole was also installed 1 meter outward from the one of the above boreholes to measure the shear wave profile of the surrounding soil. The diametric variation of the stone column with respect to depth was evaluated from the shear wave arrival times across the stone column, and shear wave velocities of crushed stone and surrounding soil. The volume calculated with these variational diameters is very close to the actual quantity of the stone filled.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.409-412
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• 2004

Over last decade extensive researches have been undertaken on the strength behaviour of Fiber Reinforced Concrete(FRC) structures. But the use of Ultra-High Strength Steel Fiber Cementitious Concrete Composites is in its infancy and there is a few experiments, analysis method and design criteria on the structural elements constructed with this new generation material which compressive strength is over 150 MPa and characteristic behaviour on the failure status is ductile. The objective of this paper is to investigate and analyze the behaviour of reinforced rectangular structural members constructed with ultra high performance cementitious composites (UHPCC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The variables of test specimens were shear span ratio, reinforcement ratio and fiber quantity. Even if there were no shear stirrups in test specimens, most influential variable to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone could be defined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1186-1191
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• 2007

The study uses the crossed wide girder(waffle slab type) in apartment structural system comparing with existing shear wall system. The crossed wide girder will be able to secure the span of the longest which is possible with minimum slab thickness by not increasing the height. The research sees continuity arranges the crossed wide girder in schedule interval following the stress distribution. Namely, it is to make the interior space with the space without column and wall in the minimum height. In order to check the numerical value of this study which it interpreted the ductile frame system due to the crossed wide girder and existing shear wall system used the Midas Gen is a program which 3-dimension laterial force designs are possible. Analysis results, the crossed wide girder system is not disadvantageously laterial drift, drift ratio and deflection of slab compares with existing shear wall system. Also the whole concrete amount is similar existing shear wall system. The crossed wide girder is advantage which secure a architectal variability.

• Polymer(Korea)
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• v.35 no.4
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• pp.356-362
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• 2011

The branched polycarbonates (B-PCs) with two different branching agents were synthesized from melt polymerization. The contents of branching agent were in the range of 0.001~0.005 mol%. The chemical structure of the synthesized PC was determined by FTIR, $^1H$ NMR, and $^{13}C$ NMR, spectroscopy. The molecular weight, glass transition and degradation temperatures were determined by GPC, DSC, and TGA. The molecular weight of the phloro type B-PC had a lower value than the other one, and the glass transition temperature increased with molecular weight. Compared with linear PC, the rheological properties of the B-PC indicated an increase of complex viscosity in the low frequency region and shear thinning tendency. Power law index(n) representing shear thinning was calculated by linear regression and the values were in the range of 0.483~0.996. The rheological properties of the B-PCs were measured by a dynamic rheometer.

• Smart Structures and Systems
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• v.22 no.6
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• pp.689-697
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• 2018

This paper presents a model of the elastic curve for rectangular beams with straight haunches under uniformly distributed load and moments in the ends considering the bending and shear deformations (Timoshenko Theory) to obtain the deflections and rotations on the beam, which is the main part of this research. The traditional model of the elastic curve for rectangular beams under uniformly distributed load considers only the bending deformations (Euler-Bernoulli Theory). Also, a comparison is made between the proposed and traditional model of simply supported beams with respect to the rotations in two supports and the maximum deflection of the beam. Also, another comparison is made for beams fixed at both ends with respect to the moments and reactions in the support A, and the maximum deflection of the beam. Results show that the proposed model is greater for simply supported beams in the maximum deflection and the traditional model is greater for beams fixed at both ends in the maximum deflection. Then, the proposed model is more appropriate and safe with respect the traditional model for structural analysis, because the shear forces and bending moments are present in any type of structure and the bending and shear deformations appear.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.37-47
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• 2019

The study purposed to investigate the optimal location of core and offset outrigger system considering floor diaphragm. To accomplish this aim, a structure design of 70 stories building was performed by using MIDAS-Gen. And the leading factors of the analysis research were the slab stiffness, the stiffness of shear wall and the outrigger position in plan. Based on the analysis results, we analyzed and studied the influences of the shear wall stiffness and the slab stiffness on optimal location of core and offset outrigger considering floor diaphragm. The results of the analysis study indicated whether the slab stiffness, the stiffness of shear wall and the outrigger position in plan had an any impact on optimal location in outrigger system of tall building. Also the paper results can give help in getting the structural engineering materials for looking for the optimal position of outrigger system in the high-rise building.

• Advances in materials Research
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• v.12 no.3
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• pp.243-261
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• 2023

This study aims to analyze the mechanical buckling behavior of a single-walled carbon nanotube (SWCNT) integrated with a one-parameter elastic medium and modeled as a Kerr-type foundation under a longitudinal magnetic field. The structure is considered homogeneous and therefore modeled utilizing the nonlocal first shear deformation theory (NL-FSDT). This model targets thin and thick structures and considers the effect of the transverse shear deformation and small-scale effect. The Kerr model describes the elastic matrix, which takes into account the transverse shear strain and normal pressure. Using the nonlocal elastic theory and taking into account the Lorentz magnetic force acquired from Maxwell relations, the stability equation for buckling analysis of a simply supported SWCNT under a longitudinal magnetic field is obtained. Moreover, the mechanical buckling load behavior with respect to the impacts of the magnetic field and the elastic medium parameters considering the nonlocal parameter, the rotary inertia, and transverse shear deformation was examined and discussed. This study showed useful results that can be used for the design of nano-transistors that use the buckling properties of single-wall carbon nanotubes(CNTs) due to the creation of the magnetic field effect.

• Steel and Composite Structures
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• v.44 no.5
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• pp.721-740
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• 2022

In this paper, an accurate kinematic model has been developed to study the mechanical response of functionally graded (FG) sandwich beams, mainly covering the bending, buckling and free vibration problems. The studied structure with homogeneous hardcore and softcore is considered to be simply supported in the edges. The present model uses a new refined shear deformation beam theory (RSDBT) in which the displacement field is improved over the other existing high-order shear deformation beam theories (HSDBTs). The present model provides good accuracy and considers a nonlinear transverse shear deformation shape function, since it is constructed with only two unknown variables as the Euler-Bernoulli beam theory but complies with the shear stress-free boundary conditions on the upper and lower surfaces of the beam without employing shear correction factors. The sandwich beams are composed of two FG skins and a homogeneous core wherein the material properties of the skins are assumed to vary gradually and continuously in the thickness direction according to the power-law distribution of volume fraction of the constituents. The governing equations are drawn by implementing Hamilton's principle and solved by means of the Navier's technique. Numerical computations in the non-dimensional terms of transverse displacement, stresses, critical buckling load and natural frequencies obtained by using the proposed model are compared with those predicted by other beam theories to confirm the performance of the proposed theory and to verify the accuracy of the kinematic model.

• Earthquakes and Structures
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• v.12 no.3
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• pp.263-270
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• 2017

In this study, two geometrically identical multi-storey steel buildings with different lateral load resisting systems are structurally analyzed under same earthquake conditions and they are compared with respect to their construction costs of their structural systems. One of the systems is a steel structure with eccentrically steel braced frames. The other one is a RC wall-steel frame system, that is a steel framed structure in combination with a reinforced concrete core and shear walls of minimum thickness that the national code allows. As earthquake resisting systems, steel braced frames and reinforced concrete shear walls, for both cases are located on identical places in either building. Floors of both buildings will be of reinforced concrete slabs of same thickness resting on composite beams. The façades are assumed to be covered identically with light-weight aluminum cladding with insulation. Purpose of use for both buildings is an office building of eight stories. When two systems are structurally analyzed by FEM (finite element method) and dimensionally compared, the dual one comes up with almost 34% less cost of construction with respect to their structural systems. This in turn means that, by using a dual system in earthquake zones such as Turkey, for multi-storey steel buildings with RC floors, more economical solutions can be achieved. In addition, slender steel columns and beams will add to that and consequently more space in rooms is achieved.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.1-4
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• 2014

The present work focuses on the analysis of the pulverized coal combustion aerodynamics of the dual swirl burner by the control of the swirl-modes such as the outer swirl intensity (OSI). The detailed structure of pulverized coal swirling flames with swirl-mode was studied experimentally by particle image velocimetry and local flame colors based on $OH^*$, $CH^*$, and ${C_2}^*$ radicals. For all co-swirling conditions, the internal recirculation zone (IRZ) was observed near the inner shear layer with respect to the processing vortex core structure. Furthermore, a co-rotating vortex in the outer shear layer and the exhaust tube vortex (ETV) along the central axis were observed. The intensity of $CH^*$ signal was higher with small coal particle size, conversely, the size of the distribution of the $CH^*$ signal becomes larger. Therefore, the control of the aerodynamics with changing swirl intensities may play an important role in improving both environmental and combustion performances.