• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.179-183
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• 2005

The High-tensile steel has been recognized as a promising concept for structural design of light weight transportation systems such as aircraft high speed trains and fast ships. Using the high-tensile steel has been widely used in ship structures, and this enables to reduce the plate thickness. Using the high-tensile steel effectively for a ship hull, the plate thickness becomes thin so that plate buckling may take place. Therefore, precise assessment of the behavior of plate above primary buckling load is important. In this study, examined closely secondary buckling behavior after initial buckling of thin plate structure which operated compressive load according to the various kinds of yield stress with simply supported boundary condition. Analysis method is F.E.M by commercial program(ANSYS V7.1) and complicated nonlinear behaviour can analyze using art-length method about secondary buckling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1900-1907
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• 2012

Since the subpanels of polygonal-section shell have the corners of an obtuse angle larger than 90 degree unlike general plate or box-section structures, this could have an influence on forming nodal lines against local plate buckling or stress distributions. However, there is not sufficient material in the relevant study results or design recommendations. The very feasible models of the initial imperfections were acquired through the literature studies and then the parametric studies were conducted along with the initial imperfection models by using the finite element method. The parameters like the size of residual stresses, the portion of compressive residual stresses, and steel grades were considered. From the parametric studies, it was found that the maximum residual stress is more influential factor than the distribution pattern of residual stresses. In addition, The design strength equations for the simply supported plates can be applicable to the determination of the local buckling strength of the polygonal cross-section shell structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.594-600
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• 2021

Curved beam structures are generally used as components in structures such as railroad bridges and vehicles. The stability analysis of curved beams has been studied by a large number of researchers. Due to the complexities of structural components, it is difficult to obtain an analytical solution for any boundary conditions. In order to overcome these difficulties, the differential quadrature method (DQM) has been applied for a large number of cases. In this study, DQM was used to solve the complicated partial differential equations for buckling analysis of curved beams. The governing differential equation was deduced and solved for beams subjected to uniformly distributed radial loads. Critical loads were calculated with various opening angles, boundary conditions, and parameters. The results of the DQM were compared with exact solutions for available cases, and the DQM gave outstanding accuracy even when only a small number of grid points was used. Critical loads were also calculated for the in-plane inextensional buckling of the asymmetric curved beams, and two theories were compared. The study of a beam with extensibility of the arch axis shows that the effects on the critical loads are significant.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.769-777
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• 2003

The strengthening of concrete structures in situ with externally bonded carbon fiber is increasingly being used for repair and rehabilitation of existing structures. Because carbon fiber is attractive for this application due to its good tensile strength, resistances to corrosion, and low weight. Generally bond strength and behavior between concrete and carbon fiber mesh(CFM) is very important, because of enhancing bond of CFM. Therefore if bond strength is sufficient, it will be expect to enhance reinforcement effect. Unless sufficient, expect not to enhance reinforcement effect, because of occuring bond failure between concrete and CFM. In this study, the bond strength and load-displacement response of CFM to the concrete by the direct pull-out test(the tensile-shear test method) were investigated using the experiment and the finite element method analysis with ABAQUS. The key variables of the experiment are the location of clip, number of clips and thickness of cover mortar. The general results indicate that the clip anchorage technique for increasing bond strength with CFM appear to be effective to maintain the good post-failure behavior.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.490-496
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• 2012

The main object of this research is to minimize the shock effects which frequently result in fatal damage in offshore wind turbine on impact of barge. The collision between offshore wind turbine and barge is generally a complex problem and it is often impractical to perform rigorous finite element analyses to include all effects and sequences during the collision. On applying the impact force of a barge to the offshore wind turbine, the maximum acceleration, internal energy, and plastic strain are calculated for each load case using the finite element method. A parametric study is conducted with the experimental data in terms of the velocity of barge, thickness of the offshore wind turbine, and thickness and Mooney-Rivlin coefficient of the rubber fender. Through the analysis proposed in this study, it is possible to determine the proper size and material properties of the rubber fender and the optimal moving conditions of barge.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.1-9
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• 2013

This paper presents high-velocity impact analysis of two-way RC slabs, including steel fibers and strengthening with fiber reinforced polymer (FRP) sheets for evaluating impact resistance. The analysis uses the LS-DYNA program, which is advanced in impact analysis. The present analysis was performed similarly to the high-velocity impact tests conducted by VTT, the technical research center of Finland, to verify the analysis results. High-velocity impact loads were applied to $2100{\times}2100{\times}250$ mm size two-way RC slab specimens, using a non-deformable steel projectile of 47.5kg mass and 134.9m/s velocity. In this research, extra impact analysis of material specimens was carried out to verify the material models used to the analysis. The elastic-plastic hydrodynamic model, concrete damage model and orthotropic elastic model were used to simulate the non-linear softening behavior of steel fiber reinforced concrete (SFRC), and material properties of normal concrete and FRP sheets, respectively. It is concluded that the suggested analysis technique has good reliability, and can be effectively applied in evaluating the effectiveness of reinforcing/retrofitting materials and techniques. Also, the Steel fiber and FRP sheet strengthening systems provided outstanding performance under high-velocity impact loads.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.1-12
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• 2012

In this paper, the reduction factors to calculate the site coefficients of an embedded foundation are estimated, considering the effect of a poor backfill for the seismic design of a building built on an embedded foundation. This is determined by utilizing in-house finite element software, P3DASS, which has the capability of horizontal pseudo 3D seismic analysis with nonlinear soil. The 30m thick soil on stiff rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were assumed to be embedded 0, 10, 20, and 30 m in the soil. Seismic analyses were performed with 7 bedrock earthquake records de-convoluted from the outcrop records; the scaling of the peak ground accelerations were to 0.1 g. The study results show that the site coefficients of a poor-backfilled foundation are gradually reduced as the foundation embedment ratio increases, except in the case of a small foundation embedded deeply in the weak soft soil. In addition, it was found that the deviation of the site coefficients due to the foundation size was not significant. Therefore, the typical reduction factors of an embedded foundation with poor backfill are proposed in terms of the shear wave velocity and site class. This is in order to find the site coefficients of an embedded foundation by multiplying the reduction factor by a site coefficient of a surface foundation specified in the design code. They can then be interpolated to determine the intermediate shear wave velocity.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.91-96
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• 2007

To improve the land use of urban, Construction of the circular steel column is required recently. The circular steel columns have a advantage for improving a load carrying capacity as wall as reducing a effective section area. However, the circular steel columns under service load, such as earthquake, shows a tendency to cause local buckling and large deformation. To prevent these phenomena, use of diaphragm is considered. It is reported that longitudinal stiffeners has a effect on improving a buckling and fatigue performance of steel structures. The research of effect on diaphragm is not sufficient. Under monotonic and cyclic loadings diaphragm make a important role to prevent local buckling and deformation of used steel structures. Therefore, influence of diaphragm on performance of used steel structures is investigated. In this study, the influence of diaphragm on seismic and deformation performance of circular steel piers was investigated by using elastic-plastic finite element analysis considered geometrical and material non-linearity. The seismic performance of circular steel columns was evaluated for analytical parameter of manufactured part. The seismic performance of circular steel columns was clarified by comparing an energy dissipation of circular steel piers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.85-92
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• 2015

It is well known that axial tension decreases the shear strength of RC & PSC beams without transverse reinforcement, and axial compression increases the shear resistance. What is perhaps not very well understood is how much the shear resistance capacity is influenced by axial load. RC beams without shear reinforcement subjected to large axial compression and shear may fail in a very brittle manner at the instance of first diagonal cracking. As a result, a conservative approach should be used for such members. According to the ACI Code, the shear strength in web is calculated by effect of axial force and the vertical force in the stirrups calculated by $45^{\circ}$ truss model. This study was performed to examine the effect of axial force in reinforced concrete beams by nonlinear FEM program (ATENA-2D).

• Composites Research
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• v.26 no.4
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• pp.207-212
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• 2013

In this study, the thickness optimization for uni-directional (UD) glass fiber reinforced polymer (GFRP) laminates of the spar cap of composite tidal blades was performed under the tip deflection constrains. The spar cap was composed of GFRP composites and carbon fiber reinforced polymer (CFRP) composites. The stress distributions in the blade as well as its material costs for the optimized results were additionally investigated. The optimized thickness was obtained by interacting a sequential quadratic programming (SQP) algorithm and an ABAQUS software to calculate an objective function. It was confirmed that the thickness of UD GFRP increased with a decrease of the restrained tip deflection when a thickness of UD CFRP laminates was constrained to 9 mm. The weight of the optimized spar-cap increased up to 96.2% while the maximum longitudinal tensile stress decreased up to 24.6%. The thickness of UD GFRP laminates increased with a decrease of the thickness of UD CFRP laminates when the tip deflection was constrained to 126.83 mm. The weight increased up to 40.1%, but the material cost decreased up to 16.97%. Finally, the relationships among the weight, internal tensile stress, and material costs were presented based on the optimized thicknesses of the spar cap.