• Journal of Korean Association for Spatial Structures
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• v.24 no.2
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• pp.31-41
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• 2024

This study aims to investigate the seismic response of a large span thin shell structures and assess their displacement under seismic loads. The study employs finite element analysis to model a thin shell structure subjected to seismic excitation. The analysis includes eigenvalue analysis and time history analysis to evaluate the natural frequencies and displacement response of the structure under seismic loads. The findings show that the seismic response of the large span thin shell structure is highly dependent on the frequency content of the seismic excitation. The eigenvalue analysis reveals that the tenth mode of vibration of the structure corresponds to a large-span mode. The time history analysis further demonstrates, with 5% damping, that the displacement response of the structure at the critical node number 4920 increases with increasing seismic intensity, reaching a maximum displacement of 49.87mm at 3.615 seconds. Nevertheless, the maximum displacement is well below the allowable limit of the thin shell. The results of this study provide insight into the behaviour of complex large span thin shell structures as elevated foundations for buildings under seismic excitation, based on the displacement contours on different modes of eigenvalues. The findings suggest that the displacement response of the structure is significant for this new application of thin shell, and it is recommended to enhance the critical displacement area in the next design phase to align with the findings of this study to resist the seismic impact.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.129-138
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• 2004

In this study we determine a dynamic analysis of the existing two-span prestressed concrete box girder bridge subjected to moving vehicle loads using the experimental measurements. The moving loads applied in this paper are classified as general travelling, suddenly brake, continuous travelling, reversely travelling and reversely travelling impact loads for increasing velocities. For each travelling load, we search dynamic behaviors and characteristic in various measuring point of box girder section. In addition, the three-dimensional numerical results analyzed by the developed finite element program using flat shell element with six degrees of freedom per a node are compared with the measured experimental data. Dynamic behaviors caused impact loads by suddenly braking, reversely travelling, are bigger than by general travelling in box girder. Three-dimensional numerical results are better than one-dimensional results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.44-52
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• 2003

Shape memory alloys (SMA) are often used in smart structures as active components. Their ability to provide large recovery forces and displacements has been useful in many applications, including devices for artificial muscles, active structural acoustic control, and shape control. Based on the 3-dimensional SMA constitutive equation in this paper, the radial displacement control of externally pressurized circular and semicircular composite cylinders under external pressure with a thin SMA layer bonded on its inner surface or inserted between composite layers in investigated using 3-dimensional finite element analysis. Upon actuation through resistive heating, SMAs start to transform from martensitic into austenitic state, simultaneously recover the prestrain, and thus cause the composite cylinders to go back to their original shapes of the cylinder cross-sections.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.713-724
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• 2004

A fatigue crack found at the coped stringer of the old dismantled Dangsan Subway Bridge was numerically simulated. A model of a single span of the plate girder bridge with its beam elements was created and analyzed in order to obtain the nominal stress history caused by trains. A detailed FEM analysis of the coped stringer was conducted using a shell element model. A fracture mechanical model was used to estimate crack propagation. The stress intensity factors were calculated using the J-Integral method. The simulation with some reasonable assumptions showed that the calculated crack lengths were comparable to those found on the site.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.149-156
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• 2011

In this paper, a methodology is proposed to improve the stress prediction of plates via Saint Venant's principle. According to Saint Venant's principle, the stress resultants can be used to describe linear elastic problems. Many engineering problems have been analyzed by Euler-Bernoulli beam(E-B) and/or Kirchhoff-Love(K-L) plate models. These models are asymptotically correct, and therefore, their accuracy is mathematically guaranteed for thin plates or slender beams. By post-processing their solutions, one can improve the stresses and displacements via Saint Venant's principle. The improved in-plane and out-of-plane displacements are obtained by adding the perturbed deflection and integrating the transverse shear strains. The perturbed deflection is calculated by applying the equivalence of stress resultants before and after post-processing(or Saint Venant's principle). Accuracy and efficiency of the proposed methodology is verified by comparing the solutions obtained with the elasticity solutions for orthotropic beams.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.357-361
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• 2014

An Ni-Fe/YSZ core-shell structured anode for uniform microstructure and catalytic activity was synthesized. Flat tubular segmented-in-series solid oxide fuel cell-stacks were prepared by decalcomania method using synthesized anode powder. The Ni-Fe/YSZ core-shell anode exhibited better electrical conductivity than a commercially available Ni-YSZ cermet anode. Also power output increased by 1.3 times with a higher open circuit voltage. These results can be attributed to the uniformly distributed Ni particles in the YSZ framework. The impedance spectra of a Ni-Fe/YSZ core-shell anode showed comparable reduced ohmic resistance similar to those of the commercially available Ni-YSZ cermet anodes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.8-9
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• 2018

3D printing has the unique advantage of the ability to customize freeform product even in small quantity. However, we need to select and apply the only necessary parts of it because of the high cost of the manufacturing technology. It is of critical importance in irregular-shaped curtain walls to ensure precision of construction as well as quality fo finish. Complex shape that have structural members at varying angles can have nodes of different shapes making it unfeasible to construct using a general node connection detail. Therefore, this study aims to utilize smart node system using 3D printing as a solution to complex irregular-shaped curtain wall design.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.6-7
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• 2021

3D printing has the unique advantage of the ability to customize freeform products even in small quantities. It was recently applied successfully in the node connection system for the irregular shaped glass design of Gwanggyo Galleria Department Store. This was achieved by applying 3D printing technology for an innovative smart node design. The novel system offers flexibility to address various design challenges in addition to maximizing construction quality and reducing construction period. In this paper, we aim to examine the use of 3D printing based innovative technologies in the construction industry. With this aim in mind, we present the case of the Gwanggyo Galleria Department Store's smart nodes. The key objective of this study is creating awareness in the construction industry of the need to utilize fourth industrial revolution technology in architecture.

• Polymer(Korea)
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• v.29 no.2
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• pp.146-150
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• 2005

A nano-stereolithouaphy (NSL) apparatus has been developed for fabrication of microstructures with the resolution of 150 nanometers. In the NSL process, a complicated 3D structure can be fabricated by building layer by layer, so it does not require any sacrificial layer or any supporting structure. A laminated layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) which was induced by a femtosecond laser. When the fabrication of a 3D laminated structure was finished, unsolidified liquid-stage resins were removed to develop the fabricated structure by dropping several droplets of solvent, then the polymerized structure was only left on the glass substrate. A microstructure is fabricated by vector scanning method to save the fabrication time. The shell thickness of a structure is very thin within 200 nm, when it is fabricated by a single contour scanning (SCS) path. So, a fabricated structure can be deformed easily in the developing process. In this work, a double contour scanning (DCS) method was proposed to reinforce the strength of a shell typed structure, and a microcup was fabricated to show the usefulness of the developed NSL system and the DCS method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.106-113
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• 1997

Dynamic loading of structures often causes excursions of stresses well into the inelastic range, and the influence of the geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. A structure in a nuclear power plant is a structure of importance which puts emphasis on safety. A nuclear container is a pressure vessel subject to internal pressure and this structure is constructed by a reinforced concrete or a pre-stressed concrete. In this study, the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion is numerically solved by a central difference scheme. The constitutive relation of concrete is modeled according to a Drucker-Prager yield criterion in compression. The reinforcing bars are modeled by a smeared layer at the location of reinforcements, and the steel layer model under Von Mises yield criteria is adopted to represent an elastic-plastic behavior. To investigate the dynamic response of a nuclear reinforced concrete containment structure, the steel-ratios of 0, 3, 5 and 10 percent, are considered. The results obtained from the analysis of an example were summarized as follows 1. As the steel-ratio increases, the amplitude and the period of the vertical displacements in apex of dome decreased. The Dynamic Magnification Factor(DMF) was some larger than that of the structure without steel. However, the regular trend was not found in the values of DMF. 2. The dynamic response of the vertical displacement and the radial displacement in the dome-wall junction were shown that the period of displacement in initial step decreased with the steel-ratio increases. Especially, the effect of the steel on the dynamic response of radial displacement disapeared almost. The values of DMF were 1.94, 2.5, 2.62 and 2.66, and the values increased with the steel-ratio. 3. The characteristics of the dynamic response of radial displacement in the mid-wall were similar to that of dome-wall junction. The values of DMF were 1.91, 2.11, 2.13 and 2.18, and the values increased with the steel-ratio. 4. The amplitude and the period of the hoop-stresses in the dome, the dome-wall junction, and the mid-wall were shown the decreased trend with the steel-ratio. The values of DMF were some larger than those of the structure without steel. However, the regular trend was not found in the values of DMF.