• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.141-148
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• 2021

In this study, the technology to prevent lateral deformation of steel dampers was reviewed and applied to the clamp type dampers. As for the experimental method, the rocking behavior was applied as in the previous study. The evaluation variables are the existing research results (SV-260) without lateral deformation prevention details and the test results (V-1, V-1R) with lateral deformation prevention details. Where, V-1 is the lateral deformation prevention detail at the lower part of the damper, and V-1R is the lateral deformation prevention detail at the lower part and upper part of the damper. As a result of evaluating the moment, drift ratio, and energy dissipation capacity relative to SV-260 at the time of maximum load, the maximum moments of V-1 and V-1R were increased by 1.22 times and 1.36 times compared to SV-260, and the maximum drift ratio increased by 2.41 times and 2.92 times. In addition, the energy dissipation capacity also increased by 1.39 times and 1.52 times, respectively. Therefore, the application of lateral deformation prevention details to the steel damper was evaluated as appropriate.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.1-8
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• 2024

In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 ℃ for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

• Journal of the Korea Convergence Society
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• v.5 no.1
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• pp.23-27
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• 2014

In case eccentric load is applied at compact tension specimen, the propagation behavior due to existence or nonexistence of hole, numbers and positions of holes near crack is investigated in this study. Strain energy, displacement and stress happened in specimen are examined through simulation analysis. And stress intensity factor is obtained by the basis of strain energy and deformation. When defect or hole exists in structure, the possibility of fracture can be thought to be verified by using the study result.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.773-776
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• 1997

This paper presents an investigation of the energy absorption of composite laminates during ballistic impact. Three components are responsible for the absorption of energy-the tensile failure of fiber, the elastic deformation of the composite, the delamination of composite laminates. The ballistic limit, V/sub 0/, of the laminates is determined using a previous model implemented to determine the energy absorption of the three components listed above. The size of the deformed zone during impact was estimated by an approximate solution for impacts on plates. The carbon/epoxy plates were examined for this research.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1161-1176
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• 2015

The connection between a column and a beam is of particular importance to ensure the safety of civil engineering structures, such as high-rise buildings and bridges. While the connector must bear sufficient force for load transmission, increase of its ductility, toughness and damping may greatly enhance the overall safety of the structures. In this work, a composite beam-column connector is proposed and analyzed with the finite element method, including effects of elasticity, linear viscoelasticity, plasticity, as well as geometric nonlinearity. The composite connector consists of three parts: (1) soft steel; (2) polymer; and (3) conventional steel to be connected to beam and column. It is found that even in the linear range, the energy dissipation capacity of the composite connector is largely enhanced by the polymer material. Since the soft steel exhibits low yield stress and high ductility, hence under large deformation the soft steel has the plastic deformation to give rise to unique energy dissipation. With suitable geometric design, the connector may be tuned to exhibit different strengths and energy dissipation capabilities for real-world applications.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.507-513
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• 2009

It is important to satisfy the requirements and standards for the protections of passengers in a car accident. There are lots of studies on the crushing energy absorption of structure members in automobiles. We have investigated collapse characteristics and moisture absorption movements of CFRP(Carbon Fiber Reinforced Plastics) hat shaped sectional members when CFRP laminates are under the hygrothermal environment. The absorbed energy, mean collapse load and deformation mode were analyzed for side members which absorbed most of the collision energy. Therefore we have made a static collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed specimen.

• Steel and Composite Structures
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• v.10 no.4
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• pp.331-348
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• 2010

Ample research effort has been oriented into developing damage indices with the aim of estimating in a reasonable manner the consequences, in terms of structural damage and deterioration, of severe plastic cycling. Although several studies have been devoted to calibrate damage indices for steel and reinforced concrete members; currently, there is a challenge to study and calibrate the use of such indices for the practical evaluation of complex structures. The aim of this paper is to introduce an energy-based damage index for multi-degree-of-freedom steel buildings that accounts explicitly for the effects of cumulative plastic deformation demands. The model has been developed by complementing the results obtained from experimental testing of steel members with those derived from analytical studies regarding the distribution of plastic demands on several steel frames designed according to the Mexico City Building Code. It is concluded that the approach discussed herein is a promising tool for practical structural evaluation of framed structures subjected to large energy demands.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.849-853
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• 1996

Hetero Dieis-Alder reactions containing phosphorus atom at various positions of diene and dienophile as well as standard Dieis-Alder reaction between ethylene and cis-l,3-butadiene have been studied using ab initio method. Activation energy showed a good linear relationship with the FMO energy gap between diene and dienophile, which can be normally used to explain Dieis-Alder reactivity. Since π-bond cleavage and σ-bonds formation occur concertedly at the TS, geometrical distortion of diene and dienophile from the reactant to the transition state is the source of barrier. Based on the linear correlations between activation barrier and deformation energy, and between deformation energy and π-bond order change, it was concluded that the activation barrier arises mainly from the breakage of π-bonds in diene and dienophile. Stabilization due to favorable orbital interaction is relatively small. The geometrical distortions raise MO levels of the TS, which is the origin of the activation energy. The lower barrier for the reactions of phosphorus containing dienophile (reactions C, D, and E) can be explained by the electronegativity effect of the phosphorus atom.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1119-1127
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• 2015

A finite-element model for beams with partially delaminated layers is used to investigate their behavior. In this formulation account is taken of lateral strains and the first-order shear deformation theory is used. Both displacement continuity and force equilibrium conditions are imposed between the regions with and without delamination. Numerical results of the present model are presented and its performance is evaluated for static and dynamic problems.

• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.435-459
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• 2015

Parametric resonance of shear deformable composite skew plates subjected to non-uniform (parabolic) and linearly varying periodic edge loading is studied for different boundary conditions. The skew plate structural model is based on higher order shear deformation theory (HSDT), which accurately predicts the numerical results for thick skew plate. The total energy functional is derived for the skew plates from total potential energy and kinetic energy of the plate. The strain energy which is the part of total potential energy contains membrane energy, bending energy, additional bending energy due to additional change in curvature and shear energy due to shear deformation, respectively. The total energy functional is solved using Rayleigh-Ritz method in conjunction with boundary characteristics orthonormal polynomials (BCOPs) functions. The orthonormal polynomials are generated for unit square domain using Gram-Schmidt orthogonalization process. Bolotin method is followed to obtain the boundaries of parametric resonance region with higher order approximation. These boundaries are traced by the periodic solution of Mathieu-Hill equations with period T and 2T. Effect of various parameters like skew angle, span-to-thickness ratio, aspect ratio, boundary conditions, static load factor on parametric resonance of skew plate have been investigated. The investigation also includes influence of different types of linearly varying loading and parabolically varying bi-axial loading.