• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.4
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• pp.187-192
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• 2023

An elastic bearing must be strong against vertical loads and flexible against horizontal loads. However, due to the material characteristics of rubber, it may show variability due to the manufacturing process and environmental factors. If the value applied in the bridge design stage and the actual measured value have different values or if the performance during operation changes, the performance required in the design stage may not be achieved. In this paper, the seismic response of bridges was compared and analyzed by assuming a case where quality deviation occurs during construction compared to the design value for elastic bearings, which have not only always served as traditional bearings but also have had many applications in recent seismic reinforcement. The bearing's vertical stiffness and shear stiffness deviation were considered separately for the quality deviation. In order to investigate the seismic response, a time history analysis was performed using artificial seismic waves. The results confirmed that the change in the bearing's shear stiffness affects the natural period and response of the structure.

• Journal of Korean Association for Spatial Structures
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• v.23 no.1
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• pp.61-68
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• 2023

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.285-293
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• 2022

Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.207-224
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• 2022

The mechanical behavior of prestressed concrete haunched beams (PSHBs) was investigated in depth using a finite element modeling technique in this study. The efficiency of finite element modeling was investigated in the first stage by taking into account a previous study from the literature. The first stage's findings suggested that finite element modeling might be preferable for modeling PSHBs. In the second stage of the research, a comprehensive parametric study was carried out to determine the effect of each parameter on PSHB load capacity, including haunch angle, prestress level, compressive strength, tensile reinforcement ratio, and shear span to depth ratio. PSHBs and prestressed concrete rectangular beams (PSRBs) were also compared in terms of capacity. Stochastic analysis was used in the third stage to define the uncertainty in PSHB capacity by taking into account uncertainty in geometric and material parameters. Standard deviation, coefficient of variation, and the most appropriate probability density function (PDF) were proposed as a result of the analysis to define the randomness of capacity of PSHBs. In the study's final section, a new equation was proposed for using symbolic regression to predict the load capacity of PSHBs and PSRBs. The equation's statistical results show that it can be used to calculate the capacity of PSHBs and PSRBs.

• Advances in concrete construction
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• v.16 no.2
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• pp.107-117
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• 2023

Textile-reinforced concrete composite (TRC) is a new alternative material that can satisfy sustainable development needs in the civil engineering field. Its mechanical behaviour and properties have been identified from the experimental works. However, it is necessary for a numerical approach to consider the effect of the parameters on TRC's behaviour with lower analysis duration and cost related to the experiment. This paper presents obtained results of the numerical modelling for TRC composite using the cracking model for the cementitious matrix in TRC. As a result, the TRC composite exhibited a strain-hardening behaviour with the cracking phase characterized by the drops in tensile stress on the stress-strain curve. This model also showed the failure mode by multi-cracking on the TRC specimen surface. Furthermore, the parametric studies showed the effect of several parameters on the TRC tensile behaviour, as the reinforcement ratio, the length and position of the deformation measurement zone, and elevated temperatures. These numerical results were compared with the experiment and showed a remarkable agreement for all cases of this study.

• Journal of Powder Materials
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• v.31 no.3
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• pp.255-262
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• 2024

Nano-oxide dispersion-strengthened (ODS) superalloys have attracted attention because of their outstanding mechanical reinforcement mechanism. Dispersed oxides increase the material's strength by preventing grain growth and recrystallization, as well as increasing creep resistance. In this research, atomic layer deposition (ALD) was applied to synthesize an ODS alloy. It is useful to coat conformal thin films even on complex matrix shapes, such as nanorods or powders. We coated an Nb-Si-based superalloy with TiO₂ thin film by using rotary-reactor type thermal ALD. TiO₂ was grown by controlling the deposition recipe, reactor temperature, N₂ flow rate, and rotor speed. We could confirm the formation of uniform TiO₂ film on the surface of the superalloy. This process was successfully applied to the synthesis of an ODS alloy, which could be a new field of ALD applications.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.223-231
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• 2024

For the OPR1000, a standard power plant in Korea, an analytical model of the containment building considering voids and deterioration was built with multilayer shell elements. Voids were placed in the vulnerable parts of the analysis model, and the deterioration effects of concrete and rebar were reflected in the material model. To check the impact of voids and deterioration on the seismic performance of the containment building, iterative push-over analysis was performed on four cases of the analytical model with and without voids and deterioration. It was found that the effect of voids with a volume ratio of 0.6% on the seismic performance of the containment building was insignificant. The effect of strength reduction and cross-sectional area loss of reinforcement due to deterioration and the impact of strength increase of concrete due to long-term hardening offset each other, resulting in a slight increase in the lateral resistance of the containment building. To determine the limit state that adequately represents the seismic performance of the containment building considering voids and deterioration, the Ogaki shear strength equation, ASCE 43-05 low shear wall allowable lateral displacement ratio, and JEAC 4601 shear strain limit were compared and examined with the analytically derived failure point (ultimate point) in this study.

• Structural Engineering and Mechanics
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• v.91 no.1
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• pp.87-102
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• 2024

In recent years, the focus on vibration analysis of multilayer smart structures has attracted considerable attention in many engineering applications. In this work, vibration analysis of a three-layer microporous beam with a core amplified by a composite material reinforced with graphene platelets and two piezoelectric thin films is discussed. It is assumed that piezoelectric layers with a thickness of 0.01 core are very thin and the properties of the matrix and reinforcement vary in the thickness directions. The governing equations of motion are obtained using an energy approach and the method of numerical differential quadrature to solve them. The results of this work are compared to other research and there is good agreement between them. The influences of the volumetric weight fraction of graphene wafers, different graphene platelets distributions, porosity distribution, mass scale parameters and thin ratio of graphene platelets take into account the natural dimensionless frequencies of the micro-beam. The results of this study show that the symmetric distribution of graphene platelets based on the symmetric porosity distribution has a great influence on the natural frequencies without basic dimension of the micro-beam, while the shape ratios of graphene platelets do not have a significant influence on natural frequency changes.

• Journal of Fashion Business
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• v.28 no.3
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• pp.69-89
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• 2024

In the era of globalization, cultural appropriation, stemming from the interaction and clash of diverse cultures, remains inadequately defined, leading to controversy in many designs. This study aims to provide a theoretical basis for understanding cultural appropriation by comparing similar concepts and examining specific cases. It proposes methods for the rational use of traditional cultures in apparel to minimize controversy. Firstly, the study investigates the concept of cultural appropriation by exploring differences among related terms. Secondly, it examines instances of cultural appropriation in fashion through form, color, pattern, and material, drawing from papers and Google searches over the past decade. Thirdly, it categorizes representative cases by domestic and foreign fashion brands, analyzing the underlying reasons. The goal is to establish a theoretical foundation for developing culturally sensitive clothing products. Based on the findings, several measures are proposed: understanding and respecting cultural backgrounds through in-depth research on the history and significance of elements; collaborating with cultural groups and consulting experts for feedback; explaining the source of design inspiration to help consumers understand the cultural elements' meanings; avoiding the reinforcement of stereotypes and respecting cultural diversity and complexity; respecting intellectual property and ensuring moral and legal appropriateness; and learning from case studies of other designers' and brands' successes and failures.

• Steel and Composite Structures
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• v.52 no.4
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• pp.451-460
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• 2024

Hollow reinforced concrete columns confined with GFRP tubes (GRCH) are composite members composed of the outer GFRP tube, the PVC or other plastic tube as the inner tube, and the reinforced concrete between two tubes. Because of their high ductility, light weight, corrosion resistance and convenient construction, many researchers pay attention to the composite members. However, there are few studies on GRCH members under eccentric compression compared with those under axial compression. Eight hollow columns were tested under eccentric compression, including one axial compression column and seven eccentric compression columns. The failure modes and force mechanisms of GRCH members were analyzed, considering the varying in hollow ratio, reinforcement ratio and eccentricity. The test results showed that configuring steel bars can greatly increase the bearing capacity and ductility of the members. Each component (GFRP tube, concrete, steel bar) had good deformation coordination and the strength of each material could be fully utilized. But for specimens with larger eccentricity ratio (e_r=0.4) and larger hollow ratio (χ=0.55), the restraining effect of GFRP tube on concrete was significantly decreased.