• Journal of the Korea Concrete Institute
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• 제11권6호
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• pp.47-56
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• 1999

In this paper, a nonlinear finite element procedure is presented for the analysis of reinforced concrete shell structures. The 4-node quadrilateral flat shell finite element with drilling rotational stiffness is developed. The layered approach is used to discretize behavior of concrete and reinforcement through the thickness. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. The steel reinforcement is assumed to be in a uniaxial stress state and to be a smeared in a layer. The proposed numerical method for nonlinear analysis of reinforce concrete shells will be verified by comparison with reliable experimental results.

• Journal of Korean Association for Spatial Structures
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• 제20권3호
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• pp.71-79
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• 2020

In this paper, the hybrid prefabricated retrofit method that improve structural performance and reduce construction period was developed by using a finite element analysis. The hybrid prefabricated retrofit method consist of a Z-shaped side plate, a L-shaped lower plate, and a bottom plate containing an steel plate with openings. This shape has advantage that a retrofit method is possible regardless of the size of the beams and a follow-up process such as reinforcement bars placing are not required. The finite element analysis of hybrid Prefabricated retrofit method showed the most ideal stress distribution when the thickness of bottom plate was 10mm, the thickness of the L-shaped lower plate was 5mm, the thickness of the Z-shaped side plate was 2.5mm, and the bolt spacing was 200mm. The bending strength equation of Hybrid prefabricated retrofit method was proposed through the plastic stress distribution method in KDS 41 31 00. The result of Comparison the proposed equation with the finite element analysis, it is determined that the design of hybrid prefabricated retrofit method is possible through the KDS 41 31 00.

• Fire Science and Engineering
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• 제34권4호
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• pp.87-95
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• 2020

This study evaluates the safety of an asylum through a fire simulation of building Type traditional markets. We derive the building's indoor temperature, use the observed variation in temperature gradient to calculate the temperature of the main structure, and finally compares the time required to attain the limit temperature of the structure its time of escape. To ensure improved security of the asylum, the government has proposed a fire-resistance improvement plan for the major structural parts of buildings are not safe with thickness of 0.01 m and 0.035 m. F.ire-resistance reinforcement for small - and medium-sized vehicles is more than 0.025 m, in thickness; moreover safety can be ensured for medium and large-sized vehicles fire using fire resistant reinforcement of over 0.035 m. Accordingly, in order to ensure the safety of an asylum, fire-resistant reinforcement measures may be considered.

• Advances in nano research
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• 제16권4호
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• pp.395-412
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• 2024

This article develops a nonclassical size dependent nanoplate model to study the dynamic response of functionally graded carbon nanotube (FGCNT) nanoplates under a moving load. Both nonlocal and microstructure effects are incorporated through the nonlocal strain gradient elasticity theory. To investigate the effect of reinforcement orientation of CNT, four different configurations are studied and analysed. The FGM gradation thorough the thickness direction is simulated using the power law. In the context of the first order shear deformation theory, the dynamic equations of motion and the associated boundary conditions are derived by Hamilton's principle. An analytical solution of the dynamic equations of motion is derived based on the Navier methodology. The proposed model is verified and compared with the available results in the literature and good agreement is found. The numerical results show that the dynamic performance of FGCNT nanoplates could be governed by the reinforcement pattern and volume fraction in addition to the non-classical parameters and the moving load dimensionless parameter. Obtained results are reassuring in design and analysis of nanoplates reinforced with CNTs.

• Advances in concrete construction
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• 제15권2호
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• pp.115-126
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• 2023

This paper investigates creep analysis of a plate made of Al-SiC functionally graded material using Mendelson's method of successive elastic solution. All mechanical and thermal material properties, except Poisson's ratio, are assumed to be variable along the thickness direction based on the volume fraction of reinforcement and thickness. First, the basic relations of the plate are derived using the Love-Kirchhoff plate theory. The solution of governing equations yields an elastic solution to start creep analysis. The creep behavior is demonstrated through Norton's equation based on Pandey's experimental results extracted for Al-SiC functionally graded material. A linear variation is assumed for temperature distribution along the thickness direction. The creep strain, as well as the thermal strain, are included in the governing equations derived from classical plate theory for mechanical strain. A successive elastic solution based on Mendelson's method is employed to derive the history of stresses, strains, and displacements over a long time. History of stresses and deformations are obtained over a long time to predict damage to the plate because of various loadings, and material composition along the thickness and planar directions.

• Journal of the Korean Society of Hazard Mitigation
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• 제3권2호
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• pp.127-137
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• 2003

In locations where the cost of concrete is relatively high, or in situations where the weight of concrete members is to be kept to a minimum, it may be economical to use hollow R.C. members. The ductility of circular hollow R.C. columns with one layer of longitudinal and spiral reinforcement placed near the outside face of the section and the steel tube placed on the inside face of the section is investigated. Such hollow sections are confined through the wall thickness since the steel tube is placed. In this study, moment-curvature analyses are conducted with Mander's confined concrete stress-strain relationship. The variables influenced on the ultimate strain is the ratio and yield strength of confining reinforcement and the compression strength for confined concrete. From this ultimate strain - the transverse reinforcement ratio relationship, the transverse reinforcement ratio for circular hollow reinforced columns with confinement is proposed. The proposed transverse reinforcement ratio is confirmed by experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• 제26권5호
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• pp.119-126
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• 2022

This study proposed a BCM(Binding Column Method) that can reinforce the insufficient seismic force of piloti buildings that are not designed for seismic resistance. In addition, 4 reinforcement specimens and 1 reference specimen were manufactured for the proposed seismic reinforcement method. The effect of improving seismic performance before and after reinforcement was examined through repeated loading tests. As a result of experiment, seismic reinforcement specimen with BCM system showed hysteretic characteristics of a large ellipse with great energy dissipation ability and increased strength and stiffness, while reference specimen showed rapid reduction in strength and brittle shear failure column. In addition, it can be seen that the reinforcing effect is improved as the gap is narrow, the torque is large, and the thickness of the L-shaped steel sheet is thicker. The SC4 specimen showed the best seismic performance reinforcement effect.

• Structural Engineering and Mechanics
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• 제71권4호
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• pp.363-375
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• 2019

A renewable energy storage pile foundation system is being developed through a multi-disciplinary research project. This system intends to use reinforced concrete pile foundations configured with hollowed sections to store renewable energy generated from solar panels attached to building structures in the form of compressed air. However previous research indicates that the compressed air will generate considerable high circumferential tensile stresses in the concrete pile, which requires unrealistic high hoop reinforcement ratio to avoid leakage of the compressed air. One possible solution is to utilize fiber reinforced concrete instead of placing the hoop reinforcement to resist the tensile stress. This paper investigates nonlinear structural responses and post-cracking behavior of the fiber reinforced concrete pile subjected to high air pressure through nonlinear finite element simulations. Concrete damage plasticity models were used in the simulation. Several parameters were considered in the study including concrete grade, fiber content, and thickness of the pile section. The air pressures which the pile can resist at different crack depths along the pile section were identified. Design recommendations were provided for the energy storage pile foundation using the fiber reinforced concrete.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.91-94
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• 2003

Laminated composites are liable to fatal damage under impact load due to the fact that they have no reinforcement in the thickness direction. To overcome the inherent weakness, three dimensional (3D) textile reinforcements have drawn much interests. In this paper, impact performance of 2D and 3D textile composites has been characterized. For 2D composites, fiber bundle size and fiber pattern have been varied. For 3D composites, orthogonal woven preforms of different density and type of through-thickness fibers have been studied. To assess the damage after the impact loading, specimens were subjected to C-scan nondestuctive inspection. Compression after impact (CAI) were also conducted in order to evaluate residual compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.471-476
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• 2001

Even though structural performance evaluation techniques for reinforced concrete structures have been improved, there are still many problems in the evaluation of structural performance for underground structures which interacts with surrounding soils. Since experimental evaluation of underground RC structures considering the interaction with the surrounding soil medium is quite difficult to be simulated, the evaluation for underground RC structures using an analytical method can be applied very usefully, For underground structures interacted with surrounding soils, it is important to consider path-dependent RC constitutive model, soil constitutive model, and interface model between structure and soil, simultaneously. In this paper, an elastoplastic interface model which consider thickness was proposed and importance of interface model is discussed. The effects of stiffness of structures to entire underground RC system are investigated through numerical experiment for underground RC structure for different reinforcement ratios and thickness of interfaces.