• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.11-18
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• 2007

Seismic performance evaluation for dam safety evaluation has been continually conducted. However the behavior analysis for the spillway pier which is known as the weak point of dam is seldom reported. Therefore, this study performed the static loading tests for a prototype structures as elementary tests for the final seismic performance evaluation of dam safety. The prototype of pier structure has 1/20 scale and it adopts to strength model. And cracking loads and ultimate loads of real structures are calculated through numerical analysis using commercial FEM program (ABAQUS). The results of this study show some difference between the results of prototype tests and the results of numerical analysis. Also, the ultimate and cracking loads can be estimated through the prototype loading test and numerical analysis.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.23-32
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• 2017

The joints between precast PSC slabs of the intermediate road slab in double deck tunnel are inevitably generated in the road traffic vehicle traveling direction. Therefore, it is important to make the behavior of parts on the joint in one piece. The imtermediate road slab system of double deck tunnel in great depth proposed in this study will be constructed with precast PSC slab in order to minimize the construction period. And the joint connection between the precast slab has been developed in two methods: the 'Transverse tendon reinforcement method' and 'High strength bolts connection method'. Also, the experiments were performed for the full scale model in order to evaluate the performance of the intermediate road deck slab with two type joints systems, the structural stability was verified through the F.E.M analsysis. The results of static loading test and F.E.M analysis investigated a very stable behavior of intermediate road deck slab in double deck tunnel applying the joint methods developed in this study, in the cracks and deflections to satisfy the design standards of Highway Roads Bridges (2011), it was determined that there is no problem even servicebility.

• Journal of the Korean GEO-environmental Society
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• v.11 no.9
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• pp.27-38
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• 2010

A series of model test as well as numerical analysis by FEM was performed to investigate lateral earth pressure acting on a buried pipe in soft ground undergoing horizontal soil movement. A model test apparatus was manufactured so as to simulate horizontal soil movement in model soft ground, in which a model rigid buried pipe was installed. The velocity of soil deformation could be controlled as wanted during testing. The model test was performed on buried pipes with various diameters and shapes to investigate major factors affected the lateral earth pressure. The result of model tests showed that the larger lateral earth pressure acted on the buried pipes under the faster velocity of soil movement. The result of numerical analysis, which was performed under immediate loading condition, showed a similar behavior with the result of model tests under 0.3mm/min to 1.0mm/min velocity of soil deformation. Most of model tests showed the soil deformation-lateral load behavior, in which the first yielding load developed at small soil deformation and elastic behavior was observed by the yielding load. Then, lateral load was kept constant by the second yielding load, in which plastic behavior was observed between the first yielding load and the second yielding one. Beyond the second yielding load, the compression behavior zone was observed. When the velocity was too fast, however, the lateral load was increased with soil deformation beyond the first yielding load without showing the second yielding load. The buried pipes with the larger diameter was subjected to the larger lateral load and the larger increasing rate of lateral load. At small soil deformation, the influence of diameter and shape of buried pipes on lateral load was small. However, when soil deformation was increased considerably, the influence became more and more.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.663-674
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• 2017

This paper presents an approach for evaluating performance of prestressed concrete (PC) bridge girders exposed to fire. A finite element based numerical model for tracing the response of fire exposed T girders is developed in ANSYS. The analysis is carried out in three stages, namely, fire temperature calculation, cross sectional temperature evaluation, and then strength, deformation and effective prestress analysis on girders exposed to elevated temperatures. The applicability of the computer program in tracing the response of PC bridge girders from the initial preloading stage to failure stage, due to combined effects of fire and structure loading, is demonstrated through a case study, and validated by test data of a scaled PC box girder under ISO834 fire condition. Results from the case study show that fire severity has a significant influence on the fire resistance of PC T girders and hydrocarbon fire is most dangerous for the girder. The prestress loss caused by elevated temperature is about 10% under hydrocarbon fire till the girder failure, which can lead to the increase in deflection of the PC girder. The rate of deflection failure criterion is suggested to determine the failure of PC T girder under fire.

• Steel and Composite Structures
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• v.37 no.5
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• pp.571-587
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• 2020

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure's behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.399-415
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• 2023

This paper presents the experimental and numerical evaluations on the circular SFRC columns reinforced GFRP rebars under the axial compressive loading. The test programs were designed to inquire and compare the effects of different parameters on the columns' structural behavior by performing experiments and finite element modeling. The research variables were conventional concrete (CC), fiber concrete (FC), types of longitudinal steel/GFRP rebars, and different configurations of lateral rebars. A total of 16 specimens were manufactured and categorized into four groups based on different rebar-concrete arrangements including GRCC, GRFC, SRCC, and SRFC. Adding steel fibers (SFs) into the concrete, it was essential to modify the concrete damage plastic (CDP) model for FC columns presented in the finite element method (FEM) using ABAQUS 6.14 software. Failure modes of the columns were similar and results of peak loads and corresponding deflections of compression columns showed a suitable agreement in tests and numerical analysis. The behavior of GFRP-RC and steel-RC columns was relatively linear in the pre-peak branch, up to 80-85% of their ultimate axial compressive loads. The axial compressive loads of GRCC and GRFC columns were averagely 80.5% and 83.6% of axial compressive loads of SRCC and SRFC columns. Also, DIs of GRCC and GRFC columns were 7.4% and 12.9% higher than those of SRCC and SRFC columns. Partially, using SFs compensated up to 3.1%, the reduction of the compressive strength of the GFRP-RC columns as compared with the steel-RC columns. The effective parameters on increasing the DIs of columns were higher volumetric ratios (up to 12%), using SFs into concrete (up to 6.6%), and spiral (up to 5.5%). The results depicted that GFRP-RC columns had higher DIs and lower peak loads compared with steel-RC columns.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.128-138
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• 2022

In this study, in order to apply ultra-high-strength concrete beams of 100 MPa or more manufactured by centrifugal molding as the superstructure of the avalanche tunnel, the purpose is to verify the structural safety of the corner rigid joint in which the centrifugal molded beam is integrated with the substructure, which is the negative moment area. A full-size specimen was manufactured, and loading tests and analysis studies were performed. In order to expect the same effect that the maximum moment occurs in the corner joint part of the upper slab end when the standard model of the avalanche tunnel is designed with a load combination according to the specification, a modified cantilever type structural model specimen was manufactured and the corner rigid joint was fixedly connected. A study was performed to determine the performance of the method and the optimal connection construction method. The test results demonstrated that the proposed connection system outperforms others. Despite having differences in joint connection construction type, stable flexural behavior was shown in all the tested specimens. The proposed method also outperformed the behavior of centrifugally formed beams and upper slabs. The behavior of the corner rigid joint analysis model according to the F.E. analysis showed slightly greater stiffness compared to the results of the experiment, but the overall behavior was almost similar. Therefore, there is no structural problem in the construction of the corner rigid joint between the centrifugally formed beam and the wall developed in this study.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.158-166
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• 2009

As a basic study for investigating the development of the stress-induced crack in Hoek-Brown rock, a homogenization technique of elastic cracks is proposed. The onset of crack is monitored by Hoek-Brown empirical criterion, while the orientation of the crack is determined by the critical plane approach. The concept of volume averaging in stress and strain component was invoked to homogenize the representative rock volume which consists of intact rock and cracks. The formulation results in the constitutive relations for the homogenized equivalent anisotropic material. The homogenization model was implemented in the standard FEM code COSMOSM. The numerical uniaxial tests were performed under plane strain condition to check the validity of the propose numerical model. The effect of friction between the loading plate and the rock sample on the mode of deformation and fracturing was examined by assuming two different contact conditions. The numerical simulation revealed that the homogenized model is able to capture the salient features of deformation and fracturing which are observed commonly in the uniaxial compression test.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.2
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• pp.71-82
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• 2022

This paper presents the effect on the inelastic behavior and structural performance of concrete and filled steel pipe through a numerical method for reliable judgment under various load conditions of the CJS composite structural system. Variable values optimized for the CJS synthetic structural system and the effects of multiple variables used for finite element analysis to present analytical modeling were compared and analyzed with experimental results. The Winfrith concrete model was used as a concrete material model that describes the confinement effect well, and the concrete structure was modeled with solid elements. Through geometric analysis of shell and solid elements, rectangular steel pipe columns and steel elements were modeled as shell elements. In addition, the slip behavior of the joint between the concrete column and the rectangular steel pipe was described using the Surface-to-Surface function. After finite element analysis modeling, simulation was performed for cyclic loading after assuming that the lower part of the foundation was a pin in the same way as in the experiment. The analysis model was verified by comparing the calculated analysis results with the experimental results, focusing on initial stiffness, maximum strength, and energy dissipation capability.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.413-418
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• 2001

Fundamental failure mode in a laminated composite pinned-joint is proposed to assess damage resulting from stress concentration in the plate. The joint area is a region with stress concentrations thus a complicated stress state exists. The modeling of damage in a laminated composite pinned-joint presents many difficulties because of the complexity of the failure process. In order to model progressive from initial to final, finite element methods are used rather than closed form stress analyses. Failure analysis must be a logical combination of suitable failure criteria and appropriate material properties degradation rules. In this study, the material properties which were obtained in previous study, the preparing process of the bearing strength test for a pinned joint CFRP composite plate subjected to in-plane loading at low temperature, and the FEM result of progressive damage model using ANSYS program are summarized to assess the structural safety of CFRP plate used in the magnetic supporting post of KSTAR(Korea Superconducting Tokamak Advanced Research).