• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.24-34
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• 1990

In this paper, the formulation of a new simplified finite element is made to analyze the ultimate strength of damaged tubular members subjected to combined axial force and end moment. A damaged tubular member that has the bending deformation and the local dent is modeled by beam elements. Tangent elastic stiffness matrix of a beam element which contains the effect of the geometric nonlinearity is derived by using the updated Lagrangian approach. Here the contribution of the stiffness in the dented area is neglected since its resistance against the external loads is considered to be small. A fully plastic interaction curve of the element under combined loads taking account of the local dent effect is selected as a yielding criterion at each nodal point. Also tangent elasto-plastic stiffness matrix of the element is formulated by plastic node method. Comparison with the present solution and the existing experimental results is made showing that the present method gives quite an accurate solution.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.449-460
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• 2020

The double-lane arrangement model is frequently used in underground coal mines because it is beneficial to improve the mining efficiency of the working face. When the double-lane arrangement is used, the service time of the reserved roadway increases by twice, which causes several difficulties for the maintenance of the roadway. Given the severe non-uniform deformation of the reserved roadway in the Buertai Coal Mine, the stress distribution law in the mining area, the failure characteristics of roadway and the control effect of support resistance (SR) were systematically studied through on-site monitoring, FLAC 3D numerical simulation, mechanical model analysis. The research shows that the deformation and failure of the reserved roadway mainly manifested as asymmetrical roof sag and floor heave in the region behind the working face, and the roof dripping phenomenon occurred in the severe roof sag area. After the coal is mined out, the stress adjustment around goaf will happen to some extent. For example, the magnitude, direction, and confining pressure ratio of the principal stress at different positions will change. Under the influence of high-stress rotation, the plastic zone of the weak surrounding rock is expanded asymmetrically, which finally leads to the asymmetric failure of roadway. The existing roadway support has a limited effect on the control of the stress field and plastic zone, i.e., the anchor cable reinforcement cannot fully control the roadway deformation under given conditions. Based on obtained results, using roadway grouting and advanced hydraulic support during the secondary mining of the panel 22205 is proposed to ensure roadway safety. This study provides a reference for the stability control of roadway with similar geological conditions.

• Steel and Composite Structures
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• v.31 no.1
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• pp.69-83
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• 2019

This paper investigates the structural behavior of very high strength concrete encased steel composite columns via combined experimental and analytical study. The experimental programme examines stub composite columns under pure compression and eccentric compression. The experimental results show that the high strength encased concrete composite column exhibits brittle post peak behavior and low ductility but has acceptable compressive resistance. The high strength concrete encased composite column subjected to early spalling and initial flexural cracking due to its brittle nature that may degrade the stiffness and ultimate resistance. The analytical study compares the current code methods (ACI 318, Eurocode 4, AISC 360 and Chinese JGJ 138) in predicting the compressive resistance of the high strength concrete encased composite columns to verify the accuracy. The plastic design resistance may not be fully achieved. A database including the concrete encased composite column under concentered and eccentric compression is established to verify the predictions using the proposed elastic, elastoplastic and plastic methods. Image-oriented intelligent recognition tool-based fiber element method is programmed to predict the load resistances. It is found that the plastic method can give an accurate prediction of the load resistance for the encased composite column using normal strength concrete (20-60 MPa) while the elastoplastic method provides reasonably conservative predictions for the encased composite column using high strength concrete (60-120 MPa).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.22-33
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• 1998

A continuum analysis of the evolution of plasticity and Bauschinger effect in a short fiber reinforced metal matrix composite, based on the FEM solution for a single fiber model has been performed to investigate the strengthening behavior. The evolution of matrix field quantities during one cycle of fully reversed loading have been examined in detail. The results indicate that the role of constrained matrix flow in generating different levels of matrix triaxiality during forward and reversed loading provides an important contribution to the developement of the Bauschinger effect in the metal matrix composite. Therefore, even when the plastic flow of the matrix material follows on isotropic hardening behavior, the Bauschinger effect is predicted for the composite material.

• Steel and Composite Structures
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• v.5 no.2_3
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• pp.203-233
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• 2005

This paper presents the findings of a design development project for perforated beams fully integrated with building services. A unified design approach for both steel and composite beams with large rectangular web openings is proposed which is based on plastic design methods and formulated in accordance with analytical structural design principles. Moreover, finite element models are established after careful calibration against test data, and comparison on the predicted ultimate loads of two composite beams with rectangular web openings from the finite element models and the proposed design method is also presented. It is demonstrated that the proposed design method is able to predict the ultimate loads of composite beams with rectangular web openings against 'Vierendeel' mechanism satisfactorily.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.153-156
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• 2004

A newly developed flexible active-matrix (AM-) electrophoretic display (EPD) is reported. The AM-EPD features: (1) low-temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology, (2) fully integrated scan- and data-drivers, (3) flexibility and light-weight realized by transferring the whole circuits onto a plastic substrate using $SUFTLA^{TM}$ (Surface Free Technology by Laser Annealing/Ablation) process. A large storage capacitor is formed in each pixel so that driving electric field can be kept sufficiently strong during a writing period Two-phase driving scheme, a reset-phase which erases a previous image and a writing-phase for writing a new image, was chosen to cope with EPD's high driving voltage. The flexible AM-EPD has been successfully operated with a driving voltage of 8.5 V.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.535-540
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• 1998

Nowadays, the pushover analysis technique is becoming a very useful tool for the prediction of inelastic behavior of structures in the seismic evaluation of existing buildings in the worldwide. However, the reliability of this analysis method has not been fully checked by the test results. The objective of this study is to verify the correlation between the experimental and analytical response of a high-rise nonseismic reinforced concrete frame using DRAIN-2DX program and the test results performed previously. This study concludes that the overall responses such as story-shear versus story-drift can be predicted with quite high reliability while the local deformations such as plastic rotations in the ends of critical members can not be described reasonably.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.4
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• pp.494-502
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• 2003

The near-tip field of mode-I dynamic cracks steadily propagating in a strain softening material is investigated under plane strain conditions. The material is assumed to be incompressible and its deformation obeys the $J_2$ flow theory of plasticity. A power-law stress-strain relation with strain softening is adopted to account for the damage behavior of materials near the dynamic crack tip. By assuming that the stresses and strain have the same singularity at the crack tip. this paper obtains a fully continuous dynamic crack-tip field in the damage region. Results show that the stress and strain components the same logarithmic singularity of (In(R/r))$\delta$, and the angular variations of filed quantities are identical to those corresponding to the dynamic cracks in the elastic-perfectly plastic material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03a
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• pp.81-90
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• 1996

In this paper, a finite element based system is presented for the prediction of the distributions of the recrystallized grain sizes in the workpiece in hot forging. The system adopts fully coupled finite element thermo-mechanical model for predicting plastic deformatin and heat transfer occuring in the workpiece, and employsexisting metallurgical models relating the recrystallization behavior with the thermo-mechanical variables such as temperatures, strain, and strain rate. The system is applied to upsetting of cylindrical preform. The predicted grain sizes are compared with the measurements . It is further applied to forging of a complex-shaped product.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.197-202
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• 2005

This study started to confirm and prove for the applicability of the dry-process waterproofing system to cover the defects of the wet-process waterproofing system according to weather circumstance, foundation condition and maintenance, etc. This process has triple combined waterproofing system using asphalt sheet, metal sheet, engineering plastic film. It is not influenced by the concrete's crack as the foundation of the roof according to the movement of the building because the waterproofing system is designed for maintaining good quality by absorbing the stress of contraction and expansion that is occurred by the variation of temperature. Ali components used in this process can be recycled environmentally. The superiority of this process proved and reconfirmed through with the investigation of about 130 fields, around 30,000nf for two years.