• Journal of Korean Society of Steel Construction
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• 제17권2호통권75호
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• pp.139-149
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• 2005

Post-local buckling behavior is a very important consideration in plastic and seismic design of steel structures. It describes the structural behavior up to the final collapse state. In order to assess the actual reliability of structures under severe repeated loading, such as strong earthquakes, it is necessary to evaluate the progressive cyclic deterioration of stiffness as well as the strength and energy dissipation capacity of the structures after local buckling happens. In this study, a simple analytical model developed for predicting post-local buckling behavior for cyclic and non-proportional loading histories, has been proposed. This analytical model uses the stress resultant model based on the two surface model. Analytical moment-curvature relationship using this model compare well with the experimental results in constant amplitude cycling, and linearized energy deterioration which is very important in seismic design can be predicted from the proposed model.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.311-330
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• 2006

Standard compression tests of steel fiber reinforced concrete (SFRC) cylinders are conducted to formulate compressive stress versus compressive strain relationship of SFRC. Axial pullout tests of SFRC specimens are also conducted to explore its tensile stress strain relationship. Cover concrete spalling and reinforcement buckling models developed originally for normal reinforced concrete are modified to extend their application to SFRC. Thus obtained monotonic material models of concrete and reinforcing bars in SFRC members are combined with unloading/reloading loops used in the cyclic models of concrete and reinforcing bars in normal reinforced concrete. The resulting path-dependent cyclic material models are then incorporated in a finite-element based fiber analysis program. The applicability of these models at member level is verified by simulating cyclic lateral loading tests of SFRC columns under constant axial compression. The analysis using the proposed SFRC models yield results that are much closer to the experimental results than the analytical results obtained using the normal reinforced concrete models are.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제14권2호
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• pp.281-290
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• 1994

This paper presents the results of an analytical investigation pertaining to the compression behavior of axially loaded plates made from pultruded fiber reinforced plastic materials. Non-dimensionalized closed-form solutions have been developed for the prediction of the buckling load in the pultruded plates with edge stiffener. These solutions were based upon the classical theory of orthotropic plates and accounted for the e1astic restraints at the juncture of plate and stiffener. The effects of edge stiffener on the flange plate were investigated in order to clarify its usefulness for increasing flange local buckling load of the pultruded structural shapes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1362-1365
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• 2003

On this study. we improved the efficiency applying algorithm that is repeatedly using orthogonal array in discrete design space and filling a defect of gradient method in continuous design space. we showed optimal ply angle that maximized buckling strength of CFRP laminated composite plate without a hole and with a hole by each aspect ratio. In the case of CFRP laminated composite plate without a hole, we confirmed the reliance and efficiency of algorithm in comparison with the result optimization achievement repeatedly using statistical orthogonal array of experimental design.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.286-293
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• 2003

In this study a story-wise distribution of hysteretic energy in multi-story steel moment-resisting framse (MRE), buckling restrained braced frames (BRBF-R), and hinge-connected framed structures with buckling restrained braces (BRBF-H) subjected to various earthquake ground excitations was investigated. According to analysis results the hysteretic energy in MRF and BRBF-R turned out to be the maximum at the base and monotonically diminishes with increasing height. In top stories the plastic deformation of members is almost negligible. However the story-wise distribution of hysteretic energy in BRBF-H was relatively uniform over the height of the structure. This is considered to be more desirable because damage is not concentrated in a single story.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.191-197
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• 2006

In this paper 35- and 72-story tube system and trussed tube system were designed and their seismic performances were evaluated by nonlinear static analysis. According to the analysis results, the tube system structures retained high stiffness and strength; however they showed brittle failure mode due to the yielding of columns. In the case of trussed tube system, columns in the side-side buckled first followed by the buckling of the braces. When buckling-restrained braces were applied, plastic hinges formed in the lower stories gradually spreads to the higher stories, resulting in ductile behavior.

• Earthquakes and Structures
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• 제10권3호
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• pp.589-611
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• 2016

This paper presents an analytical study aimed at evaluating the seismic performance of steel moment resisting frames (MRFs) retrofitted with different approaches. For this, 3, 6 and 12 storey MRFs having four equal bays of 5 m were selected as the case study models. The models were designed with lateral stiffness insufficient to satisfy code drift and hinge limitations in zones with high seismic hazard. Three different retrofit strategies including traditional diagonal bracing system and energy dissipation devices such as buckling restrained braces and viscoelastic dampers were used for seismic upgrading of the existing structures. In the nonlinear time history analysis, a set of ground motions representative of the design earthquake with 10% exceedance probability in fifty years was taken into consideration. Considering the local and global deformations, the results in terms of inter-storey drift index, global damage index, plastic hinge formations, base shear demand and roof drift time history were compared. It was observed that both buckling-restrained braces and viscoelastic dampers allowed for an efficient reduction in the demands of the upgraded frames as compared to traditional braces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.98-101
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• 1999

The plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. And also it is difficult to control precisely the shape and dimensions of forming process. It is found that instabilities of the process are mainly connected with imperfection in the lubrication billet eccentricity inclined punch alignment. In view of the direct relationship between instable material flow and quality defects of the products and it is for better control of forming operation we should necessarily find out their phenomena. In this study we used the friction disturbance due to inclined punch angle and introduced the method considering kinematic hardening effect Analysis of upset forging is carried out using the rigid plastic FEM and slab method with eccentricity.

• Journal of Welding and Joining
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• 제15권5호
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• pp.115-123
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• 1997

The buckling strength, fatigue strength, stress corrosion cracking are considerably effected on one of initial imperfections, the residual stresses produced by a circumferential weld between axisymmetric cylinders. Therefore, we study the residual stresses, plastic strain and temperature distribution with using thermal elasto-plastic analysis which are generated by a circumferential weld between axisymmetric cylinders. It is investigated that welding residual stresses have an effect on the strength of cylinder for inner and outer shell under external pressure.

• Journal of Korean Society of Steel Construction
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• 제20권3호
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• pp.377-387
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• 2008

The post-buckling behavior of slender members, such as the chord of truss structures generally implies extreme strength degradation. The buckling strength is usually determined as the performance of the compressed steel members, so it is important to understand the exact buckling behavior of a member in order to design the entire structure. A target analytical model is usually divided by beam or shell element when we simulate the buckling behavior of a compressed steel member such as atruss member. In this case, it is possible to accurately obtain the behavior, but such would be expensive and would require experience inanalysis even in monotonic loading. In this paper, we propose a consistent and convenient method to analyze the post-buckling behavior of elastoplastic compression members. The present methods are formulated to satisfy the second law of thermodynamics. Three numerical examples were tested to determine the validity of the proposed model in cyclic loading with comparable F.E.M results.