• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.475-486
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• 2013

This research is about design of slit type FLD which secure the buckling stability of compressive brace. 4 slit type and 8 slit type specimens were experimented by pure compressive loading. Comparing the experiment results with FEA results, the good correspondence is appeared each other. Also for deriving strength-displacement formular, an unit section of slit type FLD is transferred to idealized sandwich section. This formular explains satisfactorily experiment results, in given condition. The result of this research will be used as basic data in FLD design.

• Steel and Composite Structures
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• v.44 no.3
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• pp.309-324
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• 2022

The post-fire elastic stiffness and performance of concrete-filled steel tube (CFST) columns containing recycled aggregate concrete (RAC) has rarely been addressed, particularly in terms of material properties. This study was conducted with the aim of assessing the modulus of elasticity of recycled aggregate concrete-filled steel tube (RACFST) stub columns following thermal loading. The test data were employed to model and assess the elastic modulus of circular RACFST stub columns subjected to axial loading after exposure to elevated temperatures. The length/diameter ratio of the specimens was less than three to prevent the sensitivity of overall buckling for the stub columns. The gene expression programming (GEP) method was employed for the model development. The GEP model was derived based on a comprehensive experimental database of heated and non-heated RACFST stub columns that have been properly gathered from the open literature. In this study, by using specifications of 149 specimens, the variables were the steel section ratio, applied temperature, yielding strength of steel, compressive strength of plain concrete, and elastic modulus of steel tube and concrete core (RAC). Moreover, parametric and sensitivity analyses were also performed to determine the contribution of different effective parameters to the post-fire elastic modulus. Additionally, comparisons and verification of the effectiveness of the proposed model were made between the values obtained from the GEP model and the formulas proposed by different researchers. Through the analyses and comparisons of the developed model against formulas available in the literature, the acceptable accuracy of the model for predicting the post-fire modulus of elasticity of circular RACFST stub columns was seen.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.44-49
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• 1989

The primary purpose of using bracings is to improve tile lateral rigidity of main structural system, i.e., columns and beams, by reinforcing them with much smaller members. Conventional design methods consider bracings as tension-only mambers, since difficulties arise in the analysis to consider the P - effects and post-buckling behaviour of the bracing members. This is particulary true for X-bracings. Recently, however, both analytical and experimental studies have been conducted to investigate the more precise and real behaviour of bracing members, especially for the nonlinear un plastic behaviour under cyclic loads. In this study, an analytical model is proposed to investigate the nonlinear behavior of steel bracing members subjected to cyclic loads. Results of tile analysis were compared with previous experimental results, and good agreements were obtained between these results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.560-563
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• 2008

A condensed model is proposed for the simulation of forming of sandwich sheet with pyramid core. A corresponding finite element analysis for L-type bending is carried out to prove the accuracy and the effectiveness. Simulation results are compared with those of experiment. Deformation shape and post-buckling behavior by simulation are in good agreement with those of experiment for the considerable range of deformation. From the comparison of force-displacement curve, it is shown that the proposed model shows good prediction of the forming force compared to the experiment. Thus, the effectiveness of the proposed method is sufficiently demonstrated.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.227-227
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• 2000

Pressure vessels usually consist of main body and pipes which are connected with the main body. And as joining method of such main body and pipes, welding is carried out. After welding, welding residual stresses inevitably occur around welded joints. As residual stresses act harmfully on fatigue strength, corrosion and buckling strength of structure, PWHT is carried out for the purpose of removing the residual stress. But, during PWHT process, 2 ¼Cr-1Mo steels are frequently apt to generate reheat crack. For this reason, it is strongly needed to analyze and examine the mechanical behavior of welded joints before and after PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks frequently occur are selected for examining the mechanism of crack-occurrence. (Received December 2, 1999)

• Journal of Welding and Joining
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• v.18 no.2
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• pp.100-104
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• 2000

Pressure vessels usually consist of main body and pipes which are connected with the main body. And as joining method of such main body and pipes, welding is carried out. After welding, welding residual stresses inevitably occur around welded joints. As residual stresses act harmfully on fatigue strength, corrosion and buckling strength of structure, PWHT is carried out for the purpose of removing the residual stress. But, during PWHT process, $2\frac{1}{4}Cr-1Mo$ steels are frequently apt to generate reheat crack. For this reason, it is strongly needed to analyze and examine the mechanical behavior of welded joints before and after PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks frequently occur are selected for examining the mechanism of crack-occurrence.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1005-1012
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• 2011

In this paper, the effect of wrinkling on the failure behavior of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis with global-local analysis strategy. In the analysis, double-edge notched and single-edge notched tensile specimen configurations were considered. The analyses were performed for both cases with allowing and suppressing the wrinkling deformation. The results were investigated focusing on the effect of wrinkle development on the variation of J-integral values at the cut tip. The effect of cut lengths and the specimen lengths were also systematically studied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.233-242
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• 2008

This study presents a non-prismatic beam element for modeling the elastic and inelastic behavior of steel beams, which have the post-Northridge(cover plate) connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatric members with increased beam section (IBS) connection is in the closed-form. The plasticity model is of a discrete type and is composed of a series of nonlinear hinges connected by rigid links. The hardening rules can model the inelastic behavior for monotonic and random cyclic loading, and the effects of local buckling. Moreover the determination of yield surfaces, stiffness parameters, and hardening (or softening) rule parameters for IBS beam element were described. Analytical results of the IBS beam element show good correlation with test data and FEM results.

• Steel and Composite Structures
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• v.45 no.2
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• pp.293-303
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• 2022

In order to improve the seismic resilience of coupled wall structure, coupling beam with fuse has been developed to reduce the post-earthquake damage. However, the fuses often have a build-up I-shaped section and are relatively heavy to be replaced. Moreover, the fuse and the beam segments are usually connected by bolts and it is time-consuming to replace the damaged fuse. For reducing the repair time and cost, a novel quickly replaceable coupling beam with buckling-restrained energy dissipaters is developed. The fuse of the proposed coupling beam consists of two chord members and bar-typed energy dissipaters placed at the corners of the fuse. In this way, the weight of the energy dissipater can be greatly reduced. The energy dissipaters and the chords are connected with hinge and it is convenient to take down the damaged energy dissipater. The influence of ratio of the length of coupling beam to the length of fuse on the seismic performance of the structure is also studied. The seismic performance of the coupled wall system with the proposed coupling beam is compared with the system with reinforced concrete coupling beams. Results indicated that the weight and post-earthquake repair cost of the proposed fuse can be reduced compared with the typical I-shaped fuse. With the increase of the ratio of the beam length to the fuse length, the interstory drift of the structure is reduced while the residual fuse chord rotation is increased.

• Steel and Composite Structures
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• v.34 no.1
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• pp.107-122
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• 2020

Moment resisting stub columns (MRSCs) have increasingly adopted in special moment-resisting frame (SMF) systems in steel building structures, especially in Asian countries. The MRSCs typically provide a lower deformation capacity compared to shear-panel stub columns, a limited post-yield stiffness, and severe strength degradation as adopting slender webs. A new MRSC design with cored configuration, consisting of a core-segment and two side-segments using different steel grades, has been proposed in the study to improve the demerits mentioned above. Several full-scale components of the cored MRSC were experimentally investigated focusing on the hysteretic performance of plastic hinges at the ends. The effects of the depths of the core-segment and the adopted reduced column section details on the hysteretic behavior of the components were examined. The measured hysteretic responses verified that the cored MRSC enabled to provide early yielding, great ductility and energy dissipation, enhanced post-yield stiffness and limited strength degradation due to local buckling of flanges. A parametric study upon the dimensions of the cored MRSC was then conducted using numerical discrete model validated by the measured responses. Finally, a set of model equations were established based on the results of the parametric analysis to accurately estimate strength backbone curves of the cored MRSCs under increasing-amplitude cyclic loadings.