• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.485-496
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• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, three load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Steel and Composite Structures
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• v.27 no.6
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• pp.703-716
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• 2018

In this study, the different energy demands in reinforced concrete (RC) wall piers, coupled by buckling restrained braces (BRBs), are investigated. As well as this, a single plastic hinge approach (SPH) and an extended plastic hinge (EPH) approach is considered for the wall piers. In the SPH approach, plasticity can extend only in the 0.1H adjacent to the wall base while, in the EPH approach, the plasticity can extend anywhere in the wall. The seismic behavior of 10-, 20- and 30-storey structures, subjected to near-fault (NF) as well as far-fault (FF) earthquakes, is studied with respect to the energy concepts involved in each storey. Different kinds of energy, including inelastic, damping, kinetic, elastic and total input energy demand, are investigated. The energy contribution from the wall piers, as well as the BRBs in each model, are studied. On average, for EPH approach, the inelastic demand portion pertaining to the BRBs for NF and FF records, is more than 60 and 80%, respectively. In the SPH approach, these ratios are 77 and 90% for the NF and FF events, respectively. It appears that utilizing the BRBs as energy dissipation members between two wall piers is an efficient concept.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.13-24
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• 2017

System buckling analysis is usually used to determine the critical buckling load in the buckling design of cable-stayed bridges. However, system buckling analysis may yield unexpectedly large effective lengths of the members subjected to a relatively small axial force. This paper proposes a new method to determine reasonable effective lengths of girder and tower members in steel cable-stayed bridges using fictitious axial forces. An improved inelastic buckling analysis with modified tangent modulus is also presented. The effective lengths of members in example bridges calculated using the proposed method are compared with those obtained using the conventional buckling analysis method. The proposed method provides much more resonable effective lengths of the members. When girder and tower members are built with HSB800 steel instead of conventional steel, the effective lengths of the members under a small axial force slightly decreases in the inelastic buckling analysis without fictitious axial forces, while the proposed method that considers fictitious axial forces provides almost no changes in such lengths.

• Journal of Korean Association for Spatial Structures
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• v.19 no.4
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• pp.45-52
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• 2019

The purpose of the paper is to introduce a system that reduces the occurrence of weak-story in the event of earthquake. Weak-story concentrates deformation on the story and causes all member to collapse before the capacity of all member is reached. This paper introduces Strong-Back system (SB) to protect weak story. SB is a hybrid of zipper frame, tied eccentrically braced frame, and elastic truss system and it is divided into elastic and inelastic areas. Elastic areas prevent the generation of weak story by distributing energy, and inelastic areas dissipate energy through buckling or yielding. In this paper, the seismic performance is evaluated by comparing the four type braced frame with SB through push-over analysis. The four criteria are compared from the base shear, the ductility capacity, the column failure order, and the quantity of brace. As a result, SB proved to have sufficient performance to protect the weak-story.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.271-279
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• 2003

Many researches have been conducted to describe the elastic and inelastic behavior of H-shaped beams with web openings, and were generally concentrated on the uniaxial loading conditions. With previous research results, the formulae for the design of beams with web openings, considering local buckling, have been proposed by Darwin. Although the formulae are so simple and useful to apply to real situations, it needs more research on cyclic loading conditions. In this experimental study, a total of seven H-shaped beams with circular web openings under cyclic loading conditions were investigated. The dimension criteria were based on the formulae proposed by Darwin. The suitability of the existing design formulae, the effects of plastic hinges on beams with web openings, and the local bucking around the web openings to the beam strength under cyclic loading were also investigated through by the observations of the behavior of these beams with various dimensional openings.

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.305-325
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• 1998

A method that determines the minimum stiffness of baracing to achieve non-sway buckling conditions at a given story level of a multi-column elastic frame is proposed. Condensed equations that evaluate the required minimum stiffness of the lateral and torsional bracing are derived using the classical stability functions. The proposed method is applicable to elastic framed structures with rigid, semirigid, and simple connections. It is shown that the minimum stiffness of the bracing required by a multi-column system depends on: 1) the plan layout of the columns; 2) the variation in height and cross sectional properties among the columns; 3) the applied axial load pattern on the columns; 4) the lack of symmetry in the loading pattern, column layout, column sizes and heights that cause torsion-sway and its effects on the flexural bucking capacity; and 5) the flexural and torsional end restrains of the columns. The proposed method is limited to elastic framed structures with columns of doubly symmetrical cross section with their principal axes parallel to the global axes. However, it can be applied to inelastic structures when the nonlinear behavior is concentrated at the end connections. The effects of axial deformations in beams and columns are neglected. Three examples are presented in detail to show the effectiveness of the proposed method.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.159-165
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• 2003

A tubular member with through-gusset plate is often used to transmit axial compression in an electric transmission towers. In current code, the strength of tubular member is evaluated with an effective length factor k=0.9 without considering the deformation of boundary element. A buckling strength of member with end gusset plate is affected by stiffness ratio($\beta$) and the length ratio(G) between main tubular member and end gusset plate. In this study theoretical mechanism based on the elastic buckling behavior was investigated, and finite element analysis was performed to propose a formula for the buckling strength and effective length factor of tubular member in elsatic and inelastic ranges.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.27-35
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• 2007

This study presents a non -prismatic beam element for modeling the elastic and inelastic behavior of the steel beam, which has the post-Northridge connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatic members with reduced beam section (RES) 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. Verification and calibration of the model are presented in a companion paper.

• Steel and Composite Structures
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• v.6 no.1
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• pp.1-14
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• 2006

Experiments have been carried out on six composite and two plain steel plate girders under shear loading to understand the elastic and inelastic behaviour of such girders. The failure mechanism assumed and used to develop design equations is normally based on the failure patterns observed in the experiments. Therefore, different types of cracks and failure patterns observed in the experiments are reviewed briefly first. Based on the observed failure patterns, a design method to predict the ultimate shear capacity of composite plate girders is proposed in this paper. The values of ultimate shear capacity obtained using the proposed design method are compared with the corresponding experimental values and it is found that the proposed method is able to predict the shear capacity accurately.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.505-514
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• 2009

This paper describes the structural behavior and the ultimate strengths of circular hollow steel (CHS) sections based on a series of compression tests. The ultimate strengths of CHS section columns are mainly dependent on both diameter-thickness ratio and column slenderness ratio. For the CHS sections with a high diameter-thickness ratio, an elastic or an inelastic local buckling may occur prior to the overall buckling, and it may decrease the column strength. Test sections were fabricated from SM400 steel plate of 2.8 mm and 3.2 mm in thickness and were tested to failure. The diameter-thickness ratios of the test sections ranged from 45 to 170 to investigate the effect of local buckling on the column strength. The compression tests indicated that the CHS sections of lower diameter-thickness ratio than the yield limit in the current design specifications showed an inelastic local buckling and a significant post-buckling strength in the local mode. Their ultimate stresses were larger than the nominal yield stress. It was known that the allowable stresses of the sections predicted by the Korean Highway Bridge Design Specifications (2005) were too conservative in comparison with test results. The Direct Strength Method which was newly developed was calibrated for application to the CHS sections by the experimental and numerical results. The Direct Strength Method proposed can predict properly the ultimate strength of CHS section columns whether a local buckling and an overall buckling occur nearly simultaneously or not.