• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.627-636
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• 2009

The purpose of this study was to evaluate the validity of the second-order analysis using the load amplification factor suggested by design codes. For this purpose, the first-order analysis with the B1 and B2 factors suggested by KBC 2005 and the direct analysis with the load amplification factor suggested by KBC 2009 (draft) were performed for three-story -one-bay and five-story-three-bay unbraced steel frames. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the validity of the suggested methods. The main parameters of the analysis were the scale of the frame, the axial load ratio of the column, and the methods of analysis. The research results showedthat the method suggested by KBC 2005 does not properly consider the second-order effect under the high axial load ratio, but the direct analysis method suggested by KBC 2009 (draft) properly estimates the second-order effect without any serious problem.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.87-97
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• 2010

The purpose of this study was to evaluate the validity of the second-order analysis for asymmetric unbraced frame using the load amplification factor suggested by design codes. For this purpose, the first-order analysis with the B1 and B2 factors suggested by KBC 2005 and the direct analysis with the load amplification factors suggested by KBC 2009 were performed for five story - two bay and five story - four bay asymmetric unbraced steel frames. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the validity of the suggested methods. The main parameters of the analysis were the shape of the frame, the axial load ratio of the column, the methods of analysis and the location of column. The research results show that the asymmetric shape of the frame deteriorates the validity of the factor B2 and the suggested methods. The range of error is increased in case of irregular or inclined column.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.743-746
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• 2011

본 연구에서는 유한요소해석을 이용하여 차량속도 및 긴장재의 설계에 따른 CFTA 거더의 동적거동 및 동적증폭계수를 분석하였다. 긴장재의 해석변수로서는 긴장재의 양과 긴장력을 고려하였으며 차량하중은 도로교설계기준의 DB-24 하중을 선택하였다. 차량하중은 3축-2트랙에 작용하는 등가절점하중으로 변환하여 속도에 따라 시간함수로 모델링하였다. 긴장재의 양은 외측 �� 내측 덕트의 유무에 따라 변화시켰으며 긴장력은 설계긴장력의 0%에서 100%까지 25%씩 증가시켰다. 차량속도는 40km/hr에서 100km/hr까지 20km/hr씩 증가시켰으며, 해석결과 긴장재의 긴장력 변화는 거더의 동적거동에 영향을 주지 않았으며 초기처짐에만 영향을 주었다. 긴장재의 양에 따라서는 거더의 동적거동이 다르게 나타났으며 긴장재의 양이 적을 수록 동적처짐은 증가하였다. 이를 바탕으로 거더의 동적증폭계수(DAF)를 산출하였으며, 이 결과 긴장재가 없는 경우에도 도로교표준시방서에서 정한 기준 값보다 매우 작은 거동을 보였다.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.519-526
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• 2003

For preliminary structural analysis of superstructures on very large floating structures(VLFS), superstructures are analyzed considering elastic deformations of barge type lower-structures subjected to wave loads. In this case, to consider the effect of wave loads on the superstructure, initial displacements at the support points of superstructures are evaluated as input data for the analysis. However, the evaluation and application of displacement loads are tedious and very time-consuming processes. Therefore, this paper proposes a simplified static analysis method to analyze the structural behaviors of superstructures on very large floating structures subjected to wave loads. In this study, the member forces due to the variation of beam span and the amplitude and period of wave load are analyzed by using an example 4 span -3 story structure and the amplification factors for beam moments are represented by the specific regression equation.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.33-40
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• 2012

To reduce the vulnerability of torsional irregular buildings caused by seismic loads, the torsional amplification factor was introduced by the seismic code. This factor has been applied differently in a variety of seismic codes. In this study, the final static eccentricity, and the lateral and torsional stiffness ratios of buildings designed with different design eccentricities were compared. The increment of the torsional amplification factor resulted in a decrement of the final static eccentricity of the building. However, after reaching the maximum value of this factor, the final static eccentricity of the building increased again. The final static eccentricity of the building designed by multiplying the sum of the inherent and accidental eccentricity by the torsional amplification factor was zero or had a minus value, depending to the position of the vertical element.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.239-245
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• 2006

In this paper, the performance of a toggle brace-MR damper system is evaluated for the control of the structure excited by earthquake load and the non-linearity of the toggle system is investigated. Considering that the control force of MR damper described by Bingham model is a function of velocity, velocity amplification factor by the toggle brace system is calculated and the effect of toggle configuration on the amplification factor is also evaluated. Numerical results show that the control performance can be largely enhanced using toggle brace system especially for the case that the MR damper installed with conventional brace system such as Chevron and diagonal cannot provide enough control force under severe earthquake load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.211-219
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• 2010

The design concept of high speed railway bridges is applied to a method for increasing the stiffness of existing bridge structures considering the impact factor by a static load. Generally, the process of structural design would be relied upon an advanced foreign technology. However, the dynamic amplification factor (DAF) and dynamic capacity assessment of high speed railway bridges may be conducted essentially a detailed estimation because the resonance phenomenon is affected by the long length (380 m) and high speed (300 km/h) moving of a high speed railway (Korea Train eXpress: KTX). Therefore, this study will be examined the dynamic capacity of the typical PSC Box Girder high speed railway bridge efficiently, and offered the basic information for the reasonable structural design. For this, the static analysis is conducted considering the load line diagram of KTX based upon existing references. In addition, the KTX moving load is transformed into the time series load considering various analytical variables. The time history analysis is assessed reasonable using the transformed time series load. At that time, analytical variables for calculating the time series load are considered loading node distance, time increment and KTX velocity variation etc. The dynamic capacity of the PSC Box Girder high speed railway bridge is examined based upon the FE analysis result systematically. The structural safety is assessed quantitatively in accordance with the related regulation of the inside and outside of the country.

• Journal of the Korean Geotechnical Society
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• v.22 no.3
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• pp.23-35
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• 2006

Equivalent linear analysis is widely used in estimating local seismic site effects. The soil behavior in the analysis is often assumed to be rate-independent and is not influenced by the seismic loading frequency. Laboratory results, however, indicate that cohesive soil behavior is greatly influenced by the loading frequency. A new equivalent linear analysis method that accounts for the loading frequency dependent soil behavior is developed and used to perform a series of one dimensional site response analyses. Results indicate that while frequency dependent shear modulus has limited influence on computed site response, frequency dependent soil damping greatly filters out high frequency components of the ground motion and thus results in lower response.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.846-855
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• 2021

Eco-friendly and renewable energy sources are actively being researched in recent times, and of shore wind power generation requires advanced design technologies in terms of increasing the capacities of wind turbines and enlarging wind turbine installation vessels (WTIVs). The WTIV ensures that the hull is situated at a height that is not affected by waves. The most important part of the WTIV is the leg structure, which must respond dynamically according to the wave, current, and wind loads. In particular, the wave load is composed of irregular waves, and it is important to know the exact dynamic response. The dynamic response analysis uses a single degree of freedom (SDOF) method, which is a simplified approach, but it is limited owing to the consideration of random waves. Therefore, in industrial practice, the time-domain analysis of random waves is based on the multi degree of freedom (MDOF) method. Although the MDOF method provides high-precision results, its data convergence is sensitive and difficult to apply owing to design complexity. Therefore, a dynamic amplification factor (DAF) estimation formula is developed in this study to express the dynamic response characteristics of random waves through time-domain analysis based on different variables. It is confirmed that the calculation time can be shortened and accuracy enhanced compared to existing MDOF methods. The developed formula will be used in the initial design of WTIVs and similar structures.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.293-303
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• 2010

The purpose of this study was to evaluate the influence of the methods of application of the direct analysis method, using the load amplification factor suggested by the KBC 2009 design code, for the evaluation of frame stability. For this purpose, the direct analysis method was performed for three-story-one-bay and five-story-three-bay unbraced steel frames with various notional loads, bending stiffness reductions, and factor B2s. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the influence of the applied methods. The scale of the frame, the axial load ratio, and the axial load distribution pattern were added to the main parameters to investigate the external effects. The research results showed that the influence of the methods of application of the direct analysis method is not significant in the case of the required axial strength and the application of the additional notional loads; and that the application of the factor B2 with the story stiffness concept to the direct analysis method is appropriate for the required flexural strength.