• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.59-69
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• 2011

Nonlinear static procedures (NSPs) basing on the concept of performance based seismic design have become one of the promising procedures for seismic evaluation of buildings. Although it needs much less computational cost compared to nonlinear time history analysis (NTHA), its usages are limited to simple structures by its inherent restriction to structures wherein the fundamental mode dominates the response. Several new nonlinear static procedures (Modal Pushover Analysis; MPA and Improved Modal Pushover Analysis; IMPA) which can consider higher modes effect were introduced. Nonetheless, its applicability for complex structures such as cable-stayed bridge has not studied yet. This paper focuses on applicability of nonlinear static procedures for the seismic analysis of cable-stayed bridges. Moreover, reliability indexes which can predict analysis procedure's accuracy are introduced.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.633-642
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• 2007

Although the Load and Resistance Factor Design (LRFD) method is an advanced design approach, it does not accurately capture the interaction between individual members and structural system. A nonlinear inelastic analysis for the entire structure is required to solve this problem. According to many design codes of advanced countries, a nonlinear inelastic analysis can be applied to predict the structural behavior and strength reasonably. In this study, an LRFD design method using practical nonlinear inelastic analysis was proposed. Design examples using the proposed method waspresented, and the economical efficiency and adequacy of the proposed method was investigated by comparing the design results with that of the AISC-LRFD. It has been consequently demonstrated that the proposed method can reduce the construction cost through savings in steel.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.1
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• pp.17-27
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• 2004

A new earthquake design method performing iterative calculations using secant stiffness was developed. The proposed design method has the advantages of convenience and stability in numerical analysis because it uses elastic analysis. At the same time, the proposed design method can accurately estimate the strength and ductility demands on the members because it performs the analysis on the inelastic behavior of structure using iterative calculation. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. Design examples using the proposed method were presented, and its advantages were presented by the comparisons with existing design methods using elastic or inelastic analysis. The proposed design method, as an integrated method of analysis and design, can address the earthquake design strategy devised by the engineer. such as ductility limit on each member, the design concept of strong column - weak beam, and etc. In addition, through iterative calculations on the structure preliminarily designed only with member sizing, the strength and ductility demands of each member can be directly calculated so as to satisfy the given design strategy. As the result. economical and safe design can be achieved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.169-179
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• 2005

An improved method for evaluating effective buckling lengths of beam-column members in plane frames is newly proposed based on system inelastic buckling analysis. To this end, the tangent stiffness matrix of be am-column elements is first calculated using stability functions and then the inelastic buckling analysis method is presented. The scheme for determining effective length of individual members is also addressed. Design examples and numerical results ?uc presented to show the validity of the proposed method.

• Computational Structural Engineering
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• v.8 no.4
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• pp.65-74
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• 1995

Direct method developed for the inelastic analysis of planar frames subjected to monotonic loads is extended to cyclic loads. Two frame elements for Direct Method(inelastic truss and inelastic beam) are developed. The accuracy and reliability of the preposed method is verified by comparing the analysis results of example with step-by-step analysis. Direct Method is superior to Step-by-step analysis in view of reliability of solution and analysis cost.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.181-190
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• 2004

A new inelastic design method performing iterative calculations using secant stiffness was developed. Since the proposed design method uses linear analysis, it is convenient and stable in numerical analysis. At the same time, the proposed design method can accurately estimate the inelastic strength and ductility demands of the members by performing iterative calculation. In the present study, the procedure of the proposed design method was established. Design examples using the proposed method were presented, and its advantages were highlighted by comparisons with existing design methods using elastic or plastic analysis. Unlike the existing inelastic design methods performing the preliminary design on the structure and checking its validity using nonlinear analysis, the proposed integrated analysis-design method can directly calculate the strength and ductility demands of each member. In addition, the proposed design method can address the inelastic design strategy intended by the engineer, such as strength and ductility limits of members and the design concept of strong-column and weak-beam. As a result, economical and safe design can be achieved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.277-289
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• 2005

The study examines the limit strength for steel cable-stayed bridges. A case studies have been performed in order to evaluate the limit strength lot steel cable-stayed bridges using nonlinear inelastic analysis approach and bifurcation point instability analysis approach, effective tangent modulus $(E_f)$ method. To realize it, a practical nonlinear inelastic analysis condoling the initial shape is developed. In the initial shape analysis, updated structural configuration is introduced instead of initial member forces for beam-column members at every iterative step. Geometric and material nonlinearities of beam-column members are accounted by using stability function, and by using CRC tangent modulus and parabolic function, respectively Besides, geometric nonlinearity of cable members is accounted by using secant value of equivalent modulus of elasticity. The load-displacement relationships obtained by the proposed method are compared well with those given by other approaches. The limit strengths evaluated by the proposed nonlinear inelastic analysis for the proposed cable-stayed bridges with tee dimensional configuration compared with those by the inelastic bifurcation point instability analyses.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.587-588
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• 2011

본 논문에서는 강사장교의 극한강도 및 파괴모드를 간략하게 예측할 수 있는 간단하고 빠른 해석법을 제안하였다. 기존의 비탄성 고유치해석의 기본 개념을 바탕으로 기둥 요소에 대한 수렴 기준을 보였고, 사장교 구조 시스템의 거더 및 주탑 요소에서 보-기둥 거동을 고려하기 위한 새로운 수렴 기준을 제시하였다. 제시된 방법의 타당성 검증을 위하여 중앙경간 길이와 거더의 높이를 변화시킨 강사장교 모델에 대하여 제안된 비탄성 고유치 해석과 비선형 탄소성 해석 결과를 비교하였다. 해석 결과, 제안된 수렴 기준을 적용한 비탄성 고유치 해석은 기존에 기둥의 수렴기준을 적용했던 방법에 비하여 강사장교의 극한강도를 보다 정확히 예측할 수 있었다. 또한, 제안된 방법은 강사장교의 파괴모드 역시 근사하게 모사 가능함을 알 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.295-301
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• 2007

The aeroelastic characteristics of a wing with control surface freeplay are investigated. The transonic small disturbance equation is used for unsteady aerodynamic forces in subsonic/transonic region. The fictitious mass method is introduced to apply a modal approach to nonlinear structural models. Nonlinear aeroelastic time responses are calculated by the coupled time integration method. Using these methods, an efficient aeroelastic analysis is achieved for aerodynamic and structural nonlinearities simultaneously. The effects of the aerodynamic nonlinearity, initial flap amplitude, and freeplay magnitude in aeroelastic characteristics are investigated in this study.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.115-123
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• 1998

In design of tall buildings, the flows of stress and ultimate strength of structures cannot be obtained by the elastic analysis alone. The current inelastic analysis are very impractical for practical engineer due to the amount of work involved in engineering calculation. In this paper the PC-based inelastic analysis by the residual strength ratio concepts is introduced. The efficiency of inelastic analysis is evaluated by comparing the results of inelastic analysis with those of elastic analysis for the existing tall buidling located in Seoul. Some modification in terms of lateral resisting structural system is proposed to improve the system ductility.