• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.687-696
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• 2006

An efficient numerical method is developed to estimate the elasto-plastic post-buckling strength of space-framed structures. The inelastic ultimate strength of beam-columns and frames is evaluated by the parametric study. Applying the improved plastic hinge analysis that evaluate the gradual stiffness decrease effects due to spread of plasticity, elasto-plastic post-buckling behavior of steel frames is investigated considering the various residual stress distributions. Introducing the plastification parameter that represent pread of plasticity in the element and performing parametric study of equivalent element force and member idealization, finite-element solutions for the elasto-plastic analysis of space frames are compared with the results by plastic region analysis, shell elements and experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.2
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• pp.225-235
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• 2001

본 연구는 물리·역학적 특성을 고려한 점탄성 감쇠기의 수치모델에 의한 강뼈대구조물의 지진응답개선에 관해서 조사하고자 한다. 온도변화에 의한 감쇠기 이력거동에 미치는 영향을 고려하기 위하여, 점탄성 감쇠기의 모델은 온도-주기 등가원리와 더불어 개선된 분수도함수법에 기초하여 정식화하였다. 본 감쇠기 모델의 알고리즘을 일반화된 강뼈대구조물의 비선형 동적 해석 프로그램에 추가하였다. 강뼈대구조물에 대한 해석 예를 통하여, 제시된 모델에 의한 점탄성 감쇠기의 지진응답개선에 관한 효과를 확인할 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.2
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• pp.315-327
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• 2002

The main objective of this study is to develop an discrete optimization algorithm of plane steel frames with rigid using second-order-elastic-plastic hinge analysis which is considering panel zone. Conventional analyses of steel frame are usually tarried out without considering the effect of panel zone deformation on frame behavior The validity of this model is established by comparison without panel zone on joint models is analyzed numerically to demonstrate the importance of using realistic models in steel frame analysis. The objective function is taken as Weight of steel frames and the constraints we formulated based on AISC-LRFD(1994). The validity of the developed algorithm we demonstrate by comparing the result with those of SAP2000. The result of the study indicates that the optimal design algorithm considering of panel zone behavior more economic design than simple steel frame design methods.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.143-154
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• 2014

An improved method for evaluating effective buckling length of semi-rigid frame with inelastic behavior is newly proposed. Also, generalized exact tangential stiffness matrix with rotationally semi-rigid connections is adopted in previous studies. Therefore, the system buckling load of structure with inelastic behaviors can be exactly obtained by only one element per one straight member for inelastic problems. And the linearized elastic stiffness matrix and the geometric stiffness matrix of semi-rigid frame are utilized by taking into account 4th terms of taylor series from the exact tangent stiffness matrix. On the other hands, two inelastic analysis programs(M1, M2) are newly formulated. Where, M1 based on exact tangent stiffness matrix is programmed by iterative determinant search method and M2 is using linear algorithm with elastic and geometric matrices. Finally, in order to verify this present theory, various numerical examples are introduced and the effective buckling length of semi-rigid frames with inelastic materials are investigated.

• Computational Structural Engineering
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• v.7 no.3
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• pp.37-40
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• 1994

현재까지 구조해석에는 유한요소법이 가장 널리 사용되고 있으므로, 이 글에서도 유한요소법이 사용됨을 전제로 모든 과정을 논의한다. 유한요소라이브러리에서 뼈대구조물에 가장 적합한 것은 보요소(beam element)라 할 수 있다. 따라서 여기에서는 보요소를 주로 이용하는 유한요소법에 근거를 두고 뼈대구조물의 최적화 설계과정을 기술하기로 한다.

• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.339-348
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• 2002

The study developed an automatic design method of steel frames which uses nonlinear analysis. The geometric nonlinearity was considered using stability functions. Likewise, the transverse shear deformation effect in a beam-column was explained. A direct search method was used as an automatic design technique. The unit value of each part was evaluated using LRFD interaction equation. The member with the largest unit value was replaced one by one with an adjacent larger member selected from the database. The weight of the steel frame was considered as an objective function. On the other hand, load-carrying capacities, deflections, inter-story drifts, and ductility requirement were used as constraint functions. Case studies of a two-dimensional and a three-dimensional two-story frames were presented.

• Magazine of the Korea Concrete Institute
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• v.1 no.1
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• pp.87-94
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• 1989

철근콘크리트 뼈대구조와 같이 설계변수가 과다하고, 제약조건식이 복잡한 구조물의 최적화를 위하여는 구조물을 여러개의 부분구조물로 분할하여 최적해를 구하는 분할법이 많이 사용되고 있다. 그러나 기존의 분할법에 의한 최적화는 구조해석과정과 고정된 부재력에대한 단면설계변수의 부분최적화 과정만으로 이루어지기 때문에, 최적해를 구하려면 반복적인 재해석과정만을 수행하지 않으면 안된다. 따라서 본 연구에서는 다단계분할법에 의하여 철근콘크리트 뼈대구조의 최적화 문제를 3단계로 형성하고, 분할된 부분최적화문제의 최적화시 전체구조의 강성 및 부재력 변화가 반영되어 부분 구조물의 결합을 유지시킬 수 있는 최적화 알고리즘을 제안하였다. 최적화 문제에서 설계변수로는 단면의 크기, 철근량, 모멘트 재분배율등을 취하고,목적함수는 경비함수, 제약조건으로는 강도설계법에 의한 부재강도, 시방서의 요구사항등을 고려하여 문제를 형성하였다. 본 연구에서 개발한 다단계 최적화과정의 첫째 단계에서는 탄성해석에 의하여 재분배모멘트의 설계공간을 형성한다. 이 때 부재력변화량추정(forece approximation technique)에 의하여 단면치수의 변화에 따른 부재력의 변화를 제약조건식 내에 포함시킬 수 있도록 하였다. 둘째 단면에서는 첫째 단계에서 구한 부재력변화량추정이 포함된 제약조건식 내에서 무제약최소화기법에 의하여 단면치수를 최적화하도록 하였다. 셋째 단계에서는 재분배 모멘트를 최적화하였으며, 이 때 재분배모멘트의 변화에 따른 단면설계 변수의 변화는 둘째 단계에서 구한 설계민감도(design sensitivity)를 이용하여 반영시키도록 하였다. 제안된 알고리즘을 1층 2경간 및 2층 1경간 뼈대구조에 적용하여 알고리즘의 타당성과 효율성을 입증하였다. 따라서 본 연구의 알고리즘은 철근 콘크리트 뼈대구조의 최적설계에 안정성있게 적용할 수 있을 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.9-18
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• 2011

Generally the connection of structural members is assumed as hinge, rigid and semi-rigid connections. The exact tangent stiffness matrix of a semi-rigid frame element is newly derived using the stability functions considering shear deformations. Also, linearized elastic- and geometric-stiffness matrices of shear deformable semi-rigid frame are newly proposed. For the exact stiffness matrix, an accurate displacement field is introduced by equilibrium equation for beam-column under the bending and the axial forces. Also, stability functions considering sway deformation and force-displacement relations with elastic rotational spring on ends are defined. In order to illustrate the accuracy of this study, various numerical examples are presented and compared with other researcher's results. Lastly, shear deformation and semi-rigid effects on buckling behaviors of structure are parametrically investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.395-404
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• 2005

This paper presents a reliable numerical procedure for nonlinear time-history analysis of space steel frames subjected to dynamic loads. Geometric nonlinearities of member (P-$\delta$) and frame (P-$\Delta$) are taken into account by the use of stability functions in framed stiffness matrix formulation. The gradual yielding along the member length and over the cross section is included by using a tangent modulus concept and a softening plastic hinge model based on the New-Orbison yield surface. A computer program utilizing the average acceleration method for the integration scheme is developed to numerically solve the equation of motion of framed structure formulated in an incremental form. The results of several numerical examples are compared with those derived from using beam element model of ABAQUS program to illustrate the accuracy and the computational efficiency of the proposed procedure.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.153-162
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• 2001

A direct design method of three-dimensional frames using practical advanced analysis is presented. In this method. separate member capacity checks encompassed by the code specifications are not required. because the stability of separate members and the structure as a whole can be rigorously treated in determining the maximum strength of the structures. Advanced analysis accounts for geometric and material nonlinearities. The geometric nonlinearlity is considered by the use of stability function. The material nonlinearity is accounted for using CRC tangent modulus and parabolic function. The load-displacements predicted by the proposed analysis compare well with those given by other approaches. A design example has been presented for a 22-story frame. The analysis results show that the proposed method is suitable for adoption in practice.